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  • 2015-2019
  • 1990-1994  (9,691)
  • 1920-1924
  • 1990  (9,691)
  • Chemistry  (9,691)
  • 101
    Electronic Resource
    Electronic Resource
    Quantitative IR spectrophotometry of peptide compounds in water (H2O) solutions. I. Spectral parameters of amino acid residue absorption bands (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 1243-1257 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared spectra of the amino acid residues in H2O solution have been obtained in the 1800-1400-cm-1 region. It has been established that amino acid residues of arginine, asparagine, glutamine, aspartic and glutamic acids, lysine, tyrosine, histidine, and phenylalanine have intensive absorption in this spectral region. Infrared spectra for a set of model compounds have been measured. On the basis of these data, spectral parameters of amino acid residue absorption bands have been determined.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360301309
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  • 102
    Electronic Resource
    Electronic Resource
    Theoretical studies of cis-Pt(II)-diammine binding to duplex DNA (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 823-836 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of cis-Pt(II) diammine (cis-DP) to double-stranded DNA was studied with several kinked conformations that can accommodate the formation of a square planar complex. Molecular mechanics (MM) calculations were performed to optimize the molecular fit. These results were combined with quantum mechanical (QM) calculations to ascertain the relative energetics of ligand binding through water vs direct binding of the phosphate to the ammine and platinum, and to guide the selection of DNA conformations to model complex formation. Based on QM and MM calculations, models are proposed that may be characterized by several general features. A structure involving hydrogen bonding between each ammine and distinct adjacent phosphate groups, referred to as closed conformation (CC), has already been reported. This is also found in the crystal structure of small dimers. We report alternative conformations that may be important in platination of duplex DNA. They are characterized by an intermediate conformation (IC), involving hydrogen bonding between one ammine and phosphate group, and an open conformation (OC), without ammine phosphate hydrogen bonding. The IC and OC can be stabilized by water bridges in the space between the ammine and the phosphate groups. Sugar puckers alternate from the type C(2′)-endo or C(1′)-exo (S), to the type C(3′)-endo or C(2′)-exo (N), with intermediate types near O(1′)-endo (O). In general, the sugar puckers alternate from S to N to S through the platinated region (3′-TpG*pG*p-5′), with the complexed strand exhibiting, (3′)-S*-N*-S-(5′) alternation, while the complementary strand shows either (3′)-S*-N*-S(5′) or (3′)-S*-N*-O-(5′) alternation. In both the OC and IC, a hydrogen bond is found between the ammine and O4(T) on thymine (T) at the (3′) end, adjacent to the complex site. There is a continuous range of backbone conformations through the platinated region which relate the OC to the IC. The models presented suggest that the dynamics of the binding of the cis-Pt(II)-diammines to adjacent N7(G) in double-stranded DNA may encompass several conformational possibilities, and that water bridges may play a roll in supporting open and intermediate conformations. Proton-proton distances are reported to assist in the experimental determination of conformations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290416
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  • 103
    Electronic Resource
    Electronic Resource
    Ir and Raman spectroscopic studies on coulombic interaction between water-soluble porphyrins and nucleic acids (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 999-1004 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have shown previously that the N-methylpridyl group vibrations of water-soluble porphyrins, M(TMpy-P4), are shifted to lower frequencies (0.5-2.6 cm-1) as a result of coulombic interaction between the N+-CH3 group of M(TMpy-P4) and the PO2 group of a nucleic acid. We have now turned over our attention to the effect of this coulombic interaction on the PO2 group vibrations of nucleic acids. Using Fourier transform ir and Raman spectroscopy, we found that the νa(PO2) at 1221 cm-1 is shifted 12 ∼ 17 cm-1 to higher frequencies, whereas the νs(PO2) at 1087 cm-1 is shifted 18 ∼ 26 cm-1 to lower frequencies, when DNA is mixed with M(TMpy-P4). These results indicate that the N+-CH3 group of M(TMpy-P4) interacts preferentially with one of the two oxygen atoms of the PO2 group of the DNA duplex.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290611
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  • 104
    Electronic Resource
    Electronic Resource
    The interaction of cyclosporin and calmodulin (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1005-1014 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of cyclosporin A and dansyl cyclosporin A with bovine and wheat germ calmodulin has been monitored by measurements of induced changes in dansyl and bound toluidinyl naphthalene sulfonate fluorescence. The interaction is Ca2+-dependent and 1 : 1 Measurements of the efficiency of radiationless energy transfer from bound dansyl cyclosporin A to an acceptor group located on Cys-27 of wheat germ calmodulin suggest that the primary binding site is not located on the N-terminal lobe (residues 1-65). However, studies with proteolytic fragments of calmodulin indicate that elements of the N-terminal half-molecule (residues 1-77) may be involved in the stabilization of the binding site. The binding of cyclosporin alters the physical properties of calmodulin and, in particular, reduces the localized rotational mobility of a fluorescent probe.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290612
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  • 105
    Electronic Resource
    Electronic Resource
    The relative contribution of electrostatic interactions to stabilization of collagen fibrils (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1015-1026 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrostatic energies of interaction between type I collagen molecules were calculated, using models developed by Timasheff and Hill. These energies, along with a contribution from hydrophobic forces, were then incorporated into an equation due to Flory that described phase equilibria of rod-like polymers. The Flory formalism in turn permitted a calculation of the overall free energy of fibril formation (ΔFf), and an assessment of the relative contribution of electrostatic and hydrophobic forces to ΔFf. Lastly, ΔFf Lastly, ΔFf was used in a nucleation-growth model relating halftimes of fibril formation (t1/2) to ionic strength (I) and temperature. Because the theory provided no basis for setting absolute levels of the energetic contributions, five parameters in the model had to be derived from experimental data. Based on the fit of theory to experimental results both for intact and pepsinized collagen, it was found that very low electrostatic energies (about -1 kcal/mole per collagen molecule) were sufficient to explain experimental t1/2 vs I relationships. This energy is equivalent to 1 close charge-pair interaction per molecule and appears to be lower than the energy assignable to hydrophobic interactions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290613
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  • 106
    Electronic Resource
    Electronic Resource
    Binding of cationic dyes to potassium alginate: A spectrophotometric and dichroic probe (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1541-1548 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acridine orange (AO) binds to potassium alginate (KAlg) stoichiometrically as is evidenced from conductometric and spectrofluorometric titrations. However, AO as well as methylene blue (MB) exhibits weak metachromasia and no induced dichroism at any sensible polymer to dye ratio (P / D). KAlg induces large blue shifts (by as much as 125 nm) of the λmax of the strongly aggregating dyes 1, 9-dimethylmethyleneblue (DMMB) and pinacyanol at reasonable P / D values; KAlg also induces strong dichroism in these dyes. The signs of the induced CD spectra indicate KAlg to have a left-handed helical conformation. This polymer also induces red-shifted J band and dichroism in the dye N-N′-diethylpseudoisocyanine (PIC) at high P / D under which condition the signs of CD spectra in DMMB reverse with drastic reduction in [θ] values. This reversal of sign of CD or induction of J band in PIC at only high KAlg concentrations does not involve any conformational change in the polymer as indicated by the insensitivity of the UV-CD spectrum of KAlg as a function of concentration.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360291205
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  • 107
    Electronic Resource
    Electronic Resource
    Cooperativity of carbohydrate moiety orientation and β- turn stability is determined by intramolecular hydrogen bonds in protected glycopeptide modelsThis is publication No. 1708 from the Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts, 02254-9110 (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1549-1564 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2, 3, 4, 6-Tetra-O-acetyl-β-D-gluco-, and β-D-galactopyranosides, as well as approximately 4 : 1 anomeric mixtures of α- and β-mannopyranosides of Boc-X-Y-NHCH3 dipeptides (X-Y = Pro-Ser, Pro-D-Ser, Val-Ser, Val-D-Ser, and Gly-Ser) have been synthesized. CD and ir spectroscopic studies were performed to characterize the conformation of the glycosylated peptide backbone and examine the possible formation of intrapeptide and glycopeptide intramolecular H-bonds. It was found that O-glycosylated peptides containing a D-serine residue are likely to adopt a type II β-turn while those with the Pro-Ser or Val-Ser sequence feature a type I(III) β-turn in solution. Glycosylation also increases the magnitude of the CD bands, characteristic of the given type of β-turns, which can be interpreted as an indication of the stablization of the folded backbone conformation. Infrared data showed that in nonpolar solutions the peracetyl glycopeptides adopt both single- and double H-bonded conformations whose ratio, in some cases, depends on the position at C-2′ of the H-bond acceptor acetoxy group. These data suggest that five-, seven-, or ten-membered glyco-turns may play an important role in fixing the steric orientation of the carbohydrate antennae systems in glycoproteins.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360291206
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  • 108
    Electronic Resource
    Electronic Resource
    Solvent effect on the stability of isomaltose conformers (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 369-379 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational equilibria of the low-energy conformers of isomaltose have been studied in different solvents. The structure of each individual conformer was refined from the 18 distinct low-energy regions determined from potential energy function. Molecular geometry optimization was carried out using the quantum chemical method of perturbative configuration interaction with localized orbitals or PCILO and yielded to 15 distinct minima. Carbon-proton vicinal coupling constants 3JC-H have been calculated based on the finite perturbation theory formulation with the intermediate neglect of differential overlap for these minima. For evaluation of the influence of the environment on the conformational structure of isomaltose, the population of the low-energy conformers was estimated in four solvents by a method in which the total energy is divided into the energy of the isolated molecule and the solvation energy. The calculated abundances of conformers depend strongly on the solvents. Based on the determined abundance of conformers, thermodynamically averaged torsion angles and coupling constants 3JC-H describing the “average” conformation about glycosidic linkage have been calculated. Results obtained are compared with available experimental data from solution and solid state.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300314
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  • 109
    Electronic Resource
    Electronic Resource
    Hydration effects on dynamics of polyglycine and sodium poly(L-glutamate) (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 691-701 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid state nmr methods were applied to the study of the motions and structural heterogeneity in polyglycine, sodium poly (L-glutamate), and poly(L-alanine). The response of both the main-chain and side-chain resonances to the addition of water was studied using static and magic-angle sample-spinning line shapes as well as the carbon spin-lattice relaxation times, the proton spin-lattice relaxation time in the rotating frame, and the proton-carbon cross-polarization time. The polyglycine motions are not drastically affected by the addition of water when the polymer is in the 31-helix or the β-sheet structure. The sodium poly(L-glutamate), however, responds to increased hydration with little motion in the main-chain carbon atoms, but considerable flexibility of the side-chain atoms. The greatest motions are reported for the C5 carbon with rotational amplitudes about the C47-C5 bond of about of 50°. In addition, motions somewhat less than half this size are required closer to the main chain.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300705
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  • 110
    Electronic Resource
    Electronic Resource
    Conditions for the stability of the alternative structures of duplex poly(dA-dT) (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 753-761 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alternative structures of the lithium, sodium, potassium, and rubidium salts of poly(dA-dT) were studied using ir spectra of hydrated, nonoriented gels. Poly (dA-dT) · Na existed as the B structure at high hydration and as the A structure at moderate hydration. A disordered state occurred at low hydration. No hint of the C, D, or other structures was observed at any hydration for nonoriented gels containing NaCl up to 0.56 moles NaCl/mole of nucleotide residue. Poly (dA-dT) · Li existed as the B structure at high hydration, made a gradual transition to the C structure at moderate hydration, and became disordered at low hydration. Poly (dA-dT) · K and poly (dA-dT) · Rb existed as the B structure at high hydration and as the presumptive D structure at lower hydration. The addition of Zn(II) to poly (dA-dT) · Na produced a gradual transition from the B to the C structure upon dehydration. The addition of NaNO3 to poly (dA-dT) · Na gave only the A and B structures, and not the C or Z structures that are promoted by NO3 in other base sequences. The DNA secondary structure stabilized by a given ion is determined by a specific base sequence and not simply by the properties of the ion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300710
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  • 111
    Electronic Resource
    Electronic Resource
    Thermodynamic cycle-perturbation study of the binding of trifluoroacetyl dipeptide anilide inhibitors with porcine pancreatic elastase (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 773-780 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variety of results of crystallographic studies of the serine proteases complexed with isocoumnrin inhibitors presents a challenging problem to modeling methods and molecular energetics. Therefore, the thermodynamic cycle-perturbation technique has been used to study a model system of elastase and two peptidic inhibitors. Using the program AMBER, the technique correctly predicts changes of the binding constants for the trifluoroacetyl dipeptide inhibitors in comparison with available experimental (kinetic and crystallographic) data. However, the absolute values obtained are shown to be sensitive to the specific electrostatic interaction potential parameters used in the simulations. The reader and user are cautioned that thermodynamic cyle-perturbation results may be too optimistic by underestimating the accuracy of free energy values. This is especially a matter of concern for those cases where a direct comparison with experimental values is not possible, viz., (1) the simulation of binding of novel compounds, (2) structurally uncertain binding sites, or (3) structurally different binding modes. With our best 4-31G* ESP (electrostatic potential) charges we were able to reproduce experimentally determined free energy differences (ΔΔA) with an accuracy of about 1.5 kcal/mol. Dynamically induced structural changes in the binding site of elastase, and particularly changes in hydrogen-bond patterns of the binding site, are also reported.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300712
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  • 112
    Electronic Resource
    Electronic Resource
    Synthesis and 1H-nmr studies of α-deuterated analogues of des-Trp1, Nle12-human minigastrin (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 847-854 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three analogues of the tridecapeptide amide H-Leu-(Glu)5-Ala-Tyr-Gly-Nle-Asp-Phe-NH2 were synthetized with α-deuterated glutamate residues in specific positions in order to assign unambiguously the 1H nmr spectrum of the parent peptide in water and in water-trifluoroethanol mixtures. The synthetic route is described and the assignment illustrated. A previous, tentative assignment based solely on indirect evidence [Mammi, S., Mammi, N. J. & Peggioa, E. (1988) Biochemistry 27, 1374-1379] was partially modified.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300719
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  • 113
    Electronic Resource
    Electronic Resource
    Correlation between dinucleotide periodicities and nucleosome positioning on mouse satellite DNA (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 861-876 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous studies demonstrated 16 well-defined nucleosome locations (A-P) on a tandemly repeated prototype 234 base pair (bp) mouse satellite repeat unit. We have aligned the A-P fragments to search for DNA sequence elements that might contribute to nucleosome placement at these positions. Our results demonstrate a strikingly regular, uninterrupted, periodic pattern for the AA dinucleotide occurrences along the entire length of the aligned fragments. The periodicity of the AA occurrences is about 9.7 bp. The pattern exhibits a local minimum at position 74, near the nucleosome dyad axis of symmetry. Other dinucleotides - including AC : GT, CA : TG, and CC : GG - are also placed periodically, but their patterns of occurrence are less regular and less frequent than AA. The calculated spacings between consecutive preferred nucleosome locations on mouse satellite DNA are nearly identical, corresponding to multiples of 9.7 bp. The correlation between the periodicity of dinucleotide occurrences and the average spacing of nucleosome positions suggests that the preferred nucleosome locations recur at intervals that may correspond to the DNA helical repeat in the mouse satellite nucleosomes, and that the histone octamers sample (or slip along) the duplex in steps of 9.7 bp during nucleosome formation on mouse satellite DNA.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300902
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  • 114
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of Boc-D-Ala-ΔPhe-Gly-ΔPhe-D-Ala-OMe: A 310-helical dehydropeptide (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 911-920 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal and molecular structure of the pentapeptide Boc-D-Ala-ΔPhe-Gly-ΔPhe-D-Ala-OMe, containing two dehydrophenylalanine residues, was determined by x-ray diffraction. The molecule crystallizes in the orthorombic P212121 space group, with a = 10.439(3), b = 15.319(3) and c = 21.099(4) Å.In the solid state, the conformation of the pentapeptide is characterized by the presence of two type III′ β-turns. Thus the peptide assumes a left-handed 310-helical conformation, the left sense being due to the D configuration of the alanine residues. The two unsaturated residues are located in the (i + 1) position of the first β-turn and in the (i + 2) position of the second β-turn, respectively.In the crystal, the helical molecules are linked head to tail by hydrogen bonds. Lateral hydrogen bonds are also formed between molecules related by a twofold screw symmetry. This gives rise to a typical mode of packing characterized by infinite helical “chains,” smiliar to the packing found in other oligopeptides that adopt a 310-helical structure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300906
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  • 115
    Electronic Resource
    Electronic Resource
    The effect of the L-azetidine-2-carboxylic acid residue on protein conformation. II. Homopolymers and copolymers (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 961-966 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alteration of polymer conformational properties caused by the replacement of L-proline by L-azetidine-2-carboxylic acid (Aze) has been studied by means of conformational energy computations. In addition to poly (Aze), two sequential copolymers, poly (Pro-Aze) and poly(Aze3-Pro3), have been investigated. All polymers containing Aze are more flexible than poly(Pro). This is a consequence of an increased number of permitted conformational states for the Aze residue, as compared to Pro, when they are incorporated into a polypeptide, as well as of a lessened cooperativity of the trans-cis transition. The results of the computation can be used to interpret the observed physical properties of poly (Aze) and of its copolymers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300910
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  • 116
    Electronic Resource
    Electronic Resource
    Internal dynamics of tRNAPhe studied by depolarized dynamic light scattering (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 975-983 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collective internal dynamics of transfer RNAphe from brewer's yeast in solution was studied by depolarized dynamic light scattering (DDLS). Within the melting region of tRNA the depolarized spectra consist of two Lorentzian, where the narrow (slow) component describes the overall rotation of the macromolecule. The broad component is attributed to the collective reorientation of the bases within the biopolymer. At high temperature only this relaxation process is observed in the spectrum. The viscosity dependence of the collective internal relaxation process is described by the Stokes-Einstein-Debye equation for rotational diffusion. Estimates of the internal orientational pair correlation factor from the integral depolarized intensities of tRNAPhe solutions indicates that the observed dynamics correspond to the collective reorientation of approximately 5 bases. A comparison of the results presented with DDLS studies on the aggregation of the mononucleotide guanosine-5′-monophosphate confirms this result. For a further characterization of the relaxation process we studied the effect of hydrostatic pressure (1-1000 bar) on the depolarized spectra of tRNA. While other spectroscopic methods like nmr, fluorescence polarization anisotropy decay, or ESR give information about the very local motion of a single base within the DNA or RNA, this study shows that by DDLS one can characterize collective internal motions of macromolecules.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300912
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  • 117
    Electronic Resource
    Electronic Resource
    Conformational search in enkephalin analogues containing a disulfide bond (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 1011-1025 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A systematic Conformational search has been performed for the 14-membered ring in model compounds for disulfide-containing enkephalin analogues. The model compounds examined are , and the corresponding compounds with L-amino acids at the C-terminus. About 100 starting conformations were generated for each compound with the RNGCFM program and energy minimized with the AMBER program. Between 21 and 38 conformers within 3 kcal/mole of the apparent global minimum were found for each compound. There appeared to be fewer possible conformations of the disulfide-containing side chain than of the main chain. , whose parent compound is selective for opioid δ receptors, was found to prefer conformers with a positive dihedral angle of the disulfide bond, which is consistent with the previous proposal that δ-receptor selectivity may be associated with this conformational preference. Additional calculations were performed on the complete structure of (DPDPE) with various possible conformations of the tyrosine and phenylalanine side chains. Conformational free energies and entropies were computed for these conformers from the molecular vibrations obtained from a normal mode analysis. As was found previously, conformers with low energies tended to have lower entropies, which resulted in a narrowing of the free energy differences between conformers. A conformer is identified that has the lowest energy hitherto found for DPDPE. It is suggested that DPDPE may be a useful compound for evaluating conformational search strategies because of its relatively small size and the number of conformers that have already been identified. Conformational energy calculations are also reported for naltrindole using the MM2(87) program. Naltrindole, which incorporates two aromatic 6-membered rings in a rigid structure, is a highly selective and potent opioid δ-receptor antagonist and may be an important clue regarding the biologically active conformer of DPDPE. Various conformers of DPDPE have been superimposed quantitatively onto the structure of naltrindole using the SUPER program and those conformers of DPDPE that are the best fit to naltrindole are reported.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360301103
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  • 118
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    Eine neue methode zur herstellung von hydroxyterminierten polydienen (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 69-80 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: It is shown, that hydroxyterminated polydienes of good microstructure and functionality and a narrow molecular weight distribution can be prepared using di-hydroxyethyl-azo-bis-isobutyramide as an initiator. The activation energy of the initiator decay has been determined by volumetric measurement of the nitrogen evolved in this reaction.
