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  • Polymer and Materials Science  (8,109)
  • Inorganic Chemistry  (2,227)
  • Organic Chemistry  (2,071)
  • Biochemistry and Biotechnology
  • 1995-1999
  • 1980-1984  (9,414)
  • 1970-1974  (3,755)
  • 1983  (4,810)
  • 1980  (4,604)
  • 1973  (3,755)
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  • 1995-1999
  • 1980-1984  (9,414)
  • 1970-1974  (3,755)
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  • 1
    Electronic Resource
    Electronic Resource
    The extrinsic cotton effects of nitrobenzylic chromophore bound to helical poly-α,L-glutamic acid (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 121-125 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120111
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  • 2
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    Effect of degree of polymerization and steric configuration of poly(2-vinylpyridine) as catalyst in the polymerization of phenylalanine NCAThis is the sixth paper in the series of Polymerization of Amino Acid Derivatives by Polymer Catalysts. For the previous paper, see M. Sisido et al., Biopolymers, 9, 791 (1970). (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 181-191 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Despite its being weaker base poly(2-vinylpyridine) polymerized DL-β-phenylalanine NCA at a much faster rate than pyridine and α-picoline. Poly(2-vinylpyridine) adsorbs NCA by hydrogen bonding with the cooperation of a few pyridine groups. This results in a high local concentration of NCA. The syndiotactic configuration of pyridine group seemed to be least suitable for the cooperative hydrogen bonding. Adsorbed NCA is activated to form an “activated” NCA which in turn reacts with an NCA adsorbed on the same polymer chain. Since the polymer chain is flexible, this intramolecular reaction takes place frequently, resulting in the acceleration of polymerization. The intramolecular reaction along the polymer chain is dependent on the degree of polymerization of polymer catalyst. A suitable model was proposed for the intramolecular reaction to explain the effect of degree of polymerization.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120117
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  • 3
    Electronic Resource
    Electronic Resource
    Single- and double-strand breaks in 5-bromouracil-substituted DNA of B. subtilis and phage PBSH after irradiation with long-wave length UV and their correlation to intramolecular energy transfer (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 329-340 
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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-Bromouracil-substituted DNA was isolated form B. Subtilis and phage PBSH. The three DNA fractions of Different densities (TT, TB, and BB) were irradiated with u.v. (313nm). The number of single-strand and double-strand breaks was determined. The breakage rates are given. It was found that in hybrid DNA (TB) double-strand breaks occur depending linearly on dose. In BB-DNA the observed double-Strand bresks can be divided into two fractions with a linear and quadratic dose dependence respectively. The results can be explained by assuming intramolecular energy transfer from the BU-containing strand to its complementary strand.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120210
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  • 4
    Electronic Resource
    Electronic Resource
    Calorimetric investigations of crystalline 3′,5′-cyclic nucleotides (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 229-235 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differential enthalpic analysis of a series of 3′,5′-cyclic nucleotides indicates that homolytic cleavage of the six-membered phosphate ring occurs either immediately prior to or concurrent with decomposition of the crystal lattice. Homolysis is followed by a rapid polymerization to yield oligonucleotides. The enthalpies of these reactions have, with the exception of guanosine 3′,5′-cyclic phosphate, almost identical values of 25 kcal/mole. The anomalous case is attributed to a more stabilized phosphate ring as a result of hydrogen bonding through the two position of the purine ring. The pair of overlapping exothermic peaks observed in each of the thermograms for cAMP and cIMP is related to the presence of two conformational arrangements within the unit cell of each compound.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120203
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  • 5
    Electronic Resource
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    An extended Hückel molecular orbital approach to the study of the electronic structures and barriers to Syn-Anti interconversion in Syn purine nucleosides (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 243-255 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The total energy and the electronic properties of some syn purine nucleosides have been determined as a function of the rotation angle around the C-N glycosidic linkage. Invariably, the crystallographic coordinates provide a state lying at or very near the minimum on the potential energy curve according to the extended Hückel parametrization here employed. The ribose moiety always carries a net positive charge whereas the base is always negatively charged. Changes in dipole moment magnitudes for the overall structure as well as in net atomic charges are noted upon rotation around the glycosidic linkage indicating that potential functions for polynucleotides may be in error if such changes are ignored.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120205
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  • 6
    Electronic Resource
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    Showing up the thermal transconformation of Na-DNA in solution by noise spectrography (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 341-352 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measuring the equivalent noise resistance of Na-DNA solutions in NaCl provides in formation about the free ino atmosphere. In an Arrhenius type diagram, the helix → coil transition is clearly brought Out. A Calculation of the number of free ions in the solution as function of temperature, reveals once more the process of ejection of compensating Na+ ions form the macromolecules during the thermal transconformation.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120211
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  • 7
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    Circular dichroism and molecular conformation of copper(II)-gramicidin S complexes (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 423-433 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical properties in different solvents of gramicidin-bis (salicylaldimine) Cu(II) and (5-I-salicyladimine) Cu(II) chelates are intercepted in terms of their molecular structure. A molecular model for the inversion of Contton effects in two different classes of solvents is proposed. This explanation is supported by the study of optical properties of model compounds.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120217
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  • 8
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    Masthead (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973) 
    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.1973.360120301
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  • 9
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    Studies on cytochrome c. Part III. Synthesis of the protected heneicosapeptide (sequence 24-44) of Baker's yeast iso-1-cytochrome cThe amino acid residues are of L-configuration. For a simpler description the customary L-designation for individual amino acid residues is omitted. Standard abbreviations for amino acid derivatives and peptides are used according to the suggestion of the IUPAC-IUB Commission on Biochemical Nomenclature, European J. Biochem., 1, 375 (1967). (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 507-520 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses are described for two N-benzyloxycarbonylpeptide tert-butoxycarbonylhydrazides which correspond to positions 24-34 and 35-44, respectively, of the primary structure of baker's yeast iso-1-cytochrome c. The two peptide derivatives were coupled via the azide procedure to form the N-benzyloxycarbonylheneicosapeptide tert-butoxycarbonylhydrazide (sequence 24-44).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120305
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  • 10
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    The rate of γ-benzyl-L-glutamate NCA polymerizations (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 647-654 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The primary amine initiated homopolymerization of γ-benzyl-L-glutamate NCA in dioxane at 25°C, 35°C, 50°C, and 65°C has been investigated. The reactions were virtually independent of temperature indicating an activation energy of less than 1 kcal/mole. The entropy of activation was estimated to be -65 entropy units at 300°K. The reaction proceeded in two stages. The first stage was zero-order with respect to monomer, whereas the second was first-order with respect to monomer. Both stages were first-order with respect to initiator. These results were interpreted by assuming that the rate constant for propagation was not independent of the degree of polymerization up to the point where a conformational transition to α-helix occurred.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120316
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  • 11
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    Studies on cytochrome c. Part V. Synthesis of the protected decapeptide (sequence 57-66) of Baker's yeast iso-I-cytochrome cThe amino acid residues are of L-configuration. For a simpler description the customary L-designation for individual amino acid residues is omitted. Standard abbreviations for amino acid derivatives and peptides are used according to the suggestion of the IUPAC-IUB Commission on Biochemical Nomenclature,European J. Biochem., 1, 375 (1967). Moreover: -ONpo = o-nitrophenyl; Mbh = 4,4′-dimethoxybenzhydryl; for other abbreviation used see Ref. 2. (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 693-700 
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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 synthesis is described of the N-benzyloxycarbonyldecapeptide tert-butoxycarbonylhydrazide, which corresponds to the sequence 57-66 of baker's yeast iso-1-cytochrome c. The peptide derivative was synthesized coupling two smaller subunits via the Rudinger modified azide procedure.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120402
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  • 12
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    A temperature-jump kinetic study of the binding of proflavine to poly I·poly C (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 791-798 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of interaction between proflavine and poly I.poly C at 25°C, neutral pH, and moderate ionic strength have been studied by relaxation methods. The qualitative features of this system resemble those previously reported by Crothers and co-workers for proflavine-DNA and proflavine-poly A·poly U interactions-two relaxations are observed coresponding to a fast bimolecular step followed by a slower isomerization. These results can best be accommodated by a two-step mechanism leading from the free dye through an “outside-bound” complex to the intercalated complex. Quantitative comparison of the various rate constants for proflavine binding to different double-helical polynucleotides shows that the rates are slower for both ribohomopolymer pairs than for DNA. The rates for poly I·poly C are approximately three times faster than these for poly A·poly U.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120408
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  • 13
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    The vibrational spectra and structure of poly (rA-rU). Poly (rA-rU) (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 799-816 
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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: Infrared and Raman spectra of aqueous poly(rA-rU)·poly(rA-rU), the double-helical complex containing strands of alternating riboadenylate and ribouridylate residues, display significant differences from one another and from corresponding spectra of poly(rA)·poly(rU), the double-helical complex of riboadenylate and ribouridylate homopolymers. Parallel studies on the copolymer and homopolymer complexes by cesium sulfate density gradient centrifugation, ultraviolet absorption spectroscopy, hydrogenion titration, 1-N oxidation of adenine residues by monoperphthalic acid and X-ray diffraction reveal, however, that the geometry of base pairing between adenine and uracil is closely similar in each complex and apparently of the Watson-Crick type. Therefore the differences observed between vibrational spectra of poly (rA-rU)·poly (rA-rU) and poly(rA)·poly(rU) are not due to different base-pairing schemes but may be attributed to differences in vibrational coupling between vertically stacked bases. Vibrational coupling may also account for the differences between infrared and Raman spectra of the same complex. Thus, the present results indicate that infrared and Raman frequencies of RNA in the region 1750-1550 cm-1 should be dependent on the base sequence.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120409
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  • 14
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    Anomalies in sedimentation. I. Stability theory of sedimenting entanglements in the “tight-bending” limit (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 857-867 
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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 simple model is introduced to investigate the stability of a sedimenting entanglement. The sedimenting entanglement is represented by a sedimenting sieve. Solvent can pass through it, but single-chain molecules that flow into it become entangled and their flow decreases or, if permanent entanglements form, ceases entirely. With this model we are able to find the conditions under which the mass of a sedimenting entanglement remains constant, grows or decays to a stable value, grows beyond limit, or decays to the mass of a single chain. The theory is applied to the sedimentation of small concentrations of large chain molecules in solutions of small chain molecules in solutions of small chain molecules for the case in which the entanglements are long-lived. Equations are derived which, (1) give the stable entanglement mass as a function of rotor speed and concentration and, (2) for a given concentration predict the rotor speed at which the entanglement mass grows without limit. Numerical results for small concentrations of T2 DNA sedimenting in solutions of T7 DNA are presented.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120414
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  • 15
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    Interpretation of the solubilities of mixtures of β-lactoglobulins A and B (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 931-936 
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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.1973.360120420
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  • 16
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    Masthead (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120501
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  • 17
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    The solution behavior of poly-L-proline: I. Light scattering studies in water and concentrated aqueous neutral salt solutions (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 993-1010 
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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 bebavior of poly-L-proline Form II has been studied in water and aqueous salt solutions by both elastic and quasi-elastic light -scattering techniques. The results of this study suggest that polyproline Form II can exist in water at 24 °C as an associated polymer complex and that certain salts which do not appear to affect the helix integrity, e.g., guanidinium-HCl, resutl in dissociation of the aggregate. Other neutral salts, of the variety effective in mediating unfolding of the Form II helix (e.g., 4M NaClO4) also induce aggregate dissociation, but 4M CaCl2 results in enhanced aggregation of polyproline. Kinetic experiments indicate that a time of 20 hours is necessary for the completion of the “large” to “small” transformation (at 22°C) which is induced by the addition of 4M NaClO4. Thus it appears that neutral salts additives in aqueous solutions of polyproline influence both the state of aggregation and the conformation of this polymer.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120505
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  • 18
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    Dielectric behavior of DNA-Proflavine complex (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1047-1052 
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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 dielectric relaxation of namtive DNA and DNA-proflavine complexes at different DNA phosphate (P) to dye (D) ratios, were investigated in the frequency range 100 c/sec to 100 Kc/sec. The proflavine molecules were found to have a profound effect on the static dielectric constant and the relaxation time of the polymers. The static dielectric constant was oberserved to decrese with increasing level of added proflavine. At P/D = 1, the variation of dielectric constant with frequency was small. Relaxation time (τ) was greater for the DNA-proflavine complexes compared to that for free DNA, Maximum value of the relaxation time was obtained at P/D = 10. The increase in the relaxation time and decrease in the static dielectric constant were attributed to the increase in length and meutralization of surface charges of the DNA molecules, respectively, as aresult of proflavine binding.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120508
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  • 19
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    The solution behavior of poly-L-proline: II. Fluorescence behavior of labeled polyproline in water and conentrated aqueous neutral salt solytions (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1011-1019 
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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: Fluorescence depolarization experiments performed on labaled poly-L-proline Forme II suggest the occurrence of aggrgation in water while 6M guanidinium-HCl induces dissociation. The solvent 4M CaCl2 results in a reduction of polymer structural orgganization. These findings corroborate suggestion of polyproline aggregation and solution behavior in aqueous neutral salt solytion (see preceding article).
