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  • Chemistry  (17,129)
  • 1995-1999
  • 1980-1984
  • 1975-1979  (17,129)
  • 1925-1929
  • 1978  (5,931)
  • 1976  (5,694)
  • 1975  (5,504)
Collection
Keywords
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Years
  • 1995-1999
  • 1980-1984
  • 1975-1979  (17,129)
  • 1925-1929
Year
  • 101
    Electronic Resource
    Electronic Resource
    Sedimentation of generalized systems of interacting particles. I. Solution of systems of complete Lamm equations (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1685-1700 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A very general approach to the chemical equilibria between many interacting molecules during sedimentation (boundary, band, or active enzyme) taking into account boundary conditions, cell geometry, equilibrium constants, diffusion, enzyme kinetics, etc., is presented. Through a Fortran program, the method has been applied to two very simple but typical cases. With only minor adjustments, the method presented here for sedimentation studies can be extended to all sorts of problems in which “pools” of various species are interacting with each other.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140811
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  • 102
    Electronic Resource
    Electronic Resource
    Solid-state conformation of poly(O-benzyloxycarbonyl-L-tyrosine) (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1769-1772 
    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.1975.360140816
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  • 103
    Electronic Resource
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    Competitive cooperative bindings of a small ligand to a linear homopolymer. I. Extension of the Ising model to the case of two competitive interactions (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1717-1738 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The theoretical study of the cooperative binding of a small ligand to a linear homopolymer is extended to systems in which two different complexes can form. The binding isotherms are derived under the assumption that the cooperative interactions exist only between molecules belonging to the same type of binding mode and are limited to nearest neighbors (Ising model). The binding to a single-stranded chain is first considered and two extreme cases are studied: (1) the two complexes can form independently from each other (model of independent classes of binding sites); (2) only one class of binding site exists, each possessing two different states of complexation (three-state model).Binding to a double-helical chain is also considered. Three simple types of competition between the different modes of binding are distinguished. The corresponding models are defined as: (1) the model of independent classes of binding sites; (2) the model of monoexclusive interactions between the different kinds of complexes (the symmetric and asymmetric cases are both considered); (3) the model of biexclusive interactions. The comparative study of the different cases shows that the binding isotherms are very similar at large polymer-to-ligand concentration ratios, while they can be very different at low polymer-to-ligand ratios. This can be used to obtain information on the mechanism of dye binding to nucleic acids by equilibrium studies as shown in a subsequent paper.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140813
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  • 104
    Electronic Resource
    Electronic Resource
    Poly(L-valine). Conformational dependence on the degree of polymerization: Infrared studiesPublication 1009 of the Graduate Department of Biochemistry, Brandeis University. (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1755-1767 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The infrared spectra of poly(L-valine)'s with varying degrees of polymerization have been investigated, as well as copolymers of L-alanine and L-valine. The spectra of nujol mulls of various molecular-weight poly(L-valine)'s, isolated directly from the polymerization media, as well as spectra of these same samples after treatment with strong acid, are recorded. In the 700-250-cm-1 region, bands at 543 and 414 cm-1 are found to increase with increasing degree of polymerization in the nujol mulls, but are missing in the acid-treated samples. These bands are assigned to the L-valine residues with an β-helixlike local conformation. It is inferred that the polymerization proceeds initially in the β form, and after a critical degree of polymerization the chains adopt an appreciable amount of an α-helixlike local conformation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140815
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  • 105
    Electronic Resource
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    A semiempirical extension of polyelectrolyte theory to the treatment of oligoelectrolytes: Application to oligonucleotide helix-coil transitions (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 159-166 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of counterions with a suitably long, charged oligomer appears susceptible to treatment in the context of polyelectrolyte theory by the introduction of an end-effect parameter that reflects the reduced association of counterions with the terminal regions of the oligo-ion. Use of a physically reasonable value for the end-effect parameter provides excellent agreement between theory and the experimental data of Elson, Scheffler, and Baldwin [J. Mol. Biol. 54, 401-415 (1970)] on the dependences of melting temperature on salt concentration and chain length for a series of hairpin helices formed by d(TA) oligomers. The differences in behavior expected for hairpin, dimer, and oligomer-polymer helices are discussed. The salt dependence of the end-joining equilibrium investigated for λ DNA by Wang and Davidson [Cold Spring Harbor Symp. Quant. Biol. 33, 409-415 (1968)] is treated as an oligomer-polymer interconversion. The dependence of equilibrium constant for this reaction on counterion concentration is in good agreement with that predicted by theory for an end-region totalling 24 nucleotides, the known length of the λ ends.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170112
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  • 106
    Electronic Resource
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    Solvent denaturationThis paper is an expanded version of a paper dedicated to J. Sturtevant at the symposium held on March 25, 1977 in honor of his achievement of emeritus status at Yale University. (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1305-1322 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent denaturation is developed along thermodynamic lines rather than from multiple-binding theory. Almost all the relations derivable from site-binding theory have their counterparts in the thermodynamic formulation showing that the details of binding models may be sufficient but are not necessary for the general description of solvent denaturation. Equations are derived for the effect of denaturant concentration on stability at constant temperature and on tm. It is recommended that the thermodynamic treatment be used instead of binding models unless stoichiometric interactions are demonstrable experimentally.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170515
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  • 107
    Electronic Resource
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    Base stacking in A fluorescent dinucleoside monophosphate: εApεA (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1361-1372 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical properties of the 1,N6 - etheno derivative of ApA (εApεA) have been studied. Absorbance and CD measurements suggest that (1) neutral salts tend to unstack this molecule and (2) the stacking interaction is weaker than in ApA. εApεA is found to be quenched strongly with respect to the monomer. (εAMP); this quenching is solvent dependent (1M NaCl 〉 5M NaClo4〉40%glycerol) and increases with the ratio of temperature to viscosity (T/η) in each case. Fluorescence lifetime measurements also reveal a temperature- and solvent-dependent decay which is nonlinear on a semilog plot. In the presence of 95% glycerol, this decay return to linearity. These data have been considered from two points of view: (1) two-state pictures which are based on thermodynamic least-squares fit to quatum yield and CD curves, together with two exponential fits to the decay curves and (2) a dynamical model in which relatives fluorophore motion leads to deexcitation via intramolecular collision. A simple model of type (2) gives qualitative agreement with the observed behavior.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170519
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  • 108
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    Characterization of receptor affinity heterogeneity by scatchard plots (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1385-1386 
    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.1978.360170522
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  • 109
    Electronic Resource
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    Masthead (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978) 
    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.1978.360170601
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  • 110
    Electronic Resource
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    Reversible structural changes in a hydrophobic protein, elastin, as indicated by fluorescence probe analysis (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1811-1826 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fluorescent probe analysis of purified elastin using 1-anilinonaphthalene-8-sulfonate has been used to investigate reversible structural changes that accompany stretching of this rubberlike protein. There is a specific binding of 1-anilinonaphthalene-8-sulfonate to elastin with a single dye molecule attached per 74,000 molecular-weight protein subunit. When labeled elastin is stretched, the intensity of the 1-anilinonaphthalene-8-sulfonate fluorescence decreases reversibly, and this decrease appears to be linked to an increase in the environmental polarity in the immediate vicinity of the bound dye molecule. The results of experiments carried out in H2O and D2O indicate that this polarity change is due to an increase in the exposure of the 1-anilinonaphthalene-8-sulfonate to water as the hydrophobic interior of the protein subunit is unfolded during stretching. The data are consistent with the proposal that the elastin network is a two-phase system of hydrophobic protein globules surrounded by free solvent spaces.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140904
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  • 111
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    Competition between native and monoacetylated polymyxin for charged adsorption sites (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1513-1521 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The native antibiotic polymyxin B, carrying five positive charges, displaces the monoacetylated on from its adsorbed state at the interface between negatively charged lipid layers ans water. A simulation model for asdorption, governed by electrostatic forces, is presented. The model adequently representes the competitive adsorption kinetics and equilibria.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170610
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  • 112
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    Comparison of conformation and antimicrobial activity of synthetic analogs of gramicidin S: Stereochemical consideration of the role of D-phenylalanine in the antibiotic (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1549-1565 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to study the role of D-amino acid residues in keeping the stable β-sheet conformation and in the antimicrobial activity of gramicidin S (GS), the four analogs of GS containing D-Ala, L-Ala, Gly, and Aib (α-aminoisobutyric acid) in place of D-Phe were synthesized. D-Ala-and Gly-containing analogs showed antimicrobial activity, while those containing L-Ala and Aib showed no activity. Conformation of these analogs and their derivatives were studied by comparison of ORD and CD spectra and by slective methylation method. It is concluded that the biologically active analogs have β-sheet conformation while inactive analogs have a much different conformation from that of GS. This indicates that D-Ala-Pro and Gly-Pro sequences favor taking a β-bend form but L-Ala-Pro and Aib-Pro sequences do not because the presence of L-side methyl group on the α-carbon atom of LAla and Aib residues destabilizes the β-bend form. This would explain why the inactive analogs which take a different conformation from that of the active ones result in the loss of activity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170613
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  • 113
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    Dipole-dipole interaction and the relative stability of different types of aggregates of helical polypeptides (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 811-814 
    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.1978.360170321