    Notes: Es wird gezeigt, daß hydroxyterminierte Polydiene mit guter Mikrostruktur und Funktionalität sowie enger Molekulargewichtsverteilung unter Verwendung von Azobis-isobuttersäure-di-hydroxyethylamid hergestellt werden können. Die Aktivierungsenergie des Initiatorzerfalls wurde durch volumetrische Messung des bei dieser Reaktion freiwerdenden Strickstoffs bestimmt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740106
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    Elution behaviour of diolmodified epoxides in size exclusion chromatography (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 81-88 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Reaktion von Bisphenol A-diglycidether (BADGE) mit Butan-1,4-diol (BD) in Gegenwart von Mg(ClO4)2 führt in Abhängigkeit von der Reaktionstemperatur zu linearen und verzweigten Oligomeren. Bei 100°C Reaktionstemperatur läßt sich die Produktbildung bis ca. 70% Epoxid-Umsatz durch HPLC feststellen. In diesem Umsatzbereich sind alle Produkte gut in THF löslich, woudurch die Verfolgung des Molmassenanstieges mittels SEC möglich ist. Es wird eine charakteristische Molmasse-Umsatz-Beziehung erhalten sowie die SEC-Daten eines verzweigten Produktes diskutiert.
    Notes: The reaction of bisphenol A-diglycidyl ether (BADGE) with butane-1,4-diol (BD) in the presence of Mg(ClO4)2 leads to linear and branched oligomers. The formation ratio of these products depends on the reaction temperature. In experiments at 100°C, an epoxide consumption of up to 70% can be observed using HPLC. In this range all products show good solubility in THF, so that it is possible to follow the increasing molar mass by using SEC. A characteristic relation of the molar mass against the conversion rate is derived and SEC data of a branched product are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740107
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  • 120
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    Structural and mechanical changes of polyacrylate systems in correlation with their composition in degradative conditionsPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers”, in Prague (Czechoslovakia), July 24-29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 113-123 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal and photodegradation of copolymer system based on styrene, butyl acrylate, acrylic acid and N-methylolacrylamide (S/BA/AA/MAA) shows mechanical, but no structural changes in examined temperature range and after 320 h of UV irradiation (simultaneously with 256 and 366 nm lamps). Content of acrylic acid is a very important factor for the mechanical stability of these systems which can be very successfully used as the coatings in the practice. Found correlations indicate mechanism and factors having influence on the excellent stability of copolymer films.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760110
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  • 121
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    Kinetic characteristics of the light ageing of rubbers based on polydieneurethanes and polyetherurethanesPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 147-160 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of light wavelength and intensity, as well as the temperature, on photooxidation has been studied for rubbers based on polydieneurethane (PDU) or polyetherurethane (PEU). Photooxidation is shown to proceed by the chain free-radical mechanism with bimolecular (for PDU) or linear (for PEU) kinetic chain termination. The PDU oxidation kinetic parameter is equal to 0.02 [mole/(kg·s)]1/2 and does not depend on temperature. In PEU photooxidation the kinetic chain length is constant in a wide range of light intensities and is equal to 7, while the activation energy is ca 18 kJ/mole. In distinction to PEU, PDU is sensitive not only to UV but also to visible light, with this sensitivity being preserved up to high oxidation levels. The dependences of photooxidation quantum yieldes on wavelength and irradiation time have been determined.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760113
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    Influence of small amount dispersive additives on the weather ability of PVC-filmsPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Ageing and Stabilization of Polymers” in Prague (Czechoslovakia), July 24-29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 197-206 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three types of transparent PVC-films before and after exposition in the weather conditions are studied. The first film (the control) is plasticized and stabilized; the second is similar to the first but 1 part of cuprous oxide (CuzO) is incorporated in it, while in the third 1 part of aluminium (A1) powder is added. It is found that the light transparency decreases by 2-7% upon adding Cu2O and by 17-36% upon adding Al-powder. UV-visible measurements, colourimetric measurements and microscopic investigations are used for examining PVC-samples properties during weathering. The surface layer chemical changes are studied by means of MIR-IR-spectroscopy. The total colour variation (ΔE*ab) in the case of 12 months aged PVC-film, containing Cu2O, shows 11 relative units in comparison with 37 relative units for the other two materials. A retarding action of Cu2O and an accelerated effect of Al-powder on the weather degradation of clear soft PVC-films are established. The influence of the chemical properties and different size distribution of the dispersive additives on photooxidative behaviour of PVC-compositions are discussed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760117
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    Processing stabilization of polyolefinsPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 215-230 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The response of a HDPE, a L-LDPE and a PP homopolymer to processing conditions and processing stabilizer formulations in the 220°C to 280°C temperature range was investigated. The technique of multiple extrusion was used. Melt flow and melt flow ratio were measured after the first, third and fifth extrusion pass. In the case of the HDPE and the L-LDPE, degradation by cross-linking was the predominant reaction and the molecular weight distribution showed a significant broadening compared to the virgin samples. The PP homopolymer degraded by chain scission. By adding a multifunctional hindered phenol and a hydrolysis resistant phosphite, all polymers could be efficiently protected against degradation on processing. For the HDPE and the L-LDPE, increased amounts of phosphite provided increased processing stability at constant phenol concentration. A 4:1 ratio of phosphite to phenol exhibited the best performance. The most efficient ratio for protecting melt flow of the PP homopolymer was found when a two to one ratio of phosphite to phenol was added.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760119
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    Mechanisms and kinetics of photostabilization of polyolefins with halsPaper presented at the 19th Colloquium of Danubian Countries on “Ageing and Stabilization of Polymers”, Prague, Czechoslovakia, July 24-27, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 241-289 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The HALS stabilization mechanisms usually envisaged do not explain the experimental facts. New mechanisms are proposed instead. They include quenching of excited charge-transfer complexes (CTC) polymer-oxygen by CTC HALS-oxygen. In addition, the formation of CTC between peroxy radicals and NH-HALS is of prime importance. These CTC HALS-peroxy radicals can either react photolytically after absorption of UV radiation or with a second peroxy radical, thus promoting termination between two peroxy radicals.Initiation of photooxidation in HALS stabilized polyethylene involves usually CTC HALS-oxygen throughout the useful lifetime of the polymer. In contrast to that, initiation of photooxidation in HALS stabilized polypropylene is classical and due to photolysis of tertiary hydroperoxides.The formal kinetics based on the mechanisms envisaged explain the experimental results observed with HALS stabilized polyethylene and polypropylene. On the one hand, they concern, the performance of HALS: in polyethylene it is a linear function of the square root of HALS concentration whereas in polypropylene it increases linearly with HALS concentration as long as the last does not become too high. On the other hand, the experimental facts explained, concern the decrease of the HALS concentration during W exposure of HALS-stabilized polyethylene and polypropylene. The decrease is first order in both polymers but is independent of the initial HALS concentration in polyethylene, whereas it decreases with increasing initial HALS concentration in polypropylene. This is in agreement with the corresponding initiation mechanisms envisaged for polyethylene and polypropylene.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760121
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    Stabilization of linear polyethylene crosslinked by irradiationPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24-29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 303-310 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Our experiments have shown that after a complex degradative effect, such as processing, irradiation and ageing, the effects of antioxidants and their mixtures are very different.The results of our investigation support the opinion, expressed by many researchers of stabilization, that there does not exist any universally practicable antioxidative system. The optimal effect has to be determined, for each system, in the knowledge of the quality and quantity of the given oxidative load.For polyethylene crosslinked by irradiation a satisfactory stability can be attained with the aid of the usual stabilizers; however, they must be used in relatively larger quantities owing to the additional degradative action of the irradiation. There are noticeable differences between the stabilizers not only in their stabilizing action, but also in influencing the degree of discoloration and in the dose number required to produce the same degree of crosslinking.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760123
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    Stabilization of polyacetalsPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 323-332 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A brief introduction describes the main differences between homo, and copolymer polyacetals and their main degradation mechanisms. A short overview describes the importance of stabilization and the necessity of using antioxidants and costabilizers during manufacturing, processing and end use of polyoxymethylene(polyacetals). Various stabilizer systems are presented and studies on the interaction of antioxidants with costabilizers added. The criteria for testing the performance of these additives are discussed and demonstrated by many examples.In a second part the increasing importance of light stabilized polyacetal is mentioned and investigations on the performance of light stabilizer systems are highlighted.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760125
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    Properties and role of benzoquinone imines in polymer stabilizationPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 347-355 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Quinone imines are formed from aromatic amine antidegradants as a consequence of chemical transformations of the latter during the stabilization of hydrocarbon polymers. Quinone imines are deep coloured compounds and contribute to the antidegradant activity of the parent amines. The main interest is devoted to benzoquinone diimines (BQDI), generated from N,N '-disubstituted 1,4-phenylenediamines (PD). BQDI are antioxidants in unsaturated hydrocarbons, undergo hydrolytic deamination, addition and cyclization reactions, react with 2,6-dialkylphenols, thiols and C-centered radicals. PD are regenerated from BQDI in redox reactions. The active role of BQDI in antifatigue processes in rubbers has been explained using product analysis. BQDI account for staining and discoloring properties of PD but are not harmful to the polymer stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760127
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    Partikelgrößenanalyse von dispersen farbstoffsystemen, IITeil I cf. Lit.2.. Photonen-korrelations-spektroskopie an latexsuspensionen und ‚modellblindfärbungen‘ von polyethylenterephthalat-fasernHerrn Dr. Gerhard Heidemann zum 60. Geburtstag gewidmet. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 17-32 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: As a first step to analyse the particle size distribution of dyebaths, photoncorrelation-spectroscopy is used to determine the particle sizes of latex suspensions. To simulate the procedure of dyeing polyester fibres with disperse dyes, latex suspensions are used as model for dyes. The ‘dyeing’ is carried out at various temperatures and the resulting particle size distribution of the ‘dyebath’ is measured using photon-correlation-spectroscopy.
    Notes: Als Vorstufe zur Teilchengrößenanalyse von Farbstoffbädern mittels Photonen-Korrelations-Spektroskopie werden Latexsuspensionen untersucht. Eine Simulation einer Färbung von Polyestermaterial mit Dispersionsfarbstoffen wird durch eine ‘Modellblindfärbung’ unter Benutzung von Latexsuspensionen bei unterschiedlichen Farbbadtemperaturen nachgestellt. Die sich innerhalb des ‘Färbebades’ ergebenden Partikelgrößenverteilungen werden mit Hilfe der Photonen-Korrelations-Spektroskopie analysiert.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780102
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    Depolarization current of a novolac p-fluorophenol-formaldehyde resin (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 33-46 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Kondensation von p-Fluorphenol mit Formaldehyd wurde ein p-Fluorphenol-Formaldehyd-Novolak (NFF) hergestellt. Die Differential-Scanning-Calorimetrie zeigte je nach Vorgeschichte der Proben den normalen Glasübergang oder damit zusammenfallende endotherme Peaks. Es wird vermutet, daß die endothermen Peaks durch Spaltung intramolekularer Bindungen während des Glasübergangs verursacht werden. Diese Bindungen entstehen bei der Lagerung der Harze bei Raumtemperatur. Messungen des thermisch induzierten Polarisationsstroms (TSDC) wurden in einem Temperaturbereich von 290 bis 350 K an Proben mit Molekulargewichten von M̄n=375 bzw. 434 g/mol durchgeführt. Die TSDC-Kurven zeigten hauptsächlich die α-Peaks der dielektrischen Relaxation. Es wurde der Einfluß der Temperatur, der Einfluß von M̄n die Aktivierungsenergie Ea und die physikalische Alterung der Proben untersucht. Die physikalische Alterung wurde durch die reziproke Polarisierbarkeit R, als Funktion des Alters charakterisiert. Die Probe mit großerem M̄n wies eine höhere Glasübergangstemperatur, eine niedrigere Aktivierungsenergie und einen stärkeren Anstieg von Rp, auf als die Probe mit niedrigerem M̄n. Der Anstieg des Molekulargewichts verstärkte sich mit zunehmender Steifigkeit der NFF-Proben. Diese Effekte werden der starken Ausbildung von Wasserstoffbindungen zugeschrieben. Die Resultate werden mit analogen Ergebnissen von fluorfreien Phenol-Formaldehyd-Novolaken verglichen.