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120506
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  • 20
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    The effect of alkali and alkaline earth salts on the structure of hydrated collagen fibers as studied by deuterium NMR (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1053-1062 
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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 detailed study on the deuterium NMR of hydrated collagen in the presence of alkali and alkaline earth salt is reported. The effect of different salts in reducing the deuteron quadrupole splitting are similer at low molar content of salt. At higher salt contents, larger ions are more effective. The ressults are explained by the blocking of water binding sites to collagen by hydrated ions. When the temperature is reduced, only part of the adsorbed water iss frozen, and the amount of “unfreezable water” decreases with the increase in ionic sizes(LiCl 〈 MgCl2 〈 KCL 〈 KCNS). The freezing temperature is also lowered in the presence of salts. A description of the structure of hydrated collagen based upon the observed facts is given.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120509
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  • 21
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    Conformational studies of anthrax polypeptide, subtilis polypeptide, and synthetic poly-γ-Lglutamic acidPart of the Ph.D. thesis of C. C. Kalita. (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1089-1098 
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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-γ-L-glutamic acid has been synthesized by the activated pentachlorophenyl ester polymerization method and the molecule weight of the polymer was found to be 16,000. Comparative conformational studies on the synthetic and on the native polyglutamic acid mbtained from B. anthracis and B. subtilis were carried out using optical rotatory dispersion, circular dichroism, peptide absorption spectrum, and titration data. These results show that poly-γ-glutamic acid does not exhibit any conformational order under the conditions of investigation. At low degrees of ionization, restriction of conformational freedom via random “hypercoiling” of the chain appears likely.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120513
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  • 22
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    Histone IV binding of 3,4-benzpyrene, pyrene, anthracene, and 9-methylanthraceneSupported by Publice Health Service Grants CA 10679 and ES 00210. (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1149-1160 
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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: Ultraviolet absorption, fluorescence excitation and emission, and fluorescence anisotropy demonstrate that the polycyclic aromatic hydrocarbone 3,4-benzpyrene, Pyrene, anthracene, and 9-methylanthracene bind to histone IV after the sow conformational change in the presence of divalent phosphate anion. These hydrocarbons do not bind, within our limits of detection, to histone IV in the diosorderde form at low pH or to the form produced by the fast conformational change when the slow change is prevented. High anisotropy values for the bound hydrocarbon indicate a high degree of aggregation for the histone IV.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120517
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  • 23
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    The self-assembly of collagen moleculesPresented in part at the 16th Annual Meeting of the Biophysical Society, Toronto, Canada, February 24-27, 1972. (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1437-1444 
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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 aggregation of native acid-soluble collagen (N-ASC) and of pronase-treated acid soluble collagen (P-ASC) was examined in solution under conditions which varied from those of minimum collagen-collagen interaction to those leading to incipient fiber formation. Molecular weights and weight distributions were determined in the analytical ultracentrifuge using the Yphantis high speed sedimentation equilibrium and Aarchiblad approach-to-equilibrim techniques. The aggregation was pH and ionic strength dependent in each case. Under conditions of minimum aggregation (low pH, low ionic strength), N-ASC showed the presence of permant aggregates. At higher pH and ionic strength, a higher fraction of aggregate was formed but these were of the same charcter and molecular weight as the permanent aggregates. The aggregates were of a single molecular size, with a weight of 1.5 × 106 daltons, compared with a monomer collagen weight of 3.1 × 105 daltons. The P-ASC formed aggregates also but to a much lower extent and the maximum aggregate size corresponded to dimers in molecular weight. These data show the major importance of molecular end-regions in collagen aggregation to form native type fibers and, by virtue of the discrete size of the N-ASC aggregates, support the microfibrillar hypothesis for the assembly of collagen fibrills.
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    URL: http://dx.doi.org/10.1002/bip.1973.360120618
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  • 24
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    Sedimentation and intrinsic viscosity behavior of PM2 bacteriophage DNA in alkaline solution (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1387-1419 
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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 sedimentation coefficient and intrinsic viscosity of nicked and closed circular PM2 bacteriophage DNA have been measured as a function of pH in the alkaline region. A gradual increase in the sidimentation coefficient, and a corresponding decrease in the intrinsic viscosity, are observed for the superhelical (closed) circle in the pH region from 10.5 to about 10.9. This has been tentatively interpreted in terms of the known dependence of sedimentation coefficient upon the number of superhelical turns. At slightly higher pH values, the curve passes through the minimum (sedimentation coefficient) and maximum (intrinsic viscosity) expected when the superhelical turns present at neutral pH are unwound by partial alkaline denaturation. Sedimentation studies of the relaxed (nicked) circular species have revealed the existence of DNA forms in the pH region from 11.27 to 11.37 which sediment considerably faster than the closed circle in the same pH region. These have been identified as partially denatured nicked circles, in which varying fractions of the duplex structure have undergone alkaline denaturation, but strand separation has not yet occurred. Varying fractions of a slower species, either undenatured or completely denatured nicked circles, are also observed in some of these experiments. A corresponding result is observed in the intrinsic viscosity vs. pH curve.When nicked circular PM2 DNA is exposed to various alkaline pH's, rapidly neutralized, and sedimented at neutral pH, the expected sharp transition from native to denatured (strand-separated) molecules is seen. However, a very narrow pH range is noted in which native and denatured forms coexist in a single experiment. The above experiments carried out upon the closed form also reveal a narrow pH range in which the bulk of the transition from native closed circles to the collapsed cyclic coil takes place, in acccord with an earlier study on a different DNA. This transition is shown never to be completely effected, however, as there is a fraction (7-8%)of the closed circles which renature to the native form, regardless of the alkaline pH employed. This same phenomenon was not observed in the case of artificially closed λb2b5c DNA circles. Possible explanations for some of the above results are discussed.
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    Polymerization of DL-phenylalanine NCA initiated by copolymer of sarcosine and DL-phenylalanine (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1505-1513 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymerizations of DL-phenylalanine NCA by block copolymers of sarcosine and DL-phenylalanine, designated by (Phe)m(Sar)n and capable of reaction at the phenylalanyl terminal, were investigated in nitrobenzene solution at 25°C. With increasing n for constant m (m = 0, 1, 2, and 5), the polymerization rate greatly increased. Previously the acceleration of the initiation reaction in the polymerization of DL-phenylalanine NCA by polysarcosine (m = 0) was reported. The present results showing the acceleration by the copolymers of sarcosine and DL-phenylalanine indicate the presence of the polymer effect in the propagation reaction as well. However, the polymer effect was most marked with polysarcosine (m = 0), and decreased with increasing m.The same polymerizations by sequential copolymers composed of ten sarcosine units and two DL-phenylalanine units were also investigated. Again with these copolymer catalysts the polymerization rate was larger than that by monomeric amines. But the polymer effect decreased sharply when the phenylalanine units take positions near the terminal amine group of the copolymer catalyst.These two deteriorating effects of the phenylalanine unit have been interpreted in terms of the decrease of the flexibility of polymer chain, caused possibly by an intramolecular hydrogen bond of the phenylalanine unit.
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    Cooperative binding of oxygen to hemoglobin: Analysis of accurate equilibrium binding data (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2057-2073 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Accurate equilibrium binding data for the oxygenation of hemoglobin are used (a) to show that various models for cooperativity are inconsistent with the best available experimental data, (b) to determine the equilibrium constants for binding of 2,3-diphosphoglycerate to hemoglobin molecules in intermediate stages of oxygenation, and (c) to deduce a mechanism for allosteric effects in hemoglobin which is consistent with the best available experimental data. The total free energy of cooperativity is defined and discussed.
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    Dielectric relaxation and orientation of DNA molecules (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2151-2159 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A conductivity dispersion has been measured at very low frequencies (VLF) on several concentrated DNA solutions. By measuring simultaneously their electric birefringence decay, it is shown that the dielectric relaxation (which is related to the conductivity dispersion) is due to the molecular orientation. Different polarization mechanisms are discussed. It is concluded that the DNA polarizability measured in the VLF range can only be explained by the orientation of a permanent ionic dipole. It is suggested that such permanent dipoles could be caused by small differences in the ionic composition between the two molecular “ends;” the difference could either be stable (asymmetrical localization of protein impurities for instance) or transient (fluctuating dipoles explained by the Kirkwood-Schumaker theory).