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  • 114
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    Collagen fibrils and elastic fibers in rat-tail tendon: An electron microscopic investigation (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 843-855 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Earlier studies by the authors showed that the collagen fibrils in rat-tail tendon have a bi-modal distribution of fibril diameters from a time shortly after birth through to the onset of maturity at about 3-4 months. Present work has extended those observations for rats up to the age of 2 years. Histograms of the fibril diameter distributions for mature tail tendon and direct electron microscope observations show that the fibrils break down as the tendon ages. Further work on the constant diameter subfibrils of diameter 140 Å described previously, has confirmed that these are part of the elastic fibers present in tendon at all ages. It has been shown that there is relatively little variation in the collagen fibril diameter distribution as a function of the position of the specimen in the tail, and as the measured percentage of the area taken by the collagen fibrils present at any particular point. Estimation of the fibrillar collagen content of rat-tail tendon as a function of age indicates that it increases steadily from birth and reaches a maximum at the onset of maturity, beyond which the fibrillar collagen content appears to remain constant.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170404
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  • 115
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    Packaging of DNA in bacteriophage Heads: Some considerations on energetics (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 785-794 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have made quantitative estimates of some of the energetic factors to be considered in packaging of double-stranded DNA in virus particles. Numerical calculations were made using parameters appropriate for T4 bacteriophage. The unfavorable factors, and the Gibbs free energies per mole virus at 20°C associated with them, are bending, 1.5 × 103 kcal/mol; conformational restriction upon condensation, 5.1 × 102 kcal/mol; polyelectrolyte repulsion, 2.1 × 105kcal/mol; and melting or kinking, 6.9 × 103 kcal/mol. These must be counterbalanced in the assembled phage by noncovalent bonding interactions between protein subunits in the phage-head shell; by interactions between the DNA and polyvalent cations, especially putrescine and spermidine; nad perhaps by repulsive excluded volume and electrostatic interaction between the DNA and acidic polypeptides. Indeed, a rough estimate of the standard free energey of interaction between T4 DNA and the putrescine and spermidine contained in the head is --2.1 × 105 kcal/mol. In the absence of the other two sources of stabilization, each head protein subunit must contribute about 210 kcal/mol of binding energy.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170317
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  • 116
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    Extrinsic cotton effect and helix-coil transition in a DNA-polycation complex (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 815-815 
    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.1978.360170322
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  • 117
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    Application of thin film dialysis to the determination of equilibrium constants (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 837-842 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theoretical basis for thin-film dialysis involving binding between a ligand and nondialyzing species is presented. A general differential equation that applies to the case of equivalent, noninteracting sites is derived relating [A]F, [A]T, [P]T, and K. Numerical solutions to this equation are used to develop a series of escape curves corresponding to specific values of the parameters [P]T, [A]i, K, and k0. A general method for determining an equilibrium binding constant from thin-film dialysis data is given. A comparison of thin-film dialysis results predicted by this theory with literature data shows essential agreement.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170403
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  • 118
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    The electronic structure of cytosine, 5-azacytosine, and 6-azacytosine (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 887-896 
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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 normal and vacuum uv spectra of cytosine, 5-azacytosine, and 6-azacytosine thin layers were determined. The spectra were resolved into a series of Gaussian bands and the experimental band positions and oscillator strengths were compared with the calculated values. The calculations were carried out with the PPP-SCF-CI method. The agreement of the calculations with those of others and with the experiment is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170407
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  • 119
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    An electrostatic model for collagen fibrils. The interaction of reconstituted collagen with Ca++, Na+, and Cl- (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1439-1460 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for the electrostatic properties of hydrated collagen fibrils, based on the concept of a “penetrable” protein, has been evaluated through studies of collagen fibrils that had been chemically modified to change their electrostatic properties,. A value of 0.28 ± 0.07 ml/g was found for the intrafibrillar space sterically inaccessible to a molecule that had an equivalent spherical radius of 4.5 Å.The net intrinsic charge on reconstituted collagen is +14 mol/mol under physiological conditions, but decreases, at constant pH, with ionic strength. A value of 7.1 for the pK of the histidine and α-amino groups in reconstituted collagen was obtained through the application of the electrostatic model to this effect.The values obtained for calcium binding parameters for collagen fibrils, under solution conditions in which the nonspecific electrostatic properties of collagen fibrils were eliminated (3-5 M tetramethyl ammonium chloride), were in agreement with values obtained in 0.16 M NaCl solutions calculated through the use of the electrostatic theory. These are 0.73 ± 0.23 and 56.2 ± 12.3 sites per molecule with intrinsic association constants of 1101 ± 386 and 21.4 ± 5.2 M-1, respectively.The model also predicts that an average 4-mV potential difference exists between the reconstituted collagen fibrils and physiological solutions, and that collagen fibrils under such conditions have piezoelectriclike properties.The pattern of interaction of ions with collagen fibrils is such that an allosteric mechanism for the catalytic step in the mineralization of collagen is a possibility.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150802
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  • 120
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    Vibrational spectrum of the unordered polypeptide chain: A Raman study of feather keratin (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1513-1528 
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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 spectra of native and solubilized feather keratin have been obtained, and the amide I and amide III regions have been analyzed by band resolution techniques. The amide I region of the native form indicates that at least 64% of the protein has an antiparallel chain pleated sheet structure, the remainder being unordered. For the solubilized keratin all of the protein is in an unordered state. The amide III region is not as easily analyzed into component contributions. Normal vibration analyses on N-acetyl-L-alanine-N-methylamide support the conclusion that the amide III region is not as satisfactory as the amide I region in characterizing unordered structures. Even in the latter case caution must be used, since the observed amide I band is an average over the conformational distribution in the particular unordered system.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150807
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  • 121
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    The optical birefringence of DNA solutions induced by oscillatory electric and hydrodynamic fields (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1555-1572 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical birefringence induced in DNA solutions by both oscillating hydrodynamic fields (flow birefringence) and oscillating electric fields (Kerr effect) is measured over a wide frequency range. The observed frequency response of the birefrigence is compared with theories for rigid ellipsoidal particles and for Gaussian chains. DNA at 6 × 105 molecular weight is found to exhibit rigid particle hydrodynamic behavior, while DNA at 5 × 106 molecular weight behaves like a flexible chain. Characterization of the hydrodynamic relaxation spectra for the DNA's by oscillatory flow birefringence allows precise comparison between theory and the experimental Kerr effect response. The dielectric model for DNA contains both permanent and dispersionless induced dipole moments. The dielectric behavior of DNA has the character of a permanent dipole but with anomalous low-frequency dispersion in the Kerr effect. The existing theories do not adequately describe this dispersion. A fluctuation dipole mechanism with relaxation times comparable to those associated with the hydrodynamic motion could possibly demonstrate the observed polar behavior.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150810
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  • 122
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    The effects of isolated N-methylated residues on the conformational characteristics of polypeptides (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1615-1622 
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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 energies have been estimated for the tripeptide fragments L-Ala-N-methyl-L-Ala-L-Ala, L-Ala-L-Ala-N-methyl-L-Ala, L-Ala-Sar-L-Ala, and L-Ala-Gly-N-methyl-L-Ala. The peptide bonds connecting L-Ala and Gly with N-methyl-L-Ala and L-Ala with Sar were permitted to adopt the planar cis as well as the usual trans conformation. Contour maps of the conformational energies of the central residue in these tripeptide fragments are presented and compared to the conformational energy maps previously calculated for unmethylated L-Ala and Gly surrounded by residues which are also unmethylated. In generl it is observed that L-Ala and Gly residues that are either N-methylated in their conformational freedom relative to the same residues in an unmethylated polypeptide chain.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150814
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  • 123
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    Circular dichroism and structure of the complex of acridine orange with poly(L-glutamic acid) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1655-1667 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism and absorption spectra have been measured on solutions of acridine orange and poly(L-glutamic acid) mixed at two molar ratios of carboxyl group-to-dye, P/D 25 and 0.8, and at different pH's. Characteristic circular dichroism is induced at the absorption bands of acridine orange when the P/D is 25 and the solution is acidic. Another type of circular dichroism is manifest at neutral and alkaline pH when P/D is 0.8. For the induction of the former type of circular dichroism, a helical array of acridine-orange dimers bound to the α-helix is postulated, in which the dye molecular planes are almost perpendicular to the helical axis. Assuming the helical geometry and optical parameters, combined with the observed magnitude of transition electric moment, the rotatory strength of the complex is calculated to the zeroth order approximation, and the observed circular dichroism spectra have been reproduced.
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    Nmr studies of aqueous solutions of tetra and branched peptides. I. Sequence determination of amino-acid residues and the assignment of peptide hydrogen signals (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1643-1653 
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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: Sequential determination of glycyl residues (and in several cases different amino-acid residues) in tetra and branched peptides using the nmr technique is reported. The method is based on changes in the nmr spectra of (1) the peptide hydrogens of the different residues and (2) the methylene groups of the glycyl residues, as a result of increasing the rate of the base-catalyzed exchange reaction of the peptide hydrogens. Hence, the spectral changes are pH dependent. However, the exact pH dependence is a function of the location of the residue in the peptide molecule. Thus, it is possible to determine the sequence of the amino-acid residues by studying the changes in the spectra with pH.For peptide molecules of known sequences, the above method can be used for unequivocal assignment of the peptide hydrogen signals.