    Notes: A Novolac p-fluorophenol-formaldehyde (NFF) resin was prepared by condensation of p-fluorophenol with formaldehyde. DSC showed the glass transition effect or coinciding endothermal peak depending upon the thermal history of samples. It is supposed that the peaks are caused by breaking of the intermolecular bondings in the resin during the glass transition. The bondings are formed in the resin during the storage at room temperature. Thermally stimulated depolarization current (TSDC) measurements were carried out in the temperature range of 290 to 350 K, with the samples having an average number molecular weight M̄n of 375 and 434. TSDC curves mainly showed the dipolar relaxation α peaks. The influence of poling temperatures, the influence of M̄n, the activation energy Ea, and the physical ageing of the samples were investigated. Physical ageing was determined as the reciprocal polarizability Rp vs. time of ageing. Samples. with higher M̄n showed a higher glass transition temperature, a lower Ea, and a higher increase in Rp than the sample with lower M̄n. The increase in M̄n increased the rigidness of NFF samples. The effects are attributed to the strong hydrogen bonding. The comparison with analogous results in novolac phenol-formaldehyde resin without fluorine is given.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780103
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    Modification of polyamide 6 with hycar ATBN (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 85-93 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die Synthese von Blockcopolymeren aus 6-Caprolactam und einem flüssigen aminotelechelischen Copolymeren aus 1,3-Butadien und Acrylnitril (Hycar ATBN 1300X21) studiert, die eine höhere Kerbschlagzähigkeit als das geläufige Poly(6-caprolactam) aufweisen. Bei der durch das Addukt aus Phosphorsäure und 6-Caprolactam initiierten Polymerisation von 6-Caprolactam wurde der Einfluß der Konzentration des Initiators (0-5 mol-%) und der Konzentration von Hycar ATBN 1300X21 (0-50 Gew.-%) im Polymerisationsgemisch, der Zeit (4-72 h) und der Temperatur (200-280°C) auf den Umsatz von 6-Caprolactam sowie auf die Eigenschaften des entstandenen Copolymeren untersucht. Die unter optimierten Bedingungen dargestellten Blockcopolymeren wiesen eine Kerbschlagzähigkeit von 13,5 kJ·m-2 auf.
    Notes: The preparation of block copolymers from 6-caprolactam and a liquid amine terminated butadiene-acrylonitrile copolymer Hycar ATBN 1300X21 having higher notched impact strength than ordinary poly(6-caprolactam) was studied. In the polymerization of 6-caprolactam initiated by an adduct of phosphoric acid with 6-caprolactam the influence of initiator concentration (0- 50 mol-%) and Hycar ATBN 1300X21 concentration (0-5 wt.-%) in the polymerization charge, of polymerization time (4 - 72 h) and of temperature (200-280°C) on the 6-caprolactam conversion and on the properties of the copolymers formed were followed. Notched impact strength of the block copolymers prepared under optimized conditions was as high as 13.5 kJ·m-2.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780106
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    Graft polymerization of 4-vinylpyridine onto cellulosic fibres by the ceric ion method, I. The reaction time effect (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 109-118 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß der Reaktionsdauer auf die mit Cer(IV)-Ionen initiierte Pfropfung von 4-Vinylpyridin (4-VP) auf partiell carboxymethylierte Cellulose (PCMC) mit verschiedenen Substitutionsgraden (D.S.) wurde untersucht. Zum Vergleich wurde dasselbe Monomere auf Baumwolle und mercerisierte Baumwolle gepfropft. Die Pfropfparamater dieser Polymerisationsreaktionen wurden bestimmt. Der Pfropfungsgrad (G) war bei PCMC signifikant höher als bei Baumwolle und mercerisierter Baumwolle. Der durch Röntgenbeugung ermittelte Kristallisationsgrad der Pfropfcopolymeren war niedriger als der von unmodifizierter Baumwolle. Der Einfluß der Reaktionszeit auf die Pfropfung von Baumwolle mit 2-Vinylpyridin wurde ebenfalls untersucht.
    Notes: A study was made of the time affecting the ceric ion induced grafting of 4-vinylpyridine (4-VP) onto partially carboxymethylated cotton (PCMC) having different degrees of substitution (D.S.). For comparison the same monomer was grafted onto cotton and mercerized cotton. The grafting parameters of these copolymerization reactions were determined. The graft yields for PCMC were significantly higher than those for unmodified cotton and mercerized cotton. The degree of crystallinity of the graft copolymers and of the unmodified cotton and PCMC samples was determined by the X-ray method. The crystallinity index decreased with the presence of grafted polymer. The reaction time effect of the grafting of 2-VP on cotton was also studied.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051780108
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    Light induced polymer and polymerization reactions, 35Part 34 cf. J. prakt. Chem. 330 (1988) 704.. Influence of monomer structure and binder composition on the photoinduced polymerization of multifunctional acrylic esters (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 131-142 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die photoinduzierte Polymerisation von Acrylaten in verschiedenen Bindemitteln wurde mit Hilfe der Photokalorimetrie, der DSC und der ESR-Spektroskopie untersucht. Um die Reaktivität vergleichend zu diskutieren, wurden zur Auswertung photokalorimetrischer Meßergebnisse folgende Parameter ausgewählt: Grenzumsatz, maximale Polymerisationsgeschwindigkeit, Inhibierungszeit und die Zeit, welche notwendig ist, um das Maximum der Polymerisationsgeschwindigkeit zu erreichen. Zwischen dem Grenzumsatz und der chemischen Struktur der Acrylate sowie dem Glaspunkt und der Sauerstoffpermeabilität des verwendeten Bindemittels bestehen eindeutige Korrelationen. Für die anderen Größen existieren keine deutlichen Zusammenhänge, da andere Faktoren wie z. B. ein verändertes Phasenverhalten order veränderte Diffusionsbedingungen diese Werte in komplexer Weise beeinflussen können.
    Notes: Photocalorimetry, differential scanning calorimetry and ESR-spectroscopy were used to analyse the photoinduced polymerization of multifunctional acrylic esters in various polymeric binders. Limiting conversion, maximal polymerization rate, inhibition time, and the time necessary to reach the maximum of the polymerization reaction rate were used to compare the reactivity of the photopolymer systems investigated in this work. Significant correlations exist between the limiting conversion and chemical structure of the acrylic esters used. A relation was also found between the glass transition temperature and oxygen permeability of the binder and the limiting conversion measured calorimetrically. A good correlation does not exist for the other reactivity parameters, because other factors such as phase change and changing diffusion conditions can have a complex influence on those values.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780110
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    Visco-Elastic properties of blends of crystalline polymers possessing a weak phase coupling. Studies on blends of poly(ethylene) and poly(oxymethylene) (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 153-169 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Arbeit befaßt sich mit dem Einfluß einer schwachen Phasenkopplung auf die viskoelastischen Eigenschaften von heterogenen Polymermischungen im linearen und nichtlinearen Deformationsbereich. Als Modellmischungen wurden Polyethylen Polyoxymethylen-Mischungen ausgewählt. Die beiden Polymeren eignen sich als Komponenten einer Modellmischung besonders gut, da sie vollständig unverträglich miteinander sind, da die Grenzflächenenergie groß und die Ausdehnung der Grenzschicht folglich gering ist und da die mechanischen Eigenschaften der beiden Komponenten in erster Näherung ahnlich sind. Solche Mischungen sollten folglich den Beitrag der Phasenkopplung zu den viskoelastischen Eigenschaften besonders deutlich aufzeigen.Für die Modellmischung wurden die viskoelastischen Eigenschaften als Funktion der Konzentration der Komponenten durch die Erfassung des Spannungs-Dehnungsver-haltens, des komplexen Schubmodulus sowie der elastischen, anelastischen und plastischen Anteile der Deformationsenergie charakterisiert. Der experimentelle Befund ist, daß sich die meisten der genannten Eigenschaften linear mit der Mischungszusammensetzung ändern und daß folglich die schwache Phasenkopplung keinen Einfluß auf die Eigenschaften der Mischungen hat. Eine Ausnahme ist die Bruchdehnung, die bei etwa gleichen Anteilen der beiden Komponenten in der Mischung einen Minimalwert aufweist. Insgesamt gilt, daß die Gegenwart von mechanisch schwachen Phasengrenzen einen iiberraschend geringen Einfluß auf die viskoelastischen Eigenschaften der Mischungen hat.
    Notes: The investigations reported in this paper aimed at evaluating the impact of a weak interfacial strength on visco-elastic properties in multiphase polymer blends both in the linear and nonlinear deformation regime. Blends of poly(ethylene) and poly(oxymethylene) were used as model systems. The particular choice of the components of the blend was based on the fact that the two components are incompatible, possess strong interfacial energies and thus narrow and weak interfacial layers, and finally that their individual visco-elastic properties are within the same order of magnitude. This allows to evaluate the contributions of the phase boundaries to the visco-elastic properties in a transparent way.We investigated the visco-elastic properties of blends of various compositions by analyzing the stress-strain behavior, the dynamical torsional behavior as well as by determinating their cyclic stress-strain behavior. The experimental finding is that most of the properties studied vary linearly with the composition and are not influenced by the weakness of the interfacial strength-contrary to the expectation. An exception is the elongation at break which varies nonlinearly with the composition and which shows a minimum value at intermediate compositions. The impact of a weak phase coupling on visco-elastic properties is thus rather limited.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780112
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    Solution properties of polyacrylic esters. I. Light scattering and viscosity measurements in tetrahydrofuran (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 191-200 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Methyl-, Ethyl-, n-Propyl-, n-, i- und t-Butyl-, n-Hexyl-, 2-Ethylhexyl- und Laurylacrylat wurden in Benzol polymerisiert. Verdünnte Lösungen in THF einzelner Fraktionen dieser Polymeren wurden durch Lichtstreuungs- und Viskositätsmessungen untersucht. Polyacrylsäure wurde in Dioxan gemessen.Für die verschiedenen Polyacrylester und Polyacrylsäure wird die Molekulargewichtsabhängigkeit des Staudinger-Index [η] und des Trägheitsradius 〈r2w〉 angegeben.
    Notes: Dilute THF-solutions of different fractions of polymers of methyl, ethyl, n-propyl, n-, i- and t-butyl, n-hexyl, 2-ethylhexyl, and lauryl acrylate, prepared by solution polymerization in benzene, were studied by light scattering and viscosity methods. Poly(acrylic acid) was examined in dioxane. For the different polyacrylic esters the [η]-Mw-relations were established and the dependence of the radius of gyration 〈r2w〉 on the molecular weight was determined.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780114
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    Mitteilungen (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 220-220 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051780117
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    Analysis of the linear methods for determining copolymerization reactivity ratios, VIII. A critical reexamination of radical copolymerization of methylmethacrylate or styrenePart VII cf. lit.5. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 209-219 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Anhand der erweiterten Kelen-Tüdős-Methode wurden Copolymerisationsparameter für Copolymerisationen mit Methylmethacrylat bzw. Styrol geprüft. Es wurden r-Werte einschließlich des 95% Vertrauensintervalls berechnet. Zur Klassifizierung des jeweiligen Systems wurden die Größen δ und Q angewendet. Bei der Copolymerisation mit Methylmethacrylat wurden 71 Systeme ausgewertet. Hiervon wurden 40 (56,3%) System der Klasse I und 20 (28,2%) Systeme der Klasse I(!) zugeordnet. Insgesamt ist also für 60 (84,5%) Monomerpaare die konventionelle Copolymerisationsglei- chung zutreffend. Für 3 (4,2%) Systeme, die der Klasse II zugeordnet werden, ist das Zwei-Parameter-Model1 ungültig. Zur Klasse 111 gehören 8 (I 1, Woo) Monomersysteme, für die die experimentellen Daten inkonsistent und die publizierten r-Werte unzutreffend sind. Im Falle der Copolymerisation mit Styrol wurden 32 Systeme ausgewertet, und es ergab sich folgende Einteilung in Klassen: 19 (59,4%) Systeme in Klasse I, 5 (15,6%) Systeme in Klasse I(!), 2 Systeme in Klasse I1 und 6 (18,8%) Systeme in Klasse 111.
    Notes: The reactivity ratios of selected methylmethacrylate or styrene copolymerisation systems have been reviewed in terms of the extended Kelen-Tüdős method. r-values, together with their 95% confidence limits have been calculated. Quantities δ and Q, suitable for classification of the systems, have been applied. Of the 71 reevaluated methylmethacrylate systems 40 (56.3%) were found to belong to class I and 20 (28.2%) to class I(!), i. e. 60 (84.5%) systems for which the conventional copolymerisation equation was found to be adequate. For 3 (4.2%) systems belonging to class II the two-parameter model does not hold and 8 (11.3%) systems were related to class III, i. e. systems for which the experimental data are inconsistent and the published r-values meaningless. 32 styrene copolymerisation systems were reevaluated with the following classification: 19 (59.4%) systems in class I, 5 (15.6%) systems in class I(!), 2 systems in class II and 6 (18.8%) in class III.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780116
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    Material wear and erosion at the surface of plastics caused by weatheringPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24-29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 43-53 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: When exposed to the weather (moderate climate, Darmstadt), polymethylmethacrylate (PMMA) experiences weight changes, depending on the seasonal humidity, but no material loss. Polycarbonate (PC) on the other hand, and to a lesser degree PC with a “weather skin”, shows marked weight changes when exposed to artificial weathering (Xenotest 1200), which set in with some delay.Surface profile measurements across the borderline between exposed and covered material provide no evidence of material wear in the case of PMMA. With PC, and to a lesser degree with PC protected by a “weather skin”, wear does occur in the region of several μm. The extent of this material wear, which normally sets in with considerable delay after first exposure, is in good agreement with our weight loss measurements. The correlation between outdoor weathering and Xenotest weathering period (shortest wavelength 300 nm) is linear for all degrees of wear (time acceleration factor 13).Contrary to PMMA, scanning electron micrographs of PC show degradation morphologies dependent on the type of weathering which first develop after a certain weathering period.The degradation of PC occurs in two steps. Immediately after first weathering an embrittlement of the surface sets in, caused by molecular weight reduction and the formation of short-chain degradation products. Moreover, as a result of weathering-related dry/wet cycles and temperature fluctuations, the reduced elongation at break is exceeded locally and eventually cracking at the surface occurs, surface roughness and material loss increase and the gloss reduces.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760103
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    Polyethylene recycling during processingPaper presented at the 19th Colloqium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymer” in Prague (Czechoslovakia), July 24-29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 65-78 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Low-density polyethylene was recycled in blown-film production using own factory scrap material. The amounts of the addition of recycled materials to the virgin polyethylene were established, having in mind the fullfilmet of the requirements for quality performances of the obtained films.In the second part of the paper several successive injection-mouldings were made on the same low-density polyethylene. Along with the mechanical characteristics of the obtained reprocessed polyethylene samples, the newly developed method for measuring thermally stimulated depolarization current (TSDC) was evaluated. It was found that the polyethylene samples reprocessed several times differ between themselves also by the fact that the current peaks appeared at some characteristic polymer temperatures, depending on the number of reprocessing cycles, and in lesser degree also, depending on the abcence or the presence of a heat stabilizer.
    Additional Material: 9 Ill.