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    The Conformation of Polycytidylic Acid, Polyguanylic Acid, Polyinosinic Acid, and Their Helical Complexes in Aqueous Solution from Laser Raman Scattering (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2195-2195 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Synthèse et Caractérisation des Trois Premiers Oligomermères de l'Acide α-L-Glutamique. I (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2199-2209 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present work, the synthesis of the three primary oligomers of α-L-glutamic acid is described; the general formula is the following: [I] The choice of protective groups at the both ends of the chain allows for the good solubility in the water and the liberation of free carboxyl groups on the side chain. Thus, models are obtained for the study of thermodynamic properties of solutions and especially of the interactions between polyanions and cations. The prepared products are characterized by different techniques such as mass spectrometry potentiometry, tonometry, and thin-layer chromatography. The results are in agreement and lead to the conclusions that the molecules have the general formula of [I] and are stereoregular.
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    Conformational studies on pyrimidine 5′-monophosphates and 3′,5′-diphosphates. Effect of the phosphate groups on the backbone conformation of polynucleotidesThis paper was presented at the Biophysical Society Meetings, Columbus, Ohio, Febraury 28-March 2, 1973. (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2261-2277 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In continuation of our studies on the effect of the base and the phosphate groups on the glycosyl and the sugar-phosphate backbone conformation, we have carried out semi-empirical potential energy calculations on the common 5′- and 3′5′-ribopyrimidine mono- and diphosphates by considering simultaneous rotations about the glycosyl (χ) and the C(4′)-C(5′) (ψ) bonds. This calculation provides an assessment of the nature and orientation of the base on the sugar-phosphate backbone conformation of nucleotides and polynucleotides. It is found that the attractive inetractions between the 5′-phosphate group and the base mutually stabilize the antiand the gauche-gauche (gg) conformations about χ and ψ, respectively, in 5′-ribopyrimidine nucleotides. The introduction of the 3′-phosphate group as in 3′,5′-ribopyrimidine diphosphates, still leaves the anti-gg as the most favored conformation with the important difference that the probability of occurrence of the anti, gauche-trans (gt) is how substantially increased. This is dependent to a large extent on the sugar conformation and to a lesser extent on the base. Uracil and thymine show a greater probability for the anti-gt than cytosine. The syn conformation is considerably less likely and its occurrence is also dependent on the base type, cytosine showing a lesser tendency than uracil and thymine. For the syn base, the most favourec conformation for ψ is gt, since gg is sterically disallowed and tg is destabilized by electrostatic repulsive interactions between the 3′ and 5′-phosphate groups. Thus, there is a striking correlation between the glycoysl and the backbone C(4′)-C(5′) bond conformations. The rest of the bonds of the backbone are considerable less dependent on the glycosyl conformation. These studies reveal that in poly-ribopyrimidine nucletides the majority of the nucleotide residues are expected to occur in the anti-gg conformation.
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    The effect of polydispersity on the nuclear magnetic resonancxce spectra of ply-Y-benzyl-L-glutamate (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2335-2349 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of poly dispersity on the nuclear magnetic resonance spectra of samples of poly-γ-benzyl-L-glutamateein the helix-random coil transition is studied. In the transitionregion the α-CH proton resonance shows two peaks whose behavior does not change appreciably upon fractionation by gel permeation chromatography. Theoretical spectra were computed with both a polydispersity model of the transition and a model for slow nucleationof helix from completely random coil molecules. The results suggest that the double peak behavior in the nmr spectra results from a slow rate of helix nucleation rather than polydispersity.
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    Conformational studies on alamethicin (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2691-2712 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A conformational analysis has been carried out for the cyclic peptide antibiotic alamethicin. Unlikely structures were first eliminated by constructing van der Waals' energy maps for near-neighbor contacts and using these maps to generate forty complete alamethicin structures free of steric overlaps. The energies of the forty conformations were minimized; optimizing all dihedral angles first in sets and then simultaneously, to give a family of five low-energy structures. In the conformation of lowest energy three of the seven α-amino isobutyric acid residues occur in a six-residue α-helix and three at the two chain reversals. Judged by the change in conformational energy as a function of the change in dihedral angle, the flexibility of the chain is determined by both the type of peptide unit and its position in the molecule.The model has features consistent with reported circular dichorism and surface balance measurements and has two polar centers separated by a lipophilic region. It does not contain the large central pore required by some theories for the action of alamethicin on cell membrances. It therefore probably acts by altering membrance structres rather than by shuttling ions through a pore in the membrance.
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    Structure of guanosine-3′,5′-cytidine monophosphate. I. Semi-empirical potential energy calculations and model-building (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2731-2750 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation and packing scheme for guanosine-3′, 5′-cytidine monophosphate, GpC, were computed by minimizing the classical potential energy. The lowest energy conformation of the isolated molecule had dihedral angles in the range of helical RNA's and the sugar pucker was C3′ endo. This was used as the starting conformation in a packing search over orientation space, the dihedral angles being flexible in this step also. The packing search was restricted by constraints from our x-ray data, namely, (1) the dimensions of the monoclinic unit cell and its pseudo-C2 symmetry (the real space group is P21), (2) the location of the phosphorous atom, and (3) the orientation of the bases. In addition, a geometric function was devised to impose Watson-Crick base pairing. Thus, a trial structure could be sought without explicit inclusion of intermolecular potentials. An interactive computer graphics system was used for visualizing the calculated structures.The packing searches yielded two lowest energy schemes in which the molecules had the same conformation (similar to double-helical RNA) but different orientations within the unit cell. One of these was refined by standard x-ray methods to a discrepancy index of 14.4% in the C2 pseudocell. This served as the starting structure for the subsequent refinement in the real P21 cell.5
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    Hydration of stratum corneum (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2789-2802 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for the hydration behavior of human stratum corneum has been developed from measurements on in vitro samples isolated in a manner which minimized tissue treatment and trauma. Water sorption/desorption rate measurements as a function of water activity, temperature, and tissue integrity are reported. These data, together with thermodynamic data (infrared and nmr results reported earlier) are consistent with a model in which rapidly sorbed/desorbed water (ca. 0.5 mg water/mg stratum corneum) is associated with (“bound” by) the tissue, while slowly sorbed/desorbed “free” water (up to 12 mg water/mg stratum corneum) is kinetically restricted and probably intracellular in location. Both equilibrium water binding and desorption kinetic data suggest structural changes of this cellular water barrier upon hydration. Evidence for hysteresis in water sorption isotherms (reported by others) could not be reproduced.
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    Study by circular dichroism and optical rotatory dispersion of polypeptides with aromatic side-chain chromophores (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2831-2852 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(ortho-, meta-, and para-γ-nitrobenzyl-L-glutamates) were studied by circular dichroism (CD) and optical rotatory dispersion (ORD) in two helicogenic solvents, hexafluoroisopropanol (HFIP) and dichloroethane (EDC), and two non-helicogenic solvents, dichloracetic acid (DCA) and trifluoroacetic acid (TFA). The corresponding glutamates were also studied in DCA and TFA. The symmetric nitrobenzylic chromophore is optically active when the polymers are in solution in DCA and TFA. The corresponding glutamates are also optically active under the same conditions. Thus, it was not possible to explain the origin of the optical activity of the side-chain chromophore when the polymer is in solution in a helicogenic solvent. Nevertheless, from a side-chain dichroic band, a helix-coil transition curve was determined and the stability of each poly(γ-nitrobenzyl-L-glutamate) given; this stability depends on the position of the nitro substituent on the aromatic ring.
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    Reversion of the B to A transition of DNA induced by specific interaction with the oligopeptide distamycin A (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 823-831 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the DNA-binding oligopeptide distamycin A on the B to A transition of DNA in ethanol/water solutions has been studied by means of CD. (The overbars indicate that it does not matter which particular form of the corresponding families is considered.) The results show that increasing the concentration of distamycin A reverses the A conformation (in 82% ethanol) to the B conformation due to its strong binding and stabilization of the latter. In accordance with previous data for pure aqueous solutions, a site size of 3.5 base pairs is obtained from the studies in water/ethanolic solutions. From the data on the B to A transition in the presence of distamycin A, we estimated the length of the cooperativity ν0 = 10 base pairs.The results demonstrate that the oligopeptide systems of distamycin, as well as those of netropsin, are effective stabilizers of the DNA B-conformation.
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    NMR evidence for a type I β-turn in (Pro2)-tetrapeptides and interdependence of cis:Trans isomerism, ring flexibility, and backbone conformation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 781-804 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrapeptides with proline in position 2, asparagine or leucine in position 3, and glycine in positions 1 and 4, with end groups free or blocked on the N-terminal side, were studied in their various ionic states in 2H2O and in Me2SO-d6 by 1H- and 13C-nmr. In order to clarify or refine some details, successive substitutions of the residues in these peptides with amino acids enriched to 85% in 13C, or to 85% 13C plus 97% 2H were carried out. The 1H and 13C chemical shifts as well as the 1H-1H, 13C-13C, and 13C-1H coupling constants and the signal intensities show strong similarity of behavior between the tetrapeptides of asparagine and leucine. The main conformational characteristics are (1) the almost total stabilization of the trans conformer in the type I β-turn structure when the peptide is in the zwitterion state dissolved in Me2SO. This is deduced from the 3JC3αH-N3H and the 3JC2′-H3α coupling constants, which both furnish a dihedral angle of φ3 = -90°, and from the positive value of the temperature coefficient of the glycine-4 amide protons, which suggests a type 4 → 1 hydrogen bond; (2) the evolution of cis and trans isomer fractions which change with the ionic state of the peptides in Me2SO, whereas they remain constant in aqueous solution; and (3) the conformation of the pyrrolidine ring as it follows the variations in cis:trans isomer populations together with the side-chain rotamer fractions of the residue in position 3. In the β-turn conformation the isomer cis is less abundant and the pyrrolidine ring is more flexible; this explains the perfect accommodation of the proline residue in position 2 of a bend. The interdependence of these phenomena where interactive forces play a predominant role underlines the importance of cooperative effects in the molecule. The results also suggest that the cis isomer of proline can adapt itself just as well as the trans isomer to position 2 of a type I β-turn.
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    Transport properties of particles with segmental flexibility. II. Decay of fluorescence polarization anisotropy from hinged macromolecules (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 913-930 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An algorithm is presented for the Monte Carlo simulation of the decay of fluorescence polarization from segmentally flexible molecules. Based on the random walk model of Brownian motion, the treatment explicitly follows the stochastic changes in the diffusion coefficients as the molecule bends. It includes the effects of a linear restoring force opposing the bending and the effects of hydrodynamic coupling between the translational, rotational, and bending motions. One application is presented: the simulation of anisotropy decay curves for hinged rods. A variety of decay curves are obtained, including single- and multiexponential behavior, and the following conclusions are reached: (1) increasing the flexibility is usually, but not always, accompanied by a more rapid rate of depolarization; (2) reducing the size of the fluorescent subunit will usually, but not always, increase the rate of depolarization; and (3) the complex interplay between the effects of molecular shape, relative sizes of the subunits, restoring force, and orientation of the transition dipoles renders it unlikely that any simple method can be used to interpret anisotrophy data without simulation. In particular, it is not possible to determine the extent of bending by fitting the data with the two-exponential approximation used by some investigators in the past.
