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  • 1980-1984  (20,362)
  • 1970-1974  (13,585)
  • 1965-1969  (10,273)
  • 1950-1954  (3,441)
  • 1940-1944  (1,435)
  • Polymer and Materials Science  (36,124)
  • Life and Medical Sciences  (12,190)
  • Cell & Developmental Biology  (11,110)
  • Electron microscopy  (786)
  • Nuclear reactions
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Material
Years
Year
Keywords
  • 101
    Electronic Resource
    Electronic Resource
    Matrix-method calculation of linear and circular dichroism spectra of nucleic acids and polynucleotides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 435-470 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calculations of the optical properties (absorption, linear dichroism, circular dichroism, and anisotropic components of the CD) are presented for polynucleotides of random or regular sequence within the formalism of the matrix method using a set of parameters that includes only the ππ* transitions of the aromatic bases. Experimental solution spectra agree favorably with calculated CD spectra for A-RNA, A-DNA, and B-DNA, when coordinates derived from x-ray studies on fibers are used. Excessive hypochromicity is predicted when parameters intended to reproduce the vacuum-uv absorption of the chromophores are included in the calculations, but total elimination of these parameters leads to an insufficient hypochromicity for the long-wavelength absorption band. Using alternative conformations for DNA in low-salt aqueous solution did not improve the agreement between experimental and calculated spectra, but some features of the optical properties predicted for these variant structures suggest that the tilt of the bases with respect to the helical axis may be larger than that of the fiber B-form.In the case of polynucleotides with regular structure, which have been traditionally less easy to understand in terms of the standard nucleic acid conformations, a series of alternative structures has been examined. Unexpectedly, the calculated spectrum for the Z-DNA structure compares almost quantitatively with the experimental spectrum of poly(dGC·dGC) in low salt. This result, which confirms a recent report [Vasmel, H. & Greve, J. (1981) Biopolymers 20, 1329-1332], is in contrast with the current identification of Z-DNA with the high-salt form of poly(dGC·dGC). Finally, the optical properties of single-stranded polyribonucleotides appear to be better explained when alternative structures [91-helix for poly(rA) and 61-helix for poly(rC)] are introduced instead of the A-RNA form.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230305
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  • 102
    Electronic Resource
    Electronic Resource
    Total intensity light scattering from short, optically anisotropic wormlike chains (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 607-608 
    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.360230314
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  • 103
    Electronic Resource
    Electronic Resource
    Dimensions of short, rodlike macromolecules from translational and rotational diffusion coefficients. Study of the gramicidin dimer (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 611-615 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230402
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  • 104
    Electronic Resource
    Electronic Resource
    Alternative pathways in diffusion-collision controlled protein folding (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 675-694 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diffusion-collision model of protein folding has been solved exactly for a three-microdomain protein subunit. Numerical analysis shows that the exact kinetics may be excellently approximated in all cases studied by a standard chemical kinetics approach with the forward rate constants calculated from the mean folding time formula found previously.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230408
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  • 105
    Electronic Resource
    Electronic Resource
    Electric birefringence study of the purple membrane of Halobacterium halobium (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 707-718 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An electric birefringence study was carried out on aqueous suspensions of the purple membrane of Halobacterium halobium. In addition to the characterization of both native and modified membrane samples, the dependence of electric birefringence on pH and ionic strength was also investigated. The results indicate that purple membrane shows electric birefringence at a field strength as low as 200 V/cm. The permanent dipole moment and polarizability ranged from 20,500 debyes and 1.01 × 10-14 cm3 for a purple membrane concentration of 0.40 mg/mL to 41,000 debyes and 2.05 × 10-14 cm3 for a concentration of 0.80 mg/mL. It was also found that removal of the retinyl group of bacteriorhodopsin substantially decreases but does not eliminate the electric birefringence of the membrane. The solubilization of the membrane by Triton X-100, however, completely abolishes the electric birefringence. These experiments indicate that there is an interaction between adjacent bacteriorhodopsin molecules within the purple membrane via the retinyl chromophore moiety that builds up the permanent dipole moment. They also suggest that there are two types of response when purple membrane suspensions are placed in an electric field. One is an alignment of the disk-shaped particles with the field. The other is a stacking of the particles following their alignment by the electric field, which is promoted by the induced dipole moment.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230410
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  • 106
    Electronic Resource
    Electronic Resource
    Folded β-turns and collagenlike conformations of -Gly-Pro- and -Pro-Gly-sequences in synthetic polytripeptides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 617-621 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230403
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  • 107
    Electronic Resource
    Electronic Resource
    Computer building of β-helical polypeptide models (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 23-38 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general method is presented for computing the atomic coordinates of helices in which a dipeptide is the repeating unit. The method will generate both single- and double-stranded model helices having idealized bond lengths and angles, and any arbitrary, user-specified, pitch and number of residues per turn. The variation of inter- and intrastrand hydrogen bonds with pitch and number of residues per turn can thus be examined. An application of the method is the construction of a β-helix having pitch of 6.3 Å per turn and 4.85 residues per turn, a model which can pack nicely into the unit cell of crystals of cation-bound gramicidin A.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230104
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  • 108
    Electronic Resource
    Electronic Resource
    Conformational change in yeast tRNAAsp (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 71-81 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of yeast tRNAAsp in aqueous solutions has been analyzed in the light of results obtained from Raman spectra recorded at from 5 to 82°C and compared to those of tRNAPhe. Firm evidence is given of a reversible conformation transition for tRNAAsp at 20°C. This transition is observed for the first time in the tRNA series. The low-temperature conformation appears to have a more regular ribose-phosphate backbone and a more effective G base-stacking. This conformational change, which occurs essentially in the D loop, could be connected to the existence of two (A and B) crystal forms obtained depending on crystallization conditions. The melting temperatures, which are different for each base stacking in tRNAAsp, lie in a range of about 70°C, much higher than for tRNAPhe. This fact is interpreted by a higher ratio of G-C base pairs in tRNAAsp.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230107
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  • 109
    Electronic Resource
    Electronic Resource
    Interaction of poly-5-bromouridylic acid. I. Formation of helical complexes with various adenine and 2-aminoadenine derivatives (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 493-509 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexes of poly(BU) with various adenine derivatives were investigated by circular dichroism (CD) and absorption spectroscopy. A 1:2 stoichiometry was indicated on CD mixing curves for typical complexes of 9-substituted adenine and 2-aminoadenine derivatives with poly(BU). The CD spectrum of adenosine·2poly(BU) is characterized by well-resolved bands in the range of 210-350 nm. Other adenine derivative-poly(BU) complexes also afford similar CD spectra, while 2-aminoadenine derivative-poly(BU) complexes give quite different spectra. Attempts to assign representative CD spectra were made using the transition of helical poly(BU) and the respective purine polynucleotides. The similarity of the CD spectra suggests that poly(A)·2poly(BU) and adenine derivative-poly(BU) complexes are nearly identical in structure except for the ribose-phosphate linkage. The fact that the uv isosbestic point of adenosine·2poly(BU) falls in close proximity to that of the corresponding polymer complex also supports this conclusion. In the formation of stable helices, the ribose moiety is dispensable in the “strand” of purine. The Tm of 9-methyladenine·2poly(BU) is somewhat higher than that of adenosine·2poly(BU) under equivalent conditions. The Tm difference with the monomer-poly(U) system was found to be about 20°C in 0.4M NaCl-0.02M Na-cacodylate-5 × 10-4M EDTA (pH 7.0). Further, it was noted that the monomer-poly(BU) complexes are formed even when the Tm is lower than that of self-folded poly(BU).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230307
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  • 110
    Electronic Resource
    Electronic Resource
    31P-NMR studies of deoxyoligonucleotides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 575-592 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The assignments of 31P resonances of eight short oligonucleotides have been achieved through specific heterodecoupling techniques reported previously from our laboratory [Cheng et al. (1982) Biopolymers 21, 697-701]. The temperature dependence of the assigned 31P chemical shifts of these oligomers was studied and compared to the constitutive dimeric units. This comparison gives some insight to the chemical-shift values of the phosphorus resonances of oligonucleotides. (1) The 3′-end terminal phosphorus resonance in an oligomer tends to locate at a spectral position relatively close to its constitutive dimeric unit. (2) On chain elongation (from 5′-toward 3′-end), the phosphorus resonance in the oligomer will be shifted upfield by 0.2-0.3 ppm, as compared to its constitutive dimeric unit. (3) The relative positions of phosphorus resonances in an oligomer tend to remain in the same order as their constitutive dimeric units. The above obsrvations lead to the development of a new procedure to assign the 31P resonance of a single-stranded oligonucleotide.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230311
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  • 111
    Electronic Resource
    Electronic Resource
    L-Alanyl-glycylglycine: FT-IR and Raman spectroscopic evidence for tripeptide packing in a collagenlike arrangement (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 623-627 
    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.360230404
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  • 112
    Electronic Resource
    Electronic Resource
    Viscometry and sedimentation equilibrium of partially hydrolyzed hyaluronate: Comparison with theoretical models of wormlike chains (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 647-666 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fractionated samples of sodium hyaluronate of low molecular weight were used to calibrate the carbazole method for glucuronyl analsis and to determine the density increment (based on dry weight) of 0.444 (±0.003) mL/g in water and 0.386 (±0.003) mL/g for samples dialyzed against 0.2M NaCl. Weight-average molecular weights obtained by high-speed sedimentation equilibrium were used to calibrate the limiting viscosity number [η] in 0.2M NaCl, which gave [η]/Mw = 0.0028 (±0.0002) mL/g, valid to Mw = 0.0028 (±0.0002) mL/g, valid to Mw = 105. Experimental data from this work and the literature, including viscosity and light- and small-angle x-ray scattering measurements, were compared to theoretical chain models of the Kratky-Porod (KP) wormlike and the helical wormlike (HW) chain, as treated by Yamakawa and collaborators. Although either model could be fitted to experimental data about equally well with consistent parameters, provided those for the HW chain were of weakly helical nature, calculation of the unperturbed meansquare end-to-end distance as a function of chain length from a conformational model favored the KP chain alternative. The parameters that provide the best fit to experimental data for the KP wormlike model are a persistence length of 4.5-5 nm and a diameter of 1.1 nm. The latter is resonable for a hydrated hydrodynamic cylinder in view of the approximate unhydrated value of 0.7 nm estimated from the density increment.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230406