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    Competition between degradation and orientation in semicrystalline polymersPaper presented at the 19th Colloquim of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague, July 25-27, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 93-104 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This lecture summarizes some recent results and ideas about interrelations between degradation and mechanical behaviour of polyolefins. Aspects of the heterogeneous nature of oxidative degradation in the solid state, the feedback mechanism in degradation, effects of morphology, particularly orientation, on the degradation process, and the influence of degradation on plasticity and on the ultimate mechanical behaviour are discussed.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760108
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    Properties of adhesive polymer compositions in ageing conditionsPaper Presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 125-134 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In our work the degradative changes in properties of polyurethane adhesives based on aliphatic isocyanates were defined and compared with similar changes occurring when using aromatic isocyanates. The readily observed PUR adhesive discolouration in situations of its contact with leather does imply the necessity for the establishing the real proportions of the polyurethane constituents responsible for this ever-present problem. The structure-property relationship of hydroxylterminated polyester-based segmented aliphatic polyurethanes, as a component in adhesive composition were studied using wide angle X-ray diffraction spectroscopy (WAXD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) as well as attenuated total reflectance infrared spectroscopy (ATR-IR) and nuclear magnetic resonance spectroscopy (NMR). The results show that crystalline phase in segmented PUR component influence on morphological and structural properties in degradative conditions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760111
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    The effect of degradation degree of the dispersed phase on the ozone aging of rubbers filled with crushed rubber powderPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Praque (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 173-183 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of crushed rubber powder as a filler of rubber compounds on the ozone aging of vulcanizates has been investigated. It has been shown that the ozone resistance depends significantly both on the concentration and the degradation degree of the dispersed phase. Results of laboratory and atmospheric aging tests are summarized.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760115
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    Alterung und degradation des ledersVortrag anlässlich des 19. Donauländergesprächs über “Atmosphärische Alterung und Stabilisierung von Polymeren” in Prag (Tschechoslovakei), vom 24. - 29. Juli 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 207-213 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Leather has been an important natural polymer undergoing aging when exposed to physical (temperature, radiation) and chemical (oxygen, water, metal ions) deteriogens. Degradation of collagen and changes of mechanical properties of leather are the consequences. The aging has been influenced by tan process, by changes of pH due to chemical degradation and by losses of fat due to extraction or blooming. The understanding of degradation process taking place in leather is necessary for the restoration of aged products from leather having a historical value.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760118
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    Antioxidative efficiency of N-(arylamine) imides in thermal oxidation of polypropylenePaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Ageing and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 231-240 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electron-donating substituents of N-(arylamine) phthalimides and succinimides promote antioxidative efficiency of these compounds in thermooxidation of polypropylene (190°C, oxygen), while electron-withdrawing substituents contribute to a reduced volatilization of the polymer. 2,6-Ditert.butyl-4-methylphenol (ionol) raises the antioxidative efficiency of 4-methoxy and 4-methyl substituted derivatives displaying a distinct synergism.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760120
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  • 144
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    New oligomers with isatin. Condensation reactions of thiophene and 2,2′-bithiophene with isatin (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 1-16 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die seit langem in der Literatur als “Indophenin-Reaktion” bekannte Umsetzung von Isatin mit Thiophen wurde systematisch untersucht und auf die Umsetzung mit Bithiophen erweitert. Die Reaktionsprodukte wurden isoliert und durch FT-IR, UV, 1H-NMR, 13C-NMR sowie GPC charakterisiert.Im Gegensatz zu den Literaturdaten wurden Reaktionsprodukte mit höheren Molgewichten und anderer Molmassenverteilung gefunden. Die Reaktionsbedingungen - Lösungsmittel, Temperatur und Konzentration - sind für den Reaktionsablauf und die entstehenden Produkte von entscheidender Bedeutung.Füur die oligomeren Reaktionsprodukte werden neue Strukturen vorgeschlagen, die in Übereinstimmung mit allen analytischen Daten sind. Anhand eines Formelschemas werden die Reaktionen des Isatins mit Thiophen (Bithiophen) erläutert.
    Notes: A systematic study of the well-known indophenin reaction between isatin and thiophene was extended to embrace bithiophene. The products of the reactions were isolated and characterized by FT-IR, UV, 1H-NMR, 13C-NMR, and GPC. The values of the thus determined molar masses and molar mass distributions differed from the data given in the literature. The reaction conditions - solvent, temperature, and concentration - are of crucial importance for the course of the reaction and the products obtained.New structures suggested for the oligomeric reaction products agree with all the analytical data. The reactions between isatin and thiophene (bithiophene) are explained schematically.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780101
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    Unvernetzte epoxid-amin-additionspolymere, 2524. Mitteilung cf1.. Oligoether-diamine als elastifizierende comonomere für lineare epoxid-amin-additionspolymere (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 63-83 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: N,N'-Dibenzyl-3,6-dioxaoctane-diamine-1,8 and three analogous secondary diamines (EDA) all of which have long chain aliphatic ether groups were prepared and reacted with diglycidylether of bisphenol-A (DGEBA) to give well defined linear epoxide-amine addition polymers. Due to the flexible spacer in the amine component, the glass transition temperatures (Tg) of DGEBA/EDA copolymers decrease to 9-23°C. Likewise Tg's of DGEBA/polyamine networks are significantly lowered by copolymerization with EDA (Tg = 25 -100°C). Such flexible copolymers may be used as strain free optical adhesives or as the soft component in polymer blends and interpenetrating networks.Thermodynamic and kinetic polyreaction parameters were measured by DSC. In excellent correspondence with experiments, data have been calculated using a refined reaction model. This includes both noncatalyzed and catalyzed parallel reactions. The latter ones are activated by NH···HO complexation resulting from growing amounts of HO groups in the addition product.
    Notes: N,N'-Dibenzyl-3,6-dioxaoctandiamin-1,8 und drei analoge sekundäre Diamine mit langen aliphatischen Ethergruppierungen (EDA) sind hergestellt und mit Bisphenol-A-diglycidylether DGEBA polymerisiert worden. Der lineare Charakter der Additions-polymerisation wurde durch die Molmassenverteilung, Mw/Mn = 2, sowie elementaranalytische und spektroskopische Untersuchungen der Additionspolymeren und ihrer Hydroxylderivate (Acetate, Dicarbonsäurehalbester, Urethane) belegt.Durch ein verbessertes Reaktionsmodell wurde die Epoxid-Amin-Reaktion in ausgezeichneter Übereinstimmung mit dem Experiment (Zeit-Umsatz-Kurve und dynamische Wärmekapazitätsmessung) bis zum höchsmöglichen Umsatz beschrieben. Das Reaktionsmodell berücksichtigt die nichtkatalysierte Reaktion und eine durch Addukt-OH-Gruppen katalysierte Parallelreaktion.
    Additional Material: 5 Ill.
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    Influence de l'epaisseur de l'adhésif et du vieillissement sur les propriétés mécaniques dynamiques d'un assemblage: Adhésif structural/acier inoxydable (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 47-62 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Les propriétés mécaniques dynamiques d'un assemblage collé type «sandwich» - acier inoxydable/adhésif en film - sont étudiées en fonction de I'épaisseur du film d'adhésif et du temps de vieillissement en atmosphere chaude et humide.A partir d'analyses thermomécaniques dynamiques, il est montré que les températures de transition vitreuse (Tg) de l'adhésif seul et de ce même adhésif dans un assemblage métal/adhésif sont différentes.Avant collage, la surface du métal subit divers traitements chimiques ou électrochimiques qui provoquent un déplacement de la température de transition vitreuse du polymère. L'évolution de cette même température avec l'épaisseur de l'adhésif montre que le taux de réticulation est plus élevé dans les couches superficielles de l'adhésif en contact avec le métal qu'au sein du polymkre.Lors du vieillissement, l'absorption d'eau entraîne des phénomknès de plastification de l'adhésif et une baisse importante de la température de transition vitreuse est observée. L'anodisation sulfochromique du métal confère une meilleure stabilitté à l'lassemblage.
    Notes: Dynamic mechanical properties of bounded joints - stainless steel/epoxy adhesive - are investigated as a function of the thickness of the adhesive and aging conditions. The viscoelastic properties of the bounded joints have been investigated by Dynamic Thermo Mechanical Analysis (DTMA).The glass transition temperature (Tg) showed a dependence on both the chemical/electrochemical pretreatments of the substrate and the thickness of the adhesive in the bounded joint. The crosslinking density in the adhesive thus seemed more important in the interfacial region than in adhesion bulk.The water uptake induces a plasticization of the adhesive and a decrease in Tg. The most stable bounded joints were obtained by carrying out sulfochromic acid anodization as a pretreatment step. The most important stability of the bounded joints was obtained with the sulfochromic anodization of the substrate.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780104
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    Sphärische ionotrope gele carboxygruppenhaltiger cellulosederivate als trägermaterialien für biologische wirkstoffe, IVTeil III cf.4.. Synthese von carboxycellulose und ionotrope gelbildung mit calciumionen (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 95-107 
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    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Sodium carboxy cellulose with a degree of substitution up to 0.8 can be prepared by oxidation of cellulose with NaNO2/H3PO4 and subsequent treatment with NaBH4. The extent of oxidation increases with raising molecular weight ranging from 170 to 1500 of the starting material. IR and NMR studies show that only the C-6 atom of the anhydroglucose unit is oxidized. The sodium carboxy celluloses show a high tendency to form ionotropic gels even in spherical shape with calcium ions. The mechanically stable gels are characterized by investigation of the swelling behaviour and SEM.
    Notes: Natriumcarboxycellulose mit einem Substitutionsgrad bis 0,8 kann durch Oxidation von Cellulose mit einem Polymerisationsgrad im Bereich von 170 bis 1500 mit NaNO2/H3PO4 und anschließender Behandlung mit NaBH4 hergestellt werden. Das Ausmaß der Oxidation steigt mit wachsender Molmasse des Ausgangsmaterials. IR-und NMR-Untersuchungen zeigen, daß nur das C-6-Atom der Anhydroglucoseeinheit oxidiert ist. Die Natriumcarboxycellulosen weisen eine hohe Tendenz zur ionotropen Gelbildung auch in sphärischer Form mit Calciumionen auf. Die mechanisch stabilen Gele werden durch Quellungsuntersuchungen und REM charakterisiert.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051780107
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    Graft polymerization of 4-vinylpyridine onto cellulosic fibres by the ceric ion method, IIPart I cf.14.. The ph effect (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 119-129 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß des pH-Wertes auf die mit Cer(IV)-ammoniumnitrat initiierte Pfropfpolymerisation von 4-Vinylpyridin (4-VP) auf Cellulose und partiell carboxymethylierte Cellulose (PCMC) in verdünnter Salpetersäure wurde untersucht. Die Abhängigkeiten von Pfropfausbeute (GE), Pfropfungsgrad (G), Pfropfhäufigkeit (GF) und Cerionenverbrauch (Ce(IV)c) von der Salpetersäurekonzentration wurden ermittelt. Bei pH = 1 sind Gesamtumsatz und Pfropfumsatz am größten; wird die Nitratkonzentration konstant gehalten (0,86 mol/1), läßt sich der Pfropfumsatz noch erhöhen. Zum Vergleich wurden einige Experimente mit Cersulfat als Initiator durchgeführt.
    Notes: The effect of pH on the graft polymerization of 4-vinylpyridine (4-VP) onto cellulose and on partially carboxymethylated cotton (PCMC) initiated by ceric ammonium nitrate (CAN) in dilute nitric acid was examined. The grafting parameters grafting efficiency (GE), graft yield (G), graft frequency (GF), and ceric ion consumption (Ce(IV)c) were studied as a function of nitric acid concentration. Also the effect of pH on the graft polymerization was examined and the total nitrate ion concentration was maintained high and constant at 0.86 mol/1 by addition of sodium nitrate. Maximum grafting and total conversion occurred at pH 1, but these values were smaller than the ones obtained in the previous case. For comparison some experiments were carried out using ceric sulfate as initiator.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051780109
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    Oberflächenstrukturierung polymerer fasern durch UV-laserbestrahlung. 6. Zur vermeidung von vergilbungen bei der laserbehandlung von polymerenTeil 5 cf. Lit1. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 143-151 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: It is shown in this paper, that during laser treatment of polymeric materials the occurrence of discolouring layers of laser crack deposits onto the substrate can be avoided without preventing the formation of a laser-induced microstructuring of the surface. Using water, alcohols, ethers or aqueous surfactant solutions as impregnating media during laser treatment a high degree of whiteness of fabrics can be maintained.
    Notes: Es wird gezeigt, daß die Ausbildung einer Schicht von verfärbenden Lasercrackprodukten - wie sie bei der Laserbehandlung von trockenen Polymeren gebildet wird - durch Imprägnierung mit verschiedenen Lösungsmitteln während der Laserbearbeitung verhindert werden kann. Die Ausbildung einer laserinduzierten Mikrostrukturierung der Polymeroberfläche wird davon nicht beeinflußt. Es läßt sich damit auch bei stärkeren Energiedichten der Laserbehandlung ein hoher Weißgrad aufrechterhalten.Zur Verhinderung der Vergilbung sind Wasser, Alkohole, Ether und wäßrige Tensidlösungen als Imprägniermedien während der Laserbestrahlung vorteilhaft einsetzbar.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051780111
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  • 150
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    Durability of radiation-sterilized polymers, XIIIPart XI cf. lit.6.. The effects of nucleating agent on the oxidative degradation of poly(propylene-co-ethylene) (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 131-140 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Bestrahlungsstabilität von statistischen und Blockcopolymeren aus Propen und Ethen (CP, Copolymeres mit 6% Etheneinheiten) mit und ohne Keimbildner (NA) wurde in bezug auf die Bestrahlungssterilisation von medizinischen Gütern verglichen. In beiden Fällen war die Bestrahlungsstabilität von CP in Gegenwart von NA geringer als ohne.Die Zugabe von NA zu CP verbesserte zwar nicht die Transparenz, die Kristallisation erfolgte aber bei höherer Temperatur. Sie hat deshalb den Vorteil kürzerer Formzeiten bei der Produktion von medizinischen Gütern.Die Bestrahlungsinstabilität von CP mit NA rührt von einer unterschiedlichen Kristallstruktur her, weil sich die Form der Spharolite von der des CP ohne NA unterscheidet. Weiterhin wurde durch Chemiluminiszenz-Analyse ein stärkerer oxidativer Abbau in der Probe mit NA beobachtet.
    Notes: The radiation stability of the random and block poly(propylene-co-ethylene) (CP, copolymer with 6% ethylene units) with and without nucleating agent (NA) was compared in relation to radiation sterilization of medical supplies. In both cases, it was found that the radiation stability of CP in the presence of NA was lower than that of CP without NA.Addition of NA to CP did not improve the transparency but the crystallization occurred at higher temperature. Thus, adding NA to CP has the advantage of shorter moulding time in the production of medical supplies.The radiation instability of the CP with NA was due to a different crystal structure, because the spherulite shape differs from that of CP without NA. Furthermore, by the chemiluminescence analysis, a higher oxidative degradation was observed in the sample with NA.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740111
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  • 151
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    Highly active peroxides in the radical polymerization of ethylene under high pressure  -  conversion and initiator usage (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 165-175 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch die Anwendung von hochaktiven Peroxiden kann die Polymerisationstemperatur bei der Synthese von Polyethylen niedriger Dichte abgesenkt werden. Um die Eignung einer Reihe von Peroxiden als Tieftemperatur-Initiatoren zu prüfen, wruden Polymerisationsversuche bei 1900 bar, 70 bis 140°C und einer mittleren Verweilzeit von 30 s in einer kontinuierlich betriebenen, mit einem Rührautoklaven ausgestatteten Laboranlage durchgeführt. Außer einer Reihe von Perneodecanoaten wurden zwei Peroxydicarbonate, ein Sulfonylperoxid und ein bifunktionelles Peroxid eingesetzt.Bei Polymerisationstemperaturen unter 100°C war der Initiatorverbrauch hoch. Es zeigten sich große Unterschiede zwischen den einzelnen Peroxiden. Mit steigender Temperatur nahm der Initiatorverbrauch rasch ab und war über 120°C bei den einzelnen Peroxiden nahezu gleich. Als gut geeignet für die angestrebten niedrigen Polymerisationstemperaturen erwies sich die bifunktionelle Verbindung 1,4-Di-(2-neodecanoyl-peroxy-isopropy1)-benzol, die bei 100°C einen Verbrauch von 13 g Initiatorkg PE zeigte. Bei einem Einsatz von 40 g Intiatorkg PE konnte eine Reaktortemperatur von 82°C eingestellt werden. Weniger gut schnitten die Peroxydicarbonate und das tert.-Butylperneodecanoat ab.
