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  • Wiley-Blackwell  (14,393)
  • 1995-1999
  • 1980-1984
  • 1975-1979  (14,393)
  • 1925-1929
  • 1978  (7,320)
  • 1977  (7,073)
Collection
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  • 1995-1999
  • 1980-1984
  • 1975-1979  (14,393)
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    Influence of fluctuations in electron density on the excess small-angle X-ray scattering from dilute solutions of macromolecules (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 67-80 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence on the excess scattering function P(μ) of flutuations in the electron density ρ within a macromolecule is treated, to the approximation that the solvent is a structureless medium of constant electron density ρ0. The results for P(μ) and the apparent value of the mean square radius Rapp2, can be expressed as functions of the excess electron density Δρ: P(μ) = X(μ) + (Δρ)-1Y(μ) + (Δρ)-2Z(μ) and Rapp2 = Rx2 + (Δρ)-1Ry2 + (Δρ)-2Rz2, where X(μ) and Rx2 depend only on the shape of the macromolecule, while Y(μ) and Ry2 as well as Z(μ) and Rz2 depend on the shape and the fluctuations in ρ. By varying the electron density of the solvent, the contributions of the shape and the internal structure of the macromolecule can be resolved. The quantities Rx2, Ry2, and Rz2 are evaluated for seven models to illustrate the relative importance of these contributions for representative structures.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160106
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  • 2
    Electronic Resource
    Electronic Resource
    The optical properties of tyrosine-containing cyclic dipeptides (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 121-142 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiroptical properties of the cyclic dipeptides cyclo (L-alanyl-L-tyrosine) and cyclo(L-tyrosyl-L-tyrosine) have been investigated as a function of molecular conformation. Theoretical optical calculations and conformational energy calculations have been carried out as a function of the side-chain dihedral angles χ1 and χ2, and as a function of the angle of fold of the cyclic dipeptide backbone. The results of these theoretical calculations have been compared with experimental circular dichroism (CD) data. Theoretical predictions are in very good agreement with experiment for c(L-Tyr-L-Tyr). Agreement was not quite as good for c(L-Ala-L-Tyr), although the signs of all of the Cotton effects were apparently predicted correctly except for that associated with the lowest energy tyrosine absorption band.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160110
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetic analysis of the annealing period in the formation of the poly(A)·2poly(U) triple helix (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 289-298 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The slow kinetics of annealing processes in multistranded nucleic acids is spectrophotometrically investigated using poly(A)·2poly(U) as a model system. The absorbance changes at specific wavelengths show that double-helical (A·U) base pairs appear as transient intermediates. The annealing process is identified by the enlargement of triple-helical sequences at the cost of (A·U) base pairs and unpaired (U) residues. A large time range in the reorganization of mismatched chain configurations is characterized by a logarithmic dependence on time. This observation is quantitatively described by a kinetic model developed by Jackson. In Jackson's model the rate-limiting process in the slow annealing phase of maximizing triple-helical sequences, is the removal of strand entanglements, knots, and hairpin loops by complete unwinding of those helical stretches which stabilize the mismatched configurations. The results of the present study are briefly discussed in terms of optimum conditions for hybridization experiments and for the preparation of polynucleotide complexes commonly used to produce interferons.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160206
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  • 4
    Electronic Resource
    Electronic Resource
    Fluorescence of proteins in aqueous neutral salt solutions. I. Influence of anions (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 341-368 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of anions of neutral salts on the fluorescence emission of six proteins as well as on tryptophan and tyrosine were studied in relation to the structure of proteins. Most anions are good quenchers of tryptophyl and tyrosyl fluorescence, free or in proteins. The results with tryptophan and tyrosine indicate involvement of a collisional quenching mechanism due to agreement with Stern-Volmer law. The deactivation of fluorescence probably occurs because of the transition from singlet state to triplet state. Lehrer's modification of Stern-Volmer law was applied to proteins. The effective quenching constants ([KQ]eff) and the fraction of fluorescence available ([fa]eff) to the quencher are also calculated.In contrast to its effect on tryptophan, CH3COO- quenches tyrosyl fluorescence and ClO4- does not. The effects on fluorescence of ribonuclease and free tyrosine are similar and without any changes in emission maximum. The anions are divided into three groups based on the effect they have on tryptophan-containing proteins. (1) NO3-, NO2-, Br-, and I- have high [KQ]eff values and readily quench tryptophyl fluorescence of proteins causing a shift of emission maximum to a shorter wavelength. This change is due to the specific quenching of “exposed” tryptophan residues which are accessible to quenchers and the observed residual fluorescence is from the “buried” tryptophyls. (2) ClO4- and SCN- also quench fluorescence of tryptophan in proteins and have lower ([KQ]eff) values. In their presence the fluorescence maximum is shifted to a longer wavelength, which indicates the unfolding of a protein with [(fa)eff] = 1. (3) Cl-, CH3COO-, and SO4— do not have a direct effect on the fluorescence of tryptophan. Besides the “direct” effects, “indirect” effects on fluorophors in protein are also seen, pointing out that the neutral salts can interact in more than one manner with proteins. The effectiveness of anions in quenching fluorescence of proteins follows similar sequences which almost resemble the Hofmeister series, viz., SO4=, CH3COO- ≃ Cl- 〈 ClO4- 〈 SCN- 〈 Br- 〈 I- 〈 NO3- 〈 NO2-.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160210
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  • 5
    Electronic Resource
    Electronic Resource
    Co-oligopeptides of aromatic amino acids and glycine with a variable distance between the aromatic residues. V. pH-Dependent conformational changes in peptides containing two adjacent tryptophyl residues as evidenced by circular dichroism studies (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 437-448 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of pH upon CD spectra of H-Trp-Trp-OH, H-Trp-Trp-Gly-OH, and H-Gly-Trp-Trp-OH is investigated and data are compared with those obtained for peptides containing only one tryptophyl residue. A negative Cotton effect at around 225 nm, which in previous work has been related to an increase of the conformational rigidity in compounds having the sequence -CO-Trp-Trp, is also observed in the case of H-Trp-Trp-OH and H-Trp-Trp-Gly-OH upon deprotonation of the terminal α-amino group. These data, together with observations arising from solvent and temperature effects, give evidence that H-Trp-Trp-OH undergoes a conformational change upon going from acid to alkaline conditions, where the two aromatic side chains become conformationally more rigid relative to each other. This rigidity generates an exciton coupling between the Bb transitions of the two indoles. Hydrophobic forces, including stacking interactions, do not appear important in stabilizing this conformationally rigid structure. Rather, intramolecular electrostatic interactions (e.g., hydrogen bondings or polar interactions between the aromatic side chain and the peptide backbone) as well as interactions with the OH group(s) of the solvent, are suggested to be the salient forces. Possible structures which obey these requisites are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160216
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  • 6
    Electronic Resource
    Electronic Resource
    Spectral analysis on the melting fine structure of λ DNA and T2 DNA (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 427-435 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fine structure of the thermal denaturation of viral DNA's was analyzed with the spectral method established by Felsenfeld and Hirschman, and Fresco et al. A fully automated system measuring melting curves at four wavelengths at the same time was developed for this purpose. With this device, (G + C)-contents of melting components of λ DNA's were determined. The correlation between the (G + C)-content and the melting temperature of each melting component is found to be well described by the linear relationship given by Marmur and Doty. The denaturation of each component is regarded as cooperative. The Marmur-Doty relation also stands for the local denaturation of T2 DNA, which has a narrow melting range.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160215
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  • 7
    Electronic Resource
    Electronic Resource
    Relaxation times manifested by the Rouse-Zimm model in dynamic light-scattering experiments (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 461-464 
    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.1977.360160218
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  • 8
    Electronic Resource
    Electronic Resource