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    13C-nmr spectroscopy of red algal galactans (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 977-990 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C-nmr spectra of red seaweed galactans, belonging to the agar and carrageenan groups or having the “intermediate” type of structure, were interpreted on the basis of 13C-nmr spectra of model compounds. Signal assignments have been made for most of the known extreme structures of such galactans. 13C-nmr spectroscopy was shown to be a rapid and convenient method of structural analysis, which permits one to determine the type of galactan structure, the absolute configurations of its constituents (galactose and 3,6-anhydrogalactose), and the positions of the sulfate and O-methyl groups in a polysaccharide molecule.
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    Dielectric changes in hyaluronate solutions at microwave frequencies as a function of concentration, system pH, and temperature (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 931-944 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The dielectric response of human umbilical cord hyaluronic acid in various environments has been studied at microwave frquencies using a resonant microwave cavity as a probe. Both the real and imaginary parts of complex dielectric constant and the loss tangent for hyaluronate solutions are obtained by utilizing equations for perturbation of a resonant cavity. Dielectric changes at room temperature have been observed in aqueous solutions of hyaluronic acid as a function of concentration ranging from 0 to 350 mg/ml. The data indicate the existence of ordered phases in hyaluronate solutions at selective concentrations, that is, exhibiting lyotropic-type transitions. Hyaluronate solutions at 1.5 and 3 mg/ml concentrations have been studied at various pH in the range of 6-8 and at constant ionic strength 0.1. A temperature-dependent transition in hyaluronate solution of 120 mg/ml concentration has been observed at physiological temperature. It is shown that this temperature-dependent behavior can be related to the orientational polarizability term in the Debye theory of polar molecules in liquids.
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    A quantitative test of Zimm's model for the rotor-speed-department sedimentation of linear DNA molecules (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 945-964 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: In 1974, Zimm described a theory which predicts that the sedimentation coefficient of high-molecular-weight DNA will decrease as the rotor speed of measurement increases. In 1979, this theory was revised, and the new formula predicts speed-dependence effects that are substantially smaller than the predictions of the original version. This report describes the results of subjecting both the original and the revised versions of the theory to quantitative tests using a well-defined sucrose-gradient system and a DNA of known molecular weight (T4c DNA). T4c bacteriophage is a mutant, whose DNA contains the unmodified base cytosine, instead of the glucosylated hydroxymethylcytosine characteristic of the T-even bacteriophages, and has a molecular weight of 115 ± 3 × 106. The DNA of the wild-type phage (T4D+) was also used in some experiments.In addition to the quantitative tests, the experiments test for an effect first observed by Rubenstein and Leighton, which showed that the sedimentation coefficient measured for T2 DNA depended on the composition of the centrifuge tube used for the measurement (tube composition effect). It can be inferred from this observation that an interaction occurs between particle and tube wall during sedimentation, and this leads to a reduction in sedimentation velocity independent of the reduction in S described by Zimm's theory.The results show that in the range of 25,000-50,000 rpm, the original but theoretically incorrect form of the theory quite accurately describes the sedimentation behavior of both T4c and T4D+ DNA, although T4D+ was a special case in some respects. The revised (corrected) form of the theory predicts much less of a speed-dependence effect than that actually observed. The discrepancy between corrected theory and observation suggests that other factors (perhaps arising from the use of the swinging bucket rotor geometry) are causing the additional observed reduction in S20,w. However, the experiments show that the tube composition effect does not seem to be one of these.
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    Proton NMR study of the interaction of cis-dichloro-diamine-platinum(II) with poly(I) and poly(I)·poly(C) (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1299-1309 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fixation of cis (NH3)2Cl2Pt(II) to poly(I)·poly(C) leads to the formation of two complexed species. One involves coordination to a single base (accounting for about 70% of the total platinum bound over the rb range 0.07-0.25) and the other to two bases which are not adjacent to each other but may be on the same strand and separated by a loop. Reaction of the platinum compound with poly(I) gives in addition to the above two species a minor one (about 15%, independent of rb over the range 0.05-0.30) in which the platinum is bound to two adjacent bases. The availability of such coordination reduces the dominance of the 1:1 species, which, however, remains the major one (ca. 55%).
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    Heavy-atom effects associated with methylmercury (II) binding to rabbit glyceraldehyde-3-phosphate dehydrogenase (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1329-1344 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complex of CH3Hg(II) with the accessible cysteines of glyceraldehyde-3-phosphate dehydrogenase (GAPD, EC 1.2.1.12) from rabbit muscle has been studied by phosphorescence and optically detected magnetic resonance (ODMR) spectroscopy. The wavelength dependence of the phosphorescence decay kinetics has also been measured. Comparison of CH3Hg(II)-GAPD with GAPD by these methods shows that a specific optically resolved tryptophan site of GAPD is perturbed by the interaction with a nearby mercury atom. The perturbation on the luminescence and ODMR properties is typical of an external heavy-atom effect. Based on the x-ray diffraction structure of the lobster enzyme, it is proposed that the heavy-atom effect results from the interaction of tryptophan-310 with CH3Hg(II) bound to cysteine-281 in the rabbit muscle enzyme.
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    Interaction of spermine with different forms of DNA. A conformational study (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1415-1434 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The energy of interaction of a spermine molecule with the A- and B-forms of DNA has been calculated, assuming that the molecule of spermine is fixed in the narrow groove of the DNA helix with the formation of hydrogen bonds between the amino groups of spermine and the phosphate groups of DNA. The atom-atom potentials method was used. Optimal structures for the A-DNA-spermine and B-DNA-spermine complexes are suggested. It is shown that, in agreement with the experimental data, the interaction of the spermine molecule with the A-DNA is energetically more favorable than that with the B-DNA. Two main factors are responsible for this: (1) the distance between neighboring phosphates of the chain in A-DNA (which is about 1 Å less than that in B-DNA) corresponds better to the distance between the amino groups of the propyl part of spermine; and (2) the orientation of phosphate groups in A-DNA inside the groove is preferable for complex formation with spermine to the outside groove arrangement of the phosphates in B-DNA. These conclusions are further confirmed by the calculations for DNA-propane diamine complexes.
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    Crystal and molecular structure of isoleucinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-](C60H102N6O18) (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1517-1534 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic analog of valinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-] (C60H102N6O18), has been determined by x-ray diffraction procedures. The crystals are orthorhombic, space group P212121, with cell parameters a = 11.516, b = 15.705, c = 39.310 Å, and Z = 4. The atomic coordinates for the C, N, O atoms were refined in the anisotropic thermal motion approximation and for the H atoms in the isotropic approximation. Values of standard (R) and weighted (Rw) reliability factors after refinement are 0.073 and 0.056, respectively. The structure is completely asymmetric. The cyclic molecular backbone is stabilized by six intramolecular hydrogen bonds N—H…O=C, five bonds being of the 4→1 type and one being of the 5→1 type. The side chains are located on the molecular periphery. The conformational state of isoleucinomycin in the crystal is intermediate between the corresponding crystalline states of valinomycin and meso-valinomycin. The observed conformation suggests that complexation could proceed via entry of the ion at the face possessing the L-Lac residues, the less crowded face.
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    Conformational analysis of the milk oligosaccharides (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1555-1566 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Possible conformations of lacto-N-tetraose, lacto-N-neotetraose, related disaccharides, and other milk oligosaccharides have been studied by an energy-minimization procedure using empirical potential functions. Lacto-N-tetraose favors a “curved” conformation, while lacto-N-neotetraose favors an approximately “straight” conformation. These two conformations differ mainly in the position of the terminal galactose residue with respect to the rest of the molecule. This difference explains the greater strength of lacto-N-neotetraose compared with lacto-N-tetraose in its ability to inhibit the cross-reaction of blood group P1 fractions with Type XIV pneumococcal antipolysaccharide. Although the favored conformation of lacto-N-tetraose (inactive) agrees with the model proposed by the earlier workers, that for lacto-N-neotetraose (active) differs. The favored conformations for the disaccharides galactose-β(1-4)-N-acetylglucosamine, galactose-β(1-3)-N-acetylglucosamine, and lactose are similar in overall shape, differing only in the nature and orientation of the side groups. This explains their nearly equal inhibitory activity. These theoretical models also explain the increased activity of lacto-N-fucopentaose I over that of lacto-N-tetraose and the relative activities of the substituted lactoses. The present studies suggest that it is the overall shape of the molecule which is important for activity, rather than the terminal β(1-4)-linked galactose residue alone.
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    Influence of methanol on the rotational diffusion of poly(L-lysine) in the helix-coil transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1571-1585 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C spin-lattice relaxation times of poly(L-lysine) have been obtained at 67.9 MHz in aqueous solution and in a mixed solvent (40% methanol/60% water). A concomitant determination of the conformation by CD permits the correlation of conformation and rotational diffusion of the polymer. The dependence on pH of the spin-lattice relaxation times of the 13Cα and the side-chain carbon resonances reflects the diffusional motion in the random-coil conformation, in the helix-coil transition, and in the conformation of the α-helix. In the mixed solvent the reorientational correlation time of the Cα-Hα vector increases from τ = 0.37 nsec (random coil) to τ = 12.0 nsec (α-helix). In aqueous solution the correlation time of this vector increases from τ = 0.33 nsec (random coil) to τ ≫ 11 nsec. The reorientation rates of the side-chain methylene groups in the two solvents are markedly different. The reorientation of all methylene groups is reduced in the mixed solvent.
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    Solid-state conformation of copolymers of β-benzyl-L-aspartate with L-alanine, L-leucine, L-valine, γ-benzyl-L-glutamate, or ∊-carbobenzoxy-L-lysine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1603-1615 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state conformation of copolymers of β-benzyl-L-aspartate [L-Asp(OBzl)] with L-leucine (L-Leu), L-alanine (L-Ala), L-valine (L-Val), γ-benzyl-L-glutamate [L-Glu(OBzl)], or ∊-carbobenzoxy-L-lysine (Cbz-L-Lys) has been studied by ir spectroscopy and circular dichroism (CD). The ir spectra in the region of the amide I and II bands and in the region of 700-250 cm-1 have been determined. The results from the ir studies are in good agreement with data obtained by CD experiments. Incorporation of the amino acid residues mentioned above into poly[L-Asp(OBzl)] induces a change from the left-handed into the right-handed α-helix. This conformational change for the poly[L-Asp(OBzl)] copolymers was observed in the following composition ranges: L-Leu, 0-15 mol %; L-Ala, 0-32 mol %; L-Val, 0-8 mol %; L-Glu(OBzl), 3-10 mol %; and Cbz-L-Lys, 0-9 mol %.