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    Induced circular dichroism of acridine orange bound to double-stranded RNA and transfer RNA (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1693-1699 
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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: The induced circular dichroism (CD) in the visible region of acridine orange bound to the double-stranded RNA from cytoplasmic polyhedrosis virus and to yeast tRNA has been measured as a function of RNA phosphate-to-dye ratio (P/D), under the conditions of 0.01 M Na+ at pH 7.0. The shape of the CD spectrum of acridine orange bound to the double-stranded RNA was quite different from the spectrum of the dye bound to DNA. The CD spectral features of acridine orange bound to the double-stranded regions in tRNA closely resembled those of the double-stranded RNA-dye complex, suggesting that the dyes bind similarly to the two RNA's. It was further found that the CD spectrum of the tRNA-dye complex at sufficiently high P/D ratios, which is assignable to monomeric, intercalated dye to the base-paired parts in tRNA, is also distinct from the corresponding spectrum of the DNA-dye complex.
    Additional Material: 4 Ill.
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    Dinucleoside monophosphates. I. Optical properties and conformation in solution with one base charged (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1755-1773 
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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 least squares analysis of the titration properties of several dinucleoside monophosphates enables calculation of the pK's for protonation. These pK's are used to resolve the spectral properties of dinucleoside monophosphates with one base charged from the apparent spectral properties of a dinucleoside monophosphate in aqueous solution. This method is applied to dinucleoside monophosphates containing adenosine and/or cytidine. Results of CD, nmr, and CD-temperature dependence measurements are presented. The results indicate that singly protonated dimers of these nucleosides stack as do their unprotonated analogs. It is suggested that this is true for all dimers with one base charged.
    Additional Material: 7 Ill.
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    An easy method for retrieving atomic coordinates from CPK space-filling molecular models (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1825-1833 
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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: Connectors for CPK space-filling molecular models have been supplemented with pointed steel wires (φ = 1.59 mm) of appropriate lengths and positions to represent atomic bonds. For illustration purposes, the polypeptide backbone of glucagon was equipped with such wire-core connectors and given a possible conformation. The molecular model was packed into a cubic box and, using a clinical instrument, X-ray films were taken from three orthogonal directions. Atomic coordinates on the films were then corrected to real-space coordinates.This method for retrieving atomic coordinates from space-filling models of modium-sized polypeptides is easy and can be done wih equipement available everywhere. Coordinates obtained in this way should be useful as starting points for energy minimization, for the calculation of frictional coefficients, and in attempts to solve crystal structures by X-ray diffraction, using molecular replacement methodology.
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    Viscosity/molecular-weight relationship of poly(α-L-glutamic acid) in water and in water/dioxane mixtures (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1857-1862 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    The dependence of the swelling of elastin on elongation, and its importance in fluorescence probe analysis (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1853-1856 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150919
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    Polypeptide modeles of collagen. Solution properties of (Gly-Pro-Sar)n and (Gly-Sar-Pro)n (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1877-1877 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1976.360150924
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    Threshold effects observed in conformation changes induced by electric fields (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1917-1928 
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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: Single-stranded polynucleotides are used as model systems for the investigation of conformational changes induced by electric fields. It is demonstrated that the single-strand helix-coil transition in poly(A), poly(dA), and poly(C) can be induced by application of high electric fields. The transition is measured by UV absorbance using polarized light at an angle of 54.8° with respect to the vector of the electric field and by electrodichroism. A linear increase of the absorbance, reflecting the helix-to-coil transition, is observed at increasing field strength. When ions are added to the polymer, electric fields do not induce conformation changes, unless a threshold value of the electric field strength E0 is exceeded. At field strengths above this threshold, the degree of transition is a linear function of the increase in field strength. The threshold values E0 show a linear increase with the logarithm of the ion concentration. Bivalent ions cause thresholds at much lower ion concentrations than mo-novalent ions. The shielding efficiency of ions is correlated to the binding affinity of these ions to the polymer.The conformation changes induced by the field and the existence of thresholds can be explained on the basis of dissociation field effects. Similar threshold effects may be expected for other macromolecules as well as for membrane structures and may be important in the regulation of bioelectricity.
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    The effect of changes in salt concentration and pH on the interaction between glycosaminoglycans and cationic polypeptides (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1965-1977 
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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: Circular dichroism (CD) spectroscopy has been used to investigate the effects of changes in salt concentration and pH on the interactions between basic polypeptides and connective tissue glycosaminoglycans in dilute aqueous solution. The polypeptides undergo conformation-directing interactions in the presence of glycosaminoglycans, which are subject to transitions as the ionic strength and pH are varied. For poly(L-lysine), the conformational change due to interaction breaks down as the ionic strength (monovalent ions) is increased. Based on the ionic strength at which disruption occurs, the glycosaminoglycans can be placed in order of increasing strength of interaction: chondroitin 6-sulfate, hyaluronic acid, chondroitin 4-sulfate, heparin, and dermatan sulfate. Prior to the conformational transition, scattering effects are observed, indicating the development of larger aggregates. Each glycosaminoglycan induces α-helicity for poly(L-arginine), which does not break down as the ionic strength is increased, indicating a stronger interaction for this polypeptide. The pH-induced transitions are in the pH range 2.5-3.8 and are probably related to deionization of carboxyl groups. For poly(L-lysine) the conformational effect is disrupted at low pH. For poly(L-arginine), the transitions are not complete, but appear to correspond to an increase in scattering.
    Additional Material: 6 Ill.
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    Synthesis and characterization of an ionizable polyhexapeptide collagen model (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2005-2024 
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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: Poly(Lys(HBr)-Gly-Pro-Pro-Gly-Pro) has been synthesized and studied by circular dichroism (CD) spectroscopy. It is apparently the first polyhexapeptide collagen model reported with an ionizable side chain. The monomer (ε-(p-nitrobenzyloxycarbonyl)-Lys-Gly-Pro-Pro-Gly-Pro-p-nitrophenyl-ester) was prepared by a stepwise strategy employing active esters. Polymerization in N,N-dimethyl formamide, followed by removal of the Lys side chain protection with HBr/acetic acid, gave a polydisperse product. Fractionation was accomplished by gel filtration chromatography. The polydisperse material had a molecular weight (Mr = 5-17,000). High molecular weight fractions from triple helices under concentrated conditions at 2°C. The triple helical structure gives a CD pattern very similar to that of collagen and its triple helical analogs. However, unlike collagen, the polyhexapeptide undergoes spontaneous dissociation at temperatures substantially below the melting temperature from a triple helical form to single chains. This process is promoted at low concentrations, high temperature, neutral pH, and low molecular weight, and is apparently due, in large part, to unfavorable ionic side-chain interactions. In addition to this relatively slow “ionic” dissociation the triple helical polypeptide may be thermally dissociated in a manner similar to collagen. The thermal denaturation is a relatively fast process compared with ionic dissociation.A high molecular weight fraction (3 × Mr = 48,000) was found to melt at 42°C at neutral pH but increased to 54°C at pH 12 where the lysyl side chains are predominantly deprotonated. Furthermore, reconstitution of triple helices appeared to be more readily achieved at high pH. Thus it is concluded that ionic repulsion between side chains causes destabilization of the triple helix and hinders reconstitution.
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    Étude thermodynamique de la transition hélice-pelote statistique en solvants mixtes de différents esters de l'acide poly(L-glutamique) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2059-2079 
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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: Helix-coil transition of poly(γ-methyl-L-glutamate), poly(γ-ethyl-L-glutamate), and poly(γ-benzyl-L-glutamate) has been studied in mixed solvents by calorimetry, polarimetry, and viscometry. The experimental data have allowed the evaluation of solvation enthalpy Δhb, equilibrium constant K for hydrogen bond formation between the active solvent component and CO and NH groups, and the cooperativity parameter σ. The conformational transition of polypeptides in solution in a mixed solvent containing enough active solvent to maintain the coiled conformation has been produced by dilution with the helix-supporting solvent for the measurements of enthalpy of transition Δhs. The average value for Δhs is 3550 ± 300 J/mol and is practically independent of the nature of the side chain for the dichloroacetic acid-ethylene dichloride solvent pair at 25°C. A noticeable concentration effect exists in the case of poly(γ-benzyl-L-glutamate). The helical conformation is less stable for poly(γ-ethyl-L-glutamate), and this is explained by a steric effect hindering the access of dichloroacetic acid to side chains. Constant K has been calculated using polarimetric data and also from values of Δhs obtained at different temperatures using the Bixon and Lifson theory on the one hand and that of Sayama and coworkers on the other hand. Values of σ for poly(γ-ethyl-L-glutamate) have been calculated according to both theories mentioned, and the results show that the two sets of values are quite similar. The constant σ depends on the nature of the active solvent, on temperature, and on the binary-solvent composition. These conclusions are confirmed by viscometric results. Values of Δhb calculated from constant K are 5230 J/mol when Bixon and Lifson theory is used and 5569 J/mol when the theory at Sayama and coworkers is used. In both cases the value for Δhb is much lower than that of an intramolecular hydrogen bond. Experimental results suggest that the solvation mechanism would proceed in a manner so that mechanisms described in both theories are involved.