    Measurement of diffusion coefficient and electrophoretic mobility with a quasielastic light-scattering-band-electrophoresis apparatus (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1473-1488 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have constructed an apparatus for the simultaneous measurement of electrophoretic mobility, μ, and diffusion coefficient, D, of macromolecules and cells. It combines band electrophoresis in a vertical, sucrose-gradient stabilized column, with quasielastic laser light-scattering determination of the diffusion coefficient of the species within the band. The entire electrophoresis cell is scanned through the laser beam of the quasielastic laser light-scattering apparatus by a vertical translation stage. Total intensity light-scattering measurement at each point in the cell gives the macromolecular concentration at that point. Solvent viscosity and electrical potential are measured at each point in the cell. Application of this apparatus to resealed red blood cell ghosts and to bovine hemoglobin indicates that measurements of field, viscosity, and migration distance are reliable, and that electroosmosis is insignificant. Application to T4D bacteriophage gives μ20,w = (-1.05 ± 0.05) × 10-4 cm2/V sec and D20,w = (3.35 ± 0.10) × 10-8 cm2/sec for fiberless particles, and μ20,w = -(0.59 ± 0.03) × 10-4 cm2/V sec and D20,w = (2.86 ± 0.09) × 10-8 cm2/sec for whole phage with 6 fibers. Approximate analysis of these results with the Henry electrophoresis theory for spheres in dicates that each fiber contributes about 193 positive charges to the phage particle, compared with 327 from amino-acid analysis. The advantages and disadvantages of this apparatus, relative to conventional electrophoresis and to electrophoretic light scattering, are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160708
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  • 9
    Electronic Resource
    Electronic Resource
    Viscosity and potentiometric measurements of poly(L-histidyl-L-alanyl-α-L-glutamic acid) and poly(L-lysyl-L-alanyl-α-L-glutamic acid) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1541-1555 
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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(His-Ala-Glu) and poly(Lys-Ala-Glu) were examined by viscosity and potentiometric titration. These measurements were interpreted in terms of the hydrodynamic size of the above sequential polypeptides. Effects of polymer, size and concentration, and solution-salt concentration were demonstrated. Although the sequential polypeptides generally behave like polyampholytes, they do demonstrate some differences. These differences my be attributed to the ability of ionized side chains three residues apart to repel themselves, in the order His 〈 Glu 〈 Lys.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160713
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  • 10
    Electronic Resource
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    Etude experimentale de L′auto-association des molécules modèles dipeptidiques. III. Influence de la dimerisation stéréosélective sur les spectres de résonance magnétique protonique (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 715-729 
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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: Proton magnetic resonance spectra of model dipeptide molecules R1-C′1O1-N2H2-C2αH2αR2-C′2O2-N3H3-R3 in CCl4 solutions exhibit splited signals when investigating on mixtures of L and D enantiomers differing from the racemic composition. The major effect is observed on amide proton signals which are the ones most sensitive to the ratio of aggregation. The stereoselective dimerization of enantiomeric molecules in the so-called C5 conformational state is shown to be responsible for such a phenomenon, the intensity of which depends on the bulkiness of the side chain R2. A theoretical approach is proposed which gives predictions in close agreement with our own experimental findings.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360160403
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  • 11
    Electronic Resource
    Electronic Resource
    Water in keratin: Study of the depolarization thermal current peak II (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1725-1733 
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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 depolarization thermal current method is applied to the study of the polarization phenomena in the keratin-water system. Three depolarization thermal current peaks have been evidenced in hair keratin. This paper deals with the detailed study of peak II. For the first time, the mechanism responsible for this peak is ascribed to molecular reorientation. The effect of water upon the characteristics of peak II is also described, and an activation energy of 8.4 kcal/mol is computed. These results, in connection with other studies, lead us to interpret peak II as due to the reorientation in the bound or intermediate water molecules. The effect of copper confirms that the carboxyl groups are hydration sites.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160809
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  • 12
    Electronic Resource
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    Determination of the base-pairing content of four specific tRNAs by infrared spectroscopy (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1735-1745 
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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 spectroscopy was used for the determination of the base-pairing content of four specific tRNAs in deuterium oxide solution. Infrared spectra were obtained in the 1750-1550 cm-1 region at various temperatures ranging from about 15 to 90°C. Melting curves were constructed by plotting the molar extinction coefficient at ν = 1657 cm-1 versus temperature. These transition curves enabled us to determine the ranges of temperature which correspond to the ordered (partially double-stranded) or randomly coiled structure of the tRNA. For a set of wavenumbers the extinction coefficients at these temperatures were used for the calculation of the base-pairing content. The procedure employed here is based on a method described earlier by Thomas [(1969) Biopolymers 7, 325-334]. For the conditions selected for this investigation (Mg2+-free D2O-buffer; 0.01M tris-DCl, 0.015M NaCl, pD 7.5) the results of this determination agree within the limits of errors with the number of base pairs predicted by the cloverleaf model.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360160810
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  • 13
    Electronic Resource
    Electronic Resource
    Hydrodynamics of macromolecular complexes. III. Bacterial viruses (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1779-1793 
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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 calculated the translational and rotational frictional coefficients of structures related to T2 and T4 bacteriophage, using the theoretical framework developed in the preceding two papers. The structures considered were models for tail-fiberless phage, and for whole phage with fibers in the extended and retracted portions. We also computed and compared with the experiment the changes in translational frictional coefficient produced by successive addition of 1-6 fibers to the fiberless particle. Agreement with experimental results is markedly improved over previous theoretical efforts, especially with respect to the effect of tail-fiber extension. Some significant discrepancies remain, however, in the comparison of fiber-retracted and fiberless phage.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360160813
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  • 14
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    Hydrodynamics of macromolecular complexes. II. Rotation (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1765-1778 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have used the modified Oseen hydrodynamic interaction tensor along with iterative numerical solution of the coupled hydrodynamic interaction equations to calculate the rotational diffusion coefficients of macromolecular complexes composed of nonidentical spherical subunits. For the one structure, a prolate ellipsoid of revolution, for which exact solutions are available, a subunit model with the same length and volume gives asymptotic agreement with the Perrin equations. Other structures considered include plane polygonal rings, lollipops, and dumbbells.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360160812
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  • 15
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    Electronic Resource
    Masthead (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160501
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  • 16
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    Characterization of meningococcal polysaccharides by optical mixing spectroscopy. II. Effects of temperature, EDTA, and ionic strength on aggregation of group C polysaccharides in solutionWork supported by FDA. (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 945-963 
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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 effects of temperature, EDTA, and ionic strength on C-polysaccharides in solution by examining the details of the time-correlation function using a 96-channel single-clipped photon correlation spectrometer. Our linewidth results have shown that the C-polysaccharides in buffer solution form aggregates of very broad distributions. Thus, fractionation by gel-filtration chromatography is only mildly effective. Although the aggregate sizes seem to remain relatively constant from 4 to 25°C, a fraction of those aggregates break up to form smaller fragments or monomers at higher temperatures. However, the dissolution-association process is quite slow and takes days even at room temperatures before the equilibrium is reached. We have also shown that by adding an excess amoutn of EDTA, the aggregates can be broken up. Again the dramatic changes occur only at short delay times suggesting that a protion of the larger aggregates remains. Finally, the amount and size of aggregates depend upon the ionic strength which exhibit a maximum ΓT/sin2 (θ/2) around 0.1-0.2 M KCl.If the activities of polysaccharides in solution depend upon molecular size, the standard techniques such as gel-permeation chromatography and ultracentrifugation cannot properly characterize the detailed size distribution. Quasielastic laser light scattering can provide us with a qualitative model. The quantitative details must necessarily await more extensive investigations using a combination of the techniques and better fractionation procedures in an appropriate buffer solution.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360160502
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  • 17
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    Experimental and theoretical investigations on the folding modes of depsipeptide molecules (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1033-1052 