    Notes: By using highly active peroxides, it is possible to reduce the polymerization temperature necessary for the synthesis of low density polyethylene. In order to examine a number of peroxides for their suitability as low temperature initiators, polymerization tests were carried out at 1900 bar, 70-140°C, with an average residence time of 30 s in a continuously operating laboratory facility equipped with a stirred autoclave. Apart from a number of perneodecanoates, two peroxy dicarbonates, a sulphonyl peroxide, and a difunctional peroxide were used.The initiator consumption was high at polymerization temperatures below 100°C. The results obtained with the different peroxides varied considerably. As the temperature increased, the initiator consumption decreased rapidly to reach almost the same level for all the individual peroxides at above 120°C. The difunctional compound that proved highly suitable for the low polymerization temperatures desired was 1,4-di-(2-neodecanoyl peroxy isopropyl)benzene, the consumption at 100°C of which amounted to 13 g initiator/kg PE. Using a quantity of 40 g initiator/kg PE, a reactor temperature of 82°C could be employed. The peroxy dicarbonates and tertiary butyl perneodecanoate gave less satisfactory results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740114
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  • 152
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    Impact behaviour and fractographic analysis of rubber-modified polybutyleneterephthalate obtained by reactive blending concurrently with polymerization process (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 141-150 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Modifizierung von Polybutylenterephthalat mit Gummi wurde durch Zugabe geeignet funktionalisierter Copolymerer aus Ethylen und Propylen (EPR) und gleichzeitiger Hochtemperaturpolykondensation von 1,4-Butandiol mit Dimethylterephthalat erreicht. Die Schlagzähigkeit der Blends, die reines oder mit Ester- oder Hydroxylgruppen modifiziertes EPR enthielten, wurde mit Hilfe von Schlagbiegeversuchen nach Charpy bei verschiedenen Temperaturen bestimmt. Die morphologischen Merkmale der Bruchflächen wurden auch untersucht. Es wurde ein Versuch unternommen, die Morphologie dieser Flächen mit den Bruchanalysenergebnissen zu korrelieren.
    Notes: Rubber modification of polybutyleneterephthalate was accomplished by the addition of suitable functionalized ethylene-propylene copolymers (EPR) concurrently with the high temperature polycondensation of 1,4-butanediol and dimethylterephthalate.The impact properties of blends obtained with plain EPR, with ester or hydroxyl groups modified EPR were analyzed by Charpy tests performed at different temperatures with a Ceast fracture pendulum. The morphological features of fracture surfaces have also been investigated. An attempt has been made to correlate the morphology of the surfaces with the fracture analysis results.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740112
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    Detailed reaction engineering as a basis of modern slurry technology for PE-HD-productionHerrn Prof. Dr. W. Hilger zum 60. Geburtstag gewidmet (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 189-203 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Sicherung von Produktqualität und Qualitätskonstanz bei der Polymerherstellung ist eine genaue Kenntnis des Polymerisationsprozesses notwendig. Für die Suspensionspolymerisation von Ethylen mit hochaktiven Ziegler-Katalysator/Cokatalysator-Systemen wurde ein Prozeß-Modell entwickelt. Dieses Modell gibt an, welcher Satz von Prozeßparametern innerhalb bestimmter Grenzen konstant gehalten werden muß, um die Produktdaten in den vorgegebenen Abnahmegrenzen zu halten. Die Konsequenzen für eine Produktionsanlage werden diskutiert.
    Notes: Saving product quality and quality consistency in polymer production needs a detailed knowledge of the polymerization process. A process model for the slurry polymerization of ethylene with high mileage Ziegler-catalyst/cocatalyst systems has been developed. This model teaches which set of process parameters must be kept constant together with their acceptable deviations to keep product data within the required frame. The consequences for a technical production plant are also discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740116
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  • 154
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    Note on notch and unnotch toughness of PP-CaCO3 composites: Influence of filler particle size and dispersion degree (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 205-212 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the filler particle size and dispersion degree on the Charpy notch toughness (U notch) and tensile impact strength (without notch) in the polypropylene-microground calcium carbonate system was investigated. It was found that while the tensile impact strength was controlled by the content of particles and/or agglomerates coarser than about 10 µm (the strength decreased sharply with their increasing content), the Charpy notch toughness was not decreased even by large agglomerates (up to 100 µm), but dropped heavily with the increasing upper particle size of the filler measured before kneading into polymer. A model system polyethylene-glass beads revealed even an increase of the notch toughness with the increasing upper diameter of the glass beads (the upper diameter being in the 50-400 µm range).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740117
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  • 155
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    A search for optimal acrylic carriers for immobilization of penicillin acylase (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 179 (1990), S. 173-183 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Tragersubstanzen auf Acrylbasis wurden durch Aminolyse von Nitril- oder Estergruppen in Co. oder Terpolymeren aus Acrylnitril oder Acrylsäureestern und Divinylbenzol oder Ethylendimethacrylat in Gegenwart inerter Solventien hergestellt. Der Einfluß der übermolekularen Struktur dieser Trägersubstanzen, die durch Zugabe inerter Solventien während der Suspensionspolymerisation erzeugt wurde, auf deren Tragereigenschaften wurde untersucht. Geeignete Trägersubstanzen zur Immobilisierung von Penicillinacylase wurden entweder aus porösen oder ‘Sol’-Typ-Copolymeren erhalten; sie zeigten nach der Aminolyse die Struktur eines expandierten Gels.
    Notes: Acrylic carriers were obtained by aminolysis of nitrile or ester groups in copolymers or terpolymers synthesized from acrylonitrile, acrylic esters and divinylbenzene or ethylene dimethacrylate in the presence of a mixture of inert diluents. The influence of the supermolecular structure of these carriers, generated during the suspension polymerization by adding a mixture of inert diluents, on the carrier properties was observed. Acrylic carriers for immobilization of penicillin acylase should be obtained from either porous or ‘sol’-type copolymers which aquire after aminolysis the structure of expanded gel.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051790113
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  • 156
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    Oberflächenstrukturierung polymerer fasern durch UV-laserbestrahlungTeil 7 cf. Lit.8.. 8. Schwellenverhalten der laserinduzierten oberfläauchenstrukturierung von poly(ethylenterephthalat) (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 180 (1990), S. 109-120 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Irradiation of biaxially stretched poly(ethyleneterephthalate) (PETP)-films by UV-excimer wavelengths gives rise to well-known morphological surface modifications. Using a slit or a circular aperture a characteristic pattern due to Fresnel diffraction is imprinted onto this effect. The diffraction of the laser light leads to local variations of intensity on the PETP-surface. Using this diffraction effect a hitherto unknown fluence threshold for the appearance of laser induced surface morphology can be determined. This threshold is markedly lower than the threshold for ablation obtained by conventional extrapolation of laser etching data. Using elastomeric fibers furthermore it is shown that the energy limit for the onset surface structures is dependent on the amount of externally applied tension fields.
    Notes: Bei UV-Excimer-Laserbestrahlung von biaxial verstreckten Poly(ethylenterephthalat) (PETP)-Folien durch einen Spalt oder durch kreisförmige Blenden entstehen unter geeigneten Bestrahlungsbedingungen die bekannten charakteristischen Strukturierungen, welche durch Fresnelsche Beugungserscheinungen modifiziert sind. Die Beugung des Laserlichtes führt zu lokalen Intensitätsunterschieden auf der PETP-Oberfläche. Unter Ausnutzung dieses Beugungseffektes wurde eine higher nicht gemessene Grenzenergie für die laserinduzierte Ausbildung der Oberflächenmorphologie von PETP bestimmt. Wesentlich ist hierbei, daß diese Strukturschwellenenergie deutlich unterhalb der extrapolierten Ablationsschwellenenergie von PETP liegt. Darüber hinaus wird an Elastomerfasern aufgezeigt, daß die Grenzenergie zur Strukturbildung auch von der Größe eines extern aufgebrachten Spannungsfeldes abhängt.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051800108
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    Thermal degradation of poly(vinyl chloride) blendsDedicated to Prof. Dr. T. Kelen on the occasion of his 60th birthday (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 23-40 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyvinylchlorid wurde mit verschiedenen Polymethacrylaten und Polycarbonaten durch Ausfällen gemeinsamer Lösungen gemischt. Die thermische Stabilität der Proben wurde bei 180°C in einer Stickstoffatmosphäre mittels konduktometrischer Messung der abgespaltenen Salzsäure bestimmt. Um den Einfluß der Polymethacrylate auf die Länge der entstandenen Polyensequenzen zu ermitteln, wurden die abgebauten Proben UV-spektroskopisch untersucht.Wie die Experimente zeigen, ist die Estergruppe von dominierendem Einfluß auf die thermische Stabilität von Polyvinylchlorid in diesen Blends. Poly-n-butylmethacrylat stabilisiert dabei Polyvinylchlorid am besten. Die eingesetzten Polycarbonate haben Glastemperaturen, die über der Abbautemperatur liegen; sie vermindern die thermische Stabilität von Polyvinylchlorid.Stabilisierungsversuche mit Dibutylzinn-bis(isooctylthioglykolat) zeigen einen costabilisierenden Effekt der Polymethacrylate und Polycarbonate.
    Notes: Poly(vinyl chloride) was mixed with various poly(methacrylate)s and polycarbonates by combined precipitation from common solutions. The thermal stability of the samples was measured at 180°C under nitrogen, the HCl evolved was detected by conductometry.UV-Vis-spectra of degraded samples were measured to investigate the influence of the poly(methacrylate)s on the lengths of polyenes formed during the degradation of poly(vinyl chloride).The experiments show that the nature of the ester group is the dominating factor for the thermal stability of poly(vinyl chloride) in these blends. Poly(n-butylmethacrylate) exhibits the best stabilization for poly(vinyl chloride) in this series. Polycarbonates with a higher glass transition temperature than the temperature of degradation destabilize poly(vinyl chloride).Stabilization experiments with dibutyltin-bis(isooctylthioglycolate) show a costabilizing effect of the poly(methacrylate)s and polycarbonates.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810102
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    Study of multicomponent complexes between polycarboxylic acid, transition metal ions and non-ionic polymers (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 93-101 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Mehrkomponentige Komplexe eines typischen Polyelektrolyten wie Polyacrylsäure (PAA) mit nichtionogenen Polymeren (PVP and PEO) und Übergangsmetallionen (Cu(ll) und NI(II)) wurden hergestellt und mittels Viskosimetrie, Potentiometrie, Leitfähigkeitsmessungen und IR-Spektroskopie untersucht. Ein Schema, welches die Bildung dieser Komplexe erklärt, wird vorgeschlagen.
    Notes: Multicompoent complexes of a typical polyelectrolyte like poly(acrylic acid) (PAA) have been prepared by incorporating transition metal ions (e. g. Cu(ll) and Ni(ll)) and non-ionic polymers (e. g. PVP, PEO) in the polyelectrolyte chain in a definite sequence. The formation of these complexes has been studied by several techniques, such as viscometry, potentiometry, conductometry, and IR spectroscopy. A scheme is suggested to explain the mode of formation of such complexes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810108
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    Studies on the properties of glass fiber reinforced epoxy composites of DGEBA / epoxidized polyhydric alcohols with or without fortifier (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 75-84 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Härtungsreaktion von Harzen aus Bisphenol A-diglycidylether (DGEBA) und zwei-oder dreiwertigen Alkoholen mit Phthalsäureanhydrid als Härter und Triethylamin als Katalysator mit und ohne Beschleuniger wurde mit Hilfe der Differential-Scanning-Calorimetrie (DSC) ebenso untersucht wie die thermische Stabilität der gehärteten Produkte durch thermogravimetrische Analyse (TGA). Unter Berücksichtigung dieser Untersuchungen wurden glasfaserverstärkte Epoxidverbundwerkstoffe hergestellt und auf ihre mechanischen, elektrischen und chemischen Eigenschaften untersucht.Es wurden Aktivierungsenergien der Härtungsreaktion zwischen 75,1 und 88,3 kJ mol-1 gemessen. Die gehärteten Produkte zeigten eine gute thermische Stabilität; die Verbundwerkstoffe besitzen eine hohe mechanische Festigkeit, gute elektrische Isolationseigenschaften und eine hohe Chemikalienresistenz. Durch Zugabe von Beschleunigern bei der Härtung konnte die Biegefestigkeit zusätzlich um 36 bis 53% verbessert werden.
    Notes: Differential scanning calorimetry (DSC) technique was used to study the curing reaction of diglycidyl ether of bisphenol A (DGEBA) resin and different di- and trifunctional polyhydric alcohols with phthalic anhydride as curing agent and triethylamine as catalyst with or without fortifier. The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fiber reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied as well. Activation energies of curing reactions range within 75.1 to 88.3 kJ mol-1. The cured products have good thermal stability; the composites have good mechanical strength, electrical insulation properties and chemical resistance. 36 to 53% improvement in flexural strength has been observed when fortifier was added to the DGEBA-diluent systems.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810106
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  • 160
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    Propriétés électriques et adhésion aux interfaces polypropylène greffé-aluminium (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 119-128 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Strom-Spannungs-Charakteristika von Verbundwerkstoffen aus gepfropftem Polypropylen und Aluminium wurden mit Gleichstrom untersucht. Es wird ein Modell vorgeschlagen, das die elektrischen Eigenschaften der Polymer-Metall-Grenzfläche beschreibt. Es beinhaltet einen konstanten Schottky-Effekt und eine Raumladung, die von den Hafteigenschaften abhängt und den Carboxygruppen des gepfropften Polypropylens an der Aluminiumoberfläche zugeordnet werden kann.
    Notes: L'étude des caractéristiques intensité-potentiel en courant continu pour des assemblages films de polypropylènes greffés-aluminium permet de proposer un modèle électrique de I'interface polymère-métal, associant une barrière de Schottky constante à une charge d'espace modulée selon le niveau d'adhésion. Cette charge d'espace est liée à l'afflux des groupements carboxyliques greffés sur le polypropylène vers la surface de l'aluminium. La présence d'une interphase dans l'adhésion entre polyoléfine et métal est ainsi prise en compte dans les mesures électriques.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810110
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    Termination reaction in the chain oxidation of caprolactam (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 143-152 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Im Temperaturbereich 80-98°C wurde die Oxidation von Caprolactam verfolgt, die durch 0,008 - 0,82 mol/kg 1,1′-Azo-bis(cyclohexancarbonitril) initiiert wurde. In den Produkten der bis zu einem Umsatz von max. 3% durchgeführten Oxidation wurden Caprolactamhydroperoxid, Adipinsäureimid und Wasserstoffperoxid nachgewiesen. Die von der Konzentration des Initiators abhängigen kinetischen Kettenlängen der Oxidation betrugen 3 - 30, wobei die Geschwindigkeit der Wasserstoffhydroperoxidbildung halb so groß wie die Initiierungsreaktionsgeschwindigkeit war. Bei der thermisch initiierten Oxidation mit einer kinetischen Kettenlänge um 300 entstand keine nachweisbare Wasserstoffperoxidkonzentration. Es kann also angenommen werden, daß bei der bimolekularen Abbruchreaktion der Caprolactamperoxyradikale Wasserstoffperoxid und Adipinsäureimid entstehen. Adipinsäureimid wird auch durch den monomolekularen Zerfall der Peroxyradikale gebildet, die neben der Oxidation von Caprolactamradikalen auch durch den Zerfall von Caprolactamhydroperoxid entstehen können.