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  • 113
    Electronic Resource
    Electronic Resource
    Cation-induced conformational changes in tRNA molecules (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 759-766 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The uv absorption spectra and melting profiles of an initially ion-free solution of E. coli unfractionated tRNA are significantly modified by the addition of either Na+, Mg2+, or Mn2+ or of other first-series transition-metal ions such as Ni2+, Co2+, and Zn2+. The main effect of the addition of all monovalent or divalent cations examined is an increase of the ordered and stacking stabilized tRNA structure, as revealed by a drop in the absorption near 260 nm, as well as in the 4-TU absorption region. Sharp differences have, however, been detected in the 290-305-nm range in the presence of the various ions studied. When transition-metal ions were added to a tRNA solution, an absorption peak appeared at 294 nm. This effect is interpreted as a perturbation of the electronic structure of the bases due to direct binding of metal ions to the bases. An analysis of the variation in the spectrum as a function of metal concentration and of the thermal melting reversibility in the presence of various metal ions supports the conclusion that while all ions investigated are involved in binding to the phosphate groups of tRNA, transition-metal ions are also able to bind directly to the bases.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230414
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  • 114
    Electronic Resource
    Electronic Resource
    Electrostatic interactions between α-helix dipoles in crystals of an uncharged helical undecapeptide (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 809-817 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrostatic interactions between α-helix dipoles in the crystals of an uncharged helical undecapeptide have been studied in detail. The electrostatic interaction energy between one helix dipole and its 26 nearest neighbors is approximately -23 kcal mol-1. A very similar result is obtained when calculating the interactions between one helix dipole and all 988 helix dipoles occurring within a distance of 75 Å. It therefore appears that in these crystals of completely uncharged molecules large, favorable electrostatic interactions occur.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230418
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  • 115
    Electronic Resource
    Electronic Resource
    Modeling biological macromolecules in solution. II. The general tri-axial ellipsoid (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 843-843 
    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.360230421
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  • 116
    Electronic Resource
    Electronic Resource
    Most-probable distribution at enzyme depolymerization of polysaccharides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 859-876 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several research groups have studied depolymerizing processes by enzyme cleavage using product distribution. Although only the shortest chain products can be measured experimentally, interpretation of much evidence requires an assumption of the nature of high polymer distribution. The present work analyzes the high polymer distribution of products on the basis of mathematical models suggested for the two most widespread α-amylase action-mechanisms. The most-probable distribution was found to be distorted by hydrolysis only for the shortest chain products. The size of the distorted region is directly dependent on the characteristics of a specific enzyme. We studied the distribution of products for substrates of varying composition to show that it approaches the most-probable distribution at depolymerization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230504
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  • 117
    Electronic Resource
    Electronic Resource
    Conformation study on heparin by intermediate-angle X-ray scattering (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 995-1009 
    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 heparin in water was investigated by intermediate-angle x-ray scattering (IAXS). The theoretical scattering function for the coil conformation was calculated by the Monte Carlo method using the approximation of separable conformation energies and the conformation energies computed for two disaccharide pairs in heparin. From x-ray scattering in a relatively small-angle region, the conformation of heparin is not the ordered 21 helix conformation but the coil conformation obtained by the Monte Carlo calculation. It is expected, from x-ray scattering in a relatively wide-angel region, that the sulfate groups of heparin maintain about 7 Å between them.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230603
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  • 118
    Electronic Resource
    Electronic Resource
    Study of polysaccharides by the fluorescence method. III. Chain length dependence of the micro-Brownian motion of amylose in an aqueous solution (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1043-1056 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fluorescence polarization method was applied to the investigation of the micro-Brownian motion of amylose chains having a wide range of degree of polymerization (DP). We prepared two types of fluorescent conjugates of amylose: amylose conjugated with fluorescein randomly throughout the chain (F-amylose) and amylose conjugated locally on a terminal segment (t-F-amylose). The degree of fluorescence polarization of these conjugates was measured by changing the solvent viscosity at a constant temperature (25°C). The data obtained were analyzed by a Perrin-type equation to calculate the mean rotational relaxation time, 〈ρ〉. By examination of the plots of 〈ρ〉 vs DP, and by comparison of 〈ρ〉 with the theoretical rotational relaxation time of the whole molecule at a given DP, it was found that 〈ρ〉 mainly reflects the segmental motion of the amylose chain in the high-DP range. Thus, the fact that 〈ρ〉 for t-F-amylose is much smaller than that for F-amylose at a sufficiently high DP shows that a terminal segment undergoes a more rapid micro-Brownian motion than interior segments. In the low-DP range, we felt that the rotational diffusion of the whole molecule contributes significantly to the relaxation process. We also examined, for comparison, the segmental motion of dextran and pullulan in a similar manner and found that these segmental motions are more rapid than those of amylose. Based on the results obtained, the segmental mobility and conformation of the amylose molecule are discussed in relation to its chain length.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230606
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  • 119
    Electronic Resource
    Electronic Resource
    Synthesis and properties of L-cysteinyl-L-cysteine disulfides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1085-1097 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oligomeric cyclic disulfides, obtained by mild oxidation of the fully protected dipeptide L-cysteinyl-L-cysteine, have been isolated by gel and thin-layer chromatography. Polymeric material was recycled by a thiol-disulfide exchange-reaction performed at basic pH. Spectroscopic investigations of the monomer and the two dimers indicate that conformers characterized by dihedral angles about the S—S bond close to ±90° are preferred. Moreover, chiroptical and 1H-nmr data for these compounds suggest higher mobility for the two dimers. The antiparallel dimeric disulfide can be considered a model compound for the hinge region formed at the subunit interface of the bovine seminal ribonuclease, a dimeric enzyme showing a complex kinetic behavior.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230609
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  • 120
    Electronic Resource
    Electronic Resource
    Dynamic light scattering as a probe of superhelical DNA-intercalating agent interaction (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1113-1119 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polarized dynamic light-scattering measurements on superhelical pBR322-plasmid DNA solutions in 0.2M NaCl, 2 mM NaPi, pH 7.0, 2 mM EDTA result in a translational diffusion coefficient DT,20°C0 = (3.77 ± 0.10) × 10-8 cm2/s for the native molecule. Modeling the DNA, in the simplest approximation, as a 10 × 440-nm effective hydrodynamic rigid rod yields a good fit to the apparent diffusion coefficient angular-dependence data up to 70°; the model fails at higher angles, probably due to the effects of flexibility or branching of the rod. Diffusion coefficient titration experiments with a platinum complex intercalating agent (PtTS) result in a titratable superhelix density of σ = -0.079 ± 0.008 under our experimental conditions, corresponding to about 34 superhelical turns in the native DNA. The DNA contour length predicted by our two independent results, the rod dimensions and the number of superhelical turns, is in excellent agreement with the contour length calculated from the number of base pairs, supporting the hydrodynamic approximation of an effective rodlike structure for this small DNA molecule in solution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230611
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  • 121
    Electronic Resource
    Electronic Resource
    Quasi-harmonic method for studying very low frequency modes in proteins (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1099-1112 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quasi-harmonic approximation is described for studying very low frequency vibrations and flexible paths in proteins. The force constants of the empirical potential function are quadratic approximations to the potentials of mean force; they are evaluated from a molecular dynamics simulation of a protein based on a detailed anharmonic potential. The method is used to identify very low frequency (∼1 cm-1) normal modes for the protein pancreatic trypsin inhibitor. A simplified model for the protein is used, for which each residue is represented by a single interaction center. The quasi-harmonic force constants of the virtual internal coordinates are evaluated and the normal-mode frequencies and eigenvectors are obtained. Conformations corresponding to distortions along selected low-frequency modes are analyzed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230610
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  • 122
    Electronic Resource
    Electronic Resource
    Temperature dependence of the dynamic light scattering of linear φ29 DNA: Implications for spontaneous opening of the double-helix (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1137-1137 
    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.360230613
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  • 123
    Electronic Resource
    Electronic Resource
    Contributions of synthetic polymers of amino acids to knowledge of immune response (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1141-1141 
    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.360230615
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    Interaction of poly(I)·poly(C) with trans-dichloro-diammine-platinum (II) (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1143-1143 
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    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.360230616
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    Analysis of the high- and low-spin soret bands of horse-heart metmyoglobin complexes (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1147-1167 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interest in the thermodynamics of the iron-binding site in hemoproteins has increased in recent years due to refinements in x-ray crystallographic studies of hemoproteins [see Deathage, J. F., Lee, R. S., Anderson, C. M. & Moffat, K. (1976) J. Mol. Biol. 104, 687-706; Heidner, E. J., Ladner, R. C. & Perutz, M. F. (1976) J. Mol. Biol. 104, 707-722; Deathage, J. F., Lee, R. S. & Moffat, K. (1976) J. Mol. Biol. 104, 723-728; Ladner, R. C., Heidner, E. J. & Perutz, M. F. (1976) J. Mol. Biol. 114, 385-414; Fermi, G. & Perutz, M. F. (1977) J. Mol. Biol. 114, 421-431; Takano, T. (1977) J. Mol. Biol. 110, 537-568 and 569-589], the synthesis and x-ray analysis of model heme compounds [see Scheidt, W. R. (1977) Acc. Chem. Res. 10, 339-345; Kastner, M. E., Scheidt, W. R., Mashino, T. & Reed, C. A. (1978) J. Am. Chem. Soc. 100, 666-667; Mashiko, T., Kastner, M. E., Spartalian, K., Scheidt, W. R. & Reed, C. A. (1978) J. Am. Chem. Soc. 100, 6354-6362; Hill, H. A. O., Skite, P. P., Buchler, J. W., Luchr, H., Tonn, M., Gregson, A. K. & Pellizer, G. (1979) Chem. Commun. 4, 151-152; and Scheidt, W. R., Cohen, I. A. & Kastner, M. E. (1979) Biochemistry 18, 3546-3556], and the numerous data on heme-protein interactions that account for the differences observed in ligand binding between the various species of animals. Numerous probes have been used and provide information about the structure and thermodynamics of the binding site, but no single probe can provide the complete picture [see Iizuka, T. & Yonetani, T. (1970) Adv. Biophys. 1, 157-182; Smith, D. W. & Williams, R. J. P. (1970) Struct. Bond. 7, 1-45; and Spiro, T. G. (1975) Biochim. Biophys. Acta 416, 169-189].
