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  • 1
    Digitale Medien
    Digitale Medien
    Viscometric study of the proteoglycan-hyaluronate (2:1) “dimer”: Minimum hyaluronate chain length (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 2501-2506 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360221203
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  • 2
    Digitale Medien
    Digitale Medien
    Strategy for trapping intermediates in the folding of ribonuclease and for using 1H-NMR to determine their structures (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 59-67 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The major unfolded form of ribonuclease A is known to show well-populated structural intermediates transiently during folding at 0°-10°C. We describe here how the exchange reaction between D2O and peptide NH protons can be used to trap folding intermediates. The protons protected from exchange during folding can be characterized by 1H-nmr after folding is complete. The feasibility of using 1H-nmr to resolve a set of protected peptide protons is demonstrated by using a specially prepared sample of ribonuclease S in D2O in which only the peptide protons of residues 7-14 are in the 1H-form. All eight of these protected peptide protons are H-bonded. Resonance assignments made on isolated peptides containing these residues have been used to identify the protected protons. Other sets of protected protons trapped in the 1H-form can also be isolated by differential exchange, using either ribonuclease A or S. Earlier model compound studies have indicated that H-bonded folding intermediates should be unstable in water unless stabilized by additional interactions. Nevertheless, peptides derived from ribonuclease A that contain residues 3-13 do show partial helix formation in water at low temperatures. We discuss the possibility that specific interactions between side chains can stabilize short α-helixes by nucleating the helix, and that specific interactions may also define the helix boundaries at early stages in folding.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360220111
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  • 3
    Digitale Medien
    Digitale Medien
    Influence of conformation on the fluorescence of tryptophan-containing peptides (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 2459-2476 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conformational-energy calculations of the zwitterionic forms of Trp, Gly-Trp, Pro-Trp, Phe-Trp, Trp-Gly, Trp-Phe, Trp-Trp, and Trp-Gly-Gly were done using an empirical energy program for peptides (ECEPP). The resulting low-energy conformations were analyzed for the presence of hydrogen bonds, the distances between carbonyl groups and the indole ring, the distances between the N-terminal amino group and the indole ring, the dihedral angle between the planes containing carbonyl groups and the indole ring, and for dipeptides with two aromatic side chains, the dihedral angle and distance between the planes of the aromatic rings. This information was correlated with literature data from x-ray crystallographic studies, fluorescence lifetime studies, and quantum-yield experiments; proposed models of intramolecular quenching are discussed in light of the peptide conformations.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360221111
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360230406
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  • 5
    Digitale Medien
    Digitale Medien
    The He(Iα) Photoelectron Spectra of the Perfluoroderivatives of Trisannelated Benzenes and Tetrakisannelated Cyclooctatetraenes (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 47-53 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The He(Iα) photoelectron (PE) spectra of tris(perfluorocyclobuta)benzene 4(F)3,3,4,4,7,7,8,8,11,11,12,12-Dodecafluorotetracyclo[8.2.0.02,5.06,9]dodeca-1,5,9-triene, tris(perfluorocyclopenta)benzene 5(F)1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-Octadecafluoro-2,3,4,5,6,7,8,9-octahydro-1H-trindene., tetrakis(perfluorocyclobuta)cyclooctatetraene 6(F)3,3,4,4,7,7,8,8,11,1l,l2,l2,l5,15,16,16-Hexadecafluoropentacyclo[12.2.0.02,5.06,9.010,13]hexadeca-1,5,9,13-tetraene., and of tetrakis(perfluorocyclopenta)cyclooctatetraene 7(F)1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-Tetracosafluoro-1,2,3,4,5,6,7,8,9,10,11,12-dodeca-hydrotetracyclopenta[a,c,e,g]cyclooctene. are reported. A tentative assignment of the PE spectra is derived by empirical correlation with those of relevant reference compounds. The results suggest that 6(F) retains the D4h-conformation in the gas phase, i.e. A conformation with a planar cyclooctatetraene ring, as observed in the crystal. All four compounds exhibit a sharp increase of their first ionization energies, relative to the corresponding parent hydrocarbons, due to the perfluoro effect.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19840670107
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  • 6
    Digitale Medien
    Digitale Medien
    Letters to the editor (1982)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 525-525 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690280327
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  • 7
    Digitale Medien
    Digitale Medien
    Letters to the editor (1982)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 175-175 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690280130
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  • 8
    Digitale Medien
    Digitale Medien