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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 coupling of N-acyl-α-amino-acids with α-hydroxyacid-methyl amides results in depsipeptide molecules containing two chiral centers and one ester function inserted between two amide functions. Their conformational features have been investigated by IR spectroscopy, proton magnetic resonance, X-ray diffraction, and theoretical P.C.I.L.O. calculations.It is shown that most of these molecules are folded by an intramolecular 4 → 1 hydrogen bonding. Two folded conformations, similar to the well known β turn in peptides, are described, the stability of which depends on the configurational sequence in the investigated molecule.LL and LD species are folded in two different ways whereas LG sequences containing an achiral hydroxy-acid residue accommodate both of them. The presence of a N-terminal achiral amino acid noticeably decreases the folding ratio.The above conclusions are then compared with the conformational features of homologous tripeptide molecules.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360160507
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  • 18
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    An improved method of computation of density distributions (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1153-1158 
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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: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160514
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  • 19
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    Kinetics of complex formation between fluorescein mercuric acetate and DNA (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2105-2111 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of complex formation between fluorescein mercuric acetate and heat-denatured DNA were studied by measuring the fluorescence quenching of this reagent. This quenching process involved no immeasurably rapid phase and it was shown that this reaction follows simple second-order kinetics. The rate constant at 25°C was estimated to be 2.9 × 104M-1 sec-1 for calf-thymus DNA (42% G + C) and 1.1 × 104M-1 sec-1 for Micrococcus lysodeikticus DNA (72% G + C). Activation parameters for this reaction were calculated from the temperature dependence of the reaction rate, and the activation entropy was found to be highly negative (-27.5 cal/mol deg for calf-thymus DNA and -25.5 cal/mol deg for M. lysodeikticus DNA). The binding of fluorescein mercuric acetate to native DNA, which requires the opening of the double-helical structure, was also followed by measuring the absorbance change of this reagent. There was a lag phase in this binding process, and the enthalpy change for the opening step corresponded roughly to that for the opening of one base pair. These findings are discussed in relation to the results of a similar study with formaldehyde.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360161003
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  • 20
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    The mechanism of nucleation for in vitro collagen fibril formationPart of this work was presented at the 171st Meeting of the American Chemical Society in Chicago, Illinois, August 1975. (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2113-2131 
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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 formation of collagen fibrils from soluble monomers and aggregates by thermal gelation at neutral pH can be divided into two distinct stages: a nucleation phase and a growth phase. Turbidity studies of the kinetics of the precipitation reaction show that the lag-phase time or nucleation reaction time, t′l, is markedly temperature dependent while the growth reaction time is temperature independent. The activation energy of the nucleation reaction is essentially constant over the temperature range studied. In monitoring the nucleation-phase reaction by various physicochemical techniques, including viscosity, sedimentation equilibrium, and light scattering, no evidence for the formation of aggregates was observed. Enrichment of the initial collagen solution with aggregates accelerates nucleation, but de novo nuclei formation is still required even in highly aggregated collagen preparations. Removal of pepsin and pronase susceptible peptides lengthens the nucleation reaction time and increases the sensitivity of the rate of nuclei formation to changes in ionic strength. Electron microscope studies show the fibrils formed from the protease-treated collagen to be less well organized. With pepsin-treated collagen, subfibrils and obliquely striated fibrils are seen, showing that while microfibrils are formed interactions between them are modulated by the enzyme susceptible peptides in the same way that these regions modulate nuclei assembly. It appears that pepsin and pronase susceptible peptide regions of collagen play a more prominent role in the in vitro assembly of collagen molecules to form D-stagger nuclei and fibrils than do ionic interactions between helical molecular regions. A mechanism of nucleation of collagen fibrillogenesis is discussed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1977.360161004
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  • 21
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    Circular dichroism of the nucleic acid monomers (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2243-2264 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism spectra of the nucleic acid monomers have been measured in aqueous solution and extended into the vacuum ultraviolet region to about 166 nm. Measurements were made on ribo and deoxyribo derivatives of adenine, guanine, hypoxanthine, cytosine, thymine, and uracil derivatives both with and without the 5′-phosphate (with the exception of ribosyl thymine 5′-phosphate). Absorption spectra of the deoxyribonucleotides measured to about 175 nm are also presented. The results demonstrate that both the circular dichroism and absorption spectra observed below 200 nm are no more complicated than the spectra normally recorded above 200 nm. In most cases, the circular dichroism spectra of the various derivatives of a given base are similar, indicating that the conformations are similar. On the other hand, the differences among the circular dichroism spectra of the various derivatives of a given base are sufficient to identify a particular derivative. The average circular dichroism for the deoxyribonucleotides is compared with the circular dichroism of native E. coli DNA. The comparison reveals that the circular dichroism of DNA below 200 nm is due principally to the interaction between the bases rather than the intrinsic circular dichroism of the monomers. The monomer transitions are discussed in relationship to the absorption and circular dichroism spectra presented.
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    A theory for polarized fluorescence microscopy of chromosome structures (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2281-2298 
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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 theory for the determination of DNA arrangements in DNA-containing specimens, using planar aromatic dye molecules as probes for plane polarization of fluorescence, has been described. At low dye-to-DNA concentrations, the dye molecules are sandwiched between the stacked bases of DNA; hence, the fluorescence from the dye bound to a local region of DNA helix is plane-polarized with the polarization direction perpendicular to the local axis of DNA. The degree of such polarization from an aligned DNA-specimen complexed with dye is determined both by the DNA orientation and the conformational state (e.g., base tilt) of DNA into that specimen. Analysis has been made of the relationship between the degree of polarization and the orientation of the emitting dipoles of dye. The dye complexes may be aligned in a mechanical shear or electric field. However, any change in the orientation distribution of the emitting dipoles due to force fields should be taken into account. With some assumptions and approximations, the magnitude and the direction of maximum polarization can be related to different orders of DNA coiling and to their various combinations. Since the measured polarization is averaged over all DNA regions of the specimen, if the magnitude of polarization is appreciable and the polarization occurs in the specific direction of the specimen, the theory helps to eliminate several probable arrangements of DNA. The predominant molecular features of the actual DNA arrangement can be determined through this process of elimination, as explained in two subsequent papers with T-even bacteriophage and chromosome systems.
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  • 23
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    Masthead (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1977.360161101
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  • 24
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    Interaction of amylose and other α-glucans with hydrophobic fluorescent probe (2-p-toluidinylnaphthalene-6-sulfonate) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2363-2370 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Fluorescence of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) was enhanced in the presence of maltooligosaccharides, amylose, and other α-glucans. The dependence of relative TNS fluorescence intensity per glucose unit on chain length of oligosaccharides was examined. The values of binding constant and thermodynamic parameters, assuming the 1:1 complex for TNS-amylose (number-average degree of polymerization, DPN = 17), were determined by the fluorescence titration. The values of thermodynamic parameters for 1:1 complex formation of TNS-α- and β-cyclodextrins were also determined and compared with those of TNS-amylose (DPN = 17). The fluorescence intensity of TNS in the presence of amylose (DPN = 600) decreased by the action of glucoamylase and taka-amylase A. The fluorescence of TNS-amylose (DPN = 17) system increased with the increased ionic strength. In the presence of pullulan, TNS fluorescence was also enhanced and decreased by the action of pullulanase. Amylopectin enhanced TNS fluorescence rather more strongly than amylose (DPN = 17) at the same concentration. In the presence of dextran, the fluorescence of TNS was scarcely enhanced. The degree of fluorescence enhancement of TNS in the presence of α-glucans seems to reflect the structures of α-glucans in solution, since TNS fluorescence is enhanced in the hydrophobic environment or by the disturbance of free intramolecular rotation.