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230702
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    Conversion from a virtual-bond chain to a complete polypeptide backbone chain (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1207-1224 
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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: A method for generating a complete polypeptide backbone structure from a set of Cα coordinates is presented. Initial trial values of φ and ψ for a selected residue are chosen (essentially from an identification of the conformational region of the virtual-bond backbone, e.g., and α-helical region), and values of φ and ψ for the remaining residues (both towards the N- and C-terminus) are then computed, subject to the constraint that the chain have the same virtual-bond angles and virtual-bond dihedral angles as the given set of Cα coordinates. The conversion from Cα coordinates to full backbone dihedral angles (φ,ψ) involves the solution of a set of algebraic equations relating the virtual-bond angles and virtual-bond dihedral angles to standard peptide geometry and backbone dihedral angles. The procedure has been tested successfully on Cα coordinates taken from standard-geometry full-atom structures of bovine pancreatic trypsin inhibitor (BPTI). Some difficulty was encountered with error-sensitive residues, but on the whole the backbone generation was successful. Application of the method to Cα coordinates for BPTI derived from simplified model calculations (involving nonstandard geometry) showed that such coordinates may be inconsistent with the requirement that φPro be near -75°. In such a case, i.e., for residues for which the algebraic method failed, a leastsquares minimizer was then used in conjunction with the algebraic method; the mean-square deviation of the calculated Cα coordinates from the given ones was minimized by varying the backbone dihedral angles. Thus, these inconsistencies were circumvented and a full backbone structure whose Cα coordinates had an rms deviation of 0.26 Å from the given set of Cα coordinates was obtained.
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    URL: http://dx.doi.org/10.1002/bip.360230706
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    Conformation of P-form DNA (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1269-1281 
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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 P-Form of DNA has been studied by use of ir spectroscopy and electron microscopy (EM). The ir data show that the P-form has little or no hydrogen bonding, while the data from EM show that the P-form has a condensed tertiary structure. In earlier work, we demonstrated that the P-form is devoid of base stacking. When that information is combined with the new ir data, we conclude that the P-Form is denatured because it lacks any of the interactions associated with a normal secondary structure. This is in apparent contradiction to earlier work that showed that the P-form may be easily transformed back to a native state by adding water. However, the lack of secondary structure can be overcome by the presence of a collapsed tertiary state that does not allow non-hydrogen-bonded strands to separate. Thus, the complementary strands can renature quickly on addition of water. The collapse to a condensed tertiary structure occurs when roughly 90% of the charge on the DNA molecule is neutralized by counterion condensation, as calculated by the Manning polyelectrolyte theory, and is consistent with other collapsed DNA states in this respect. This structure explains all physical properties of the P-form that have been observed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230711
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    The effects of alkali-metal chlorides and of spermidine and spermine on the swelling pressures of DNA gels in the ultracentrifuge (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1307-1313 
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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 effects is solution of the alkali-metal chlorides on the gel-like phase of DNA formed in the ultracentrifuge cell have been studied. The polycations, spermidine and spermine, also were shown to affect strongly the swelling pressure of the DNA gel, with evidence for the destabilization of DNA in very dilute spermine, below 10-6 M, and for the collapse of DNA in both spermine and spermidine solutions above 10-6 M.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230714
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    Effect of cationic surfactants on the conformation and aggregation of poly(L-glutamic acid) (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1333-1346 
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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 effects of three cationic surfactants, dodecylammonium chloride (DAC), dodecyldimethylammonium chloride (DDAC), and dodecyldimethylammonium chloride (DTDAC), on the conformation of poly(L-glutamic acid) and at neutral pH were examined by CD. The maximum extent of the α-helix induction occurs for each surfactant when the mixing ration is about unity. Different effects specific to each surfactant, as described below, appear in the range of mixing ratios larger than that required for the maximum induction. In the case of DTAC, the α-helices disintegrate into random coils. In the case of DDAC, the aggregation of α-helices takes place eventually leading to precipitation. Solubilization of the precipitates occurs at high mixing ratios. The most complex behavior is seen in the case of DAC; aggregation of α-helices occurs only to a small extent and the formation of a small complex predominates over aggregation takes place again as DAC concentration increases further. Induction of the α-helix is favored by dilution at a constant mixing ratio but is suppressed by the addition of NaCl.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230717
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    Locally oscillatory motion of RNA helix derived from linear relationships of backbone torsion angles (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1169-1184 
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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: A linear relationship in each of the torsion angle pairs, α-β, β-∊, ∊-ζ, and α-γ, has been found by applying a statistical method based on the concept of circular variates to backbone torsion angle data of helical in yeast tTNAPhe. A series of helical dimer models generated with these relationships have been found to be stereochemically acceptable, and the models also indicate that the backbone unit in the RNA helix is geometrically capable of an oscillatory motion with the distance of about 3.4 Å between adjacent bases. The motion of the backbone unit is analogous to that of a helical spring. The adjacent bases, because of being attached to the backbone, oscillate in a manner similar to the oscillatory dimer model proposed by Davis and Tinoco [Davis, R. C. & Tinoco, I., Jr. (1968) Biopolymers 6, 223-242]. Here, the oscillation of the backbone unit in the RNA helix is discussed in terms of two geometrical quantities: the torsion (τ) and curvature (κ) of the helix. On these lines, a stereochemical model of RNA strand separation is proposed.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230703
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    The speed of sound in DNA (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1185-1192 
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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: We have used Brillouin scattering to determine the speed of sound in (and hence longitudinal modulus of) A- and B-DNA fibers. The speed of sound is very sensitive to the degree of hydration of the fibers, and measurements have to be made at laser powers below 5 mW to avoid local heating and dehydration. Under those conditions, we obtain sound speed perpendicular to the fiber axis of about 2.2 and 1.9 km/s in A- and B-DNA fibers, respectively. A-DNA fibers show a small anisotropy with sound speeds along the fiber axis higher by up to 10% B-DNA fibers appear to be isotropic.
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    URL: http://dx.doi.org/10.1002/bip.360230704
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    Interaction of metal ions with gastrointestinal hormones: Binding studies of Mg++ to biologically active analogs of little gastrin and minigastrin (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1225-1240 
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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 interaction of magnesium ions with Des-Trp1-Nle12-minigastrin I (Nle11-HG-13) and Nle115-little gastrin I (Nle15-HG-17) has been studied by CD and spectrophotometric techniques in trifluoroethanol. Spectrophotometric titrations using murexide as a metallochromic indicator showed that there are three binding sites for magnesium ions in Nle11-HG-13, with binding constants of the order of (6 ± 2) × 106, (1.7 ± 0.5) × 106, and (5.0 ± 0.5) × 105M-1. These figures have been independently confirmed by CD measurements in the far-uv in the presence of increasing amounts of magnesium ions. Elongation of the peptide chain from Nle11-HG-13 to Nle15-HG-17 does not provide any additional binding site for the metal ions. In both hormones, we have observed different responses in the near- and fur-uv CD properties with regard to added magnesium. The intensity of the CD bands in the aromatic region changes cooperatively with the ion/hormone molar ratio. These findings lead us to conclude that at the C-terminal, the biologically important sequence, -Trp-Nle-Asp-Phe-Nh2, is directly involved in the interaction with magnesium.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230707
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    Kinetics of irreversible dissociation for proteins bound cooperatively to DNA (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1249-1259 
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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: We consider the irreversible dissociation kinetics of proteins that bind cooperatively and nonspecifically to DNA. Our model consists of an infinitely long one-dimensional nucleic acid lattice on which are bound protein ligands. A set of adjacent bound proteins forms a cluster of length n. A protein molecule may dissociate from any site within the bound cluster, not only from the ends, as was assumed in a previous model of this process due to Lohman [(1983) Biopolymers 22, 1697-1713]. By considering this additional pathway, we present a more general treatment of the dissociation kinetics of cooperatively bound ligands. We show that dissociation from the (n-2) internal positions of an n-cluster is an important pathway when the initial fractional saturation of the lattice is close to unity and the co operatively is low. When the fractional saturation is initially equal to 1 and the co operatively is low, our model does not give the zero-order dissociation kinetics predicted by the Lohman model.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230709
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    Comments on the “ordinary-extraordinary phase transition” of poly(lysine) (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1637-1646 
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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 “ordinary-extraordinary phase transition” of poly(lysine), first reported by Lin et al. [(1978) Biopolymers 17, 1041-1064], has been reexamined as a function of the data collection interval (Δt) and scattering angle (θ). These data suggest that the relaxation domains “split” as the ionic strength is lowered through the transition region. In contrast, fluorescence photobleaching recovery data of Ware and coworkers (personal communication) indicate the tracer diffusion coefficient is not sensitive to the “ordinary-extraordinary phase transition.” The apparent discrepancy between these two techniques is here proposed to be due to small ion effects on both the dynamics and the scattering power of the polyelectrolytes.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230903
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    Counterion binding and hydration of hyaluronate and chondroitin in solution: An 17O, 23Na, and 25Mg nuclear-magnetic-relaxation study (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1683-1699 
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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: Nuclear magnetic relaxation rates of H217O, 23Na+, and 25Mg2+ have been measured in aqueous hyaluronate solutions. The dependence on solution pH of the relaxation rates has been investigated, as well as the competition behavior of Na+ with Ca2+ and Mg2+. H217O and 23Na+ relaxation rates in chondroitin and hyaluronate solutions have been compared in the interval, 2 ≲ pH ≲ 12.5. The ion binding of hyaluronate can be fully accounted for by Coulomb interactions, with no need to involve chemical specificity. The hydration is only slighly pH dependent, and is comparable in magnitude to hydration of synthetic polyelectrolytes and monosaccharides. Ion-binding and hydration properties of hyaluronate and chondroitin are quite similar, except at elevated pH. At alkaline pH, an increase in charge density with pH is seen in hyaluronate and, to a much lesser degree, in chondroitin, possibly due to the titration of hydroxy groups. H217O data indicate an alkali-induced transition in both glycosaminoglycans.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360230906
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    Dielectric properties of slightly hydrated collagen: Time-water content superposition analysis (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1725-1734 
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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 frequency dependences of the dielectric constant, ε′, and the loss factor, ε″, in collagen were measured at several water contents from 0.1 to 0.3 g/g collagen over a frequency range of 30 Hz to 100 kHz and at a temperature of 20°C. Remarkable dispersion was observed at the lower frequencies for higher water contents. According to accumulated results on the thermodynamic and structural investigations, the dispersion has some analogy to the surface conduction proposed by B. V. Hamon [(1953) Aust. J. Phys. 6, 304-315]. An empirical relation bewteen ε″ and frequency, f, ε″ ∝ fn, where 0 〈 n 〈 1, suggests that the dielectric and conductive properties of hydrated collagen are related to carrier jumps between neighboring sites. For the polarization mechanism of this dispersion, we supposed a model of the transfer of protons between absorbed water molecules, and found that the time-water content superposition procedure is applicable to slightly hydrated collagen. The results derived from the superposition procedure show that the water content, φ, is related to the conductivity, σ, or the dielectric loss factor by the following equations: σ (φ, f) = const. × φnm-1f1-n and ε″ (φ, f) = const. φnmf-n, respectively, where m is a constant independent of φ and f. These results agree with that derived by another treatment of the same data. The role of water molecules in the conduction and polarization in slightly hydrated collagen is considered to be not far from that assumed in the model.