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    Solvent accessibilities in the dimeric subunits of RNA and DNA (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2503-2518 
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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: To obtain information on the solvent-solute interactions in the dinucleoside monophosphates pertaining to the dimeric subunits of RNA and DNA, we have computed the accessibility of a water molecule to the oxygen atoms of the subunits following the method of Lee and Richards [J. Mol. Biol. 55, 379-400 (1971)]. The solute molecules (dimeric unit) is represented by a set of interlocking spheres of appropriate van der Waals radii assigned to each atom, a solvent (water) molecule is rolled along the envelope of the van der Waals surface, and the total surface accessible to the solvent molecule - and hence the solvent accessibility of various atoms of the solute molecule for different conformations - are computed. From the calculated atomic accessibilities, solvation maps in the (ω′,ω) space have been constructed, keeping ψ at 60°, 180°, and -60°. The C(3′)-endo sugar system in the case of DNA subunit have been considered. The solvation maps describing the solvatability of single and groups of atoms give significant information on the backbone conformational domains that are preferred for solvent interaction, thus adding knowledge to the relative stability of the various possible conformations. The B-DNA-type conformer exposes three polar atoms - namely, PO1, O(3′), and O(1′) - to external solvent, whereas the A-DNA- and C-DNA-type conformers expose only one polar atom - O(3′) and O(1′), respectively - to the solvent. The O(2′) atom of the furanose ring system in the RNA subunit could give added stability via solvent association or interunit hydrogen bonding with or without a bridging water. The superposition solvation maps describing the accessibility of a group of polar atoms help to interpret a good number of phosphodiester conformations observed in a energetically less favored conformational domains in the tRNAPhe crystal. Another intresting fact that results from this study is the prediction that the trans oriented of ω is the most favorable conformations of random-coil polynucleotides in solution.
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    Conformational properties of the N-terminal residues of S-peptide. II. The guanidine hydrochloride-water-trifluoroethanol system (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2545-2559 
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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 Conformational properties of synthetic S-peptide analogs, in which the residues in the N-terminal sequence 1-6 were progressively deleted or replaced with amino acids of lower helical propensity, were studied by CD. Increasing the concentration of guanidine hydrochloride and decreasing the temperature were found to produce progressive destruction of ordered conformations, in the parallel with the increasing solubility of the peptide unit, while increasing the concentration of trifluoroethanol and decreasing the temperature produced the opposite effect. The maximum helicity determined in the these sets of experiments is found equal to or greater than that determined in the formation of the ribonuclease S′ complexes. With some peptides the maximum value of predicted helical conformation is reached, and the tendency of tertiary structure to reduce the maximum possible helicity is evident. We discuss the validity of the procedure by which conformational information, drawn from measurements in helicogenic solvents, is related to the state in native protein.
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    Thermal perturbation techniques in characterizing ligand-macromolecule interactions: Theory and application to the proflavin-α-chymotryspin system (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1773-1792 
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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 thermal perturbation curve (TPC) is defined to be the derivative of the fractional degree of saturation, f, with respect to temperature, considered as a function of the natural logarithm of free ligand concentration, y. The theoretical framework for the use of such curves in the thermodynamic analysis of ligand binding to macromolecules is presented. The thermal perturbation curve either provides or complements the information obtained from the derivative binding isotherm ∂f/∂y. For a single set of identical and independent sites the TPC is identical to the derivative binding isotherm. Analysis of such a curve directly yield ΔH0 and ΔG0 for the binding reaction. In actual experimental work, however, the TPC can only be approximated because of “self-buffering” effects relations between the parameter of the approximate curve and the thermodynamic quantities have been developed. This technique is applied to the proflavin-α-chymotryspin system to demonstrate its usefulness. The general features of thermal perturbation curves for cases of multiple sets of independent sites and cooperatively interacting sites have also been developed. The analysis of thermal perturbation curves in combination with other methods should provide a more powerful approach to the characterization of ligand-macromolecule interactions.
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    Conformational studies of sequential polypeptides containing lysine and tyrosine (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1837-1848 
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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 conformation of three sequential copolypeptides, poly(L-tyrosyl-L-lysine), poly(L-tyrosyl-L-lysyl-L-lysine), and poly[L-tyrosyl-(L-lysyl)2-L-lysine] have been studied by a variety of techniques, including CD, ir spectroscopy, analytical ultracentrifugation, and x-ray diffraction. Depending upon the pH and sovent composition, poly(L-tyrosyl-Llysyl-L-lysine) and poly [L-tyrosyl-(Llysyl)2-L-lysine] can adopt either the α-helical or random-coil conformation, while poly(L-tyrosyl-L-lysine) forms either inter- or intramolecular β-structures.
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    Proton magnetic relaxation in solid poly(L-alanine), poly(L-leucine), poly(L-valine), and polyglycine (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1913-1925 
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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: Molecular motion in solid poly(L-alanine), Poly(L-leucine), poly(L-valine), and polyglycine has been investigated through measurement of the portion spin-lattice relaxation time at 30 and 60 MHz between 110 and 350°K. Rapid random reoriention of sied-chain methyl groups provides the dominent source of relaxation in the first three; activation energies are 10.5 ± 1 1, 8.5 ± 1 kJ/mol, respectively, significantly lower than in the monomeric crystals. Relaxation times in poyglycine are two orders of magnitude longer than in the monomeric crystals. Relaxation times in polyglycine, significantly lower than in the monomeric crystals. Relaxation times in polyglycine are two orders of magnitude longer and are attributed mainly to segmental motions of the polymer chains. Evidence of nonexponential recovery of nuclear magnetization was encountered in the first three homopolyamino acids but not in polylycine, and was attributed to the correlated time to characterize these motions gave quite good agreement with the data; some improvement was obtained for two polymers using a Cole-Davidson distribution of correlation times. For biopolymers using a Cole-Davidson distribution of correlation times. For biopolymers generally it is concluded that rapid methyl group reorientation is a common dynamical feature and an important source of nuclear magnetic relaxation.
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    Measurement of the strongly held water of myoglobin by drying (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1957-1972 
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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 karl Fischer reagent method has been used to study the drying of whale skeletal muscle myoglobin. Drying curves for metmyglobin were obtained by mechanical pumping (moderate vacuum) and diffusion pumping (high vacum) at 20, 10, 0, -10, and -20°C. Strongly held water is present in about the same amounts as were previously observed with lysozyme. Nearly all of this strongly held water is still present during the drying of acid denatured metmyoglobin. This suggest that a core structure containing strongly held water is still present at pH 4.0. Comparison of the drying of metmyoglobin, deoxymyoglobin, and oxymyoglobin indicates that the iron-coordinated water of methyoglobin is the second most strongly held water of the molocule.
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    Some global β-sheet characterstics (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2033-2037 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1978.360170817
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    Tail-fiber attachement in bacteriophage T4D studied by quasielastic light scattering-band electrophoresis (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2015-2028 
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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: Mixtures of bacteriophage T4D particles with up to six tail fibres attached were seprated and analyzed in a quasielastic light scattering-band electrophoresis apparatus. The electrophoretic mobilities and diffusion coefficients of the seprated bands were determined during the same experiment. Species differing in mobility by 0.05 × 10-4 cm2/V sec were resolved. Henry's electropheresis theory for spheres indicates that each tail fiber contributes about 140 effective positive charges to the phage structure. Estimate of the charge using the permanent dipole moment and the electrophorectic mobility (Bontje et. al. (1977) Biopolymers 16, 551-572) gives an effective charge of + 230 to -250 per tail fiber. The charge distribution on the fiberless particles was estimated to be -3380 on the head and -290 on the tail if the dipole moment was assumed positive and -1400 on the head and -1000 on the tail for a negative dipole. Tail-fiber attachement does not proceed to completion in our invitro system, as substantial distributions as a function of tail-fiber input indicates the reaction is a random, noncooperative process.
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    Conformational properties of the N-terminal residues of S-peptide. I. The ribonuclease S′ system (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2525-2543 
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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 contribution of the 1-6 N-terminal sequence to the conformational properties of the S-peptide (the 1-20 sequence of ribonuclease A) was assessed by determining in the ribonuclease S′ system the helical content and the binding capability of synthetic [Orn10]-S-peptide analogs, in which lysine1, glutamic2 and threonine3 were progressively deleted, alanine4 and alanine5were alternatively replaced by serine, and alanine6 was substituted by serine or proline. Both the deletion of the three N-terminal residues and the alanine6/proline replacement produces the loss of the helical structure up to lysine7. No or minor effects are found in all other cases. From the comparison of the binding data, the energy for the conformational stabilization of the N-terminal region was calculated to amount to 1.4 kcal/mol. The results are discussed in comparison with the known x-ray data of the enzyme, with some predictive rules of secondary structure which were applied to this region and with the known phylogenetic variance of the residues in this region.
    Additional Material: 10 Ill.
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    Solvent effect in the stereoselective polymerization of α-amino acid N-carboxyanhydride and some considerations on the mechanism of stereoregulation (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2561-2572 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the Polymerization of phenylalanine N-carboxyanhydride (NCA) in No2Oh initiated by MeNHBzl, L-,D-, and DL-NCA As were polymerized at the same rate, and no stereoselectivity was observed. When the same experiment was carried out in HCONEt2, however, L- and D-NCA were both polymerized at a rate which was about twice as large as that of DL-NCA. In this case, the polymerization is stereoselective, ascribable to a preferable reaction between the optical enantiomorphs of the terminal residue of the growing chain and the NCA of the same chirality. On the other hand, the polymerization initiated by SarNMe2 and MeNH(CH2)2CONMe2 were stereoselective in NO2Ph and HCONEt2, but they were not stereoselective in m-(MeO)2Ph. These findings indicate that the polymerizations initiated by a strong base in highly dipolar solvents are stereoselective. Apparently, the reaction between a chiral, cyclic terminal of growing chain and a chiral, cyclic activated NCA in the activated-NCA mechanism is highly stereoselective. In addition, from a kinetic investigation on on the copolymerization between L- and D-NCAs, the penultimate chiral centers were also suggested to contribute to the stereoselection. Stereoselection by the α-helical conformation of the growing chain and by a chiral, linear terminal amine have been considered so far, and the contribution from the present type of stereoselection must have been overlooked.