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    Helix-coil stability constants for the naturally occuring amino acids in water. XIV. Methionine parameters from random poly(hydroxypropylglutamine,L-Methionine) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2447-2467 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Water-soluble, random copolymers containing L-methionine and N5-(3-hydroxypropyl)-L-glutamine have been prepared, fractionated, and characterized. The thermally induced helix-coil transitions of these copolymers in water have been investigated, and it has been found that incorporation of L-methionine increases the helix content of the polymers at all temperatures in the range of 0-60°C. The Zimm-Bragg parameters σ and s for the helix-coil transition in poly(L-methionine) in water were deduced from an analysis of the melting curves of the copolymers using the methods described in earlier papers.
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    Vibrational modes of A-DNA, B-DNA, and A-RNA backbones: An application of a green-function refinement procedure (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2491-2506 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Normal vibrational analysis was carried out for DNA molecules in both A and B conformations as well as for A-RNA. A simplified backbone model was examined and expanded to include the backbone phosphate-group and the ribose ring. We applied the new force-constant refinement procedure discussed in the preceeding paper [Van Zandt, L. L., Lu, K.-C. & Prohofsky, E. W. (1977) Biopolymers, 16, 2481-90] to fit some observed frequencies in the Raman spectra for all three nucleic acids with the same set of force constants. The results indicate that the observed frequency shift can be attributed to the conformational change solely. We ignored the second-order differences in force constants for the different geometries. The agreement between the observed and calculated frequencies derived from the final refined set of force constants is good and apparently justifies this assumption. Two modes previously assigned to the symmetric diester O-P-O stretch and the symmetric dioxy O‥P‥O stretch are actually fitted. They are mainly backbone phosphate-group modes. The refined ribose-ring force-constants were transferred to the calculation of the vibrational spectrum of tetrahydrofuran. The overall agreement is again good. We discuss these calculations and the resulting normal modes. We also discuss the application of the Green-function refinement scheme and several strategies adopted to bias the convergence of the procedure.
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    Conformational energy calculations for dinucleotide molecules: A study of the nucleotide coenzyme nicotinamide adenine dinucleotide (NAD+) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1971-1986 
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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 conformational states of the dinucleotide coenzyme NAD+ has been made using semiempirical energy calculations. Taking low-energy mononucleotide structures as starting conformations, energy minimizations have been performed. The lowest energy states are stacked structures, with interactions between the adenine and nicotinamide rings. Some structures show stabilization gained from electrostatic attractions between the positively charged nicotinamide and negatively charged phosphate oxygens. These predictions correlate well with the available experimental data.
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    Block copolymers of amino acids. I. Synthesis and structure of copolymers of L-alanine or L-phenylalanine with D,L-lysine-d7 or D,L-lysine (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2005-2028 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Water-soluble block copolymers of the type (A)m-(B)n-(A)p, where (A)m,p was either poly(D,L-lysine-α,β,β,γ,γ,δ,δ-d7) or poly(D,L-lysine) and (B)n was either poly(L-alanine) or poly(L-phenylalanine), were synthesized for conformational studies by proton magnetic resonance spectroscopy. Analytical determination of the amount of the initiator fragment (n-hexylamine) at the C-terminus of the copolymers was used to obtain the number-average degrees of polymerization, DPn, and thereby, together with the amino acid composition, to establish the covalent structures of the polymers. The values of DPn were found to be much lower than those deduced from sedimentation equilibrium or form viscosity measurements. These deviations, which also are thought to have arisen in similar studies reported in the literature, are attributable to intermolecular aggregation; the relation of such aggregation to covalent structure (and its effect on the polymerization reaction) is discussed in terms of the conditions and mechanism of synthesis of block copolymers of amino acids.
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    The analysis of circular dichroism spectra of natural DNAs using spectral components from synthetic DNAs (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 85-106 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have tested 21 different basis sets of synthetic DNA circular dichroism spectra and have slected one for use in spectral analyses of natural DNAs. This “standard” set consists of spectra of eight polymers: poly[d(A-A-T)·d(A-T-T)], poly[d(A-G-G)·d(C-C-T)], poly[d(A-T)·d(A-T)], poly[d(G-C)·d(G-C)], poly[d(A-G)·d(C-T)], poly[d(A-C)·d(G-T)], poly[d(A-T-C)·d(G-A-T)], and poly[d(A-G-C)·d(G-C-T)]. This basis set, applied according to the first-neighbor polymer procedure of Gray and Tinoco, allows a more uniformly accurate spectral analysis of six natural complex DNAs and eight (A+T)-rich satellite DNAs for base composition and first-neighbor frequencies than was previously possible. We find that spectra of poly[d(A)·d(T)] and/or poly[d(A-C-T-)·d(A-G-T)] are not generally required for good analysis results but we show in this and the following paper that these spectra are needed for the most accurate analyses of some satellite DNAs.
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    Masthead (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Interaction between poly(L-lysine48, L-histidine52) and DNA (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1879-1894 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Poly(Lys48, His52), a random copolypeptide of L-lysine (48%) and L-histidine (52%), was used as a model protein for investigating the effects of protonation on the imidazole group of histidines on protein binding to DNA. The complexes formed between poly(Lys48, His52) and DNA were examined using absorbance, circular dichroism (CD), and thermal denaturation. Although increasing pH reduces the charges on histidine side chains in the model protein, the protein still binds the DNA with approximately one positive charge per negative charge in protein-bound regions. Nevertheless, CD and melting properties of poly(Lys48, His52)-DNA complexes still depend upon the solution pH which determines the protonation state of imidazole group of histidine side chains. At pH 7.0, the complexes show two characteristic melting bands with a tm (46-51°C) for free base pairs and a t′m (94°C) for protein-bound base pairs. The t′m of the complexes is reduced to 90°C at pH 9.2, although at this pH there is still one lysine per phosphate in protein-bound regions. Presumably, the presence of deprotonated histidine residues destabilizes the native structure of protein-bound DNA. The binding of this model protein to DNA causes a red shift of the crossover point and both a red shift and a reduction of the positive CD band of DNA near 275 nm. This phenomenon is similar to that caused by polylysine binding. These effects, however, are greatly diminished when histidine side chains in the model protein are deprotonated. The structure of already formed poly(Lys48, His52)·DNA complexes can be perturbed by changing the solution pH. However, the results suggest a readjustment of the complex to accommodate charge interactions rather than a full dissociation of the complex followed by reassociation between the model protein and DNA.
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    Theoretical conformational analysis of Asn1, Val5 angiotensin II (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1929-1943 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theoretical analysis of the conformation of the octapeptide hormone Asn1, Val5 angiotensin II has been carried out by semiempirical potential energy calculations. A preliminary study of the Ala6-Pro-Ala molecule, which mimics the angiotensin backbone, provided us with likely backbone structures on which the effect of the full side chains of the hormone could be assessed. For angiotensin II, the calculations show that only a small number of folded, compact conformations have a high probability of existence. This is the consequence of favorable packing and of the presence of proline in position 7. These results are consistent with various experimental data, both structural and biological. This method is readily applicable to the study of analogs of the hormone or to other peptides of comparable size.