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    URL: http://dx.doi.org/10.1002/bip.360230908
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    Thermodynamic stability of the ordered conformations of carrageenan polyelectrolytes (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1771-1794 
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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: Manning's counterion condensation theory has been applied to the temperature-induced conformational transition of κ- and ι-carrageenan in the solution and gel states. The formalism of the theory has been extended to transitions between conformations with charge densities below or across the counterion condensation threshold. Measurements of the dependence of the melting temperature on ionic strength, and of the enthalpy of melting, are interpreted with the theory as indicating that the conformational transition is intramolecular and that side-by-side dimerization of chains gives rise to the gel structure.
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    URL: http://dx.doi.org/10.1002/bip.360230911
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    Azobenzene-Containing polypeptides: Photoregulation of conformation in solution (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1423-1437 
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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: Photochromic polypeptides, with 16 to 56% azobenzene groups in the side chains, have been prepared by reaction of poly(L-glutamic acid) with p-aminozaobenzene, both in the presence of dicyclohexyl carbodiimide/N-hydroxybenzotriazole and of pivaloyl chloride. Analogous modification reactions carried out on poly(L-aspartic acid) were unsuccessful owing to the formation of N-succinimide rings. In trimethylphosphate, all the azopolypeptides exhibit the α-helix CD pattern. Irradiation produces the trans-to-cis isomerization of the azo side chains, but does not induce any variations of the backbone conformation. In water, the CD spectra indicate the presence of appreciable amounts of α helix in 16 and 21% mol azo-containing poly-(Lglutamates), while a β structure is present in a 36% mol azopolypeptide. Light produces conformational changes of the polypeptide conformation which are completely reversed in the dark. The extent and kind of photobehavior depend on the azo content and the pH value at which irradiation is carried out. The light-induced effects are discussed on the basis of the pH-induced order-disorder conformational transitions. In fact, the pK values and the transition curves of the dark-adapted samples were found to be different from those of the irradiated ones.
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    URL: http://dx.doi.org/10.1002/bip.360230723
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    Vibrational circular dichroism of polypeptides. II. Solution amide II and deuteration results (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1519-1532 
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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: Vibrational CD (VCD) of amide I and II vibrations of several α-helical polypeptides have been measured in solution. For the amide II as well as the amide I [previously published: Lal, B.B. & Nafie, L.A. (1982) Biopolymers 21, 2161] we find the VCD to be characteristic of the polypeptide secondary structure. Amide II bands of right-handed α helices were all found to have negative VCD and to have their maximum rotational strength for the parallel (low-energy) component. However, left-handed α helices formed from L-amino acids gave positive amide II bands at higher frequencies than found for the right-handed helices, indicating that the VCD was sensitive to the stereochemical difference. The amide-I VCD spectra of some deuterated right-handed α-helical polypeptides have a new negative feature to low frequency that does not reflect theoretical predictions but also appears to be stereochemically sensitive. Amide-II and amide-A VCD of a few deuterated polypeptides imply retention of the secondary-structure-dependent characteristics seen in the hydrogenated VCD.
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    URL: http://dx.doi.org/10.1002/bip.360230808
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    Vibrational circular dichroism of polypeptides. III. Film studies of several α-helical and β-sheet polypeptides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1533-1545 
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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: Vibrational CD (VCD) of amides A, I, and II vibrations of a variety of polypeptide films have been measured. VCD of films of α-helical and β-sheet structures are compared in the three regions. Reproducible spectra could only be obtained for thin films free of orientation dependence. The sign and band shape of the VCD of films are not always the same as that in solution. However, the magnitude of the observed VCD seems to correlate with the secondary structure such that α-helical molecules typically have much larger Δε/ε values than do β-sheet molecules. The possibility of interference by artifacts owing to light-scattering effects is discussed.
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    URL: http://dx.doi.org/10.1002/bip.360230809
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    Masthead (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984) 
    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.360230901
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    Structure determination of the adduct formed between the signal nucleotide diadenosine 5′, 5‴-P1, P4-tetraphosphate (Ap4A) and cis-[Pt(NH3)2Cl2] (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1623-1635 
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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: Diadenosine 5′,5‴-P1,P4-tetraphosphate (Ap4A), an intracellular regulatory nucleotide, has been found to react with the antitumor drug cis-diamminedichloroplatinum(II) and its aqua derivative to form a single complex. This complex has been purified by high-performance liquid chromatography and characterized by 1H-nmr and CD spectroscopy. In this complex, Ap4A takes a very particular conformation. It is an N7-N7 chelate of the metal with the two adenines in a head-to-head arrangement and an anti-anti conformation of the adenosines. Platinum chelation leads to a large decrease of the Ap4A conformational flexibility.
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    URL: http://dx.doi.org/10.1002/bip.360230902
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    Reversing-pulse electric birefringence of poly (γ-benzyl-L-glutamate). II. Field-strength dependence of steady-state and decay signals of well-fractionated samples (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1667-1681 
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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 electric field dependence (up to 21 kV/cm) of the steady-state and decay signals has been examined on the four well-fractionated samples of poly(γ-benzyl-L-glutamate), [Glu(OBzl)]n, in N,N-dimethylformamide at 535 nm and 20°C. Together with the data previously obtained from the reversing-pulse electric birefringence [Ueda, K., Nomura, M. & Yamaoka, K. (1983) Biopolymers 22, 2077-2090], the steady-state birefringence and field-free relaxation time were analyzed by a method that takes into account the polydispersity of the chain length. The weight-average chain length, (lw), permanent dipole moment, (μw), electric polarizability anisotropy, (Δαw), and the length-independent optical anisotropy factor were evaluated. The axial translation per residue was calculated for the [Glu(OBzl)]n helix, but the uncertainly involved in the weight-average molecular weights, determined from light scattering by different investigators, makes the determination of the exact conformation of [Glu(OBzl)]n difficult. The contribution of Δαw to electric field orientation was found to be significant, since Δαw was approximately proportional to lw. A linear relationship also exists between μw and lw, when the [Glu(OBzl)]n helix is shorter than about 1200 Å.
    Additional Material: 9 Ill.
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    Molecular theory of the helix-coil transition in polyamino acids. V. Explanation of the different conformational behavior of valine, isoleucine, and leucine in aqueous solution (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1961-1977 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Even though poly(L-valine) and poly(L-isoleucine) both contain residues that are branched at their β-carbon atoms, they exhibit a different behavior of their Zimm-Bragg helix-growth parameter s in aqueous solution. This quantity increases with temperature for poly(L-valine) but decreases for poly(L-isoleucine). The origin of this behavioral difference was examined by computing theoretical values of s versus temperature from interatomic interaction energies, taking solvent (hydrophobic and hydrophilic) effects into account. The calculated s versus temperature curves for both homopolymers are consistent with the observed experimental behavior. The two homopolymers behave differently because of differences in the change in the number of hydration-shell water molecules accompanying their helix-coil transitions. The larger isoleucine side chains are more crowded together in both the α-helical and coil forms than are those of valine. Therefore, there is a smaller change in hydration of the isoleucine side chains compared to that of the valine side chains in the helix-coil transition. By analyzing the effects of hydration on the s versus temperature curves, it is possible to account also for the experimental curve for poly(L-leucine), which exhibits an intermediate behavior between those for poly(L-valine) and poly(L-isoleucine).