    Additional Material: 7 Ill.
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    Physical aging of dry elastin (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1667-1673 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dry purified ligamentum nuchae elastin has been investigated for physical aging. The samples were quenched from a temperature (197°C) close to the softening point to a number of measuring temperatures ranging from -20 to +180°C. At each temperature, the small-strain torsional creep properties were determined at a number of elapsed intervals after the quench. Aging effects were found over the whole temperature range, and the creep and aging behavior of elastin turned out to be very similar to that of synthetic polymers.
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    DNA backbone conformation in cis-syn pyrimidine[]pyrimidine cyclobutane dimersPresented at the American Society of Biological Chemists and Biophysical Society Meeting, June 1-5, 1980, New Orleans, Louisiana [(1980) Fed. Proc. 39, 1879]. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1695-1701 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
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    Toroidal elastic supercoiling of DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1705-1713 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Covalently closed circular DNA can exist in different configurations known as circular, toroidal, and interwound. Changes among these forms can be made in several ways, including the insertion of dye molecules between adjacent base pairs, which tends to untwist the double-helical structure. The aim of this paper is to discuss these configurations, and the changes among them, in the context of classical elastomechanics. The concepts of twisting, linkage and writhing are explained. Simple experiments on a twisted linear-elastic rod are described, and it is shown that although the circular and interwound forms may be modeled in this way, the toroidal form does not occur, being mechanically unstable. Theoretical energy calculations by Levitt on bent and twisted DNA show that DNA exhibits a particular kind of nonlinear elasticity in which there is an unusual coupling between bending and twisting. The aim of the paper is to show qualitatively that this special kind of elasticity can stabilize the toroidal form of closed circular DNA.
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    Physicochemical investigation of k-carrageenan in the random state (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1357-1374 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Light-scattering, viscosity, and sedimentation experiments on aqueous solutions of k-carrageenan show that this sulfated polygalactose is an expanded flexible random coil. This expansion is due to long-range interactions that are predominantly electrostatic. Extrapolation of viscosity data to infinite ionic strength provided values for the intrinsic viscosity which were subjected to the Stockmayer-Fixman analysis, giving a value for the Mark-Houwink coefficient under theta-conditions, Kθ, of 0.27. The characteristic ratio, C∞, under these conditions is 7.8, and the conformation factor σ is 2. In a solution of 0.118 ionic strength, where a Mark-Houwink exponent aη of 0.86 is found, the radii of gyration calculated from viscosity data are lower than those found from the angular dependence of scattered light. On the other hand, the radius of gyration found from the sedimentation rate agrees well with the light-scattering radius. The relations between molecular parameters are corrected for the poly-dispersity of the sample.
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    An interaction of albumin with hyaluronic acid and chondroitin sulfate: A study of affinity chromatography and circular dichroism (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1407-1414 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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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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    The translational friction of toroids (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1475-1489 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: An approximate analytic expression for the translational friction coefficient of a toroid modeled as a continuous shell of frictional elements is derived using the Kirkwood approximation. The accuracy of this expression was determined by comparing the friction coefficients predicted by it to those predicted by extrapolated shell-model calculations using the modified Oseen tensor. To show that these calculations do indeed yield the correct friction coefficients, actual translational friction coefficients were determined by observing settling rates of macroscopic model rings or toroids in a high-viscosity silicone fluid. Our conclusion is that the approximate expression yields friction coefficients that are about 1.5-3% low for finite rings. For thin rings, a comparison is also made with the exact result of Yamakawa and Yamaki [J. Chem. Phys. 57, 1572 (1972); 58, 2049 (1973)] for the translational friction of plane polygonal rings. This comparison shows that the approximate expression yields results which are low by 2-3% unless the rings are extremely thin, in which case the error is larger. In the limit of an infinitely thin ring the approximate expression reduces to the Kirkwood result [J. Polym. Sci. 12, 1 (1954)], which is low by 8.3%. We discuss briefly how this work may be useful in determining the structure of DNA compacted by various solvent-electrolyte systems and polyamines.
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    Dynamic light scattering studies of internal motions in DNA. II. Clean viral DNAs (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1451-1474 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Internal Brownian motions of clean φ29 and λ-DNAs have been studied using photon-correlation techniques at both visible (λ0 = 632.8 nm) and uv (λ0 = 363.8 nm) wavelengths. The present dynamic light scattering data, which extend to K2 = 19 × 1010 cm-2, can in every case be satisfactorily simulated by a Rouse-Zimm model polymer with an appropriate choice of the three model parameters. The effects of pH, salt concentration, single-strand breaks, and molecular weight on those model parameters have also been investigated. Intact clean DNAs exhibit surprisingly little variation with pH from 7.85 to 10.25, with salt concentration from 0.01 NaCl to 5.4M NH4Cl, or with molecular weight or GC content. The single-strand breaks have no effect at pH 9.46, but produce dramatic changes in the model parameters at pH 10.0 and 10.25, indicating the introduction of titratable joints at those pHs. The failure of either single-strand breaks or a large change in GC content to alter the model parameters in the neutral pH range is a strong indication that local denaturation is not required for those flexions and torsions that dominate the relaxation of fluctuations in the scattered light. The Langevin relaxation time for the slowest internal mode of a particular Rouse-Zimm model derived from the dynamic light scattering data is compared with pertinent literature data extrapolated to the same molecular weight. The present algorithm for determining model parameters from the light-scattering Dapp vs K2 curve actually yields a Langevin time in fairly good agreement with the literature value. For unknown reasons the light-scattering D0 values generally exceed those obtained from the molecular weight and sedimentation coefficient by about 20%.
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    Ultraviolet Raman spectroscopy of polyribouridylic acid: Excitation profile of the hypochromism induced by order-disorder transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1507-1515 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Raman spectra of polyribouridylic acid excited in the uv region, from 363 to 290 nm, are reported. The conformational changes of the polymer from random coil to ordered structure with stacked bases at high and low temperature, respectively, are reflected by important changes in the Raman line intensities; this Raman hypochromism is itself a function of the excitation wavelength - its profile has been determined and shows negative values in the region of 290 nm (near resonance), i.e., hypochromism becomes hyperchromism. Thus the knowledge of the hypochromism excitation profile is important in following order-disorder transition of a polymer using resonance Raman spectroscopy. Theoretical attempts are proposed for explanation, involving not only the relative variations of the molar extinction coefficient on the order-disorder transition of the polymer, but also the damping factors of the vibronic levels. The theoretical curve is found to fit adequately the experimental data over the excitation range, using only the frequency of the O-O transition of uracil and a vibronic linewidth of 2200 cm-1.
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    Interaction of poly(α-L-glutamic acid) and sodium poly(α-L-glutamate) with solvent components in water-2-chloroethanol mixtures (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2177-2190 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preferential interaction of sodium poly(α-L-glutamate) and poly(α-L-glutamic acid) with the solvent components in water/2-chloroethanol mixtures has been determined using density-increment measurements. The degree of preferential interaction was deduced from the density increments at constant molality of 2-chloroethanol and at constant chemical potential of 2-chloroethanol. Sodium poly(α-L-glutamate) and poly(α-L-glutamic acid) are both preferentially hydrated in the whole range of solvent composition. A dehydration process occurs during the 2-chloroethanol-induced coil-to-helix transition of sodium poly(α-L-glutamate). This dehydration process was attributed to the release of some moles of water from the neighborhood of the peptide bond during the nucleation of the helix. After the conformational transition, sodium poly(α-L-glutamate) is solvated by one 2-chloroethanol molecule. The location of water and 2-chloroethanol molecules in the different parts of the residue (more polar and less polar portions) is also discussed.
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    Effects of pD on ring-stacking interactions between dinucleoside phosphates and tryptamine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2223-2245 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complex formation between tryptamine and mononucleotides and dinucleoside phosphates containing adenine and/or cytosine has been studied at five pD's ranging from 1.1 to 7.4 by proton magnetic resonance spectroscopy. Chemical shifts of base ring protons and the ribose anomeric proton in the nucleotides and indole ring protons in tryptamine were monitored and their changes with pD and intermolecular interactions interpreted qualitatively. Stacked complexes were found to exist at all pD's in the range studied. Complex geometries differ depending on pD. An electrostatic interaction between the tryptamine amino group and the nucleotide phosphate group contributes to complex formation above pD 4 but is not strong enough to shift the dinucleoside phosphate equilibrium towards the unstacked conformer.
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    Conformational energy studies on N-methylated analogs of thyrotropin releasing hormone, enkephalin, and luteinizing hormone-releasing hormone (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1943-1973 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Empirical conformational energy calculations have been carried out for N-methyl derivatives of alanine and phenylalanine dipeptide models and N-methyl-substituted active analogs of three biologically active peptides, namely thyrotropin-releasing hormone (TRH), enkephalin (ENK), and luteinizing hormone-releasing hormone (LHRH). The isoenergetic contour maps and the local dipeptide minima obtained, when the peptide bond (ω) preceding the N-methylated residue is in the trans configuration show that (1) N-methylation constricts the conformational freedom of both the ith and (i + 1)th residues; (2), the lowest energy position for both residues occurs around φ = -135° ± 5° and ψ = 75° ± 5°, and (3) the αL conformational state is the second lowest energy state for the (i + 1)th residue, whereas for the ith residue the C5 (extended) conformation is second lowest in energy. When the peptide bond (ωi) is in the cis configuration the ith residue is energetically forbidden in the range φ = 0° to 180° and ψ = -180° to +180°. Conformations of low energy for ωi = 0° are found to be similar to those obtained for the trans peptide bond. In all the model systems (irrespective of cis or trans), the αR conformational state is energetically very high. Significant deviations from planarity are found for the peptide bond when the amide hydrogen is replaced by a methyl group. Two low-energy conformers are found for [(N-Me)His2]TRH. These conformers differ only in the φ and ψ values at the (N-Me)His2 residue. Among the different low-energy conformers found for each of the ENK analogs [D-Ala2,(N-Me)Phe4, Met5]ENK amide and [D-Ala2,(N-Me)Met5]ENK amide, one low-energy conformer was found to be common for both analogs with respect to the side-chain orientations. The stability of the low-energy structures is discussed in the light of the activity of other analogs. Two low-energy conformers were found for [(N-Me)Leu7]LHRH. These conformations differ in the types of bend around the positions 6 and 7 of LHRH. One bend type is eliminated when the active analog [D-Ala6,(M-Me)Leu7]LHRH is considered.