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    Effect of charge density of cationic polyelectrolytes on complex formation with DNA (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1993-2004 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction between DNA and ionen polymers, -[N+(CH3)2(CH2)mN+(CH3)2(CH2)n]l-, with m-n of 3-3, 6-6, and 6-10 were examined in order to know how the binding behavior of cationic polymers with DNA depends on the charge density of polycation. The ionen polymer has no bulky side chain and the binding forces with DNA would be attributed mainly to electrostatic interaction. When 3-3 ionen polymers were added to DNA solution, precipitable complexes with the ratio of cationic residue to DNA phosphate (+/-) of 1/1 and the free DNA molecules were segregated, while 6-6 and 6-10 ionen polymers formed soluble complexes with DNA molecules up to (+/-) = 0.5. This suggests that 3-3 ionen polymers bind cooperatively with DNA while 6-6 and 6-10 ionen polymers bind noncooperatively. The cooperative binding of 3-3 ionen polymer and the noncooperative binding of 6-6 ionen polymer were also supported by the thermal melting and recooling profiles from the midpoint between first and second meltings. It was concluded that the charge density of DNA phosphate is a critical value determining whether the ionen polymers bind to DNA by a cooperative or by a noncooperative binding, since the distance between successive cationic charges of 3-3 ionen polymer is shorter than that between successive phosphate charges on DNA double helix and those of 6-6 and 6-10 ionen polymers are longer.
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    Masthead (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1977.360161001
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    Quasielastic light scattering: Effect of ionic strength on the internal dynamics of DNA (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2091-2104 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quasielastic light scattering is used to study the effect of ionic strength on the dynamic behaviour of DNA. In a first approach the spectrum of scattered light is analyzed in terms of a single relaxation process. The large difference between the observed behaviour and that expected according to a pure diffusional process reflects the contribution associated with internal modes, which increases with decreasing ionic strength. Such behaviour is better analyzed in terms of a double relaxation process by using two relaxation times, the reciprocals of which are equal to DK2 and DK2 + τi-1 (K), respectively, where τi (K) is an average value describing the set of modes observed at a given K value. Relative intensity and relaxation times, which are the more accurate parameters, were used to interpret the results. The observed increase of the relative contribution of internal modes with decreasing ionic strength is actually a relative decrease of the diffusional contribution induced by a corresponding increase of the radius of gyration RG. On the other hand, the reciprocal τi-1 (K) of the relaxation time is a linear function of K2 in the analyzed KRG range and is insensitive to ionic strength between 10-2M and 1M. These results, when discussed according to Rouse's model, lead to define for each value of τi-1 (K) a corresponding mean-squared equilibrium length 〈μi2〉 which is found to be a linear function of K-2.
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    Proton magnetic resonance and model peptides conformations (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2755-2771 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Derivatives and peptides of β-nitrobenzyl-L-aspartates were studied with high-field nmr. Differences were observed between the chemical shifts of protons located near the extremity of the principal chain as a function of the terminal group. These differences are explained by conformational calculations which exclude the existence of an hydrogen bond and demonstrate the influence of the aromatic ring position on the protons of the main chain. Both nmr experiments and conformational analysis indicate that conformations are nearly the same for ortho, meta, and para nitro substitution. These conclusions are in good agreement with Karplus relationship applied to the α and β protons.
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    A semiempirical extension of polyelectrolyte theory to the treatment of oligoelectrolytes: Application to oligonucleotide helix-coil transitions (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 159-166 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The interaction of counterions with a suitably long, charged oligomer appears susceptible to treatment in the context of polyelectrolyte theory by the introduction of an end-effect parameter that reflects the reduced association of counterions with the terminal regions of the oligo-ion. Use of a physically reasonable value for the end-effect parameter provides excellent agreement between theory and the experimental data of Elson, Scheffler, and Baldwin [J. Mol. Biol. 54, 401-415 (1970)] on the dependences of melting temperature on salt concentration and chain length for a series of hairpin helices formed by d(TA) oligomers. The differences in behavior expected for hairpin, dimer, and oligomer-polymer helices are discussed. The salt dependence of the end-joining equilibrium investigated for λ DNA by Wang and Davidson [Cold Spring Harbor Symp. Quant. Biol. 33, 409-415 (1968)] is treated as an oligomer-polymer interconversion. The dependence of equilibrium constant for this reaction on counterion concentration is in good agreement with that predicted by theory for an end-region totalling 24 nucleotides, the known length of the λ ends.
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    Solvent denaturationThis paper is an expanded version of a paper dedicated to J. Sturtevant at the symposium held on March 25, 1977 in honor of his achievement of emeritus status at Yale University. (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1305-1322 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Solvent denaturation is developed along thermodynamic lines rather than from multiple-binding theory. Almost all the relations derivable from site-binding theory have their counterparts in the thermodynamic formulation showing that the details of binding models may be sufficient but are not necessary for the general description of solvent denaturation. Equations are derived for the effect of denaturant concentration on stability at constant temperature and on tm. It is recommended that the thermodynamic treatment be used instead of binding models unless stoichiometric interactions are demonstrable experimentally.
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  • 39
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    Base stacking in A fluorescent dinucleoside monophosphate: εApεA (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1361-1372 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical properties of the 1,N6 - etheno derivative of ApA (εApεA) have been studied. Absorbance and CD measurements suggest that (1) neutral salts tend to unstack this molecule and (2) the stacking interaction is weaker than in ApA. εApεA is found to be quenched strongly with respect to the monomer. (εAMP); this quenching is solvent dependent (1M NaCl 〉 5M NaClo4〉40%glycerol) and increases with the ratio of temperature to viscosity (T/η) in each case. Fluorescence lifetime measurements also reveal a temperature- and solvent-dependent decay which is nonlinear on a semilog plot. In the presence of 95% glycerol, this decay return to linearity. These data have been considered from two points of view: (1) two-state pictures which are based on thermodynamic least-squares fit to quatum yield and CD curves, together with two exponential fits to the decay curves and (2) a dynamical model in which relatives fluorophore motion leads to deexcitation via intramolecular collision. A simple model of type (2) gives qualitative agreement with the observed behavior.
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    Characterization of receptor affinity heterogeneity by scatchard plots (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1385-1386 
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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.1978.360170522
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    Masthead (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978) 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1978.360170601
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    Competition between native and monoacetylated polymyxin for charged adsorption sites (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1513-1521 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The native antibiotic polymyxin B, carrying five positive charges, displaces the monoacetylated on from its adsorbed state at the interface between negatively charged lipid layers ans water. A simulation model for asdorption, governed by electrostatic forces, is presented. The model adequently representes the competitive adsorption kinetics and equilibria.
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    Comparison of conformation and antimicrobial activity of synthetic analogs of gramicidin S: Stereochemical consideration of the role of D-phenylalanine in the antibiotic (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1549-1565 
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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: In order to study the role of D-amino acid residues in keeping the stable β-sheet conformation and in the antimicrobial activity of gramicidin S (GS), the four analogs of GS containing D-Ala, L-Ala, Gly, and Aib (α-aminoisobutyric acid) in place of D-Phe were synthesized. D-Ala-and Gly-containing analogs showed antimicrobial activity, while those containing L-Ala and Aib showed no activity. Conformation of these analogs and their derivatives were studied by comparison of ORD and CD spectra and by slective methylation method. It is concluded that the biologically active analogs have β-sheet conformation while inactive analogs have a much different conformation from that of GS. This indicates that D-Ala-Pro and Gly-Pro sequences favor taking a β-bend form but L-Ala-Pro and Aib-Pro sequences do not because the presence of L-side methyl group on the α-carbon atom of LAla and Aib residues destabilizes the β-bend form. This would explain why the inactive analogs which take a different conformation from that of the active ones result in the loss of activity.
    Additional Material: 7 Ill.