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231012
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    Vibrational analysis of peptides, polypeptides, and proteins. XXIV. Conformation of poly(α-aminoisobutyric acid) (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2025-2065 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raman and polarized ir spectra have been obtained on built-up monomolecular films of poly(α-aminoisobutyric acid), and analyzed in the context of normal mode calculations on 310-, α-, and α′-helix conformations of this molecule. The average discrepancy between observed and calculated frequencies is significantly smaller for the 310-helix than for the other structures. This, together with the more satisfactory explanation of several special features of the spectra, indicates that this polypeptide adopts a 310-helix conformation in such thin films.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231016
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    Resonance Raman spectra of mononucleotides obtained with 266 and 213 nm ultraviolet radiation (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2067-2081 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Resonance Raman spectra of the nucleoside 5′-monophosphates UMP, CMP, AMP, and GMP have been obtained with 266- and 213-nm radiation, the fourth and fifth harmonics of a Nd:YAG laser. The 266-nm radiation is resonant with the states giving rise to the first absorption band of the bases. The resulting spectra are in agreement with those reported previously using similar wavelength excitation but are generally of better quality. The 213-nm radiation is resonant with those states giving rise to the second strong absorption band of the bases. The spectra obtained with this wavelength show several new features relative to the 266-nm spectra, including strong enhancement of modes of the pyrimidines with a character similar to the e2g ν8 mode of benzene, relative enhancement of ring modes at 1580 and 729 cm-1 in AMP, and strong enhancement of the 1670-cm-1 C = O mode of GMP. These enhancements are discussed in terms of previously reported preresonance behavior and predicted intensities based on CNDO bond-order changes and normal-mode calculations. The results of a preliminary study of the effect of the interaction of GMP with cis-dichlorodiammineplatinum(II) on the 213-nm resonance Raman spectrum is also discussed.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231017
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    DNA gelation in concentrated solutions (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2141-2155 
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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: Sonicated calf-thymus DNA (200 ± 30 base pairs) spontaneously forms viscoelastic gels over a wide range of concentration, temperature, and buffer conditions. Quasielastic light scattering (QLS) can be used to monitor this process, because the ratio of dynamic-to-static scattering intensity decreases dramatically as gelation occurs. Using QLS, we have explored the effects of DNA concentration and mono- and divalent cations on the thermal stability of DNA gels. We found that the gel-sol transition temperature (Tgel) varies linearly with [DNA] from 7.5 to 17 mg/mL. Both Na+ and Mg2+ strongly stabilize the gel state. The sharpness of the transition increases with increasing ionic and DNA concentrations. Analysis of the Na+-dependent gelation indicates that the process requires the association of one Na+ per 118 base pairs. Mg2+ effectively stabilizes the gel at concentrations 10-fold below those required for Na+. The unexpectedly large effect of Mg2+ suggests that ion-specific interactions may play an important role in determining gel stability.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231104
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  • 148
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    Large-amplitude bending motions in phenylalanine transfer RNA (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2173-2193 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy calculations on yeast tRNAPhe reveal several likely modes of intramolecular bending, including both hingelike motions (rotations about a discrete point) and distributed flexibility (deformations that bend a double-helical segment along a smooth curve). By combining these modes of motion, the molecule can be bent from the L-shaped crystallographic structure to two extremes. It can be straightened into a nearly linear conformation at an energy cost of about 50 kcal/mol, and it can be doubled over to a conformation where the anticodon and the amino acid acceptor terminus are separated by about 40 Å at an energy cost of less than 100 kcal/mol. A bending range of over 100° can be covered for 50 kcal/mol, and we estimate that this value could be cut in half with a minimization algorithm that produced optimum stereochemistry. These energies are comparable to those that would be associated with changes in solvation due to changes in surface area as the molecule bends, indicating that there are no major steric barriers to tRNA flexibility and that variations in solvent conditions and interactions with other molecules may produce large changes in the overall conformation of tRNA.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231106
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    Premelting and the hydrogen-exchange open state in synthetic RNA duplexes (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2099-2125 
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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: Here we attempt to relate equilibrium temperature-dependent spectral changes in two synthetic RNA homopolymer duplexes - poly(rA) · poly(rU) and poly(rI) · poly(rC) - to the conformational opening detected in stopped-flow hydrogen-deuterium exchange experiments on these molecules. We are concerned with changes in several spectral properties that occur well below onset of the thermally induced helix-coil “melting” transition in these systems. These are known as “premelting” transitions, and can be detected in uv CD spectra as well as in vibrational bands of the bases in the ir. Both CD and ir spectra exhibit isoelliptic or isosbestic points consistent with a well-defined two-state premelting process. Application of a least-squares analysis to two-state models for premelting using data from different bands in the CD and ir shows that the enthalpies are substantially greater than that of the hydrogen-exchange opening. Thus the hydrogen-exchange open state represents only one premelting reaction among several that lead to equilibrium changes in helix geometry or base vibrational modes. The latter include processes that occur on a rapid time scale, including potential base-pair openings not productive for the exchange reaction. It appears that the former, and not the hydrogen-exchange opening, dominates the premelting alterations monitored by ir and CD spectroscopy.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231102
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    Solvation effects on the 31P-nmr chemical shifts and infrared spectra of phosphate diesters (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2157-2172 
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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 effects of organic solvents on the 31P-mr chemical shifts of various phosphate diesters have been investigated in water and mixed-organic solvent systems. The addition of organic solvents to cyclic phosphates and to diethyl phosphate causes large upfield shifts of the phosphorus resonance which are attributed to solvent-induced changes in the local hydration of the phosphodiester group. This is consistent with the fact that there is an inverse correlation between the hydrogen-bond-donating ability of the solvents and the magnitude of the shifts they induce. Other possible interpretations, such as solvent-induced ion pairing and solvent-induced conformational changes, appear to be eliminated. Fourier-transform ir study of the cyclic nucletides reveals that there are also large solvent-induced shifts in the frequency of the antisymmetric OPO stretching frequency, and a comparison of the two types of measurements indicates that there is a linear correlation between shifts observed in the ir and in the 31P-nmr spectra. With UpU, the solvent-induced 31P-nmr shifts are ∼3 times smaller than those observed with the cyclic phosphates and the solvent-induced shift of the OPO band is reduced (factor of ∼1.7) as compared with the cyclic phosphates. With the single-stranded polynuclotides, poly(C) and poly(U), the solvent-induced shifts in both the nmr and ir are quite small (∼0.1 ppm and ∼1 cm-1). The very small solvent effects observed with poly(U) and poly(C) are attributed to a combination of steric effects and a polyelectrolyte effect which maintains a high density of counterions with waters of hydration in the vicinity of the charged backbone and makes the phosphates much less susceptible to solvent-induced changes in hydration.
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    URL: http://dx.doi.org/10.1002/bip.360231105
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    Conformation of cyclic analogs of enkephalin. II. Analogs containing a cystine bridge (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2325-2334 
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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: A systematic survey has been made, using molecular mechanics, of the conformation of the ring entity of the enkephalin analogs, [D-Cys2-L-Cys5]-enkephalinamide and [D-Cys2-D-Cys5]enkephalinamide. These molecules are considerably more flexible than the analog Tyr-cyclo(Nγ-D-A2bu-Gly-Phe-Leu-), but the favored conformations of all three are very similar. The results of these studies are compatible with a Gly3-Phe4 type II′ bend in the active conformation of enkephalin.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231114
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    Conformational transitions and geometry differences between low-energy conformers of N-acetyl-N′-methyl alanineamide: An ab initio study at the 4-21G level with gradient relaxed geometriesPaper 34 in the series “Ab Initio Studies of Structural Features Not Easily Amenable to Experiment.” (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2335-2347 
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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: Energy pathways between the αR, β′, C7eq, and β-regions of the conformational energy surface of N-acetyl-N′-methylalanyl amide were obtained by SCF ab initio calculations on the 4-21G level, with gradient geometry optimization at each point. The calculations indicate that no barrier exists at this computational level between αR and β′. The variation of geometry (bond distances and bond angles) with conformation is analyzed in detail, and the most important geometrical parameters that should be treated as variables in both empirical energy calculations and in the fitting of polypeptide chains in proteins by x-ray methods are identified. In addition to the φ,ψ correlation discussed previously for the helical state, a correlation of these dihedral angles in the β-region is described.
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    URL: http://dx.doi.org/10.1002/bip.360231115
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    Calorimetric study of 2U:1A three-stranded complexes formed between poly(U) and adenine dinucleotides: ApA and diastereoisomers of nonionic adenine dideoxyribonucleoside methyl phosphonate (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2361-2382 
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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: Melting parameters of 2U:1A complexes formed by polyuridylic acid [poly(U)] and three adenine dinucleotides, diribonucleoside monophosphonate ApA and diastereoisomers of dideoxyribonucleoside methyl phosphonate [(dApA)1 and (dApA)2], in 1M NaCl and at a number of dinucleotide concentrations were obtained from differential scanning microcalorimetric data and interpreted in terms of the theory of helix-coil equilibrium in oligonucleotide-polynucleotide systems. The apparent binding constant, 1/cm, at 39°C and melting temperatures, Tm, at 1 × 10-3 M dinucleotide concentration indicate the following order of thermodynamic stability of the complexes: 2 poly(U) · (dApA)2 (2.27 × 103M-1, 44.2°C) 〉 2 poly(U) · (dApA)1 (9.9 × 102M1, 39.2°C) 〉 2 poly(U) · (ApA) (5.9 × 102M-1, 35.8°C). Corresponding calorimetric enthalpies of melting, ΔHm: 13.5, 12.7, and 12.8 kcal/mol (UUA base triplets) were found to be considerably lower than the van't Hoff enthalpies, ΔHapp: 29.4, 16.2, and 16.2 kcal/mol, respectively, evaluated from the dependence of the melting temperatures on dinucleotide concentration. Self-association of dinucleotides and their simultaneous binding as monomers, dimers, and higher-order associated species is suggested as the most probable cause of the differences between ΔHm and ΔHapp values. The differences in thermodynamic properties of the complexes formed by (dApA)1 and (dApA)2 diastereoisomers are discussed in connection with their known conformational properties. The higher and essentially enthalpic stability of the 2 poly(U) · (dApA)2 complex correlates with a lower degree of intramolecular stacking of the (dApA)2 isomer. The hydrophobically enhanced strong self-association of the latter greatly influences the thermodynamics of its complex formation with poly(U) and results in ΔHapp/ΔHm = 2.3.
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    URL: http://dx.doi.org/10.1002/bip.360231117
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    Differential electrostatic stabilization of A-, B-, and Z-forms of DNA (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2743-2759 
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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 static accessibility discrete charge algorithm for protein charge interactions is extended to the case of linear polyelectrolytes. In this model, the effective dielectric value between surface charge sites depends predominantly on the solvent ionic strength and the solvent accessibilities of the charge sites. This treatment accounts for the phenomena of specific ion binding in the context of a general electrostatic effect [Matthew and Richards (1982) Biochemistry 21, 4989]. Specific ion sites are determined by locating areas of high electrostatic potential at the solvent interface of the macromolecule. At a given ionic strength the calculated potential at a site is taken to describe a binding constant and therefore the ion site occupancy. For a 20-base-pair fragment of B-DNA, net charge of -40, 16 ion sites are indicated in the minor groove. The partial occupancy of each site increases from 0.2 to 0.5 as the ionic strength is increased from 0.01 to 0.50. Over the same range of ionic strength, the electrostatic free energy of this charge array is calculated to change from +0.6 to -0.05 kcal/bp. Parallel behavior is predicted for A- and Z-DNA charge geometries. The most stable configuration, based on electrostatic criteria, at high ionic strength (I = 0.1-0.5) is that of Z-DNA. In this range, the ratio of “bound” sodium to phosphate is predicted to be less than 0.4.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231205
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    Role of proline … proline interactions in the packing of collagenlike poly(tripeptide) triple helices (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2781-2799 
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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: Conformational energy computations were carried out on the packing of two identical collagenlike poly(tripeptide) triple helices in order to determine the energetics of favorable packing arrangements as a function of composition and chain length. The triple helices considered were [CH3CO-(Gly-Pro-Pro)nt-NHCH3]3 and [CH3CO-(Gly-Pro-Ala)nt-NHCH3]3, with nt = 3, 4, and 5. The packing arrangements were characterized in terms of their intermolecular energies and orientation angles Ω0 of the axes of the two triple helices. For short triple helices (nt = 3 or 4), many low-energy orientations, with a wide range of values of Ω0, can occur. When the triple helices are longer (nt = 5), the only low-energy packing arrangements of two poly(Gly-Pro-Pro) triple helices are those with a nearly parallel orientation of the two helix axes, with Ω0 ≈ -10°. This result accounts for the observed parallel (rather than antiparallel) arrangement of collagen molecules in microfibril assembly and stands in contrast to the preferred antiparallel arrangement of a pair of α-helices. Since the preference for a parallel arrangement of these collagenlike triple helices is less pronounced in the case of poly(Gly-Pro-Ala), it appears that this preference is a consequence of the frequent presence of imino acids in position Y of the Gly-X-Y repeating triplet. In poly(Gly-Pro-Ala), most of the low-energy packing arrangements are parallel, but a few arrangements with low energies and high values of |Ω0| occur. These packing arrangements have a high energy, however, when Pro is substituted for Ala, and thus they are not accessible for collagen with natural amino (imino) acid sequences. The computations reported here account for some of the characteristic features of collagen packing in terms of the local interaction energies of a pair of triple helices.