    Additional Material: 5 Ill.
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    Transient electric birefringence of T-even bacteriophages. IV. T2L0 and T6 with extended tail fibers (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2689-2702 
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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: Transient electric birefringence measurements of the bacteriophages T2L0 and T6 were performed under such conditions that the tail fibers are extended. The data obtained are compared to previously reported data for T4B. For all T-even phages the degree of extension of the tail fibers is a function of pH, ionic strength, and temperature. For T4B, much higher ionic strengths are needed than for T2L0 and T6 to accomplish complete tail-fiber extension. The rotational diffusion coefficients of the phages with fully extended fibers are equal to 120 ± 3 sec-1, 132 ± 5 sec-1, 157 ± 4 sec-1 for T2L0, T4B, and T6, respectively. The respective optical anistropies are - (2.66 ± 0.05) × 10-4, and - (3.07 ± 0.15) × 10-4. The differences in the rotational diffusion coefficient and optical anisotropy arise because the conformation of the fully extended tail fibers is different for the three phages. The tail fibers of T2L0 project further into the solution (away from the head) than do those of T4B and T6. The apparent permanent dipole moments of T2L0 and T6 decrease with increasing ionic strength. This decrease is caused by the screening of the surface charges on the phage body by the counter-ions in the solution. The biological relevance of this decrease is illustrated by the fact that the adsorption rate of T6 phages to E. coli B bacteria shows a similar dependence of ionic strength. Evidence is pressented that the tail fibers may move more or less independently of the phage body when an electric field is applied to the suspension.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1978.360171115
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    Nichtstarre Moleküle (1975)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 9 (1975), S. 10-17 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19750090103
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    Masthead (1975)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 9 (1975) 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19750090201
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    Internationale Regeln für die chemische Nomenklatur und Terminologie. Bd. 1. Deutsche Ausgabe. Hrsg. vom Deutschen Zentralausschuß für Chemie. Verlag Chemie GmbH, Weinheim 1975. 1. Aufl., Loseblattwerk, Ringbuch, DM 58,- (1976)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 10 (1976), S. 30-30 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/ciuz.19760100105
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    Die Silberfarbbleich - Farbphotographie (1976)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 10 (1976), S. 131-138 
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    Keywords: Chemistry ; Chemistry
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    Topics: Chemistry and Pharmacology
    Additional Material: 9 Ill.
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    Die Chemie der Feuerwerkskörper (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 12-22 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 7 Ill.
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    Konstitution und Lichtabsorption organischer Farbstoffe (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 1-11 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    Vektorielle Biokatalyse (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 33-40 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 7 Ill.
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    Masthead (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978) 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    mini-chiuz (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. A4 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19780120107
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    Atomorbitale (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 23-26 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 30 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120104
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    Chronik (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 32-32 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/ciuz.19780120106
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    Das Portrait: Rudolf Criegee (1902-1975) (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 49-55 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Der feste Zustand - Eine Einführung in die Festkörperchemie anhand sieben ausgewählter Beispiele. Von W. J. Moore. Friedr. Vieweg & Sohn Verlagsges. mbH, Braunschweig 1977. VIII, 164 S., 76 Abb., brosch. DM 22,80 (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 64-64 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Behandlung hochradioaktiver Abfälle (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 82-88 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 9 Ill.
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    mini-chiuz (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. A32 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120307
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    Wie schmutzig ist der Rhein?? (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 111-122 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Rheinanliegerstaaten haben im gemeinsamen Bemühen um die Qualität des Rheinwassers schon 1963 die „Internationale Kommission zum Schutze des Rheins gegen Verunreinigung“ (IKSR) ins Leben gerufen. Die IKSR überwacht die Wasserqualität und gibt einen jährlichen Bericht mit Analysendaten heraus. Außerdem erarbeitet sie Vorschläge für Maßnahmen zum Schutze des Stroms. In Ergänzung der jeweiligen nationalen Gewässerschutzmaßnahmen haben die Rheinanliegerstaaten 1976 das Übereinkommen zum Schutze des Rheins gegen chemische Verunreinigung (Chemieabkommen) abgeschlossen. Das Chemieakbkommen, durch das die Ableitung bestimmter gefährlicher Stoffe aus den Stoffgruppen und -familien: Queck-silber- und Cadmiumverbindungen, organische Halogen-, Phosphor- und Zinnverbin-dungen, cancerogene Stoffe so weit wie möglich verhindert und aus weiteren Stoffgruppen und -familien, darunter den meisten Metallen, streng überwacht und eingeschränkt werden soll, hat einen langfristigen präventiven Charakter. Das Chloridabkommen soll dagegen sofort zu Maßnahmen führen. Zu diesen Abkommen der Rheinanliegerstaaten treten eine Reihe weiterer internationaler Abkommen und Vereinbarungen mit Auswirkungen auf den Rhein, verschiedene Richtlinien der Europäischen Gemeinschaft, ein geplantes Abkommen der Länder im Europarat, ein Abkommen zum Schutze der Nordsee und des Nordatlantiks gegen die Verschmutzung vom Lande aus.
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    „Senföle“ (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 182-188 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/ciuz.19780120603
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    Lorenz Crell und das erste chemische Periodicum 1778 (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 199-200 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19780120605
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    Chronik (1975)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 9 (1975), S. 33-34 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19750090106
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    Optical rotatory dispersion and circular dichroism of silver(I):Polyribonucleotide complexes (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1847-1861 
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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: Optical rotatory dispersion (ORD) and circular dichroism (CD) spectra of single- and multistranded polyribonucleotides undergo extensive changes on binding of the silver ion. These changes are consistent with the proposition that Ag(I) binds to the heterocyclic bases and not to the phosphate groups of polynucleotides. ORD and CD of silver complexes of poly(A)·poly(U) and double-helical rice dwarf viral RNA display negative Cotton effects when there is more than one Ag(I) per two nucleotide residues in solution. These observations suggest a significant distortion of the double-helical conformation as a result of Ag(I) binding. Silver(I) binding sites of pyrimidine polynucleotides are apparently saturated when there is one Ag(I) per two nucleotide residues and those of purine polynucleotides at one Ag(I) per nucleotide in solution. These data are consistent with the supposition that some Ag(I) binding sites exist on the pyrimidine ring and additional sites on the imidazole ring of polynucleotides. The sedimentation coefficient of poly(A) increases by severalfold when one Ag(I) is present per nucleotide residue. Silver(I) may introduce intra- and interstrand cross-links (through bidentate chelates) in single-stranded polynucleotides, resulting in structures with high sedimentation coefficients. Among the polynucleotides studied, poly(U) was an exception. Silver(I) did not affect the optical properties (absorbance, ORD, and CD) of poly(U) at neutral pH.
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    URL: http://dx.doi.org/10.1002/bip.1975.360140907
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    Estimation of the zero shear rate viscosity for dilute solutions of rigid macromolecules with complex configurations (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1915-1932 
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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 estimating the zero shear rate viscosity for dilute solutions of rigid macromolecules with complex configurations is proposed; this method is based on the macromolecular kinetic theory of Curtiss, Bird, and Hassager. Macromolecular models constructed from a collection of spheres, cylindrical rods, circular discs, and parallelepipeds with arbitrary dimensions and relative orientations can be easily handled by this method. Comparison with available experimental data for several biopolymers shows excellent agreement. As an application to this method, we investigate the effect of surface roughness on the intrinsic viscosity of spherical particles.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1975.360140911
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    Measurements and interpretation of the conductance of DNA in simple salt solutions (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1991-1993 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/bip.1975.360140915
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    The use of nanosecond fluorometry in detecting conformational transitions of an allosteric enzyme (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1933-1949 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analysis of the time decay of fluorescence of 1-anilino-naphthalene-8-sulfonate bound to phosphorylase b reveals the presence of two components with different decay times. In glycylglycine buffer, pH 7.0, the addition of the activators AMP or IMP, or the conversion to phosphorylase a results in a preferential decrease in the amplitude of the component of longer decay time, arising probably from a preferential dissociation of 1-anilino-naphthalene-8-sulfonate from the corresponding site as a consequence of a change in molecular state.
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    Masthead (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975) 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1975.360141001
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    Gel formation from solutions of single-chain gelatin (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1995-2005 
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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 changes in conformation undergone by α-gelatin molecules on quenching aqueous solutions to below the temperature at which they can gel have been monitored by nuclear magnetic resonance and dielectric relaxation techniques. The relative rates of these conformational transitions are compared with changes in rheological properties. The nmr spectral intensity changes for 0.2 and 0.5% w/v α-gelatin solutions correspond to a unimolecular process with k ∼ 10-2 min-1 at 15°C; this process occurs independently of whether or not the solution is concentrated enough to form a gel. The process involves a slow intramolecular nucleation step, followed by a rapid conformational change of the whole molecule from random coil to a rigid stage. Comparison with other data suggests that the transition gives rise to a triple collagen-like helix. In dilute solution (but above the critical concentration for gel formation, e.g., 0.5% w/v), the gelatin process follows the formation of the rigid molecular species. It probably involves the formation of junction zones consisting of three polypeptide chains in a collagen-like triple-helical conformation. These junctions may form, at low concentrations, from a reorganization of previously formed, intramolecular, triple helices. Solutions below a concentration of about 0.4% w/v α-gelatin cannot gel by this mechanism, and only form viscous liquids.