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    Dipole-dipole interaction and the relative stability of different types of aggregates of helical polypeptides (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 811-814 
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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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    Collagen fibrils and elastic fibers in rat-tail tendon: An electron microscopic investigation (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 843-855 
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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: Earlier studies by the authors showed that the collagen fibrils in rat-tail tendon have a bi-modal distribution of fibril diameters from a time shortly after birth through to the onset of maturity at about 3-4 months. Present work has extended those observations for rats up to the age of 2 years. Histograms of the fibril diameter distributions for mature tail tendon and direct electron microscope observations show that the fibrils break down as the tendon ages. Further work on the constant diameter subfibrils of diameter 140 Å described previously, has confirmed that these are part of the elastic fibers present in tendon at all ages. It has been shown that there is relatively little variation in the collagen fibril diameter distribution as a function of the position of the specimen in the tail, and as the measured percentage of the area taken by the collagen fibrils present at any particular point. Estimation of the fibrillar collagen content of rat-tail tendon as a function of age indicates that it increases steadily from birth and reaches a maximum at the onset of maturity, beyond which the fibrillar collagen content appears to remain constant.
    Additional Material: 6 Ill.
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    Packaging of DNA in bacteriophage Heads: Some considerations on energetics (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 785-794 
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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 made quantitative estimates of some of the energetic factors to be considered in packaging of double-stranded DNA in virus particles. Numerical calculations were made using parameters appropriate for T4 bacteriophage. The unfavorable factors, and the Gibbs free energies per mole virus at 20°C associated with them, are bending, 1.5 × 103 kcal/mol; conformational restriction upon condensation, 5.1 × 102 kcal/mol; polyelectrolyte repulsion, 2.1 × 105kcal/mol; and melting or kinking, 6.9 × 103 kcal/mol. These must be counterbalanced in the assembled phage by noncovalent bonding interactions between protein subunits in the phage-head shell; by interactions between the DNA and polyvalent cations, especially putrescine and spermidine; nad perhaps by repulsive excluded volume and electrostatic interaction between the DNA and acidic polypeptides. Indeed, a rough estimate of the standard free energey of interaction between T4 DNA and the putrescine and spermidine contained in the head is --2.1 × 105 kcal/mol. In the absence of the other two sources of stabilization, each head protein subunit must contribute about 210 kcal/mol of binding energy.
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    Extrinsic cotton effect and helix-coil transition in a DNA-polycation complex (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 815-815 
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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.1978.360170322
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    Application of thin film dialysis to the determination of equilibrium constants (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 837-842 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theoretical basis for thin-film dialysis involving binding between a ligand and nondialyzing species is presented. A general differential equation that applies to the case of equivalent, noninteracting sites is derived relating [A]F, [A]T, [P]T, and K. Numerical solutions to this equation are used to develop a series of escape curves corresponding to specific values of the parameters [P]T, [A]i, K, and k0. A general method for determining an equilibrium binding constant from thin-film dialysis data is given. A comparison of thin-film dialysis results predicted by this theory with literature data shows essential agreement.
    Additional Material: 4 Ill.
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    The electronic structure of cytosine, 5-azacytosine, and 6-azacytosine (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 887-896 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The normal and vacuum uv spectra of cytosine, 5-azacytosine, and 6-azacytosine thin layers were determined. The spectra were resolved into a series of Gaussian bands and the experimental band positions and oscillator strengths were compared with the calculated values. The calculations were carried out with the PPP-SCF-CI method. The agreement of the calculations with those of others and with the experiment is discussed.
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    Solvent accessibilities in the dimeric subunits of RNA and DNA (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2503-2518 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To obtain information on the solvent-solute interactions in the dinucleoside monophosphates pertaining to the dimeric subunits of RNA and DNA, we have computed the accessibility of a water molecule to the oxygen atoms of the subunits following the method of Lee and Richards [J. Mol. Biol. 55, 379-400 (1971)]. The solute molecules (dimeric unit) is represented by a set of interlocking spheres of appropriate van der Waals radii assigned to each atom, a solvent (water) molecule is rolled along the envelope of the van der Waals surface, and the total surface accessible to the solvent molecule - and hence the solvent accessibility of various atoms of the solute molecule for different conformations - are computed. From the calculated atomic accessibilities, solvation maps in the (ω′,ω) space have been constructed, keeping ψ at 60°, 180°, and -60°. The C(3′)-endo sugar system in the case of DNA subunit have been considered. The solvation maps describing the solvatability of single and groups of atoms give significant information on the backbone conformational domains that are preferred for solvent interaction, thus adding knowledge to the relative stability of the various possible conformations. The B-DNA-type conformer exposes three polar atoms - namely, PO1, O(3′), and O(1′) - to external solvent, whereas the A-DNA- and C-DNA-type conformers expose only one polar atom - O(3′) and O(1′), respectively - to the solvent. The O(2′) atom of the furanose ring system in the RNA subunit could give added stability via solvent association or interunit hydrogen bonding with or without a bridging water. The superposition solvation maps describing the accessibility of a group of polar atoms help to interpret a good number of phosphodiester conformations observed in a energetically less favored conformational domains in the tRNAPhe crystal. Another intresting fact that results from this study is the prediction that the trans oriented of ω is the most favorable conformations of random-coil polynucleotides in solution.
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    Conformational properties of the N-terminal residues of S-peptide. II. The guanidine hydrochloride-water-trifluoroethanol system (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2545-2559 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Conformational properties of synthetic S-peptide analogs, in which the residues in the N-terminal sequence 1-6 were progressively deleted or replaced with amino acids of lower helical propensity, were studied by CD. Increasing the concentration of guanidine hydrochloride and decreasing the temperature were found to produce progressive destruction of ordered conformations, in the parallel with the increasing solubility of the peptide unit, while increasing the concentration of trifluoroethanol and decreasing the temperature produced the opposite effect. The maximum helicity determined in the these sets of experiments is found equal to or greater than that determined in the formation of the ribonuclease S′ complexes. With some peptides the maximum value of predicted helical conformation is reached, and the tendency of tertiary structure to reduce the maximum possible helicity is evident. We discuss the validity of the procedure by which conformational information, drawn from measurements in helicogenic solvents, is related to the state in native protein.
    Additional Material: 7 Ill.
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    Thermal perturbation techniques in characterizing ligand-macromolecule interactions: Theory and application to the proflavin-α-chymotryspin system (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1773-1792 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A thermal perturbation curve (TPC) is defined to be the derivative of the fractional degree of saturation, f, with respect to temperature, considered as a function of the natural logarithm of free ligand concentration, y. The theoretical framework for the use of such curves in the thermodynamic analysis of ligand binding to macromolecules is presented. The thermal perturbation curve either provides or complements the information obtained from the derivative binding isotherm ∂f/∂y. For a single set of identical and independent sites the TPC is identical to the derivative binding isotherm. Analysis of such a curve directly yield ΔH0 and ΔG0 for the binding reaction. In actual experimental work, however, the TPC can only be approximated because of “self-buffering” effects relations between the parameter of the approximate curve and the thermodynamic quantities have been developed. This technique is applied to the proflavin-α-chymotryspin system to demonstrate its usefulness. The general features of thermal perturbation curves for cases of multiple sets of independent sites and cooperatively interacting sites have also been developed. The analysis of thermal perturbation curves in combination with other methods should provide a more powerful approach to the characterization of ligand-macromolecule interactions.
    Additional Material: 8 Ill.
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    Conformational studies of sequential polypeptides containing lysine and tyrosine (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1837-1848 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of three sequential copolypeptides, poly(L-tyrosyl-L-lysine), poly(L-tyrosyl-L-lysyl-L-lysine), and poly[L-tyrosyl-(L-lysyl)2-L-lysine] have been studied by a variety of techniques, including CD, ir spectroscopy, analytical ultracentrifugation, and x-ray diffraction. Depending upon the pH and sovent composition, poly(L-tyrosyl-Llysyl-L-lysine) and poly [L-tyrosyl-(Llysyl)2-L-lysine] can adopt either the α-helical or random-coil conformation, while poly(L-tyrosyl-L-lysine) forms either inter- or intramolecular β-structures.