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    URL: http://dx.doi.org/10.1002/bip.360231207
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    Low-frequency dynamics of solid poly(L-alanine) from Raman spectroscopy (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 2891-2899 
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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: Raman modes from amorphous α-helical poly(L-alanine) in the low-frequency region 〈 150 cm-1 have been observed and assignments and values compared with mode-analysis calculations. The temperature dependence of the complete Raman spectrum of α-poly(L-Ala) is also reported.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360231213
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    A monte-carlo estimate of DNA loop formation (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 601-605 
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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 ends of rather short double-helical DNA segments (approximately two persistence lengths) can be enzymatically joined to form closed circles. Such covalent closure into circles is a measure of the likelihood of the two ends of the DNA coming into close contact. There is a length of DNA for which loop formation is most likely to occur. We have determined the chain-length dependence of loop formation for stiff chains using computer-generated chains of cylinders. The distribution from which the values for the angles between cylinders were chosen relates the chain parameters to a given chain persistence. Our results are compared with those of other theories, including a statistical wormlike chain model, and with the experimental measurements for ring closure of DNA restriction fragments.
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    URL: http://dx.doi.org/10.1002/bip.360230313
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    Masthead (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984) 
    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.360230401
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    Intercalation of cationic dyes in the DNA double helix: Introductory theory (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 629-645 
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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 effect of salt on the intercalation of acridine dyes and DNA is rather well explained by the Gouy-Chapman double-layer theory as applied to a cylinder model of the DNA-dye complex. The free energy of transfer of a dye ion from the bulk solution to the complex is divided into several parts, one of which, ΔF0, accounts for the short-range, nonelectrostatic interactions. The assumption that ΔF0 should not depend on the amount of dye in the complex leads to an internal dielectric constant of the cylinder of about Di = 7. The scatter in ΔF0 values, as calculated from individual experimental points, is of order 0.5 kT per dye ion. This scatter is large enough to mask possible effects of heterogeneity in DNA sequences. The calculations are made for a long cylinder with radius 10 Å, with the DNA phosphate charges smeared uniformly at the surface, a uniform spacing of dye charges at the cylinder axis, and a length of b = 3.37 Å per base pair. Each intercalated dye ion also adds a length b to the total length of the cylinder. The salt-dependent part of the electric free energy of intercalation, ΔF1, is tabulated for complexes with r = 0-0.24 dye ions per DNA phosphate in 0.002-0.2M monovalent salt and dye solutions.
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    URL: http://dx.doi.org/10.1002/bip.360230405
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    Proton polarizability of poly(L-tyrosine)-hydrogen phosphate hydrogen bonds as a function of alkali cations (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 695-705 
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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: We studied films of poly(L-tyrosine) with hydrogen phosphate (residue/phosphate, 1:1) by ir spectroscopy. The influences of the alkali cations (Li+, Na+, K+) and of the degree of hydration were clarified. If Li+ ions are present, the OH⃛-OP hydrogen bonds formed in the dried films between the tyrosine OH groups and hydrogen phosphate are asymmetrical. The formation of hydrogen phosphate-hydrogen phosphate hydrogen bonds is prevented by the presence of the Li+ ions. With an increase in the degree of hydration, the tyrosine-phosphate bonds are not broken but become slightly stronger. Completely different behaviour is found if K+ ions are present. In dry films, the OH⃛-OP ⇌ O-⃛HOP hydrogen bonds formed between tyrosine and hydrogen phosphate show large proton polarizability. The tyrosine proton has a noticeable residence time at the acceptor O atom of the phosphate. The difference in the behaviour of the system with K+ ions when compared to the system with Li+ ions can be explained, since the hydrogen acceptor O atom of phosphate ions is more negatively charged due to the weaker influence of the K+ ions. Furthermore, POH⃛-OP hydrogen bonds between hydrogen phosphate molecules are formed. With an increase in the degree of hydration, the tyrosine-hydrogen phosphate hydrogen bonds are broken, all tyrosine protons are found at the tyrosine residues, and the -PO3- groupings are in a symmetrical environment, indicating that the K+ ions are removed from these groupings. If the degree of hydration increases further, hydrogen-bonded systems such as hydrogen phosphate-water-hydrogen phosphate are formed that show large proton polarizability due to collective proton motion. When Na+ ions are present, the OH⃛-OP ⇌ O-⃛HOP hydrogen bonds formed in dry films still show proton polarizability, but the residence time of the tyrosine proton at the phosphate is very short.
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    URL: http://dx.doi.org/10.1002/bip.360230409
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    Mechanism of gel formation in κ-carrageenan (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 735-745 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a general view of κ-carrageenan gelation and some new experimental results concerning their behavior in the presence of Na+, K+, or Rb+ counterions in semidilute concentration. The gelation mechanism is based on the aggregation of helical dimers.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230412
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    Masthead (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984) 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560401
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  • 163
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    Aufgabengerechte Informationssammlung für die VerfahrensentwicklungPoster auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 272-278 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Information system for process development. An essential requirement for successful process development is the availability of relevant specialist information. Structuring the necessary activities by the techniques of systems engineering during the course of process development can provide detailed knowledge of the information required. However, comparison of available supply and demand shows that an essential part of the information, i.e. the solutions of unit operations and the accompanying equipment, have not hitherto been collected in systematic information systems. There fore principles are developed for the creation of information systems for process development and are demonstrated by the example of a „solution catalogue“ for filter equipments for the solid/fluid separation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560403
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  • 164
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    Neue konstruktive und prozeßtechnische Konzepte für die Wasserstoff-Gewinnung durch ElektrolyseVortrag auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 265-272 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New design and process engineering concepts for production of hydrogen by electrolysis. Electrolytic production of hydrogen has attracted particular interest in connection with expansion of nuclear generating capacity in France, Belgium, Canada, and Japan as a means of balancing load, and for developing countries with hitherto untapped hydroenergy resources it provides a means of supplying fertilizers with any need for oil imports. However, the present state of the art of water electrolysis leads to excessively high production costs owing to excessively high investment costs and to high an energy consumption, far above the thermodynamically calculated energy requirements: reduction of production costs will require satisfaction of opposing demands for raising the space-time yield of electrolyzers by increased current density while simultaneously lowering the energy consumption by reducing the cell potential. This contribution describes measures intended to save 20 to 30% in energy requirements; the production costs will fall by about 20 to 25%.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560402
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  • 165
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    Einfluß der Wandreibung auf die Dimensionierung von Bunkern  -  Verfahrenstechnische und statische GesichtspunkteVortrag auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 291-298 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Influence of wall friction on the design of silos - Aspects of process technology and statics. Mass flow and funnel flow are distinguished when considering the discharge of stored bulk solids. In order to cause mass flow to occur, i. e. the complete bunker filling is in motion, hopper walls need to be steep. Conditions close to the outlet are decisive, a large value of wall friction requiring steep hopper walls. For a safe design of bunker walls with respect to mechanical strength, DIN 1055, part 6 is commonly applied; it is currently being revised. From this regulation a strong influence of the angle of wall friction can be inferred, small values of the angle being associated with high horizontal pressures. In case the angle of wall friction depends on pressure and other parameters and safety factors are included there may be a considerable difference between the angle used by a process engineer and by a civil engineer.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560406
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  • 166
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    Einsatzbereich des Werkstoffes Glas in der AnlagentechnikVortrag auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 299-305 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Scope of glass as material of construction in plant engineering. In conjunction with PTFE as sealing material, borosilicate glass is nowadays recognized as a material for plant construction. A complete modular system of individual components with suitable connecting pieces is available. Moreover, a variety of equipment has been developed for accomplishing various processes while paying due attention to the special material properties of the material glass. In combination with other materials, primarily in the field of heat exchangers and evaporators, numerous processes are now conducted without any difficulty in glass plant. In this range of processes, a special place is assumed by those which urgently require glass for corrosion reasons, such as chlorination or bromination reactions or concentration of acids, because specialized know-how is sometimes required.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560407
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  • 167
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    Biologische AbluftreinigungVortrag auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 279-286 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biological purification of exhaust gases. The biological purification of exhaust typically employs microorganisms to transform undesired components, particularly those with pronounced odours into innocuous products. Since the activity of these organisms is localized in water, the odiferous substances must be transferred from the air to water. Oxygen must also be supplied to the water for product transformation. Large scale plant for biological purification of waste air from agricultural and industrial operations were introduced in Europe in the early 1960's. Since then this new technology has undergone remarkable developments. The principal plant types are biofilters, dripping units, and bioscrubbing units. In compost production and agriculture there is a current preference for biofilters and drip units, while biofilters and bioscrubbers are preferred in industry. Such plant already largely satisfy demands on purification performance and reliability. Further development in the direction of even higher performance and more compact plant is expected.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560404
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  • 168
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    Ullmanns Encyklopädie der technischen Chemie, Bd. 23: Textilhilfsmittel bis Vulkanfiber. Herausgeg. von E. Bartholomé, E. Biekert, H. Hellman, H. Leyd̊, W. M. Weigertd̊ und E. Weise. Verlag Chemie, Weinheim - Deerfield Beach - Basel 1983. 4. neubearb. u. erweit. Aufl., XV, 750 S., 274 Abb., 212 Tab., Halbleder, DM 545,-. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 305-305 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560408
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  • 169
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    Behandlung sowie Beseitigung der bei Lagerung und Verladung brennbarer Flüssigkeiten entstehenden DämpfeVortrag von H.-J. Schwefer auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 286-291 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Handling and removal of vapors generated on storage and loading of inflammable liquids. On storage and loading of liquid mineral oil products of high vapor pressure - e.g. gasoline and aromatic hydrocarbons - significant quantities of hydrocarbons will be lost. Mixtures with air can be inflammable. The limits of flammability of the three-component mixture of burning gas, oxidizer, and inert gas can be described in a diagram. The occurrence of inflammable mixtures in recovery and combustion plants can be reduced by appropriate measures. The hydrocarbon content in waste gases of recovery plants can be reduced to few grams per cubic meter. The limits for emissions defined in the „Technische Anleitung zur Reinhaltung der Luft“ (TA Luft) generally can only reached by thermal oxidation. Two plants are presented, in which vapors of mineral oil products are handled and combusted.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560405
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  • 170
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    Farbelimination in kommunalen Kläranlagen (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 310-312 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560411
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  • 171
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    Entfernen von Reinigungs- und Desinfektionsmitteln aus Rohren und PlattenwärmeaustauschernVortrag von E. A. Plett auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 306-308 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560409
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  • 172
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    Ein Beitrag zum Stofftransport in einem DoppelschneckenkneterVortrag auf dem Jahrestreffen der Verfahrens-Ingenieure, 28. bis 30. Sept. 1983 in Nürnberg. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 317-317 
    Details
    ISSN: 0009-286X
    Keywords: Dispersionsmodell ; Doppelschneckenkneter ; Konzentrationsverteilung ; Stofftransportmodell ; Tracer-Versuche ; Verweilzeitverteilung ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560413
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  • 173