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    Interactions of molecules with nucleic acids. III. Steric and electrostatic energy contours for the principal intercalation sites, prerequisites for binding, and the exclusion of essential metabolites from intercalation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2067-2089 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on steric and electrostatic considerations, the prerequisites for binding to DNA via the intercalation mechanism are proposed. Steric contour energy curves are presented to demonstrate the region inaccessible to an intercalant. They are calculated with a 6-n (n = 14) potential. This method is a soft potential analog of an excluded-volume approach. Electrostatic contours on the steric surface illustrate the relatively positive and negative regions of the binding site. The principal intercalation sites, predicted to fit into B-DNA via a tetramer-duplex unit, and the unconstrained dimer-duplex units, obtained in crystal structures, are examined. These contours illustrate the requirements of size, conformation, and net atomic charges necessary for intercalation and optimum binding. Based on the limited space available for intercalation by the presence of the backbone and the maximum base-pair separation of 8.25 Å, an Essential Metabolite Exclusion Hypothesis is presented.
    Additional Material: 9 Ill.
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    The chiroptical properties of proteins. II. Near-ultraviolet circular dichroism of lysozymeTaken in part from the Ph.D. dissertation of W. J. G. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2191-2208 
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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 study of the near-uv CD spectrum of lysozyme was carried out in the presence and absence of the inhibitor tri-N-acetylglucosamine, and theoretical chiroptical calculations based on the tetragonal crystal structure of the enzyme and the enzyme-inhibitor complex were performed. The results of these calculations indicate that the near-uv CD spectrum of lysozyme can be adequately explained in terms of negative rotatory strengths arising from the tryptophan 1La (293-300 nm) and the disulfide n-σ* bands (250 rm), and positive rotatory strength contributions from the tryptophan 1Lb bands (291 nm) and the tyrosine 1Lb bands (275 nm). Contributions to the rotatory strength of each band were approximated in terms of specific interactions between chromophores. It was found that the rotatory strength of most of the near-uv transitions arises primarily from coupling interactions involving other side-chain chromophores and amide groups which are in close proximity. Changes which are observed in the lysozyme CD spectrum on binding of tri-N-acetylglucosamine may be explained in terms of changes in the rotatory strength which result from interactions of the 1La transitions of the active-site tryptophans with the acetamide groups of the inhibitor. The reasonable agreement which is found between the experimental and calculated rotatory strengths implies that the crystal conformation of lysozyme must resemble the solution conformation.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360191205
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    Relationship between conformation and physicochemical properties of polypeptides. I. Synthesis of homo- and co-oligopeptides by the liquid-phase method (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 173-187 
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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 synthesis of the following oligo- and co-oligopeptides by the liquid-phase method is described: (L-Met)15 (I), [L-Glu(OBzl)]20 (II), (L-Val)8-Gly (IV), (L-Ile)8-Gly (V), (L-Ile)4-Gly-(L-Ile)4 (VI), (L-Ile)4-Pro-(L-Ile)4 (VII), (L-Met)5-L-Pro-(L-Met)5 (VIII), [L-Glu(OBzl)]7-L-Pro-[L-Glu(OBzl)]7 (IX). The oligomers are covalently bound to bifunctional polyethylene glycol (PEG) and monofunctional PEG-M of Mr 5 × 103-2 × 104. Analytical controls were carried out after each step of synthesis in order to ensure quantitative coupling yields. All products could be obtained in high purity as indicated by amino acid analysis, thin-layer chromatography and chiroptical methods. The solubility of the oligomers was strongly enhanced by the presence of the C-terminal PEG group, enabling conformational investigations in a variety of solvents. A significant relationship between conformation and physicochemical properties of the oligopeptides was observed. Oligomers with tendencies to adopt α-helical (I, II) or unordered structures (VI-IX) showed no pronounced change in solubility or coupling kinetics during chain elongation, whereas the onset of a β-structure (IV, V) was paralleled by a drastic decrease in solubility and reactivity of the terminal amino groups. Most notably, the insertion of a proline or glycine in the middle of a β-forming peptide chain (VI, VII) resulted in a considerable increase in solubility compared to the corresponding homo-oligomers. The impact of the conformational properties of a peptide chain on strategic considerations of peptide synthesis in solution is delineated.
    Additional Material: 4 Tab.
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    Circular dichroism and conformational analysis of the membrane-modifying peptide -N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu-(OBzl)-Gln-OMe with respect to alamethicin (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 203-214 
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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 analysis of the CD spectrum is reported for the synthetic and membrane-modifying nonadecapeptide analog of alamethicin N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu(OBzl)- Gln-OMe. The CD data are evaluated according to three different methods and are discussed with respect to those obtained from natural alamethicin and suitable models such as N-t-Boc-(Aib-L-Ala)7-OPOE, fragments of the synthetic nonadecapeptide, and the hexadecapeptide N-t-Boc-(Aib-L-Ala)5-Pro-Ala-Aib-Aib-Glu(OBzl)-Gln-OMe. The synthetic nonadecapeptide with the longer helical region exhibits membrane activities comparable to those of alamethicin, whereas the hexadecapeptide with the shorter helix is inactive.
    Additional Material: 4 Ill.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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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.1980.360190201
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    Dynamic light scattering in a flow - a new method of particle anisotropy investigation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 231-240 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper deals with the light scattering from particles rotating in a flow with a transverse velocity gradient. It is theoretically substantiated and experimentally proved that the scattered light spectrum contains reliable information of the particle configuration and dimensions. The proposed technique may prove also very promising for the analysis of particle polydispersion.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190203
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    Poly(ε-L-lysine): Synthesis and conformationPart of this work was presented at the International Symposium on Biomolecular Structure held in Madras, India, in January 1978. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 219-229 
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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 synthesis of poly(ε-L-lysine) is described. This is a poly(ε-amino acid) in which the ε-amino group of lysine is condensed with the α-carboxyl group to produce a chain backbone that is a variant of the usual one seen in proteins and the side chain is the α-amino group. Conformational studies of poly(ε-L-lysine) and its t-butyloxycarbonyl derivative suggest the likelihood of a chain order that is formally similar to the antiparallel pleated-sheet conformation of proteins.
    Additional Material: 4 Ill.
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    Contribution of electrodiffusion to the dynamics of electrically stimulated changes in mechanical properties of collagen membranesPresented at the Third International Congress of Biorheology, August 28-September 1, 1978, La Jolla, California. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 241-262 
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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 kinetics of oscillatory tensile forces in collagen membranes. These forces were generated by sinusoidal electric fields applied across the membrane. Both the magnitude and phase of the measured force changed with frequency over a three-decade range. The membrane-separated electrolyte baths had different ionic strength but identical non-isoelectric pH. Changes in intramembrane ionic strength due to the electric field were calculated over the same frequency range via an electrodiffusion model that was generalized to include convection and electrokinetic coupling. A comparison of the experimental and theoretical phases and amplitudes versus frequency suggests that electrodiffusion is the dominant rate-limiting process in this electromechanochemical transduction. These results are relevant to electrostatic interactions in connective tissues and to membrane-based filtration devices in which membrane permeability may be actively varied and controlled by an applied electric field.
    Additional Material: 8 Ill.
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    Heat capacity changes and partial molal heat capacities of some di- and tripeptides in water (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 263-272 
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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: Integral enthalpies of solution of several dipeptides and tripeptides in water at low concentrations have been determined at 25 and 35°C. These data have been used to derive the changes in heat capacity on dissolution at infinite dilution ΔCp0 at 30°C. Limiting partial molal heat capacities ΔCp20 have been determined by combining ΔCp0 with Cp2 (heat capacity of pure solid peptides). Using the data on ω-amino acids and these peptides, the partial molal heat capacity of a peptide group —CONH— was semiquantitatively estimated.
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    Heat capacities of transfer of some amino acids and peptides from water to aqueous urea solution (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 273-284 
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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: Integral enthalpies of solution at low concentrations of several amino acids and peptides in 2 and 6M urea solutions have been determined at 25 and 35°C. These data have been used to derive the enthalpies of transfer (at 25 and 35°C) and heat capacities of transfer (at 30°C) of these amino acids and peptides from water to aqueous urea solutions. Furthermore, the enthalpies of transfer and heat capacities of transfer per CH2 group and per peptide group —CONH— have also been estimated. These results show that while the enthalpies and heat capacities of transfer per CH2 group are positive and negative, respectively, the reverse is true for —CONH— group. The implications of these results in the mechanism of the denaturation of proteins by urea are discussed.
    Additional Material: 4 Ill.
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    Studies on transfer ribonucleic acids and related compounds. XXVI.Paper XXV: Ohtsuka, E., Miyake, T. & Ikehara, M. (1979) Chem. Pharm. Bull. 27, 341-345. Circular dichroic properties of cyclic oligoribonucleotides and their linear counterparts (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 285-296 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CD spectra of cUpUp, cCpCp, and cGpGp derived from DCC-catalyzed polymerization of the relevant protected ribonucleoside 3′-phosphates are described. Similar studies on Up, U 〉 p, and cUp, as well as cUpUpUp and cUpUpUpUp, are presented. The spectral properties of the cyclic oligomers are compared with those of the corresponding linear oligomers with terminal 3′-phosphates so as to demonstrate that disruption of normal right-handed base stacking is considerable in these RNA loops.
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    Chemical synthesis of (1 → 2)-α-D-mannopyranan (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 297-309 
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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 polymerization of 1,2-anhydro-3,4,6-tri-O-benzyl-β-D-mannopyranose proceeds in the presence of Lewis acids, cationic coordination catalysts, and strong bases. Debenzylation of the products yields oligomeric saccharides or low polymers. Polymerization in toluene by means of potassium alkoxide complexed with crown ethers leads to essentially stereoregular (1 → 2)-α-D-mannopyranan. The original derivatives have been characterized by optical rotation, viscosity, molecular weight, gel permeation chromatography, and spectrometry. The free polysaccharides have been characterized by optical rotation, molecular weight, and 1H- and 13C-nmr spectrometry and compared to yeast mannan hydrolysate oligomers.
    Additional Material: 4 Ill.
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    Physical association of two simple alkylators to some DNA sequences (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 311-324 
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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 mechanics calculations have been used to determine the preferred physical association sites of the known alkylating agent dimethyl aziridinium ion (Az+) and a CH3+ prototype test probe with B-form, tetrameric DNA sequences. Electrostatic interactions are most important in determining these preferential physical association sites. In turn, the intermolecular energy minima depend on the charge distribution assigned to the DNA sequence. However, for three reported DNA charge distributions, only two distinct sets of energy minima were obtained for the CH3+-like ion interacting with (G-C)4, (A-T)4, and [(G-C)·(A-T)]2 deoxyribonucleic acids. These minima correspond to physical association geometries in which the CH3+-like ion is near known alkylation sites. The results of the Az+ … [(G-C)·(A-T)]2 interaction are virtually identical to those found for the CH3+-like ion. Aqueous solvation energetics have little effect on the physical association of Az+ with [(G-C)·(A-T)]2.