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    Preparation and characterization of α-L-glutamic acid oligomers (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2035-2048 
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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 preparation and characterization of α-L-glutamic acid oligomers with degree of polymerization (DP) up to 12 are described. The preparation of polymers with low DP corresponding to various A/I ratios (where A and I are monomer and initiator concentrations, respectively) with end groups blocked is given. The conditions of the fractionation, which separates the different oligomers by ion-exchange chromatography, are discussed. Finally, the isolation from salt solutions of the pure acidic form is given. Each polymer obtained for a given A/I is characterized at the end of the polymerization by its molecular-weight distribution. The average DP values calculated are compared to the A/I values; agreement is very good. Potentiometric behaviour during neutralization is obtained as a function of the degree of polymerization and the elaboration of the polyelectrolytic phenomenon is discussed.
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    Ordered forms of 5′-8-aminoguanylic acid (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2095-2106 
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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: 5′-8NH2GMP forms an ordered structure in moderately acid (pD 4.7) solution. We propose for this ordered form a novel hemiprotonated G·G structure with a twofold rotation axis and three hydrogen bonds between each pair of guanine residues. Gel formation does not occur with this nucleotide in either neutral or acid solution. In neutral solution 5′-8NH2GMP also forms a regular, ordered structure, quite different from the acid form and similar to that formed by 5′-GMP under the same neutral conditions. We suggest that this ordered structure consists of a regularly stacked array of planar tetramers, similar to that proposed for 3′-GMP at pH 5.2
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    Immobilization of polyribonucleotides in agarose gels at high ionic strength (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1905-1913 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Purine polyribonucleotides poly(A), poly(G), and poly(I) associate reversibly with agarose gels at high NaCl molarities over the pH range 6-10, at 20°-40°C. Pyrimidine polyribonucleotides poly (C) and poly(U) could not be immobilized in agarose gels under the above conditions. However, poly(C) could be immobilized in agarose without precipitation between pH 3.2 and 4.0.Association of poly(G) and poly(I) with agarose appears to decrease progressively with deprotonation of their purine residues, and both polymers interact with the gel very weakly above pH 10 regardless of NaCl concentration. The binding to agarose of these polymers at pH 7.5 is also strongly influenced by temperature in the range 20°-40°C. The association of single-stranded poly(A) is only shifted toward higher NaCl molarities by increased pH; its binding is also little affected by temperature in the above range.At NaCl molarities effecting the saturating retention in agarose and at neutral pH, the immobilization of several polynucleotides could be prevented by urea in a concentration-dependent manner. The corresponding profiles of urea molarity appear to disclose a number of hydrophobic interactions between polynucleotides and agarose, some of which could be relatively strong, especially in the case of poly(A).
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    Vibrational spectra of oligomers of glycine in relation to polyglycine (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1987-1990 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    The association reaction of collagen model polypeptides (Pro-Pro-Gly)nTaken, in part, from a thesis submitted by B. R. Shaw in partial fulfillment of the requirements for the Ph.D. degree, University of Washington, June 1973. (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1951-1985 
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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 characterization of recently synthesized (Pro-Pro-Gly)n, n = 7, 8 is described, along with melting profile studies of its association equilibrium, and thermal quenching studies of the kinetics of its association reaction. The order of the kinetic reaction is about 3, implying that three peptide chains are involved in the activated state of the rate-limiting step. The reaction rate was found to exhibit a negative temperature coefficient. With the (Pro-Pro-Gly)7 peptide, the concentration dependence of the (Pro-Pro-Gly)n association equilibrium was observed for the first time.Detailed thermodynamic analysis for these n = 7, 8 data, together with literature data for n = 10, 15, 20 were carried out for both the simple “all-or-none” binding model and for a series of complex equilibrium models. For the latter, all of the (Pro-Pro-Gly)n data (in 10% acetic acid) are fit best with a maximally cooperative near-neighbor model with a standard enthalpy change ΔH = -650 cal/mole of residues, and a standard entropy change ΔS = -14.63 -10/n cal/deg-mole of residues, wherein the -10 eu represents an end-effect contribution to the binding free energy.With regard to optical rotatory properties and thermodynamic parameters, the data for the new n = 7, 8 peptides match rather well with the literature data for the n = 10, 15, and 20 peptides.The enthalpic stabilization per residue of the triple-helical form of (Pro-Pro-Gly)n was nearly an order of magnitude smaller than the enthalpic stabilization per additional proline obtained from direct calorimetric measurements on native collagens of different (and much lower) proline contents by Privalov and Tiktopulo. [Biopolymers (1970) 9, 127-139.] Possible explanations for this phenomenon are discussed.
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  • 176
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    Kinetics of proton transfer reactions of lysozyme with p-nitrophenol near neutral pH - a study of dynamic properties of Glu 35 and His 15 (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2007-2024 
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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: Kinetics of proton transfer between lysozyme and a pH indicator p-nitrophenol (p-Np) were measured by the temperature-jump method in a pH range of 6.0-7.0. Two well-defined relaxation processes were observed. The fast process (τ ≃ 15 μsec) was also observed for a lysozyme derivative succinylated at the terminal α-amino group of Lys 1. Therefore, the fast process was found to be attributable to the proton transfer reaction of His 15 with p-Np. The slow process (τ ≃ 50 μsec) was found to be characteristic of the proton transfer reaction of Glu 35, because it disappeared completely in solution containing a lysozyme derivative having an ester crosslink between the carboxyl group of Glu 35 and indol C-2 of Trp 108. The rate constants for proton transfer from Glu 35 and His 15 to p-Np were found to be 9 × 106/sec/M (±65%, 23°C) and 3 × 108/sec/M (±20%, 25°C), respectively. These data indicate that the proton of the carboxyl group of Glu 35 is kinetically stabilized in lysozyme.
    Additional Material: 9 Ill.
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  • 177
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    Cu(II)-poly(L-arginine) complexes. Potentiometric and spectral characterization of amine and peptide nitrogen ligands (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2247-2262 
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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 study of Cu(II)-poly(L-arginine) complexes by potentiometric titration, as well as by optical, circular dichroism, and infrared spectra, provides information about the nature of ligands and the coordination sphere around the metal ion. Three different complexes have been identified. The first, which is formed below pH 8, contains two guanidinium nitrogens and two water molecules at the corners of the coordination square. The constant of the overall process as determined by the Gregor method equals 2.0 ± 0.1 × 10-9. The two other complexes form between pH 8 and 10.5 and they contain two guanidinium and two peptide nitrogens as nearest ligands. One of them is a monomer and the other probably a dimer, which differ in the symmetry of the coordination sphere around the cupric ion. The optical spectra of the three complexes show an absorption band at 260 nm that we have assigned to a charge-transfer transition between a σ metal nitrogen (amine) molecular orbital and a dx2-y2 metal orbital. The spectra of the two complexes containing peptide nitrogens exhibit another absorption band at 320 nm, which we have assigned to a charge transfer from a π orbital of the amide group to the dx2-y2 metal orbital.
    Additional Material: 8 Ill.
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  • 178
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    Equilibrium mechanisms of length regulation in linear protein aggregates (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2297-2309 
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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: Statistical thermodynamic theories have been developed in order to explore the consequences of two prominent models of length regulation in linear protein aggregates: the length-determining factor model and the cumulated strain model. In the former, the possibility that the final subunit is bound with extra stability has been incorporated. Calculations explore the dependence of the sharpness of the onset of extensive polymerization, and the breadth, shape, and most probable value of the distribution as functions of concentrations of template and polymerizing subunit, of subunit association constant, of the strain free energy, and of the maximum length and extra stability of the last subunit in the length-determining factor model. Numerical calculations are made with particular reference to the parameters of bacteriophage T4 tail-core polymerization. Both models predict suitably narrow length distributions with plausible values of the thermodynamic parameters. The length-determining factor model may exhibit highly cooperative behaviour, with either fully polymerized or very short aggregates being observed as the product K[C] of association constant and free monomer constant is varied. This cooperativity is accentuated as binding of the final subunit becomes more stable. Species of intermediate length will be observable only if the length-determining factor is shortened. In the cumulated strain model, if K[C] is lowered at constant strain free energy per subunit, shorter aggregates will be observed; but increasing K[C] will not yield appreciably longer polymers. As [C] is lowered, the distribution will remain narrow.
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    The structure of fibrin. An electron microscopic investigation (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2363-2372 
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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: An electron microscopic investigation on the structure of fibrin is reported. Fibrin morphology was investigated in a wide variety of experimental conditions, and by carefully controlled staining procedures. Two main band patterns A (230-Å-spaced main dark bands) and B (230-Å-spaced main light bands) are observed for stained fibrin; it is shown that the former results from the superimposition of both positive and negative staining, and the latter is given by positive staining. By suitable denaturation experiments, it was found that the fiber is composed of a regular alternation of lose and dense regions along the axis.We have assumed that the monomer of fibrin is described by the three-nodular model of Hall and Slayter, as supported by recent investigations. The monomers are arrayed according to a head-to-tail sequence along the fiber, and to a staggered lateral association. This model accounts for all the experimental observations, and predicts well the high-resolution band pattern of fibrin. It further agrees with the results of a recent work on the early stages of the fibrinogen-to-fibrin conversion.