    Additional Material: 6 Ill.
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    Proton magnetic relaxation in solid poly(L-alanine), poly(L-leucine), poly(L-valine), and polyglycine (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1913-1925 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular motion in solid poly(L-alanine), Poly(L-leucine), poly(L-valine), and polyglycine has been investigated through measurement of the portion spin-lattice relaxation time at 30 and 60 MHz between 110 and 350°K. Rapid random reoriention of sied-chain methyl groups provides the dominent source of relaxation in the first three; activation energies are 10.5 ± 1 1, 8.5 ± 1 kJ/mol, respectively, significantly lower than in the monomeric crystals. Relaxation times in poyglycine are two orders of magnitude longer than in the monomeric crystals. Relaxation times in polyglycine, significantly lower than in the monomeric crystals. Relaxation times in polyglycine are two orders of magnitude longer and are attributed mainly to segmental motions of the polymer chains. Evidence of nonexponential recovery of nuclear magnetization was encountered in the first three homopolyamino acids but not in polylycine, and was attributed to the correlated time to characterize these motions gave quite good agreement with the data; some improvement was obtained for two polymers using a Cole-Davidson distribution of correlation times. For biopolymers using a Cole-Davidson distribution of correlation times. For biopolymers generally it is concluded that rapid methyl group reorientation is a common dynamical feature and an important source of nuclear magnetic relaxation.
    Additional Material: 7 Ill.
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    Measurement of the strongly held water of myoglobin by drying (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1957-1972 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The karl Fischer reagent method has been used to study the drying of whale skeletal muscle myoglobin. Drying curves for metmyglobin were obtained by mechanical pumping (moderate vacuum) and diffusion pumping (high vacum) at 20, 10, 0, -10, and -20°C. Strongly held water is present in about the same amounts as were previously observed with lysozyme. Nearly all of this strongly held water is still present during the drying of acid denatured metmyoglobin. This suggest that a core structure containing strongly held water is still present at pH 4.0. Comparison of the drying of metmyoglobin, deoxymyoglobin, and oxymyoglobin indicates that the iron-coordinated water of methyoglobin is the second most strongly held water of the molocule.
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    Some global β-sheet characterstics (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2033-2037 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    Tail-fiber attachement in bacteriophage T4D studied by quasielastic light scattering-band electrophoresis (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2015-2028 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of bacteriophage T4D particles with up to six tail fibres attached were seprated and analyzed in a quasielastic light scattering-band electrophoresis apparatus. The electrophoretic mobilities and diffusion coefficients of the seprated bands were determined during the same experiment. Species differing in mobility by 0.05 × 10-4 cm2/V sec were resolved. Henry's electropheresis theory for spheres indicates that each tail fiber contributes about 140 effective positive charges to the phage structure. Estimate of the charge using the permanent dipole moment and the electrophorectic mobility (Bontje et. al. (1977) Biopolymers 16, 551-572) gives an effective charge of + 230 to -250 per tail fiber. The charge distribution on the fiberless particles was estimated to be -3380 on the head and -290 on the tail if the dipole moment was assumed positive and -1400 on the head and -1000 on the tail for a negative dipole. Tail-fiber attachement does not proceed to completion in our invitro system, as substantial distributions as a function of tail-fiber input indicates the reaction is a random, noncooperative process.
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    Effect of the fluctuations in electron density within a globular protein on the excess small-angle X-ray scattering (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 81-94 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Excess small angle X-ray scattering in solvents of differing electron density has been calculated from the crystal structures obtained for rubredoxin, trypsin inhibitor, myogen, ferricytochrome c2, ribonuclease S, lysozyme, nuclease, myoglobin, α-chymotrypsin, elastase, subtilisin, carboxypeptidase A, thermolysin, methemoglobin, deoxyhemoglobin, and a single polypeptide chain of M4 lactate dehydrogenase. The scattering curves for each protein can be reproduced by the sum of three curves, with the weighting of the three curves depending on the electron density of the solvent. The radius of gyration obtained from the small angle X-ray scattering by globular proteins in aqueous solution will usually exceed the values defined by the shape of the macromolecule. Deviations for certain of the proteins cited are calculated to be as large as 6%. These deviations arise from the tendency for the amino acid residues with low electron density to be situated closer to the center of the protein than the amino acid residues of high electron density. An upper limit of 19% is obtained for the discrepancy between the radius of gyration defined by the shape of a spherical globular protein of typical amino acid composition and the apparent radius of gyration measured for that protein in water by small angle X-ray scattering.
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    Ion complexation in nonactin, monactin, and dinactin: A Raman spectroscopic study (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 157-185 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability of the macrotetrolide nactins to complex selectivity with a wide variety of cations makes these ionophorous antibiotics important model systems for the study of biologic ionic transport. We report a Raman spectroscopic investigation of the Na+, K+, Rb+, Cs+, Tl+, NH4+, NH3OH+, C(NH2)3+, and Ba++ complexes of nonactin, monactin, and dinactin in 4:1 (v/v) CH3OH/CHCl3 and in the solid state. The nactins display characteristic spectral changes upon complexation, some of which are specific for a given cation. In the K+, Rb+, Cs+, NH3OH+, and C(NH2)3+ complexes, which are apparently isosteric, the ester carbonyl stretch frequency is found to be linearly proportional to the cation-carbonyl electrostatic interaction energy, as calculated from a simplified model. Deviations for the Na+, NH4+, Tl+, and Ba++ complexes are interpreted as arising from additional nonelectrostatic interactions. Additional information is obtained from other spectral regions and from measurements of depolarization ratios. Spectra of the nactin complexes differ from each other more in the solid state than in solution, reflecting the effects of crystalline contact forces.
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    Reversible change in ψ structure of DNA-poly(Lys) complexes induced by metal binding (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 225-230 
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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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    Interaction of water with native collagen (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 231-246 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of water with collagenous tissue was investigated using dynamic mechanical spectroscopy and cryogenic X-ray techniques. The loss spectrum was found to be very sensitive to water which is highly associated with the macromolecule. Two water-sensitive loss peaks were observed below 0°C: the β2 or “water dispersion” at 150°K and the β1 at 200°K which is attributed to motion of polar side chains. Changes in peak temperature and intensity were not continuous with water content, but exhibited regimes in behavior which were associated with two types of nonfreezable water, structural and bound water. In cryogenic X-ray experiments, specimens which contained some freezable water exhibited reflections identified with the cubic form of ice. These ice crystals underwent an irreversible transition to the more common hexagonal form when warmed above 200°K. On the basis of these experiments, a model for the hydration of native collagenous tissue was proposed.
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    Conformational behavior of polyethylenimine derivatives revealed by fluorescence spectroscopy (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 299-316 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformation behavior of polyethylenimine has been examined by studies of the fluorescence characteristics of derivatives of the polymer containing pyrenyl ligands. Excimer formation within the macromolecular matrix serves as a sensitive probe of group proximities. The experimental observations combined with nearest neighbor analyses lead to quantitative assessments of the extent of interaction between polymer side chains.
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    Chiroptical properties of S-proline conformational isomers (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 387-401 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiroptical properties of S-proline conformational isomers are examined on a theoretical model in which electronic wave functions are obtained from semiempirical molecular orbital calculations. The CNDO/S molecular orbital model is used to perform SCF-MO calculations on ground state electronic structure and excited states are constructed in the virtual orbital-configuration interaction approximation. Electronic rotatory strengths and dipole strengths are calculated directly from the complete (but approximate) molecular electronic wave functions. Zwitterionic, cationic, and anionic S-proline structures are studied twotypes of conformational variables are represented in the calculations: (1) pyrrolidine ring conformation; and (2) rotation about the Cα-COO- bond. Rotatory strengths are found to be somewhat sensitive to rotational isomerism about the Cα-COO- bond, but are found to be rather insensitive to conformational changes within the pyrrolidine ring. The CD spectrum of zwitterionic S-proline down to ∼160 nm appears to be well accounted for by the theoretically calculated results if conformational preferences with respect to rotation about the Cα-COO- bond can be assumed to exist in solution media. Furthermore, spectra-structure correlations are offered for the anionic and cationic forms of S-proline in solution.