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    Computergestützte Auswertung von Informationssammlungen in der Verfahrenstechnik (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 350-355 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computer-aided retrieval of data collections in chemical engineering. Data collections are an important tool for more efficient and economical engineering in the various fields of chemical process technology. The computer-aided utilization of available data collections has major advantages compared with manual processing. Computer-aided utilization can be based on the identification retrieval or rank retrieval method. The advantage of the rank retrieval method is that it provides a spectrum of solutions sorted by the degree of coincidence with the ideal solution. Rank retrieval can be integrated into larger program packages within an integrated computer system which supports the design of chemical plants.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560503
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  • 174
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    Schwingungserscheinungen in ChemieanlagenVortrag auf dem 13. Konstruktions-Symposium der DECHEMA „Schwingungsprobleme an chemischen Apparaten“, 7./8. Dez. 1983 in Frankfurt/M. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 343-350 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Vibrational phenomena in chemical plant. This article draws on the practical experience of the author to provide a survey of vibrational problems in chemical plant and of their sources. Even though it is not always possible to eliminate all potential sources of vibration by appropriate calculation and design measures during the planning stage, they can usually be quickly identified subsequently by suitable measuring techniques and countermeasures adopted.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560502
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  • 175
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    Verbrauchssenkung für großtechnische NH3-Anlagen durch Wärmerückgewinnung im Abhitzesystem (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 356-360 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Energy savings in industrial NH3 plant by heat recovery in the waste heat system. Minimization of energy consumption is nowadays a primary goal in the design of NH3 plant. In this context two aspects are particularly important: first, the process steps and their combination must be selected in such a way that the level of energy that has to be supplied to the plant is kept low from the very beginning; second, heat recovery must be optimized by the choice of process conditions and use of appropriate equipment. An industrial NH3 plant built according to these principles can operate at a consumption of as low as 29.5 GJ/t NH3, using proven processes and equipment. The first plant of this new generation with a capacity of 1120 t/d is currently under construction for Canadian Industries Ltd. (CIL) in Canada.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560504
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  • 176
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    Development and Control of Dust Explosions. Von J. Nagy und H. C. Verakis (Occupational Safety and Health Series, Vol. 8). Marcel Dekker, Inc., New York - Basel 1983. X, 279 S., zahlr. Abb. u. Tab., geb., SFr. 147,-. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 376-376 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560507
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  • 177
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    Sichere Druckwasserstoff-Logistik  -  Speicherung und Transport (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 370-376 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Safe handling of pressurized hydrogen - storage and transport. For the necessary future transition to non-fossile energy sources hydrogen is considered to be the ideal energy vector and will therefore assume ever-increasing importance. However, safe handling of the gas will be a basic requirement. A particular difficulty with pressurized hydrogen is its relative incompatibility with many materials which are commonly used for pressure vessels, either for transportation or for storage. The paper summarizes the major factors instrumental in hydrogen embrittlement. In particular, it stresses the role played by service conditions and by the quality of the internal surface of the vessels when exposed to the gas. On the basis of these findings a number of recommendations are given with respect to vessel design and operating measures in order to secure safe working with high pressure hydrogen gas.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560506
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  • 178
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    Einfluß von Betriebsparametern auf die Phasengrenzfläche in Blasensäulen-Abstromreaktoren (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 402-403 
    Details
    ISSN: 0009-286X
    Keywords: Blasensäulen ; Reaktionsapparate ; Abstromreaktoren ; Grenzfläche ; Mehrphasenströmung ; Betriebsparameter ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560517
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  • 179
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    EDV-Unterstützung der technischen Planung von Chemieanlagen (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 408-409 
    Details
    ISSN: 0009-286X
    Keywords: Anlagenplanung ; Anlagenbau ; Datenverarbeitung ; Computer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560520
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  • 180
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    Masthead (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984) 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560601
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  • 181
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    Maßnahmen zur Intensivierung des Wärmeübergangs (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 427-431 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Measures for intensifying heat transfer. Various approaches to the intensification of heat transfer have occupied engineers for many years. Many proposals failed to be accepted while others have been adopted in practice and have led to considerable savings in energy and materials. This article considers a number of topical developments in the improvement of convective heat transfer, heat transfer on evaporation, and heat transfer on condensation. The authors cite primarily review articles from among the extensive body of literature pertaining to this field of study.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560602
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  • 182
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    Phosphates and Phosphoric Acid. Raw Materials Technology, and Economics of the West Process. Von P. Becker. Marcel Dekker Inc., New York - Basel 1983. 1. Aufl., XV, 608 S., zahlr. Abb. u. Tab., geb., SFr. 253,-. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 431-431 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560603
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  • 183
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    Encyclopedia of Emulsion Technology, Vol. 1 : Basic Theory. Herausgeg. von P. Becher. Marcel Dekker, Inc., New York - Basel 1983. 1. Aufl., XIV, 744S., zahlr. Abb. u. Tab., geb., SFr 270,-. (1984)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 56 (1984), S. 463-463 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330560608
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  • 184
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    New electrophysical properties of polymer films and composites (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 6 (1984), S. 239-243 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The abrupt decrease of electric resistance of thin polymer dielectric films and metal-polymer compositions has been observed in the course of their uniaxial compression. At pressures exceeding the critical one the conductivity of some metal-polymer compositions has been found to be as high as that for such metals as titanium. The dependences of specimen resistance on thickness, temperature and uniaxial pressure strongly support a new mechanism fo polymer dielectric conductivity based on the pressure induced injection of current carriers from a metal to the dielectric conduction band.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.020061984118
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  • 185
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    Cinétique et mécanisme de la polymérisation de i'acrylamide initiée par le système réadox: Fe3+/complexe organique de Fe(III)/Na2S2O5 (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 429-439 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The initiation of acrylamide polymerisation in aqueous media with a redox system of the type Fe3+/organic complex of Fe(III)/Na2S2O2 was studied. Several carboxylated amines containing the iminodiacetate group as a basic structural unit were used as complex forming reagents. A direct relation between complex stability and initiation efficiency was found. The polymerisation kinetics were studied with the most effective intiating system. Several kinetic parameters were determined and an essential relationship between polymerisation behaviour, polymer characteristices and component ratio of the initiation and polymerisation system was found. An attempt was made to explain these results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850301
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  • 186
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    HPLC analysis of cyclo-oligoamides 6 and 66 (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 459-465 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new HPLC method for cyclo-oligoamides 6 and 66 separation is proposed. Using an RP 8 column and an H2O/CF3CH2OH mixtures, all cyclic amides up to the decamer were separated and quantitative results were obtained using an internal standard.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850304
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  • 187
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    Dynamic viscoelasticity of polyacetylene during oxidation (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1063-1068 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic viscoelasticity measurements at 90°C suggest an oxidation process for pristine polyacetylenes (PA's). For cis-rich PA, the oxidation can be divided into three regions: surface oxidation, bulk oxidation, and crosslinking. Crosslinking also occurs at the end of the surface oxidation period but does not occur in the bulk reaction period. For trans-rich PA, oxygen doping was complete after the first 15 min and occurred to a smaller extent than that of the cis-rich PA. The rate of reaction of trans PA chains with oxygen is slow in comparision to that of crosslinking by radical combination or addition reactions with the PA chains. In the case of trans PA the concentration of radical chains formed by reaction with oxygen retains a steady value after the initial period up to the end of oxidation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850517
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  • 188
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    Hydroperoxydation primaire de terpolymères d'éthylène/propylène/éthylidene-5 norbornène-2 (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1095-1104 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ethylene/propylene/5-ethylidene-2-norbornene terpolymers (1) are very sensitive to photooxidation. In the early stages, hydroperoxidation occurs specifically at the carbon atom in α-position to the ethylidene group. Isolated and hydrogen-bonded hydroperoxides can be detected by IR spectrophotometry at 3550 and 3380 cm-1, respectively. In post-thermolysis experiments at temperatures above 60°C the associated hydroperoxides were found to be less stable than the isolated hydroperoxides. Saturation of the ethylidene groups is concomitant with the decomposition of associated hydroperoxides, which are transformed thermally and photochemically into alcohols and cyclic saturated ketones. The lack of vinyl groups shows that hydroperoxidation proceeds only at the norbornene cycle.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850603
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  • 189
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    The influence of the valence state of titanium in MgCl2-supported titanium catalysts on olefin polymerization (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1133-1138 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relationships between the valence state of titanium in MgCl2-supported titanium catalysts and polymerization performances for ethylene and propylene were studied. When the titanium species of the supported titanium catalyst 1 was preliminarily reduced by treating it with AlEt3, the resulting catalyst system 2 had lost the activity for propylene polymerization completely. The catalyst activity for ethylene polymerization was found to be reduced to 20% of that of the original catalyst 1. In the AlEt3-pretreated catalyst 2 no Ti4+ is found and 80% of the total titanium is present as Ti2+. The catalyst system 2 plus AlEt3, however, does exhibit activity towards ethylene-propylene copolymerization, propylene insertion being possible if the end of the growing polymer chain is an ethylene unit. The titanium in the AlEt3-reduced catalyst 2 could be oxidized again by treatment with various agents. The oxidized catalysts 3, in conjunction with freshly added AlEt3 as cocatalyst, are active for propylene polymerization and show increased activity for ethylene polymerization in relation to the extent of oxidation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850606
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  • 190
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    The interaction of comonomers in the solution copolymerization of N, N-dimethyl-2-aminoethyl methacrylate with methacrylic acid (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1177-1186 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolymerization parameters of N,N-dimethyl-2-aminoethyl methacrylate (DAMA) with methacrylic acid (MAA) were determined at 50°C in benzene, dimethylformamide, and pyridine solutions. The Alfrey-Price constants e and Q of the two monomers were determined by copolymerization of DAMA and MAA with styrene in the same solvents. Using these constants, the copolymerization diagrams of the pair DAMA-MAA were calculated and compared with the experimentally determined ones. The mutual interaction between the comonomers is discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850611
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  • 191
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    Comments on G. Pruckmayr's criticisms on our paper “influence of water in the polymerization of tetrahydrofuran” (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1233-1234 
    Details
    ISSN: 0025-116X
    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/macp.1984.021850616
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  • 192
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    Beitrag zur Diskussion um die Morphologie von polyacetylen (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1265-1275 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We analysed by raster electron microscopy Luttinger-polyacetylene as a powder and as a film, both in pristine and (SbF6--electrochemically) doped form. The samples had been intensively washed with MeOH/HCl. One sample had, according to the results of transmission electron microscopy, fiber morphology. All samples show globules as primary structure arranged in clusters (in powder), mono-layers, or chains (in film) (which previously led to “fibril theory”). The primary spherical particles have diameters from 0,02-0,05 μm. The “fibril” sample has very small spherical primary particles, which may develop using low catalyst amounts. Our results support that the conductivity characteristics is governed by phenomena antiparallel to the chain direction (change-transfer-complexes).