    Notes: The oxidation of caprolactam initiated with 0.008-0.82 mol/kg 1,1′-azo-di(cyclohexane carbonitrile) was studied in the temperature range 80-98°C. At the conversion lower than 3%, caprolactam hydroperoxide, adipimide, and hydrogen peroxide were determined in the oxidation products. Depending on the initiator concentration, the kinetic chain length of oxidation ranged between 3 and 30. The formation rate of hydrogen peroxide was equal to one half of the rate of initiation reaction, i. e. to one half of the rate of bimolecular termination in the steady state. It may be assumed that hydrogen peroxide is formed by the bimolecular termination reaction. This is in agreement with the fact that hydrogen peroxide was not found in the thermally initiated oxidation of caprolactam which proceeded with the kinetic chain length more than 300. Another product of the bimolecular termination reaction of caprolactam peroxy radicals is adipimide, which is also formed by their monomolecular decomposition.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810112
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  • 162
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    Introduction of hydroxyethyl and glycidyl ester groups into methyl methacrylate copolymers by polymer analogous reactions (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 171-182 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Reaktion von 2-Chlorethanol und Epichlorhydrin (ECH) mit Alkalisalzen von partiell hydrolysierten Methylmethacrylat-(MMA)-Polymeren sowie MMA-Copolymeren, die freie Carboxygruppen enthielten, wurde untersucht. Quaternäre Ammoniumhalogenide R4NX sind effektive Katalysatoren dieser Reaktionen. Bis zu 80% der Carboxylatgruppen wurden in Hydroxyethylestergruppen unter Bildung vollständig löslicher Copolymerer umgewandelt. Bei der Reaktion von ECH mit Alkalisalzen der Copolymeren wurden vernetzte Produkte erhalten. Bei Durchführung der Reaktion in Gegenwart von R4NX konnte der Gelanteil von 87% auf 5% vermindert werden.MMA-Copolymere mit freien Carboxygruppen reagieren mit überschüssigem ECH in Gegenwart von R4NX über die Chlorhydrinester-Stufe mit nachfolgender Dehydrochlorierung (Transepoxidierung) unter Bildung vollständig löslicher Glycidylester-Copolyrnerer mit niedrigem Chlorgehalt (≤ 0.4%) und Ausbeuten an Epoxidgruppen ≤ 95%.
    Notes: The reactions of 2-chloroethanol and epichlorohydrin (ECH), respectively, with alkali salts of partially hydrolyzed methyl methacrylate (MMA) polymers as well as with MMA copolymers containing free carboxy groups were studied. Quaternary ammonium halogenides R4NX are effective catalysts of these reactions. Up to 80% of alkali carboxylate groups were converted into hydroxyethyl ester groups to yield completely soluble copolymers. By reaction of ECH with alkali salts of the copolymers, crosslinked products were obtained. The gel fraction may be reduced from 87% to 5% if the reaction is carried out in the presence of R4NX. MMA-copolymers containing free carboxy groups react with an excess of ECH in the presence of R4NX via the chlorohydrin ester and dehydrochlorination (transepoxidation) to produce completely soluble glycidyl ester copolymers of low chlorine content (≤0.4%). Yields of epoxy groups up to 95% have been attained.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810114
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  • 163
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    Water-soluble polyamides as potential drug carriers, IIPart I cf. ref.1. Amine-functionalized poly (α,β-d,l-aspartamide) derivativesPresented in part at the Jubilee Convention, South African Chemical Institute, Durban, Natal, 6 to 10 July 1987. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 153-170 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Einige Abkdmmlinge der Poly(α, β-,L-asparaginslure) (2) rnit Aminogruppen in der Seitenkette wurden zur Verwendung als makromolekulare Wirkstofftrager hergestellt. Die Strukturen der Zielpolymeren wurden im Hinblick auf vollstandige Wasserlöslichkeit als Voraussetzung fur eine schonende intraven6se Anwendung gewtihlt; die Strategie dieser Seitenkettenmodifizierung bringt die gestellte Forderung zum Ausdruck, alle Reaktionsschritte in teilweise oder vollstandig waRriger Phase durchzufuhren. Die Poly(asparaginsaure) (2)  -  ein bekanntes Polyamid, hergestellt aus Poly(bernsteinsaureimid) (1) und sowohl mit α- als such P-Peptideinheiten in der Polymerkette  -  wurde rnit Ethylendiamin, Diethylentriamin, N-(2-Hydroxyethyl)-ethylendiamin und Hydrazin in Gegenwart wasserldslicher Carbodiimide umgesetzt. Dies fiihrte zu den modifizierten Poly(asparaginen) 3 bis 6 rnit primaren Aminogruppen in der Seitenkette. Wirksamer und unter Umgehung der Poly(asparaginsaure) (2) als Zwischenstufe erwies sich die direkte nucleophile Offnung des Imidringes in 1 mit den gleichen Aminen. Die wasserloslichen Poly(asparagine) 3 bis 6 wurden analytisch und spektroskopisch charakterisiert; sie zeigten inharente Viskositaten (qinh) zwischen 5 und 20 ml g-1 und besaRen die strukturellen Voraussetzungen zur Verankerung von Wirkstoffen an der Seitenkette bedingt durch die Modifizierung rnit Aminogruppen. Die Substituierbarkeit dieser funktionellen Gruppen als ein Ma6 fur die Fahigkeit zur Wirkstoffimmobilisierung wurde anhand der Umsetzung von 5 und 6 zu den N-acryloylierten Derivaten 7 und 8  -  und weiterer Umsetzung von 7 zu 9  -  und anhand der Kondensation von 5-Formylsalicylsaure mit der  -  zweizahnigen  -  Etylendiaminseitengruppe in 4 zur entsprechenden Verbindung 10 rnit einer bioaktiven Salicylgruppe als Seitenkettenkomponente gezeigt.
    Notes: Several derivatives of poly(α,β-D,L-aspartic acid) (2) comprising amine functions as side chain components are synthesized for use as macromolecular drug carriers. The structures of the target polymers are designed so as to provide complete solubility in water, a prerequisite for smooth intravenous administration, and the strategy of derivatization reflects the requirement for the performance of all reaction steps in a partially or entirely aqueous phase. The poly(aspartic acid) (2)  -  a known synthetic polyamide obtained from poly(succinimide) (1) and composed of both α- and β- peptide units in the chain  -  is coupled with ethylenediamine, diethylenetriamine, N-(2-hydroxyethyl)ethylenediamine, and hydrazine, respectively, in the presence of water-soluble carbodiimides. This gives the poly(aspartamides) 3 to 6 possessing primary amino side groups. More efficaciously, circumventing the intermediacy of the polyacid 2, polymers 3 to 6 are obtained through nucleophilic opening of the imide rings in 1 by the same amine reactants. The analytically and spectroscopically characterized, water-soluble target polymers 3 to 6 have inherent viscosities ranging from 5 to 20 ml g-1 and possess the structural prerequisites for side-chain drug anchoring involving the spacer-bound amino groups. The susceptibility of these functional groups to substitution as a measure of their drug binding capabilities is demonstrated by conversion of 5 and 6 to the N-acryloylated derivatives 7 and 8  -  with 7 further derivatized to give 9  -  and by condensation of 5-formylsalicylic acid with the bidentate  -  ethylenediamine side group in 4 to give the conjugate 10 containing the bioactive salicylyl group as a side-chain component.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810113
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  • 164
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    Synthesis and properties of a new o-cresol novolak epoxy resin containing oxyethylene units (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 199-205 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein neues o-Kresol-Novolak-Epoxidharz mit Oxyethylen-Einheiten wurde hergestellt und charakterisiert. Die thermischen und mechanischen Eigenschaften des mit Methylhexahydrophthalsäureanhydrid gehärteten Harzes wurden untersucht und mit einem konventionellen o-Kresol-Novolak-Epoxidharz (EOCN 1020) verglichen; das neue Epoxidharz zeigte dabei nach dem Härten eine höhere Flexibilität als das herkömmliche.
    Notes: A new o-cresol novolak epoxy resin containing oxyethylene units was synthesized and characterized. The mechanical, thermal, and dynamic mechanical properties of resins cured with methyl hexahydrophthalic anhydride were examined and compared to those of a conventional o-cresol novolak epoxy resin (EOCN 1020). This new epoxy resin gives a cured resin with higher flexibility, compared to the conventional one.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810117
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  • 165
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    Graft copolymerization of methyl methacrylate onto modified plantain pulp in the presence of ceric ions (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 182 (1990), S. 63-72 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Papierzellstoff wurde aus Bananenstaudenholz hergestellt und mit Allylchlorid in Diisopropylether bei 60 °C modifiziert; dabei wurde ein durchschnittlicher Substitutionsgrad von 0,215 Allylchlorid-Bausteinen pro Anhydroglucose-Einheit (AGU) erreicht. Die Pfropfcopolymerisation von Methylmethacrylat auf modifizierten und nicht modifizierten Papierzellstoff wurde bei 29 °C mit Ammoniumcer(IV)-sulfat ((NH4)4 Ce(SO4)4) als Initiator durchgeführt. Aus der Abhängigkeit der Pfropfausbeute von der Cer(IV)-Konzentration wurde gefunden, daß der Abbruch der Pfropfpolymerisation im wesentlichen durch Reaktion mit Cer(IV)-Ionen erfolgt und daß die Pfropfausbeute durch die Modifizierung ausgesprochen erhöht wird. Der Einfluß von Isopropanol in verschiedener Konzentration auf die Pfropfausbeute von modifiziertem Material wurde ebenfalls untersucht.
    Notes: Plantain pulp was modified by treatment with allyl chloride in diisopropyl ether at 60 °C which results in an average degree of substitution of 0.215 allyl chloride moieties per anhydroglucose unit (AGU). Graft copolymerization of methyl methacrylate onto modified and unmodified pulp was carried out at 29 °C using various concentrations of ceric ion initiator. It was found from the dependence of the extent of graft polymer formation on ceric ion concentration that termination of graft polymerization occurred mainly by the interaction of growing graft polymer chains with ceric ion and that the extent of graft polymer formation was markedly enhanced by the modification of the plantain pulp. The effect of isopropanol on the extent of graft polymer formation on the modified material was also examined.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051820105
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  • 166
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    Oberflächenstrukturierung polymerer fasern durch uv- laserbestrahlung. 10. UV-laserinduzierte pfropfcopolymerisation von acrylsäure auf polypropylenTeil 9 cf. Lit.9 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 182 (1990), S. 177-186 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Hydrophobic surfaces of poly(propylene) (PP)-films are modified to hydrophilic ones by UV-laser-induced grafting of acrylic acid. The dependence of graft yield on experimental conditions is investigated. In contrast to grafting with low intensity UV-radiation (high pressure mercury lamp) the UV-laser-induced grafting is very effective because of short radiation times needed and because no photoinitiators and photosensibilisators are required.
    Notes: Oberflächen von Polypropylen (PP)-Folien werden durch UV-laserinduzierte Pfropfcopolymerisationsreaktionen von Acrylsäure anionisch modifiziert. Die Bestrahlung der hydrophoben PP-Folien erzeugt hierbei eine Hydrophilie. Die Ausbeute von aufgepfropften Polyacrylsäure-Seitenketten wird in Abhängigkeit der experimentellen Parameter bestimmt. Im Gegensatz zu Pfropfcopolymerisationsreaktionen mit herkömmlichen UV-Strahlungsquellen (Hg-Hochdruckdampflampen) kann schon mit sehr kurzen UV-Laserbestrahlungszeiten eine chemische Modifizierung der PP-Oberfläche erzielt werden. Darüber hinaus ist die Verwendung von Photoinitiatoren und Photosensibilisatoren nicht notwendig.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051820112
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  • 167
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    Mitteilungen (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 182 (1990), S. 205-205 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051820115
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  • 168
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    Polyurethane-crosslinked epoxy resins. I. Mechanical behavior (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 182 (1990), S. 193-203 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyurethanpräpolymere (PU) auf der Basis von Poly(butylenadipaten) (PBA) bzw. Poly(oxytetramethylen) polyolen (PTMO) wurden als Vernetzer für Bisphenol-A-diglycidylether (DGEBA) eingesetzt. Anschließend wurde DGEBA mit einem tertiären Amin zu einem PU-vernetzten DGEBA ausgehärtet. Die Reißfestigkeit sowohl von PU(PBA)-als auch von PU(PTMO)-vernetzten Systemen stieg mit steigendem PU-Gehalt bis zu einem Maximum an, um bei noch höheren Gehalten von PU wieder abzufallen. Hinsichtlich der Izod-Schlagzähigkeit brachte die Vernetzung des DGEBA mit PU(PBA) eine wesentlich bedeutendere Verbesserung als mit PU(PTMO). Andererseits zeigten PU(PTMO)-vernetzte DGEBA-Polymere viel höhere Werte der Bruchenergie G1 C als PU(PBA)-vernetzte.
    Notes: Polyurethane (PU) prepolymers based on poly(butylene adipate) (PBA) and poly(oxytetramethylene) (PTMO) polyols were employed as a crosslinking agent to the diglycidyl ether of bisphenol A (DGEBA). Then the DGEBA was cured with a tertiary amine catalyst to form PU-crosslinked DGEBA.The tensile strength of both the PU(PBA)-crosslinked DGEBA and PU(PTMO)-crosslinked DGEBA systems increased to a maximum value with increasing PU content in the system and then decreased with further increasing PU content.Izod impact property of these PU-crosslinked DGEBA indicated that the PU(PBA)-crosslinked DGEBA had much more significant improvement than the PU(PTMO)-crosslinked DGEBA. On the contrary, the fracture energy (G1 C value) of the resultant PU-crosslinked DGEBA showed that the PU(PTMO)-crosslinked DGEBA had much higher G1 C values than the PU(PBA)-crosslinked DGEBA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051820114
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  • 169
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    Photosensibilisierte radikalische PolymerisationVortrag anläßlich der gemeinsamen Vortragstagung “Polymere und Licht” der GDCh-Fachgruppe Makromolekulare Chemie und des DPG-Fachausschusses Polymerphysik; 7. - 9.5.1990 in Bad Nauheim (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 17-43 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Nach einem kurzen überblick über die verschiedenen lichtinduzierten radikalischen Polymerisationen werden die wichtigsten Anwendungen solcher Reaktionen beschrieben. Ausführlich wird über die Verwendung von Azaaromaten als Photosensibilisatoren und die damit ausgelösten Startmechanismen berichtet.
    Notes: After a short survey on the various types of light-induced free radical polymerisations the most important applications of such reactions are summarized. In some detail is reported on the use of aza-aromatic compounds as photo-sensitizers and their initiation mechanism is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830102
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  • 170
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    Wirkungsweise von stabilisatoren in polymeren unter berücksichtigung der 2-hydroxyphenylbenzotriazoleVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Polymere und Licht”, in Bad Nauheim vom 7. bis 9. Mai 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 67-101 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the first part a survey is given on UV screeners, UV absorbers, quenchers of excited states, antioxidants and peroxide decomposers.In the second part UV absorbers, e. g. Tinuvin P (2-(2'-hydroxy-5'-methylphenyl) benzotriazole, Scheme 8) are described in detail where intramolecular proton transfer occurs in the excited state (TIN(intra) ). This proton transfer may be accompanied and/or followed by very fast and effective temperature dependent radiationless deactivation processes which are promoted by internal vibrations and librations of the molecule. - In polar solvents or in polymers with polar groups some of the molecules convert their intramolecular hydrogen bond into an intermolecular one (TIN (inter) ). TIN (inter) cannot be considered any longer as UV stabilizer. Due to its high triplet quantum yield it may even initiate photodegradation processes of itself and of the polymer. From this follows that the TIN molecule can only act as stabilizer if the intramolecular hydrogen bond is intact. This can be answered from the UV absorption spectrum.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830104
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  • 171
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    Spectral holes as probes for structural transitions in polymersVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Polymere und Licht”. in Bad Nauheim vom 7. bis 9. Mai 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 115-122 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We show how narrow spectral holes burnt into the inhomogeneous absorption of dye doped polymers can be used as extremely sensitive detectors for measuring structural rearrangement processes. A model is suggested which relates the observed hole burning phenomena to the specific heat of the conformation phase space.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830106
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  • 172
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    Oriented polymer networks obtained by photopolymerization of liquid-crystalline monomersPaper presented at the meeting of the GDCh-Fachgruppe “Makromolekulare Chemie” on “Polymers and Light” in Bad Nauheim (W-Germany), May 7-9, 1990 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 45-66 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird eine neue Klasse von orienterten Polymeren vorgestellt: hoch-vernetzte Polymere, geschaffen durch Photopolymerisation von orientierten flüssigkristallinen (LC) Monomeren. Die Orientierung dieser Polymere kann in ähnlicher Weise induziert werden wie bei konventionellen LC's, wie es in LCD's angewandt wird: mit Hilfe eines elektrischen oder magnetischen Feldes oder durch Oberflälchenorientierung.Die Photopolymerisation bietet den Vorteil, daß eine Temperatur genau im LC-Bereich gewählt werden kann.Die resultierenden Polymernetzwerke zeigen einen hohen Ordnungsgrad, welcher einigermaßen abhängig ist von der Polymerisationstemperatur, wie nachgewiesen durch Doppelbrechungsmessungen. Diese Ordnung wird über einem weiten Temperaturbereich aufrechterhalten, im Gegensatz zu der Ordnung in LC-Seitenkettenpolymeren. Abgesehen von ihren optischen Eigenschaften, zeigen unaxial geordnete Polymernetzwerke Anisotropie auch in anderen physikalischen Eigenschaften, wie im thermischen Ausdehnungskoeffizienten und im Elastizitätsmodul.