    Additional Material: 6 Ill.
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    Chemical reactivity of protonated aziridine with nucleophilic centers of DNA bases (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 325-340 
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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 series of molecular orbital calculations, using MINDO/3 and CNDO/2L methods, have been used to characterize the chemical reaction of protonated aziridine with DNA nucleophilic base sites. The N-7 atom of guanine is found to be the preferred alkylation site only when the O-6 atom of guanine is involved in base-pair hydrogen bonding. Otherwise O-6 is the predicted major site of alkylation. This indirectly suggests that protonated aziridine alkylation processes involve base-paired DNA structures, since N-7 guanine is the observed major site of alkylation. Alkylation of N-3 adenine is predicted to be more favorable than chemical attack of the N-7 adenine position. Both of these sites, however, are predicted to be less reactive than N-7 of guanine. These chemical reactivity studies resolve alkylation specifically not achieved in the DNA-alkylator physical association calculations reported in the preceding paper.
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    Conformational analysis of somatostatin and selected analogs in oriented polyoxyethylene by infrared dichroism (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 341-352 
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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: Infrared dichroic studies and deuterium exchange measurements of somatostatin and some of its analogs incorporated in uniaxially oriented polyoxyethylene are described. Band positions and dichroic ratios in the N-H stretching and amide I and II regions are similar to those of flexible and nonordered peptides like valinomycin and poly[Glu(ONa)]. This information, together with fast deuterium exchange rates, suggests that somatostatin exists in a flexible nonordered conformation in polyoxyethylene. One analog, di-S3,14-acetamidomethyl dihydrosomatostatin, was found to exist in both nonordered and β-like conformations.
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    Monte carlo simulation of the solvent structure in crystals of a hydrated cyclic peptide (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 395-418 
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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 Monte Carlo simulation of the structure of the 16 ordered and disordered waters in the unit cell of crystals of the cyclic peptide cyclo(-L-Ala-L-Pro-D-Phe)2 is reported. The water structure has been characterized in terms of the statistically averaged positions of the individual molecules, their root-mean-square movements about these positions, the probability of finding a water in a given spatial position in the crystal (probability maps), and examination of individual configurations of the system. In this way a picture is obtained of the water structure, including water orientations (hydrogen positions), the hydrogen-bonding network, and fluctuations in these structural features, to a degree hitherto unavailable either from experimental or theoretical studies. In addition, the variation in water structure in various peptide environments was studied and correlated with the energetics of the individual water molecules. Variations in the crystalline environment of different water molecules lead to energy differences of as much as 4-5 kcal/mol in their average energies. Similarly, differences are observed in the water-peptide and water-water components of the energy. Two different water potentials were tested. The results were compared with experimental data in terms of mean positions, root-mean-square movements, and the Fourier transform of the simulated water structure. The agreement factor (R factor) calculated from the theoretical water probability distribution was 18.8% compared to the x-ray value of 14.5%, and the value of 28% when the water is omitted.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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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.1980.360190301
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    Polymeric model system for protein-bilirubin interaction (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 445-448 
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    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.1980.360190217
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    Conformational flexibility of peptides containing α,β-unsaturated amino acid residues. I. Conformational analysis of N-acetyl-N′-methylamides of dehydroalanine and N-methyldehydroalanine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 469-475 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy calculations on the N-acetyl-N′-methylamides of dehydroalanine and N-methyldehydroalanine indicate that their conformational behavior is very different from that of the corresponding saturated compounds. The conformational data in the literature from x-ray and nmr investigations on peptides containing α,β-unsaturated residues are discussed on the basis of these theoretical results.
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    Synthesis and ordered structure of amphipatic block copolymers with a saccharide and a peptide block (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 493-507 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amphipatic block copolymers (OβEb) with a hydrophilic saccharide block and a hydrophobic polypeptide block were synthesized. In these copolymers the saccharide block is the glyco-amino acid Oβ from ovomucoid and the peptide block (Eb) is a poly(γ-benzyl-L-glutamate) block. Copolymers OβEb exhibit, in the solid state and in Me2SO concentrated solutions, mesomorphic lamellar structures where the polypeptide chains are in an α-helical conformation. Depending on the molecular weight of the polypeptide block, three types of lamellar structures are obtained, and they differ by the mode of organization of the polypeptide chains in their lamellae and by the T or Y conformation of the saccharide block.
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    Spectroscopic and equilibrium dialysis studies of poly(α-L-glutamic acid)-Cu(II) complexes in the pH range 4-7For the preceding paper of the Macromolecule-Metal Ion Complex series, see Macromolecules 12 (1979) in press. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 477-491 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of complex between the Cu2+ ion and poly(α-L-glutamic acid) [poly(Glu)] in 150 mM NaCl solutions was studied by uv-visible absorption and equilibrium dialysis methods at the mixing ratios of Glu residues to Cu2+, R, of 32, 16, and 8 and in the pH range 4-7. The results showed that more than 90% of Cu2+ ions bind to the poly(Glu) at pH 〉 4.9, but the bound Cu(II) begins to dissociate with a decrease in pH. The absorption spectra of bound Cu(II) varied with pH and R in a complicated manner. Three different component spectra were disclosed from the analysis of the pH dependence of the bound spectra. We concluded that poly(Glu)-Cu(II) complexes fall into three classes in the pH range 4-7, with the proportions of these complexes varying with both pH and R. The three complexes predominate either in the helix or extended-coil region, in the helix-coil transition region, or in the helix-aggregate region. The stability constant and binding mode of each Cu(II)-Glu complex were estimated from the dialysis data. With these results, the possible structure of each complex is discussed.
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    Nearest-neighbor and next-nearest-neighbor effects in the proton NMR spectra of the oligoribonucleotides ApGpX and CpApX (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 557-573 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variable-temperature proton nmr spectra of the oligoribonucleotides in the series CpApX and the series ApGpX, X = A, G, C, U, together with the parent dimers CpA and ApG have been measured. A complete analysis of all the nonexchangeable base proton resonances and ribose H-1′ proton resonances was made. The presence of trends in the shielding abilities of the various bases at both the nearest-neighbor and next-nearest-neighbor positions were identified. The observed shieldings could be used to predict the chemical shifts of protons in related systems. Based on the empirical results from ribodinucleoside monophosphates, the temperature-dependent behavior of the J1′2′ coupling constants of the triribonucleotides suggested that the compounds in the CpApX series stacked from the 5′-end to the 3′-end, while those in the ApGpX series stacked from the 3′-end to the 5′-end.
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    Monte carlo computation of the supercoiling energy, the sedimentation constant, and the radius of gyration of unknotted and knotted circular DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 619-637 
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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: Closed random Gaussian polygonal chains of N (6 〈 N 〈 150) bonds of equal length b and thickness d have been generated on a computer. The knot type, the writhing number w, the radius of gyration, and the average of the inverse of the distance between two apices have been determined for each chain. For all the studied knot types - 0, 31, 41, 51, and 52 - the probability density of finding a given w is Gaussian. The Gaussian is centered about 0 for the amphichiral knots. Therefore, for long circular DNAs, the contribution to the supercoiling energy, which depends on w only, may be considered as purely entropic and may be expressed as ARTw2/N, in agreement with previous semiempirical considerations. The parameter A increases with chain thickness, it decreases as N gets larger but rapidly reaches a plateau. Comparison with experimental data from the literature would suggest that the ratio of the writhing to the constraint increases with ionic strength. The ratio of sedimentation constant of the supercoiled DNA to the sedimentation constant of the nicked DNA varies as N1/4 (w/N)2, and therefore depends on the writhing density and on the length of the DNA.
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    Application of band centrifugation to the study of the assembly of alfalfa mosaic virus (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 575-595 
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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 band-centrifugation method for the analysis of an assembly reaction of a simple virus from its RNA and protein is described. The experiment was carried out by sedimenting a band of viral RNA through a solution of depolymerized coat protein. The resulting radial distribution of the reaction products, followed as a function of time, was analyzed by a computer simulation of the series of reaction. This method is based on a numerical solution of the continuity equation for the sedimentation-diffusion process [Claverie, J.-M., Dreux, H. & Cohen, R. (1975) Biopolymers 14, 1685-1700; Cohen, R. & Claverie, J.-M. (1975) Biopolymers 14, 1701-1716]. A numerical method for the simulation of the chemical reaction is derived. From the simulated reaction series, equilibrium constants emerge for the successive addition of protein subunits to the growing nucleoprotein particle.The method is applied to the assembly of alfalfa mosaic virus. If the reaction between RNA and protein is carried out in 0.32M CsCl, pH 7.0, two stages during particle growth are resolved, each characterized by an equilibrium constant K. The determined values for K range from 5 × 105 to 3 × 106 l. mol-1. The existence of these two stages may have a structural implication in the assembly, as they likely represent an elongation and a termination stage. If the reaction is carried out under more favorable conditions (0.25M CsCl, pH 7.0), a kinetic constant of at least 105 l. mol-1 sec-1 is derived for each reaction step. Under these conditions the assembly appears to be completed within 1 min, which is too fast to detect distinct stages by band sedimentation.
    Additional Material: 7 Ill.
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    Characterization of molecular motions in 13C-labeled aortic elastin by 13C-1H magnetic double resonance (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 597-617 
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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: Purified insoluble elastin samples labeled with [1-13C]valine, [1-13C]alanine, and [1-13C]-lysine were prepared from chick aorta in culture. The molecular mobility at the labeled sites was investigated using 13C-1H magnetic double-resonance spectroscopy. Linewidths, T1, and nuclear Overhauser effect (NOE) values of the labeled carbons alone were obtained from dipolar decoupled difference spectra. Analysis of these parameters together with signal intensity measurements showed that essentially all the valyl residues, ca. 75% of the alanyl residues, and ca. 60% of the lysyl residues were characterized by rapid backbone motions having τ = 65 nsec. Resonances due to the remaining alanyl and lysyl residues were detected in cross-polarization experiments, which enhance the signals of motionally restricted carbons. Since lysyl and alanyl residues are found in the crosslink regions of elastin, whereas valyl residues are not, we conclude that crosslinks rather than secondary structures in the extensible region of the protein are the main source of motional restrictions in the protein. Elastin chain mobility was monitored by linewidth measurements over the range -90 to +70°C. When the swelling solvent (0.15M NaCl) was fixed at 0.6 g/g of elastin, a rapid monotonic reduction in chain mobility was observed as the temperature was lowered from 50 to 5°C. Liquidlike mobility was completely lost at 5°C. In contrast, the same sample in contact with excess solvent retained its liquidlike molecular mobility until -13°C, where it abruptly became rigid. The molecular mobility of this sample was temperature insensitive in the physiologically interesting range, 20-40°C, as a consequence of the opposing influences of temperature and swelling. Taken together these nmr data indicate that under physiological conditions, elastin is a network of mobile chains whose motions are strongly influenced by protein-solvent interactions.