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    A range of G+C-independent denaturation solvents for DNA (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2417-2420 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    Brownian motion of an ellipsoid. A correction to Perrin's results (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2421-2423 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 182
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    Transient electric birefringence of sonicated DNA (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2441-2443 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    Synthesis of protected oligo (γ-methyl-L-glutamates) and study of their conformation in solution and at the air-water interfaceThis work was presented at the 13th European Peptide Symposium, Jerusalem, May 1974. (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2263-2279 
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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: Oligopeptides having the general formula N-carbobenzoxy(γ-methyl-L-glutamyl)n-dimethyl-L-glutamate (with n = 1, 3, 5, 7, 11) were prepared, using both solid-phase synthesis and conventional peptide couplings in solution. The appearance of an ordered structure with increasing chain length was studied in organic solvents and at the air-water interface. The results obtained by thin-layer chromatography were interpreted. All the studies have demonstrated a very similar behaviour of this type of oligopeptide in solution and in monolayers.
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    Nonactin, monactin, dinactin, trinactin, and tetranactin. A Raman spectroscopic study (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2311-2327 
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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 spectra are reported for crystalline nonactin, monactin, dinactin, trinactin, and tetranactin and their solutions in CCl4, CHCl3, CH3OH, and 4:1 (v/v) CH3OH:CHCl3. The macrotetrolide nactins selectively bind a wide variety of cations, and are important model compounds for the study of ion complexation. The conformations of nonactin, monactin, and dinactin in solution are similar. Their conformations are found to be sufficiently open to permit the ester carbonyl groups to form hydrogen bonds with CH3OH; this gives rise to characteristic changes in the vibration frequencies associated with the ester groups. Nonactin, which is the least soluble of the nactins in CH3OH, is also the least effective at forming hydrogen bonds with CH3OH. The greater ability of the higher nactins to form hydrogen bonds with CH3OH may be due to the increased inductive effect of ethyl over methyl side chains, which may increase the dipole moment of the ester carbonyl groups. Spectra of crystalline nonactin, monactin, and tetranactin are fairly similar, while the spectra of dinactin and trinactin comprise a second, distinct family. This is consistent with X-ray crystallographic studies, which show that nonactin and tetranactin form monoclinic crystals, while trinactin is triclinic.
    Additional Material: 6 Ill.
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    Levans. V. Kinetics of the acid hydrolysis of Streptococcus salivarius levan (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2373-2385 
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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 kinetics of the acid hydrolysis of Streptococcus salivarius levan were studied by examining the weight-average molecular weight. The molecular weights were obtained in a continuous manner from light scattering. Two first order reactions were observed: an initial rapid reaction in competition with a slower reaction.Activation energies, activation entropies, as well as the rate dependence upon substrate and hydrogen ion concentrations were determined. The data seem to indicate that the fast reaction is related to the breaking of branch-point bonds while the slower reaction is related to the breaking of main-chain bonds. Thus, levan hydrolysis seems to be fundamentally different from the completely random degradation of other branched polysaccharides, i.e., dextran, glycogen, and amylopectin.
    Additional Material: 9 Ill.
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    Backbone conformations in deoxyribonucleic acids. Conformational role of the 2′-hydroxyl group on the internucleotide phosphodiester conformations (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2387-2399 
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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 conformations accessible to the internucleotide phosphodiester group in deoxydinucleoside monophosphates, deoxydinucleoside triphosphates, and deoxypolynucleotides have been explored in detail by potential energy calculations. The two most predominant conformations for the nucleotide moiety (3E and 2E) and their possible combinations (3E-3E, 3E-2E, 2E-2E, 2E-3E) have been employed, similar to our earlier studies on polyribonucleotides. The internucleotide P-O bond torsions are very sensitive to the sugar pucker (3E and 2E) and sugar type (ribose and 2′-deoxyribose) on the 3′-residue of dinucleoside phosphates. The preferred phosphodiester conformations found for the deoxydinucleoside monophosphates and triphosphates, in general, follow the same pattern as those obtained for ribose sugars when the sugar on the 3′-side of the molecule has the 3E sugar-ring conformation. The internucleotide P-O bonds show a greater degree of conformational freedom when the 3′-sugar has the 2E pucker. The double gauche g-g- conformation for the phosphodiester, which leads to the overlap of the adjacent bases, is shown to be one of the energetically most favored conformations for all the sequence of sugar puckers. It is found that the 2E-2E sequence of sugar puckers shows a greater energetic preference for the stacked helical conformation (g-g-) than the (3E-3E) and the mixed sugar-pucker combinations. This effect becomes more pronounced in going from a dinucleoside monophosphate to a dinucleoside triphosphate suggesting that the 2′-deoxy sugars favor the 2E sugar pucker in di-, oligo-, and polydeoxyribonucleotide structures. In addition to g-g-, the conformations g+g-, tg-, g-t, tg+, and g+t are also found to be possible for the phosphodiester in a polydeoxyribonucleotide and their populations depend to some extent on the sugar-pucker sequence. It is shown that the short-range intramolecular interactions involving the sugar and the phosphate groups dictate to a large extent the backbone conformations of nucleic acids and polynucleotides.
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    Studies on interaction between poly(L-lysine) and DNA of varied G + C contents (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2401-2415 
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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: Interaction between polylysine and DNA's of varied G + C contents was studied using thermal denaturation and circular dichroism (CD). For each complex there is one melting band at a lower temperature tm, corresponding to the helix-coil transition of free base pairs, and another band at a higher temperature t′m, corresponding to the transition of polylysine-bound base pairs. For free base pairs, with natural DNA's and poly(dA-dT) a linear relation is observed between the tm and the G + C content of the particular DNA used. This is not true with poly(dG)·poly(dC), which has a tm about 20°C lower than the extrapolated value for DNA of 100% G + C. For polylysine-bound base pairs, a linear relation is also observed between the t′m and the G + C content of natural DNA's but neither poly(dA-dT) nor poly(dG)·poly(dC) complexes follow this relationship. The dependence of melting temperature on composition, expressed as dtm/dXG·C, where XG·C is the fraction of G·C pairs, is 60°C for free base pairs and only 21°C for polylysine-bound base pairs. This reduction in compositional dependence of Tm is similar to that observed for pure DNA in high ionic strength. Although the t′m of polylysine-poly(dA-dT) is 9°C lower than the extrapolated value for 0% G + C in EDTA buffer, it is independent of ionic strength in the medium and is equal to the tm0 extrapolated from the linear plot of tm against log Na+. There is also a noticeable similarity in the CD spectra of polylysine· and polyarginine·DNA complexes, except for complexes with poly(dA-dT). The calculated CD spectrum of polylysine-bound poly(dA-dT) is substantially different from that of polyarginine-bound poly(dA-dT).
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    Masthead (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1975.360141201
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    Influence of Mn2+ ion coordination on tRNAVal1 macrostructure and determination of some coordination sites of Mn2+ ions in tRNAVal1 (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2445-2456 
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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: Electron paramagnetic resonance spectroscopy has been used to study the coupling of Mn2+ ions with the tRNAVal1 modified with a spin label at four pseudouridylic residues and with the valyl-tRNAVal1 modified with a spin label at the α-amine group of the valyl residue. A sharp increase of spin-label mobility has been found in these samples, due to the conformational transition induced by the first and second Mn2+ ions. Analysis of dipole-dipole couplings of spin labels with the coordinated ions revealed a definite order in the occupation of ion coordination sites in the tRNA. For some valyl-tRNAVal1 molecules, the second Mn2+ ions were shown to coordinate on the α-amine group of the valyl residue at a distance of 15-25 Å from a spin label. As a result of the conformational transition, a coordination site appeared in the tRNA at one of the pseudouridylic residues, its distance from the spin label being less than 10 Å. It has been suggested that the conformational transition induced by ions excluded some bases from the system of hydrogen bonds at the level of the tRNA tertiary structure. As a result, these bases acquired sufficient sterical freedom to participate in the Mn2+ ion coordination.
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    Premelting effects in DNA under saltfree conditions (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2525-2535 
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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 studied the electrical conductivity of NaDNA solutions under “saltfree” conditions at temperatures well below the melting point of DNA, using radio-frequency dielectric and noise measurements. A conductivity discontinuity is observed at a temperature well below that at which the usual denaturation processes and trans conformation may commence. The radio-frequency permittivity also exhibits a discontinuity at the same temperature. For the premelting phase, the conductivity versus temperature curves consist of two linear regions with a change in slope occurring at 23°C. This effect is related to the behavior of the ionic sheath covering the DNA macromolecule. The activation energy of the alternative current conductivity as well as that the equivalent noise conductivity results as 3.11 kcal/mole below and 4.08 kcal/mole.
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    Ethidium bromide-dinucleotide complexes. Evidence for intercalation and sequence preferences in binding to double-stranded nucleic acids (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 197-210 
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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 solution complexes of ethidium bromide with nine different deoxydinucleotides and the four self-complementary ribodinucleoside monophosphates as well as mixtures of complementary and noncomplementary deoxydinucleotides were studied as models for the binding of the drug to DNA and RNA. Ethidium bromide forms the strongest complexes with pdC-dG and CpG and shows a definite preference for interaction with pyrimidine-purine sequence isomers. Cooperativity is observed in the binding curves of the self-complementary deoxydinucleotides pdC-dG and pdG-dC as well as the ribodinucleoside monophosphates CpG and GpC, indicating the formation of a minihelix around ethidium bromide. The role of complementarity of the nucleotide bases was evident in the visible and circular dichroism spectra of mixtures of complementary and noncomplementary dinucleotides. Nuclear magnetic resonance measurements on an ethidium bromide complex with CpG provided evidence for the intercalation model for the binding of ethidium bromide to double-stranded nucleic acids. The results also suggest that ethidium bromide may bind to various sequences on DNA and RNA with significantly different binding constants.