    Notes: In this paper a new class of oriented polymers is introduced: highly crosslinked polymer networks obtained by photopolymerization of oriented liquid crystalline (LC) monomers. Orientation of these monomers can be induced in the same manner as usual for conventional LCs applied in LCDs: with the aid of an electric or a magnetic field, or using surface orientation. Photopolymerization offers the advantage that a temperature can be chosen right within the LC temperature region.The resulting polymer networks show a high degree of ordering which is somewhat dependent on the polymerization temperature, as demonstrated by the amount of birefringence. This ordering is maintained over a wide temperature region, contrary to that in LC side-chain polymers. Apart from their optical properties, uniaxially ordered polymer networks show anisotropy also in other physical properties, such as the thermal expansion coefficient and modulus.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830103
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  • 173
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    OPTISCHE UND ELEKTRO-OPTISCHB SCHALTPROZESSB IN POLYMEREN FLÜSSIGKRISTALLENVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Polymere und Licht” in Bad Nauheim vom 7. bis 9. Mai 1990 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 167-195 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Low molar mass and polymeric liquid crystals display extremely large electro-optical and nonlinear optical responses, due to a combination of orientational long range order and fluidity. These responses are controlled on the one hand by the intrinsic anisotropic dielectric and optical properties of these phases and on the other hand by their peculiar curvature elastic and viscous properties.Polymeric liquid crystals, although having the disadvantage of longer response times, offer the advantage that the liquid crystalline state and any modulation imposed on it can be frozen in a glassy state. Polymeric liquid crystals can thus be used in various applications related to the control of light propagation, optical information storage and the manufacturing of holographic optical elements.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830110
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  • 174
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    TRANSPARENTE POLYMERE MEHRPHASENSYSTEMEVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker uber “Polymere und Licht”, in Bad Nauheim vom 7. bis 9. Mai 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 221-241 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Usually two phase polymer blends are not transparent because of differences in the refractive indices of their components and the resulting light scattering. By means of model calculations on the basis of the Mie-theory, the conditions for transparency in two-phase polymer blends are investigated. The models used are homogeneous spheres or spheres with a core-shell morphology imbedded in the polymer matrix. The light scattering of these particles is calculated as a function of diameter, refractive index, wavelength and particlecomposition. Results are presented that show the limits of diameter and difference in the refractive indices between matrix and particle for homogeneous particles to obtain transparency. In the case of large differences in the refractive indices or of large diameters the use of spheres with a core-shell morphology is favourable. Depending on the refractive indices of the respective phases, there exists an optimal composition of these spheres to obtain transparent polymer-blends. Another way to transparency is the minimization of light scattering by interparticle interferences, which can be achieved by special types of block-copolymers.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830112
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    Construction, expression, and preliminary characterization of chimeric class μ glutathione S-transferases with altered catalytic properties (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 159-169 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An expression plasmid for isoenzyme 3-3 of rat liver glutathione S-transferase has been constructed from the cDNA clone pGTA/C44 and the pAS expression vector pMG27NS, and used for the efficient production of the enzyme in the Escherichia coli strain M5219. The plasmid has also been manipulated, through theuse of synthetic linkers, to encode chimeric polypeptides in which short sequnces of the closely related isoenzyme 4-4 have been substituted into the N-terminal and C-terminal variable domains of isoenzyme 3-3. The chimeric polypeptides designated 493208, 320948, and 49320048 are expressed with varying degrees of efficiency in E. coli. The active dimeric holoenzymes 3-3, (493208)2, (320948)2, and (49320048)2 can be isolated. The spectroscopic and kinetic properties of the chimeric enzymes are significantly different than the native enzyme.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290121
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    Conformations of proline residues in membrane environments (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 149-157 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although noted as hydrophilic residues with helix-breaking potential, proline residues are observed in putatively α-helical transmembrane (TM) segments of many channel-forming integral membrane proteins. In addition to the recognized property of X-Pro peptide bonds (where X = any amino acid) to occur in cis as well as trans isomeric states, the tertiary amide character of the X-Pro bond confers increased propensity for involvement of its carbonyl group in specific H-bonded structures (e.g., β- and γ-turns) and/or liganding interactions with positively charged species. To examine this latter situation in further detail, we identified Leu-Pro-Phe as a consensus sequence triad based on actual occurrences of intramembranous Pro residues in transport protein TM segments. Accordingly, we have undertaken the synthesis of hydrophobic peptides with potential membrane affinity, of which t-butyloxycarbonyl-L-Ala-L-Ala-L-Leu-L-Pro-L-Phe-OH (t-Boc-AAALPF-OH) is an initial compound. Partitioning of this peptide into model membrane environments composed of lipid micelles induces specific conformations(s) for the membrane-bound hexapeptide, as monitored by 75-MHz 13C-nmr spectral behavior of 13C-enriched Leu and Pro carbonyl carbons, and by 300-MHz 1H-nmr spectra of peptide α, β, and aromatic protons. Data are interpreted in terms of an intramolecularly H-bonded inverse γ-turn conformation in the membrane environment involving the Leu-Pro-Phe triad. The inherent structureal instability of a Pro-containing segment in a TM helix due to the multiplicity of possible local conformations is discussed as a functional aspect of membrane-buried prolines in transport proteins.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290120
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    Conformationally constrained α-helical peptide models for protein ion channels (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 205-213 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently we described the design, synthesis, and characterization of some simple amphiphilic α-helical models for protein ion channels. These peptides, composed of only Leu and Ser residues, are hypothesized to form helical bundles capable of passing ions across phospholipid bilayers. In an effort to demonstrate that the peptides are, in fact, helical in their active ion-conducting state, the conformationally constrained amino acid, Cα, Cα-dimethylglycine (α-aminoisobutyric acid, Aib), was introduced simulataneously at three positions into one of the model peptides, H2N-(Leu-Ser-Leu-Leu-Leu-Ser-Leu)3-CONH2, giving H2N-(Leu-Ser-Leu-Aib-Leu-Ser-Leu)3-CONH2. Examination of a tetrameric model for the channel suggested that this substitution should have a minimal effect on conductance. CD spectroscopy of the Aib-modified and original peptide in phospholipid vesicles indicated that both were highly α-helical. Furthermore, the Aib-containing peptide formed proton channels nearly identical in conductance to the original peptide.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360290125
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    Fluctuation and linkage relations in macromolecular solution (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 215-224 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown in the appendix that the derivatives of the excess free energy of a macromolecule in solution, with respect to the activities of other solution components, lead to fluctuation and linkage relations among these other components. Solution fluctuation theory is used, but it is specialized to the fluctuations and correlations associated with the presence of a macromolecule, and is developed with a modified ensemble.The relations of the appendix are used to analyze the interaction of two solution components, A and B, with the macromolecule and with one another. Three cases are considered: (1) A and B are ligands that bind stoichiometrically to the macromolecule. This case reduces to Wyman's binding polynomial analysis. (2) A and B are tow substances at high concentration that interact selectively with the macromolecule. (3) A is a species that binds stoichiometrically to the macromolecule, while B is a component at high concentration that interacts weakly with the macromolecule.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290126
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    Applications of simulated annealing to peptides (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 225-235 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report the application of a new conformation searching algorithm called simulated annealing to the location of the global miniumum energy conformation of peptides. Simulated annealing is a Metropolis Monte Carlo approach to conformation of generation in which both the energy and temperature dependence of the Boltzmann distribution guides the search for the global minimum. Both uphill and downhill moves are possible, which allows the molecule to escape from local minima. Applications to the 20 natural amino acid “dipeptide models” as well as to polyalanines up to Ala80 are very successful in finding the lowest energy conformation. A history file of the simulated annealing process allows reconstruction and examination of the random walk around conformation space. A separate program, Conf-Gen, reads the history file and extracts all low-energy conformations visited during the run.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290127
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    SV40 Large T-antigen nuclear signal analogues: Successful nuclear targeting with bovine serum albumin but not low molecular weight fluorescent conjugatesPresented in part at the University of California, Los Angeles, Colloquia, Synthetic Peptides: Approaches to Biological Problems, January 31 to February 4, 1988, Park City, Utah. (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 197-203 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The signal sequence of a nuclear-directed protein encodes the necessary information for targeting the attached proteins to the cell nucleus. The sequence/structural requirements for a functional transport signal were explored with a series of peptides derived from the simian virus 40 large T-antigen nuclear signal 126-134 (CPKKKRKVED-NH2, wild type) conjugated to bovine serum albumin (BSA) through an N-terminal Cys (1) with m-maleimidobenzoyl-N-hydroxysuccinimide ester. Nuclear accumulation was virtually complete 15 min after microinjection into green monkey kidney cells (TC-7). Peptides with Asn, Orn, and Gln substituted for Lys128, the reverse wild-type peptide (DEVKRKKKPC-NH2) and the long 34-residue wild-type analogue (CYDDEATADSQHSTPPKKKRKVEDPKDFESELLS-NH2), were synthesized and conjugated similarly to BSA. The Orn peptide and the 34-residue wild-type analogue conjugated to BSA also transported to the nucleus but at a slower rate than 1. The reverse wild-type, Asn- and Gln-BSA conjugates of these signal analogues did not show transport to the nucleus after 6 h of incubation. In an effort to learn if such signal sequences would also target a small molecule such as a fluorescent tag to the nucleus, 1 fluorescently tagged with monobromobimane was prepared and microinjected into TC-7 cells. The peptide was distributed throughout the cell. These results support the notion that a positively charged residue at position 128 is needed for rapid nuclear transport and that the intracellular transport machinery has spatial recognition. The results with fluorophore-peptide conjugates suggest nuclear localization of these low molecular weight peptides will be difficult to attain even if attached to a functional nuclear localization sequence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290124
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    Synthetic probes for the α-factor receptor (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 237-245 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of the tridecapeptide yeast mating phermone, α-factor, to its receptor represents an excellent model for the investigation of peptide hormone-receptor interactions. In this paper we present a number of strategies to probe the binding site of the α-factor receptor, and discuss the synthesis of probes containing radioactive and affinity tags. Preferential acylation of the α- or ε-amine in [Nle12]-α-factor was accomplished using 3-[3,5-diiodo-4-hydroxyphenyl] propanoic acid hydroxysuccinimide ester (diiodo Bolton-Hunter reagent). At pH 8.0 in a N-N-dimethylformamide/water mixture the ratio of ε- to α-acylation was 2.15 to 1, whereas at pH 6.5 in a 1,2-dimethyoxyethane/water mixture α-acylation was favored by more than 3 to 1. The product distribution was sound to depend on pH, organic cosolvent, and the ratio of organic solvent and aqueous buffer. Product distributions were followed using analytical high performance liquid chromatography and the products were characterized enzymatically and by mass spectrometry. Citraconic anhydride preferentially α-acylated [Nle12]-α-factor and served as a temporary masking group during the synthesis of ε-Bolton-Hunter acylated phermone. Biotin or diiodo Bolton-Hunter reagents were also directly incorporated into [Nle12]-α-factor or Lys[Nle12]-α-factor during peptide synthesis. The peptides were assembled on a chloromethyl polystyrene resin or on a (phenylace-tamido)methyl resin, and cleaved using anhydrous hydrogen fluoride (HF). Probes were inserted on amino groups either prior (biotin) or subsequent (Bolton-Hunter reagent) to HF cleavage. The biological activity of the synthetic peptides was characterized using growth arrest assays. These studies provide insights into the structural requirements for binding of α-factor to its receptor and form a basis for detailed investigation of the receptor using biochemical procedures.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290128
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    Assignment of the 13C-nmr spectra of virgin and reactive-site modified turkey ovomucoid third domain (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 461-467 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The virgin (reactive-site Leu18-Glu19 peptide bond intact) and modified (reactive-site Leu18-Glu19 peptide bond hydrolyzed) forms of turkey ovomucoid third domain (OMTKY3 and OMTKY3*, respectively) have been analyzed by proton-detected 1H{13C} two-dimensional single-bond correlation (1H{13C}SBC) spectroscopy. Previous 1H-nmr assignments of these proteins [A. D. Robertson, W. M. Westler, and J. L. Markley (1988) Biochemistry, 27, 2519-2529; G. I. Rhyu and J. L. Markley (1988) Biochemistry, 27, 2529-2539] have been extended to directly bonded 13C atoms. Assignments have been made to 52 of the 56 backbone 13Cα-1H units and numerous side-chain 13C-1H groups in both OMTKY3 and OMTKY3*. The largest changes in the 13C chemical shift upon conversion of OMTKY3 to OMTKY3* occur at or near the reactive site, and tend toward values observed in small peptides. Moreover, the side-chain prochiral methylene protons attached to the Cγ of Glu19 and Cδ of Arg21 show nonequivalent chemical shifts in OMTKY3 but more equivalent chemical shift in OMTKY3*. These results suggest that the reactive site region becomes less ordered upon hydrolysis of the Leu18-Glu19 peptide bond. Comparison of 13Cα chemical shifts of OMTKY3 and bovine pancreatic trypsin inhibitor [D. Brühuiler and G. Wagner (1986) Biochemistry 25, 5839-5843; N. R. Nirmala and G. Wagner (1988) Journal of the American Chemical Society, 110, 7557-7558] with small peptide values [R. Richarz and K. Wüthrich (1978) Biopolymers, 17, 2133-2141] suggests that 13Cα chemical shifts of residues residing in helices are generally about 2 ppm downfield of resonances from nonhelical residues.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290216
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    Viscoelastic and rheological properties of concentrated solutions of proteoglycan subunit and proteoglycan aggregate (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1587-1592 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oscillatory and steady shear rheological properties of concentrated solutions of proteoglycan subunit (PGS) and aggregate (PGA) from bovine articular cartilage have been studied using a Rheometrics fluids spectrometer. At comparable concentrations in the physiological range tan δ increases from 0.5 to 1.0 for PGA as the oscillation frequency (ω) increases from 10-1 to 102 rads / s, compared to a decrease from 40 to 5 for PGS. Thus PGA solutions exhibit predominantly elastic response whereas those of PGS exhibit primarily viscous behavior. PGA solutions show pronounced shear-thinning behavior at all shear rates (γ) in the range 10-2 〈 γ (s-1) 〈 10 2, whereas PGS solutions exhibit predominantly Newtonian flow. For PGA, the small-strain complex viscosity η* (ω) is substantially smaller than the steady-flow viscosity η (γ) at comparable values of ω and γ. These observations indicate that the presence of proteoglycan aggregates leads to formation of a transient or weak-gel network. Since aggregation leads to a large increase in molecular hydrodynamic volume and hence in the relaxation times for macromolecular rotation, it appears that role of aggregate formation is to shift the linear viscoelastic response from the terminal viscous flow into the plateau elastomeric regime of relaxational behavior. Normal or pathological changes that produce a decrease in aggregation will result in a loss of elastomeric behavior of the proteoglycan matrix.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360291208
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    Masthead (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300101
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    A molecular dynamics investigation of the elastomeric restoring force in elastin (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1613-1631 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A repetitive polypentapeptide organized as a connected chain of β-bends is believed to be an important structural element of elastin, the major elastomer in biological systems. Molecular dynamics simulations were carried out on hydrated polymers of (Val-Pro-Gly-Val-Gly)18 at various extensions. Analysis of the fluctuations of backbone angles in relaxed elastin showed that particularly large-amplitude torsional motions occur in φ and ψ angles of residues connecting sequentially adjacent hairpin bends. Many such motions reflect peptide plane librations that result from anticorrelated crankshaft rotations of ψi and φi+1. These effects were much reduced in stretched polymer models. The conformational entropy of relaxed and stretched elastin models was estimated using a treatment due to Meirovitch, and gave a calculated decrease in entropy of about 1 cal/mol deg when the polymer was stretched to 1.75 times its original length. There are large changes in solvent-accessible surface area during the intitial stages of elastin stretching. Collectively these results suggest that hydrophobic interactions make contributions to elastin entropy at low extensions, but that librational mechanisms make large contributions to the elastic restoring force at longer extensions.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360291211