    Additional Material: 8 Ill.
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    Measurement of preferential solvation of some glucans in mixed solvent systems by gel-permeation chromatography (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 639-653 
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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: Preferential solvation of the glucans amylose, pullulan, and dextran in binary dimethyl-sulfoxide/water (DMSO/H2O) solvent mixtures has been measured using gel-permeation chromatography. The preferential solvation behavior of the three glucans in DMSO/H2O solvent mixtures is indistinguishable in the experiments reported. In solvent mixtures with mol ratio DMSO/H2O less than 1:2, all three glucans are solvated preferentially by H2O. The maximum extent of preferential solvation by H2O is about 2.5 mol H2O/mol of glucose residues. When the DMSO/H2O mol ratio exceeds 1:2, DMSO solvates the glucans preferentially to a maximum extent of about 1 mol DMSO/mol of glucose residues. An interpretation of the change in preferential solvation with mixed solvent composition is suggested in terms of the known characteristics of the binary solvent system, and the relationship of preferential solvation, reported here, to the absolute solvation of the glucan chains is discussed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190313
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    Electrical conductivity of single crystals of lysozyme (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 669-679 
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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 dc electrical conductivity of large single crystals of hen egg-white lysozyme has been measured. The samples were grown from aqueous solution and dried in air with silica gel. The temperature dependence of the conductivity obeyed the relation σ = σ0 exp(- ΔE/kT), with ΔE = 1.2 eV. The ΔE value agreed with most of the previous results for various proteins in the form of lyophilized powder. On the other hand, log σ0, being between 7 and 11, was much larger than the previously reported values and differed among the samples. An irreversible decrease in σ0, without affecting ΔE, was observed on heating the samples above 85°C. It was shown that the set of results can be explained if the charge carriers responsible for the observed conduction are regarded as protons, originating from residual water molecules. Photoresponse of the samples to uv radiation below 305-315 nm was also observed. Reproducible and reliable results were obtained relatively easily in the present experiments, which is thought to be the main advantage of using single-crystalline samples.
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    Masthead (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983) 
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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.360220101
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    Theory of protein secondary structure and algorithm of its prediction (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 15-25 
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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 molecular theory of protein secondary structure is presented that takes account of both local interactions inside each chain region and long-range interactions between different regions, incorporating all these interactions in a single Ising-like model. Local interactions are evaluated from the stereochemical theory describing the relative stabilities of α- and β-structures for different residues in synthetic polypeptides, while long-range effects are approximated by the interaction of each chain region with the averaged hydrophobic template. Based on this theory, an algorithm of protein secondary structure prediction is proposed and examples are given of “blind” predictions made before the x-ray structural data became available.
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    Monte carlo simulations of peptide solvation (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 27-31 
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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 increase our understanding of peptide-water interactions, we are simulating the behavior of water molecules in the intermolecular channels of [Phe4Val6]antamanide dododecahydrate crystals. There is good overall agreement between the positions predicted using two alternative potential functions and those that have been observed by x-ray diffraction. Detailed differences between the predictions for the two potential functions are discussed.
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    An empirical approach to protein conformation stability and flexibility (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 49-58 
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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: Experimental measurements of disulfide bond stability at various stages of protein folding are considered in terms of the effective concentrations of the thiol groups relative to each other; values of up to 107M are observed, so that intramolecular interactions within the interior of a protein are much more stable, and provide greater stability to the folded conformation, than those on the surface or in a flexible segment. Intramolecular interactions can have substantially lower free energies than intermolecular, for solely entropic reasons; this implies that polar interactions, such as hydrogen bonds and salt bridges, can provide net stabilization to a folded conformation, in spite of the unfolded protein having intermolecular interactions with the solvent. These considerations can account for the lower free energy and enthalpy of the folded state and are useful for considering protein flexibility.
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    Conformational properties of microtubule protein: Their relation to the self-assembly process in vitro (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 87-91 
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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: Near- and far-uv CD spectra of microtubule protein preparations have been examined to study the possible role of protein conformation in relation to the kinetics of the self-assembly of these proteins into microtubules in vitro. Although tubulin can form conformations with high helical content under apolar solution conditions, this transformation is apparently not involved in self-assembly. There is no major perturbation of tubulin near-uv CD by reagents and solution conditions favoring assembly. Thus, in these preparations, tubulin, as dimer and as oligomer with MAPs, is effectively in the conformation in which it undergoes self-assembly. This conclusion is consistent with a hybrid model of assembly of microtubule protein involving direct incorporation of oligomeric species as an alternative to the condensation polymerization of tubulin dimer as the exclusive assembly mechanism.
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    URL: http://dx.doi.org/10.1002/bip.360220114
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    The unfolding mechanism of thermolysin (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 101-105 
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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 ligand-modulated kinetics of the autoproteolysis of thermolysin and the high-molecular-weight products of the reaction provide evidence for the conclusion that separation of the two structural domains is most probably the first step on the unfolding pathway of the protein under native conditions.
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    Genetic and biochemical analysis of in vivo protein folding and subunit assembly (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 125-129 
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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: The in vivo pathway of folding and subunit assembly of a trimeric bacteriophage protein has been studied by characterizing precursors to the native protein and by analyzing temperature-sensitive mutations that kinetically block the pathway. The native trimer is formed via an intermediate composed of three partially folded chains, the protrimer. At 39°C, temperature-sensitive mutations prevent the formation of both the native trimer and the protrimer, possibly by destabilizing earlier intermediates. However, the mutations do not affect the stability of the native protein, formed at 30°C. Thus, these mutations identify amino acid residues involved in interactions that determine the folding pathway.
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    URL: http://dx.doi.org/10.1002/bip.360220120
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    Transport properties and hydrodynamic centers of rigid macromolecules with arbitrary shapes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 751-766 
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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 general formalism, which includes translation-rotation coupling, is proposed for calculating translational and rotational transport properties, as well as intrinsic viscosities, of rigid macromolecules with an arbitrary shape. This formalism is based on Brenner's theory of translational-rotational dynamics and on methods for the calculation of hydrodynamic properties that have been already presented, and can be regarded as a generalization of the one proposed by Nakajima and Wada. The calculated transport properties depend on the origin as predicted by Brenner's theory, but in a disagreement with him, the center of resistance and the center of diffusion do not coincide. As one can define several hydrodynamic centers, which in practice turn out to be located at different points, the influence of the choice of the center on the calculated transport properties is discussed. An analysis of the translation-rotation coupling effects in translational diffusion reveals that they arise exclusively from hydrodynamic interactions and are rather small in some cases of interest. Finally, we present a study of the rotational diffusion of rigid bent rods with a fixed length-to-diameter ratio. The diffusion coefficients obtained can be useful to estimate changes with respect to a straight rod.
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    Conformational and functional properties of hemoglobin in perturbed solvent: Kinetics of O2 release (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1677-1696 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the kinetics of O2 release by oxyhemoglobin caused by sodium dithionite, in the presence and in the absence of organic cosolvents (monohydric alcohols and formamide) at 10°C. This study was performed by using standard stopped-flow techniques coupled with microprocessor-based data acquisition. We have fitted the experimental data to a mathematical expression obtained on the basis of a two-state model that takes into account the kinetic heterogeneity between α- and β-chains and the presence of αβ-dimers in oxyhemoglobin solutions. Results indicate that the cosolvents mainly affect the allosteric parameter L, i.e., the T ⇄ R conformational equilibrium of hemoglobin, leaving the intrinsic deoxygenation rates of both R and T states almost unaltered. The L values obtained in the present work are in excellent agreement with analogous values previously estimated from oxygen equilibrium measurements.
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    URL: http://dx.doi.org/10.1002/bip.360220706
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    Solution properties of porcine submaxillary mucin (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1657-1675 
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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: Porcine submaxillary mucin (PSM) is a glycoprotein composed of a protein core and frequent, short oligosaccharide side chains. We report static and dynamic light scattering experiments and intrinsic viscosities for PSM in aqueous solvent systems. In 0.1M NaCl solution, the data suggest PSM exists as large, internally branched, highly hydrated, polydisperse aggregates that slowly dissociate to give a stable species of weight-average molecular weight (Mw) 7.4 × 106. In 6M GdnHCl solution, the noncovalent bonds between PSM molecules are broken, giving a highly elongated molecule of Mw = 2.0 × 106. The irreversible nature of this dissociation suggests that the forces that stabilize the native aggregates of PSM in 0.1M NaCl are specific in nature. On reduction of PSM with mercaptoethanol, the polydispersity decreases and Mw also decreases to 9 × 105. A discrete change is observed in the solution properties of PSM in 0.1M NaCl at a concentration of 2mg/mL, manifested by a sudden decrease in the translational diffusion coefficient, an increase in viscosity number, and a decrease in slope of the osmotic compressibility. We tentatively propose that a weak and reversible secondary association process occurs at this concentration, although a purely hydrodynamic interaction cannot be ruled out.
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    Linear dichroism studies of nucleic acids. III. Reduced dichoism curves of DNA in ethanol-water and in poly(vinyl alcohol) filmsFor Part II in this series, see Matsuoka, Y. & Nordén, B. (1982) Biopolymers 21, 2433-2452. (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1731-1746 
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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 uv linear dichroism of calf thylus DNA has been studied at different degrees of orientation both in flow-oriented ethanol-water solutions and in a stretched aqueous host of poly(vinyl alcohol) (PVA). The reduced dichroism (LDR) curves in the region 250-290 nm for DNA in PVA films at 75 and 100% relative humidity (r.h.) are in fair agreement with the curves calculated for the A- and B-forms of DNA, based on the fiber structures and the π-π* transitions of the free bases. This suggests that DNA adopts its A and B conformations in PVA at 75 and 100% r.h. In ethanol, on the other hand, a deviation from the A-form spectrum shows that the conformation of DNA in the solution can differ from the fiber structure. At shorter wavelenghts, a positive contribution to LDR is explained in terms of an out-of-plane polarized n-π* transition.
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    Localized vibrational modes at a double-helix-single-strand junction (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1759-1767 
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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 vibrational analysis has been performed for a double-helix-single-strand junction. A Green's function technique has been used in treating the junction as a defect on an otherwise perfect system of infinite chain homopolymers. We calculate that the hydrogen-bond stretching at the junction is amplified by a factor of two relative to the interior of the double helix, B poly(dG)-poly(dC). Breathing modes localized near the junction have also been predicted at 77 and 94 wave numbers. The calculated results are shown to be consistent with predictions from recent nmr studies.
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    Masthead (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220801
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