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    Optical activity of polypeptides in the infrared. Predicted CD of the amide I and amide II bands (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 173-196 
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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 Miyazawa-Blout-Krimm (M-B-K) treatment of polypeptide absorption in the infrared is extended to the calculation of circular dichroism (CD), linear dichroism, and oriented CD for the amide I and amide II transitions. Matrix methods are applied to the α helix and β structures using measured values for the strengths and directions of the transition dipole moments and empirical values from M-B-K for the coupling constants.Relatively small aggregates, a 36-residue helix, and 8-chain × 4-residue β sheets, are large enough to show calculated absorption agreeing with M-B-K results, which are based on infinite lattices.In all cases the predicted CD is an approximately conservative couple. The strongest CD should appear in the α helix, Δε/ε ≃± 10-3 for both transitions. The amide II transition should show moderate CD couples in both β structures, Δε/ε ≃ (+2 to -1) × 10-4. The amide I transitions in β structures should show weak CD couples, Δε/ε = (+3 to -2) × 10-5, except that the negative branch in the antiparallel structure may be detectable (Δε/ε ≃ -2 × 10-4) because absorption is very low at its wavelength peak.CD on oriented samples should be enhanced over the unoriented cases, giving values as large as Δε/ε = 3 × 10-3 because particular directions of observation allow the light to avoid much of the absorption in the sample.If all three structures are considered as helices, then the larger distance of the transition dipoles from the axis in the α helix, and the orientations of the transitions in the different structures, are the factors that, in terms of our previous theoretical work [Snir and Schellman (1973) J. Phys. Chem. 77, 1653] satisfactorily explain the calculated results. Simple dipole-dipole interaction is calculated to make a substantial contribution to the coupling between groups.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1975.360140113
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    The structure of the anticodon loop of tRNAPhe from yeast as deduced from spectroscopic studies on oligonucleotides (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 155-171 
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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 hexanucleotide Gm-A-A-Y-A-ψp excised from the anticodon loop of yeast tRNAPhe and its constituent oligonucleotides have been studied by ultraviolet absorption spectroscopy, static fluorescence, and circular dichroism. Gm-Ap has a melting point of 45°C and a high melting enthalpy when compared with G-Ap; hence 2′-O-methylation seems to stabilize stacking interactions. The nucleobase Y adjacent to the 3′-side of the anticodon triplet interacts stronger with its 3′-neighboring A than with its 5′-neighboring A. It is concluded that the base Y disconnects the stack of the anticodon itself from the stack of the anticodon stem, thereby setting a reading frame for the mRNA in the course of protein biosynthesis. From the opposite signs of the short-wavelength Cotton effects in the spectra of Gm-A-A-Y-Ap and Gm-A-A-Y, it is concluded that Y after removal of its 3′ neighbor undergoes a dramatic change in its conformation. The fluorescence of the nucleobase Y upon addition of Mg2+ is enhanced in oligonucleotides longer than two. An identical enhancement is observed for tRNAPhe, indicating that this Mg2+ effect is a property of an oligonucleotide segment and does not reflect conformational changes of the whole tRNA. The data presented here reveal that the basic structural features of the anticodon loop are already present in the hexanucleotide Gm-A-A-Y-A-ψp and are not determined by the overall structure of tRNA.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1975.360140112
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    Circular dichroism in the 220-250-nm region of homopolypeptides of aliphatic amino acids in the random-coil conformation in trifluoroacetic acid (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 237-240 
    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.
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    URL: http://dx.doi.org/10.1002/bip.1975.360140117
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  • 195
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    Circular dichroism of histone-bound regions in chromatinPresented in part at the 1974 Biochemistry/Biophysics Meeting, Minneapolis, Minn. (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 211-226 
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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: Native, NaCl-treated, trypsin-treated, and polylysine-bound nucleohistones were studied in 2.5 × 10-4 M EDTA, pH 8.0, using circular dichroism (CD) and thermal denaturation. Removal of histone I by 0.6 M NaCl has a much smaller effect on both Δε220 and Δε278 than the removal of other histones. This indicates that histone I has less helical content and less conformational effect on the DNA in nucleohistone. By extrapolating to 100% binding by histones other than I, the positive CD band near 275 nm is close to zero. Comparison is also made between the effects of binding by the more basic and the less basic halves of histones by trypsin-digestion and polylysine-binding experiments. Trypsin digestion of nucleohistone reduces melting band IV at 82°C much more than melting band III at 72°C. However, the CD changes of Δε278 and Δε220 induced by trypsin digestion are small, unless melting band III is also reduced by the use of a higher trypsin level. This implies that the less basic halves of histones, which stabilize DNA to 72°C (melting band III), have more helical structure and are more responsible for conformational change in DNA than are the more basic halves, which stabilize DNA to 82°C (melting band IV). Polylysine binding to nucleohistone diminishes melting band III but has no effect on melting band IV. This binding affects only slightly the Δε220 of nucleohistone, indicating that polylysine interferes very little with the structure of the less basic halves of bound histones. The implications of these studies with respect to chromatin structure are discussed.
    Additional Material: 5 Ill.
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    Structure of guanylyl-3′,5′-cytidine monophosphate. II. Description of the molecular and crystal structure of the calcium derivative in space group P21 (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 227-236 
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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 structural features of calcium guanosine-3′,5′-cytidine monophosphate (GpC) have been elucidated by X-ray diffraction analysis. The molecule was crystallized in space group P21 with cell constants of a = 21.224 Å, b = 34.207 Å, c = 9.327 Å, and β = 90.527°, Z = 8. The hydration of the crystal is 21% by weight with 72 water molecules in the unit cell. The four GpC molecules in the asymmetric unit occur as two Watson-Crick hydrogen-bonded dimers related by a pseudo-C face centering. Each dimer consists of two independent GpC molecules whose bases are hydrogen bonded to each other in the traditional Watson-Crick fashion. Each dimer possesses a pseudo twofold axis broken by a calcium ion and associated solvent.The four molecules are conformationally similar to helical RNA, but are not identical to it or to each other. Instead, values of conformational angles reflect the intrinsic flexibility of the molecule within the range of basic helical conformations. All eight bases are anti, sugars are all C3′-endo, and the C4′-C5′ bond rotations are gauche-gauche. The R factor is 12.6% for 2918 observed reflections at 1.2-Å resolution.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1975.360140116
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    Irreversible thermodynamic analysis of electrophoretic light scattering experiments (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 21-28 
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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 fluctuation theory for electrolyte solutions is developed based on the coupling between the equations of nonequilibrium thermodynamics and the Poisson equation. The resulting fluctuation theory is applied to the analysis of electrophoretic light scattering. It is shown that in a binary electrolyte solution (two ionic species), the Doppler shift is not determined by the electrical mobility of either ion, but depends instead on the rate of change of transference number with salt concentration. In addition the ionic relaxation time is shown to be proportional to the conductivity of the solution.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150104
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    Binding of proflavin to T2L bacteriophage and its DNA (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 97-111 
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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 measured the binding equilibria of proflavin to T2L bacteriophage, in both “slow” and “fast” sedimenting forms, and to free T2L DNA. Measurements were carried out by difference spectroscopy at 430 nm at temperatures from 13 to 43°C and at pH 5.6 and 7.6. We found no significant difference in the binding parameters of the two phage forms. Also, the fraction of nucleotides available as binding sites for proflavin was the same for both free and intraphage DNA. However, the binding constant is about an order of magnitude lower for encapsulated than for free T2L DNA, due to the decreased exothermicity of the binding reaction within the phage head.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150108
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  • 199
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    Application of the nearest-neighbor ising model to the helix-coil transition of polypeptides in mixed organic solvents (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 113-129 
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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: Using the formalism of nearest-neighbor Ising model and assuming that the allowed states for a monomeric unity of a polypeptide chain in solutions containing strong acids are E (helix), C (coil), and CS (solvent-bonded coil), the partition function of the system was deduced analytically. Equations were obtained which permitted the prediction of the characteristic thermodynamic behavior of the helix-coil transition under these conditions. These equations were used to examine critically the possible correlations between experimental data obtained using different techniques. Particular attention was devoted to quantities called “transition enthalpies,” obtained from the slope of the transition curves at the point where the helix fraction is one-half (ΔHoptexp), or for measurements of the heat of solution of the polymer over the total range of solvent composition (ΔHsolexp), or from heat capacity measurements taken at various temperatures (ΔHcalexp). Literature data of ΔHjexp(j = opt, sol, cal) for the system poly-γ-benzyl-L-glutamate in mixtures of dichloroacetic acid and 1,2-dichloroethane were carefully analyzed.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150109
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    Kinetic study of cooperative binding reaction of toluidine blue to poly(α,L-glutamic acid) by means of the electric-field pulse method (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 187-201 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interaction of toluidine blue with helical and randomly coiled poly(α,L-glutamic acid) was studied with absorption spectra, titration, and electric-field pulse measurements. The obtained values of various parameters for the helical form of poly(α,L-glutamic acid)differed from those for its coiled form. The difference of parameters in these two forms of poly(α,L-glutamic acid) was attributed to differences of the binding mechanism in both forms. Furthermore, the binding of toluidine blue to poly(α,L-glutamic acid) was considered to be due to hydrogen binding in the helical conformation and ionic interaction in the coiled conformation of the polymer.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150113
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