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    The europium (III)-induced conformational transitions of poly(dG-dC) · poly(dG-dC) and poly(dG-m5dC) · poly(dG-m5dC) as studied by europium(III) luminescence, UV, and CD spectroscopy (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 33-43 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Eu3+ ion induces a B to Z transition in poly(dG-dC) · poly(dG-dC) and poly(dG-m5dC) · poly(dG-m5dC). Other conformations were also elicited by this ion. The conformational changes of these polynucleotides were followed by CD and uv spectroscopy. Eu3+ excitation spectra and Eu3+ excited-state lifetimes were measured for the Eu3+ ion bound to the duplexes in various conformations. B-form poly(dG-dC) and poly(dG-m5dC) appear to have a single class of the Eu3+ binding site while the Z-form observed conformation exhibits two. The numbers of H2O molecules coordinated to the Eu3+ ion bound to the various conformations of the duplexes were determined by measuring Eu3+ excited-state lifetimes in H2O and D2O. The first-order rate constants for the Eu3- and [Co(NH3)6]3+ induced B to Z transitions were measured. The Eu3+ mediated conversion is much faster than the [Co(NH3)6]3+ induced conversion in both polynucleotides.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300106
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    Crystal structure and solution conformation of S,S′-bis(Boc-Cys-Ala-OMe): Intramolecular antiparallel β-sheet conformation of an acyclic cystine peptide (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 73-85 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of the acyclic biscystine peptide S,S′-bis(Boc-Cys-Ala-OMe) has been studied in the solid state by x-ray diffraction, and in solution by1H- and13C-nmr, ir, and CD methods. The peptide molecule has a twofold rotation symmetry and adopts an intramolecular antiparallel β-sheet structure in the solid state. The two antiparallel extended strands are stabilized by two hydrogen bonds between the Boc CO and Ala NH groups [N⃛O 2.964 (3) Å, O⃛HN 2.11 (3) Å, and NH⃛O angle 162 (3)°]. The disulfide bridge has a right-handed conformation with the torsion angle CβSSCβ = 95.8 (2)°. In solution the presence of a twofold rotation symmetry in the molecule is evident from the1H- and13C-nmr spectra. 1H-nmr studies, using solvent and temperature dependencies of NH chemical shifts, paramagnetic radical induced line broadening, and rate of deuterium-hydrogen exchange effects on NH resonances, suggest that Ala NH is solvent shielded and intramolecularly hydrogen bonded in CDCl3 and in (CD3)2SO. Nuclear Overhauser effects observed between Cys CαH and Ala NH protons and ir studies provide evidence of the occurrence of antiparallel β-sheet structure in these solvents. The CD spectra of the peptide in organic solvents are characteristic of those observed for cystine peptides that have been shown to adopt antiparallel β-sheet structures.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300109
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    Helix-coil stability constants for the naturally occurring amino acids in water. XXIII. Proline parameters from random poly(hydroxybutylglutamine-CO-L-proline) (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 107-120 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Water-soluble random copolymers containing L-proline and N5-(4-hydroxybutyl)-L-glutamine were synthesized by copolymerization of the tripeptides H-L-Glu(OBzl)-L-Glu(OBzl)-L-Glu(OBzl)-OH and H-L-Glu(OBzl)-L-Pro-L-Glu(OBzl)-OH, using ben-zotriazolyl-N-oxy-tris(dimethylamino)-phosphonium hexafluorophosphate as condensing reagent, and subsequent aminolysis of the Bzl ester groups with 4-amino-1-butanol. These copolymers were found to contain significant amounts of N5-(4-hydroxybutyl)-D-glutamine, thus requiring the synthesis of a binary copolymer containing only D- and L-N5-(4-hydroxybutyl)glutamine residues in order to evaluate the possible effects of the D-residues on the conformational properties of poly(hydroxybutylglutamine-co-L-proline). The different copolymers were fractionated, and their thermally induced helix-coil transition curves were obtained in water at neutral pH. When proper corrections were applied for the helix-destabilizing properties of N5-(4-hydroxybutyl)-D-glutamine, the Zimm-Bragg parameters σ and s for L-proline could be deduced from the melting curves of poly (hydroxybutylglutamine-co-L-proline). The results indicate that L-proline acts as a very strong helix breaker over the entire temperature range from 0 to 60°C.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300112
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    Analysis of side-chain conformational distributions in neutrophil peptide-5 nmr structures (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1807-1822 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The side-chain conformations have been analyzed in the antimicrobial peptide, Neutrophil Peptide-5(NP-5), whose structure was independently generated from nmr-derived distance constraints using a distance geometry algorithm. The side-chain and peptide dihedral angle distributions in the nmr structures were compared with those constructed from a data base of high-resolution protein crystal structures. The side-chain conformational preferences for NP-5 in solution are significantly different from those observed in the crystal structure data base. These results indicate that the side-chain conformations are quite disordered for many of the residues of NP-5. The absence of a correlation between the width of the conformational distribution and surface accessibility suggests that the disorder may be due to limitations in the structural information extracted from the nmr data rather than to molecular motion. However, it is also observed that the degree of conformational disorder is only weakly correlated with the number of nuclear Overhauser enhancements to a given side chain. Possible reasons for this are discussed. Molecular mechanics refinement of these structures did not significantly change the side-chain populations. Anomolously wide distributions are observed for rotations about the peptide bonds and the disulfide bonds in the NP-5 distance geometry structures, which are improved by the refinement. The very high degree of order observed for the central dihedral angle of the disulfide bond in the high-resolution crystal data base suggests that the rotation about this bond in proteins is determined by the local potential.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360291412
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    Protein folding and chain collapse (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1823-1833 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is currently assumed that the folded structure of a globular protein is controlled in a highly deterministic way by its amino acid sequence. We show here that a very different although not necessarily contrasting viewpoint can be adopted. From statistical treatment of x-ray results, we suggest that the folding pattern essentially follows the collapse to be expected on statistical-mechanical grounds for an ideal chain effectively experiencing self-attraction and comprising identical units, whose conformational properties are obtained as an average over the actual amino acid units. The local details of folding of each protein, obviously dictated byits amino acid sequence, can be regarded as statistical fluctuations.We consider 31 globular fragments belonging to 21 different water-soluble, nonmembrane proteins. By the theory of chain collapse proposed by two of us [G. Allegra and F. Ganazzoli (1985) J. Chem. Phys. 83, 397], all the average intramolecular distances may be obtained. Accordingly, first an average plot of the mean-square distances between kth neighboring amino acid units is constructed, starting from the observed crystallographic coordinates. Then the plot is basically reproduced with a wormlike chain model undergoing collapse as a result of intramolecular attractive forces. Agreement is especially good for short amino acid sequences (k ≲ 30), in which case the statistical sampling is more accurate, enabling us to determine the model parameters. The resulting mean-square radius of gyration is also in good agreement with the experimental average, whereas the unperturbed characteristic ratio is roughly consistent with results from conformational calculations by W. L. Mattice [(1977) Macromolecules 10, 516], based on the rotational isomeric state approach.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360291413
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  • 191
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    Helix aggregation in peptide crystals: Occurrence of either all parallel or antiparallel packing motifs for α-helices in polymorphs of Boc-Aib-Ala-Leu-Ala-Leu-Aib-Leu-Ala-Leu-Aib-OMe (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1835-1845 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three crystalline polymorphs of the helical decapeptide, Boc-Aib-Ala-Leu-Ala-Leu-Aib-Leu-Ala-Leu-Aib-OMe, have been obtained. Antiparallel helix aggregation is observed in crystals grown from methanol (A), while completely parallel packing is observed in crystals from isopropanol (B) or an ethylene glycol-ethanol mixture (C). Crystals B and C are very similar in molecular conformation and packing. The packing motifs in crystals A and B consist of rows of parallel molecules, with an almost identical arrangement in both crystals. In crystal A, adjacent rows assemble with helix axes pointed in oppsite directions, whereas in crystal B all rows assemble with helix axes pointed in the same direction. Electrostatic interactions between helix dipoles do not appear to be a major determinant of packing modes. The structures also do not provide a ready rationalization of packing preferences in terms of side-chain interactions or solvation. The α-helix of the peptide in crystal A has seven 5 → 1 hydrogen bonds; the helix in crystal B is a mixed 310/α-helix. The crystal parameters are as follows. Crystal A: C51H92N10O13·CH3OH, space group P21 with a = 10.498(1) Å, b = 18.189(3) Å, c = 16.475(3) Å, β = 99.28(1)°, Z = 2, R = 9.6% for 1860 data. Crystal B: C51H92N10O13·C3H7OH, space group P21 with a = 10.534(1) Å, b = 28.571(4) Å, c = 11.055(2) Å, β = 95.74(1)°, Z = 2, R = 6.5% for 3251 data. Crystal C: C51H92N10O13·C2H5OH, space group P21, with a = 10.450(1) Å, b = 28.442(5) Å, c = 11.020(2) Å, β = 95.44(1)°, Z = 2, R = 14.8% (isotropic) for 1948 data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360291414
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  • 192
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    Secondary structure effects on the interaction of different polynucleotides with Ca2+ (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 325-333 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of Ca2+ ions in 10 mM NaCl at 17°C with polynucleotides of different primary and secondary structure has been investigated. The experimental results show the following: 1The affinity for calcium ion depends on the secondary structure of the polynucleotide and not, within the experimental error, on the base sequence.2The following hierarchy in calcium ion binding can be established: A-RNAs 〉 B-DNAs 〉 single-stranded RNAs. The polyG binding curve is analogous to that of A-RNAs; this strongly suggests that it does not adopt a single-stranded structure in our experimental conditions.3Apart from the case of single-stranded RNAs, where both Manning's and Poisson-Boltzmann models seem to fit the data well, the Poisson-Boltzmann equation reproduces the experimental points better than the Manning's theory, which overestimates the affinity of the double-stranded nucleic acids for calcium ion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300310
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  • 193
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    On the multiple-minima problem in the conformational analysis of polypeptides. IV. Application of the electrostatically driven monte carlo method to the 20-residue membrane-bound portion of melittin (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 165-176 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational space of the membrane-bound portion of melittin has been searched using the electrostatically driven Monte Carlo (EDMC) method with the ECEPP/2 (em-pirical conformational energy program for peptides) algorithm. The former methodology assumes that a polypeptide or protein molecule is driven toward the native structure by the combined action of electrostatic interactions and stochastic conformational changes associated with thermal movements. The algorithm produces a Monte Carlo search in the conformational hyperspace of the polypeptide using electrostatic predict ions and a random sampling technique, combined with local minimization of the energy function, to locate low-energy conformations. As a result of 8 test calculations on the 20-residue membrane-bound portion of melittin, starting from six arbitrary and two completely random conformations, the method was able to locate a very low-energy region of the potential with a well-defined structure for the backbone. In all of the cases under study, the method found a cluster of similar low-energy conformations that agree well with the structure deduced from x-ray diffraction experiments and with one computed earlier by the build-up procedure.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300116
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  • 194
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    A new mechanism of mechanochemical coupling: Stretch-induced increase in carboxyl pKa as a diagnostic (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 215-218 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300122
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  • 195
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    Masthead (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300301
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  • 196
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    Bond-Optimized ring closure for proline: Comparison of conformations and semiempirical energies with small molecule X-ray structures (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 437-450 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for generating proline ring structures by successive addition of atoms, wherein ring closure is achieved by optimizing the fit to known ring bond-angles and one closing bond-length (“bond-optimized ring closure”). Two ring torsion angles are fixed independently within broad, allowed ranges, and the remaining torsion angles are determined uniquely in most cases. The independent torsion angles are chosen as φ and χ2, and ring closure is achieved without prohibitive strain through most of the ranges -130° 〈 φ 〈 -20° and -60° 〈 χ2 〈 60°. Comparisons of predicted ring structures to 191 X-ray diffraction structures from the literature, starting with the known values of φ and χ2, yielded root-mean-square deviations of 4.8° in χ1, 4.7° in χ3, 8.3° in χ4, and 0.3-2% in the ring bond angles and the N-Cδ distance. Semiempirical energies were calculated for the optimized structures using three sets of energy parameters from the literature. The energy surfaces show broad minima coinciding with the torsion angle regions in which the highest concentrations of observed structures are found. Two of the sets of energy parameters produce double minima corresponding to the “up” and “down” puckered conformations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300321
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  • 197
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    An optimal formulation of the matrix method in statistical mechanics of one-dimensional interacting units: Efficient iterative algorithmic procedures (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 481-497 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Statistical mechanical calculations for one-dimensional interacting units have undergone great development in many fields of macromolecular science. The partition function is the most rigorous description of an ensemble of molecules in equilibrium. Specific methodological formulations and algorithms were developed to handle numerically the inclusion of long-range effects (as compared to usual nearest neighbor Ising models) and known sequence-dependent heterogeneities of biological macromolecules. The most successful approach in formulating these problems in a very general and tractable framework was the so-called matrix method. Despite several improvements, it was claimed that in practical applications this approach had fundamental limitations inherent to any “matrix” formulation. We show here that a new conceptual formulation allows us to overcome these limitations completely. We propose a general iterative procedure that combines the theoretical advantages of the matrix method with the possibility of highly optimized and efficient numerical algorithms.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300502
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  • 198
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    Electronic Resource
    Conformational analysis and helical preferences of normal and α,α-dialkyl amino acids (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 533-546 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Energy calculations have been performed on right-handed helical structures of L-alanine and α-methylalanine oligomers. A new ′3.610′-helix is described for α-methylalanine peptides. The dependence of the relative stability of the α, 310, and 3.610 structural forms on helix length, dielectric, and force-field, in the gas phase, has been studied. Potential energy surfaces for the interconversion of helices have been generated. The 310-helix in α-methylalanine oligomers exhibits a degree of enthalpic and entropic stabilization not observed for alanine. The relevance of the results to the formation of voltage-sensitive ion channels is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300506
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  • 199
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    Structure of the hydration shells of oligo(dA-dT)·oligo(dA-dT) and oligo(dA)·oligo(dT) tracts in B-type conformation on the basis of Monte Carlo calculations (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 563-581 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monte Carlo simulations [(N, V, T)-ensemble] were performed for the hydration shell of poly(dA-dT)·poly(dA-dT) in canonical B form and for the hydration shell of poly(dA) ·poly(dT) in canonical B conformation and in a conformation with narrow minor groove, highly inclined bases, but with a nearly zero-inclined base pair plane (B′ conformation). We introduced helical periodic boundary conditions with a rather small unit cell and a limited number of water molecules to reduce the dimensionality of the configuration space. The coordinates of local maxima of water density and the properties of one- and two-membered water bridges between polar groups of the DNA were obtained.The AT-alternating duplex hydration mirrors the dyad symmetry of polar group distribution. At the dApdT step, a water bridge between the two carbonyl oxygens O2 of thymines is formed as in the central base-pair step of Dickerson's dodecamer. In the major groove, 5-membered water chains along the tetranucleotide pattern d (TATA) · d (TATA) are observed.The hydration geometry of poly (dA) · poly(dT) in canonical B conformation is distinguished by autonomous primary hydration of the base-pair edges in both grooves. When this polymer adopts a conformation with highly inclined bases and narrow minor groove, the water density distribution in the minor groove is in excellent agreement with Dickerson's spine model. One local maximum per base pair of the first layer is located near the dyad axis between adjacent base pairs, and one local maximum per base pair in the second shell lies near the dyad axis of the base pair itself. The water bridge between the two strands formed within the first layer was observed with high probability. But the water molecules of the second layer do not have a statistically favored orientation necessary for bridging first layer waters. In the major groove, the hydration geometry of the (A · T) base-pair edge resembles the main features of the AT-pair hydration derived from other sequences for the canonical B form. The preference of the B′ conformation for oligo(dA) · oligo(dT) tracts may express the tendency to common hydration of base-pair edges of successive base pairs in the grooves of B-type DNA.The mean potential energy of hydration of canonical B-DNA was estimated to be -60 to -80 kJ/mole nucleotides in dependence on the (G · C) contents. Because of the small system size, this estimation is preliminary.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300509
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  • 200
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    Molecular topology and dimerization of recombinant bovine somatotropin (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 645-647 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300516
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