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850619
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  • 193
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    Dilute solution properties of poly(methyl methacrylate) in acetonitrile + carbon tetrachloride mixtures (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 797-805 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Heterotactic poly(methyl methacrylate) (PMMA) is studied by light scattering and viscometry in the mixture acetonitrile + CCl4. Both liquids are poor solvents of PMMA, but their mixture is a very good solvent of this polymer. The total sorption potential of the coil is calculated from second virial coefficient and intrinsic viscosity results. Unperturbed dimensions, Mark-Houwink exponent, Schulz-Blaschke constant, and coil expansion factor are also determined. The enhanced total solvent sorption is larger in this mixture than in any other cosolvent system of PMMA thus far studied. This is due to the strong repulsive interactions between acetonitrile and CCl4. Such interactions also determine the inversion in preferential sorption that occurs close to equimolar composition. Acetonitrile can interact favourably with the ester group of PMMA and unfavourably with its methylene backbone. The role of such opposing interactions and of liquid order in acetonitrile are taken into account to discuss the results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850416
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  • 194
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    Modification au deuxième degré de polymères époxydés, 2.Partie 1: cf.1. Addition de l'acide benzoïque sur polyènes époxydés (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 839-846 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The addition of benzoic acid to the oxirane ring of epoxidized polymers of dienes is limited by side reactions which are promoted by increase of time, temperature, or epoxide concentration. Only high [Acid]/[Epoxide] ratios afford good yields of modification of the epoxidized polymers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850501
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  • 195
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    Enantioselective hydrolysis of dipeptide amino acid esters by di- and tripeptide-type L-histidine derivatives in a bilayer vesicular system (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 891-897 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enantioselective hydrolysis of dipeptide-type amino acid esters (Z-(L)-Ala-(L or D)-Ala-PNP (5a), Z-(L)-Ala-(L or D)-Leu-PNP (5b), and Z-(L)-Ala-(L or D)-Phe-PNP (5c)) by di- or tri-peptide nucleophiles (Z-(L)-Leu-(L)-His (2a), Z-(L)-Phe-(L)-His (2b), and Z-(L)-Leu-(L)-His (3)) in the bilayer vesicular aggregates of didodecyldimethylammonium bromide (6) resulted in the enantiomer rate ratio of LL/LD = 1, 1 to 18, the value of which was considerably higher than that (L/D = 1,0 to 4,6) in the hydrolysis of Z-(L or D)-Ala-PNP (4a), Z-(L or D)-Leu-PNP (4b), and Z-(L or D)-Phe-PNP (4c) by the identical vesicular system and that (L/D = 0,7 to 3,1) in the hydrolysis of the dipeptide substrates 5a - c by Z-(L)-His (1) and 6. The high enantioselectivity (LL/LD = 18) in the hydrolysis of 5c by the system of 2a and 6 was enhanced to be LL/LD = 36 by lowering the temperature from 25 to 10°C.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850505
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  • 196
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    Solution behaviour of hydrolysed polyacrylamides in 0,12 M NaClNCL Communication No. 3325 (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 957-967 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Six unfractionated samples of polyacrylamide were hydrolysed to varying extents. The partially hydrolysed polyacrylamides were investigated by viscosity, osmatic pressure and light scattering techniques in 0,12 M NaCl. The molecular weights of the hydrolysed polyacrylamides confirmed the absence of main chain degradation during hydrolysis. Intrinsic viscosities and dimensions increased with increasing extent of hydrolysis. On correlating the intrinisic viscosities with the extent of hydrolysis, a linear relationship between intrinsic viscosities and the square root of the extent of hydrolysis was obtained.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850510
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  • 197
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    Expansion coefficients of hydrolysed polyacrylamides from light scattering measurementsNCL Communication No. 3327. (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 983-989 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dimensions of partially hydrolysed polyacrylamides with varying molecular weights and extents of hydrolysis determined by light scattering were used to verify the relative applicability of the various macroion expansion theories. Expansions attributable solely to the presence of electrostatic charges were evaluated with references to the dimensions of the polyacrylamides used for hydrolysis. Total expansions and expansions due to long-range interactions were evaluated with reference to the estimated unperturbed dimensions of the strating polyacrylamides and the hydrolysed polyacrylamide samples, respectively. The expansion coefficients obtained from light scattering measurements were higher than those evaluated from intrinsic viscosities. The differences were maximum (30 - 100%) for the total expansion coefficients. Considering the variation of the Flory viscosity constant Φ with molecular weight and charge density, these differences were ascribed to the uncertainty in the applicability of the light scattering method for the determination of the dimensions of polyelectrolytes. However, the variation of the expansion coefficients with the extent of hydrolysis and molecular weight were similar to those of the expansion coefficients obtained from viscosity measurements. The total expansion coefficient was qualitatively in confirmity with the theory of Chien and Ishihara with reference to its dependence on charge density.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850512
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  • 198
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    Charakterisierung von disperisionen durch gekopplete H2O/D2O-ultrazentrifugenmessungenVortrag, gehalten am 4. März 1983 auf dem Makromolekularen Kolloquium in Freiburg/Breisgau.Herrn Professor H. -J. Cantow zum 60. Geburtstage gewidmet (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1025-1039 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The particle size distribution is one of the most important characteristics of aqueous polymer dispersions (diameter range 20 〈 D 〈 2000 nm). In addtion, the knowledge of the average particle density ρPM, the density distribution, and the particle refractive index nPM gives information about the chemical composition of dispersions. We report of an ultracentrifuge method which allows to determine all these values simultaneously in one single run. For that purpose the dispersion is measured simultaneously in 3 media of different density, i.e., in H2O, H2O/D2O (1:1, by wt.), and D2O. We use a preparative ultracentrifuge with an analystical rotor with trubidity optics, but instead of an 1-cell-rotor an 8-cells-rotor and a multiplexer are used. In order to measure very small and very large particles simultaneously in one single run we do not work at the usual constant number of rotor revolutions, but at a rate of revolutions increasing from 0 to 40000 min-1. The ultracentrifuge is connected with a computer on-line. The calculations are based on Stokes' law and Mie's light scattering theory for homogeneous isotropic spherical particles.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850515
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  • 199
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    Electronic Resource
    Stereochemistry in “living” coordination polymerization of propene initiated by vanadium-based catalytic systems (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1827-1833 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Soluble catalysts of V(acac)3 and AIR2X (R = C2H5, n-C3H7, i-C4H9; X = Cl, Br) initiate a living polymerization of propene at -78°C to afford monodisperse polymers of syndiotactic structure. The stereochemistry of the living polymerization was investigated by examining the structures of monomdisperse polypropylenes and of propylene-ethylene block copolymers by means of 13C NMR spectroscopy. It was found that syndiotactic- and regio-specificities of the soluble vanadium-based catalysts are not influenced by the sequence length of the living polymer chain.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850905
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  • 200
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    Etude du couplage chromatographie d'exclusion-diffusion de la lumière, 1. Dispositif expérimental et étude de polystyrènes «références» (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1145-1154 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The possibilities of coupling size exclusion chromatography with light scattering (GPC-DDL) are studied. The continuous light scattering detector is a modified (laser He-Ne excitation) classical light scattering apparatus Fica 42000, equipped with a flow cell of low capacity (120μl). With this cell, a detection of the scattered light is obtained only at an angle of 90°. The light scattering detector is coupled with a GPC apparatus (packed with 10 μm gel particles). The precision, reproducibility and limitation to obtain molecular weight distribution curves of “standard” linear polystyrenes are studied.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850608
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