    Sequence dependence of the circular dichroism of synthetic double-stranded RNAs (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 1337-1382 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have synthesized and studied the CD spectra of five new double-stranded RNA polymers: poly[r(A-G)·r(C-U)], poly[r(A-U-C)·r(G-A-U)], poly[r(A-C-U)·r(A-G-U)], poly[r(A-A-C)·r(G-U-U)], and poly[r(A-C-C)·r(G-G-U)]. Together with previously published spectra of seven other RNA sequences, the spectra of these new sequences provide a library sufficient to approximate the spectra of all other RNA sequences by first-neighbor formulas and, in addition, give four spectra with which we may test the validity of first-neighbor approximations. (1) We find that the spectra of RNA sequence isomers are very different, but that the spectra essentially do obey first-neighbor relationships. (2) We have derived tentative first-neighbor assignments of negative bands at about 295 and 210 nm in the CD spectra. (3) A test of spectral independence shows that among the 12 polymer spectra there are at least seven significant independent spectral shapes, one less than the eight needed to give the most accurate spectral analysis of an unknown RNA sequence for its first-neighbor frequencies. (4) Spectra are calculated for RNAs of random base composition, approximating natural RNAs having complex sequences. (5) A T-matrix of spectral components assigned to the first-neighbor base pairs is derived from 10 of the spectra. This matrix allows an estimation of the CD spectrum of any other known RNA sequence or an analysis of the spectrum of an unknown sequence for its distribution of first-neighbor base-pair frequencies. (6) Test analyses of two of the synthetic polymers and of two natural RNAs set a probable limit on the accuracy of first-neighbor frequency determinations using this T-matrix. (7) Finally, we summarize in an appendix the melting temperatures for all the RNA and corresponding DNA sequences; it appears that the Tm values of both DNAs and RNAs approximately obey first-neighbor relationships.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1981.360200702
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  • 9
    Digitale Medien
    Digitale Medien
    On the limiting viscosity number of hyaluronate in potassium phosphate buffers between pH 6.5 and 8 (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 589-591 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360220202
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  • 10
    Digitale Medien
    Digitale Medien
    Monomolecular condensation of λ-DNA induced by cobalt hexammine (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1595-1620 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Measurements of static and dynamic light scattering have been used to distinguish between monomolecular DNA condensation and aggregation of condensed molecules. In low salt, using Co3+(NH3)6 as the condensing agent, and at λ-DNA concentrations below 0.2 μg/mL, the transition curves for monomolecular condensation and aggregation are well separated for times of 16 h. In these conditions, the intensity of scattered light (90°) and also the diffusion coefficient of the condensed DNA show reasonable values for monomolecular condensation that are independent of DNA concentration and also of Na+ Co3+(NH3)6 concentrations for which monomolecular condensation is complete. At higher Co3+(NH3)6 concentrations, which produce aggregation (as judged by the intensity of scattered light), the diffusion coefficient decreases sharply.The transition curve for monomolecular condensation is independent of DNA concentration but shows a hysteresis loop. The kinetics of condensation are slow in the forward direction and fast in the reverse direction, indicating that the actual transition curve is measured closely by reversal experiments. Aggregation is blocked kinetically in both the forward and reverse directions when Co3+(NH3)6 is the condensing agent at low Na+ concentrations. When spermine or spermidine is the condensing agent and observations are made at 16 h, it is not possible to separate the transition curves for monomolecular condensation and for aggregation in conditions that are successful with Co3+(NH3)6.Some interesting properties of monomolecular condensation are noted. (1) The transition is not a two-state reaction, as judged by measurements of the diffusion coefficient through the transition zone. (2) The transition for monomolecular condensation is diffuse. (3) The dimensions of the monomolecular condensates have been calculated from the translational diffusion coefficient for an assumed toroidal shape by the formula derived by Allison and coworkers [(1981) Biopolymers 20, 469-488]. These dimensions are in reasonable agreement with ones deduced from electron microscopy by Chattoraj and coworkers [(1978) J. Mol. Biol. 121, 327-337]. (4) The phase diagram relating the Na+ to the Co3+(NH3)6 concentrations needed for condensation has a slope of 0.6 in a log-log plot. According to numerical solutions of Manning's theory for the atmospheric binding of competing cations to DNA, this means that condensation occurs at a late stage in the replacement of Na+ by Co3+(NH3)6 around the DNA. The fraction of DNA phosphate charge neutralized at condensation is computed to be in the neighborhood of 0.9, as found by Wilson and Bloomfield [(1979) Biochemistry 18, 2192-2196], but to vary with the Na+ concentration.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360220612
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