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    Synthesis of linear stereoregular glucomannan heteropolysaccharides (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 415-426 
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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 stereoregular α-(1 → 6) linked glucomannans have been prepared by Lewis acid-catalyzed copolymerization of anhydro sugar derivatives followed by debenzylation. The products have been characterized for mole fraction of the individual monomer, and sequence lengths have been calculated from copolymerization data. The viscosity, specific rotation, and 13C nmr spectra have been correlated with the structure of the various copolymers.
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    Apparent molal heat capacities in aqueous solution of molecules containing the peptide linkage: Cyclic and open chain dipeptides (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 465-467 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Theory of protein molecule self-organization. I. Thermodynamic parameters of local secondary structures in the unfolded protein chain (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 469-495 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents the results of a stereochemical analysis of local interactions in unfolded protein chains (sterical repulsions, hydrogen, and hydrophobic bonds, etc.) by means of space-filling modeles. On the basis of this analysis, an evaluation is made of thermodynamic parameters controlling the building-in of all the 20 natural amino acid residues in all the physically possible position of local secondary structures (α-helices, including α-helices with short fragments of helices 310 at the C-terminus; β-bends of different types, helices 310, and their combinations) as well as thermodynamic parameters of separate hydrogen bonds of polar side groups with the neighbor peptide groups (“local contacts”). The accuracy of the obtained results is discussed.
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    Translational diffusion coefficient of α-chymotrypsinogen A by laser-light-scattering spectroscopy (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 545-549 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The translational diffusion coefficient of a pure sample of α-chymotrypsinogen A is measured by laser light scattering to give a value of D20,w0 = (8.40 ± 0.15) × 10-7 cm2/sec.
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    Nuclear magnetic resonance studies of exchangeable protons. II. The solvent exchange rate of the indole nitrogen proton of tryptophan derivatives (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 623-629 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exchange rate of the indole nitrogen proton with solvent water protons was measured as a function of pH and temperature for tryptophan, N-methyl tryptophan, glycyl tryptophan, tryptophanamide, tryptophylglycine, and tryptophylglycyl glycine. The nmr observation was by long-pulse Fourier transform methods, and kinetics were inferred from saturation recovery, H2O transfer of saturation, and linewidth. There are observable differences between the rates of these compounds, but all are describable within a factor of two by specific acid and base-catalyzed rates kH = 100 and kOH = 108 1/mol-sec at 27°C. It is concluded that this behaviour is representative of this proton on the indole side chain in a random-chain peptide exposed to water.
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    Thermodynamics of mucopolysaccharide-dye binding. I. Identification of free and bound dye via membrane filtration: Acridine orange-dermatan sulfate system (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 685-693 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stoichiometric mixtures of acridine orange with dermatan sulfate at total dye concentrations ≤ 1 × 10-5 M show fluorescence maxima at 540 nm and 660 nm on excitation at 436 nm. By means of membrane filtration, it is directly demonstrated that the species emitting at 540 nm is due only to unbound dye whereas the 660-nm emitting species is due to bound dye. It is, therefore, possible to differentiate unbound acridine orange from its dermatan sulfate complex solely by spectroscopic methods. Thermodynamic binding parameters can be calculated from rapid spectroscopic measurements without disturbing the system.
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    Masthead (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
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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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    Kinetic analysis of the reversible folding reactions of small proteins: Application to the folding of lysozyme and cytochrome c (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 731-747 
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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 kinetic analysis for unimolecular three-species models is presented. Criteria are established for each model in order to allow selection among alternative models on the basis of their amplitude behavior. These criteria are applied to the previously reported kinetic data for the folding transitions of lysozyme and cytochrome c in guanidine hydrochloride. The degree of success in applying these criteria is found to depend on the extent to which the apparent rate constants, λ1 and λ2, approach each other in certain conditions. Ikai and Tanford have presented a similar kinetic analysis, although these authors considered only the case where no intermediate kinetic species was populated initially. For one protein system, namely, ribonuclease A (RNase A), at least one stable intermediate exists after unfolding outside of the equilibrium transition zone. The criteria developed by Ikai and Tanford cannot be applied to RNase A kinetics and, therefore, a more general analysis is presented. Previously published studies of the reversible folding kinetics of lysozyme and cytochrome c are reexamined using the current amplitude analysis, and it is found that both of these folding transitions can be described by the three-species model, \documentclass{article}\pagestyle{empty}\begin{document}$$ U_{1} \rightleftharpoons U \rightleftharpoons N $$\end{document} used previously to describe the folding kinetics of RNase A (U1 and U2 are two forms of unfolded enzyme and N is the native species). These results suggest that this three-species model may provide a fairly general description of the reversible folding kinetics of small proteins. As an outgrowth of the current analysis, several suggestions for experimental design in studying protein folding will be presented and discussed.
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    Reduction of ferriprotoporphyrin IX to the ferroderivative by copoly(4-vinylpyridine-N-(p-vinylbenzyl)-3-carbamoyl-1,4-dihydropyridine) in dimethyl sulfoxide (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 845-855 
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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 copolymer which has both ligand sites (4-vinylpyridine) and redox sites (N-(p-vinylbenzyl)-3-carbamoyl-1,4-dihydropyridine) was synthesized by the dithionite reduction of the copoly(4-vinylpyridine-N-(p-vinylbenzyl)-3-carbamoylpyridinium chloride) and the reduction of a central ferric-iron of ferriprotoporphyrin IX by the above-described copolymer was studied spectrophotometrically in dimethyl sulfoxide. The rate of the reduction by the copolymer was much faster than by N-benzyl-3-carbamoyl-1,4-dihydropyridine. This acceleration by the copolymer could be explained by the intramolecular reduction of ferriprotoporphyrin IX which was coordinated by the pyridine residue of the copolymer.
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    Conformational properties of the N-terminal residues of S-peptide. I. The ribonuclease S′ system (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2525-2543 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The contribution of the 1-6 N-terminal sequence to the conformational properties of the S-peptide (the 1-20 sequence of ribonuclease A) was assessed by determining in the ribonuclease S′ system the helical content and the binding capability of synthetic [Orn10]-S-peptide analogs, in which lysine1, glutamic2 and threonine3 were progressively deleted, alanine4 and alanine5were alternatively replaced by serine, and alanine6 was substituted by serine or proline. Both the deletion of the three N-terminal residues and the alanine6/proline replacement produces the loss of the helical structure up to lysine7. No or minor effects are found in all other cases. From the comparison of the binding data, the energy for the conformational stabilization of the N-terminal region was calculated to amount to 1.4 kcal/mol. The results are discussed in comparison with the known x-ray data of the enzyme, with some predictive rules of secondary structure which were applied to this region and with the known phylogenetic variance of the residues in this region.
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    Solvent effect in the stereoselective polymerization of α-amino acid N-carboxyanhydride and some considerations on the mechanism of stereoregulation (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2561-2572 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the Polymerization of phenylalanine N-carboxyanhydride (NCA) in No2Oh initiated by MeNHBzl, L-,D-, and DL-NCA As were polymerized at the same rate, and no stereoselectivity was observed. When the same experiment was carried out in HCONEt2, however, L- and D-NCA were both polymerized at a rate which was about twice as large as that of DL-NCA. In this case, the polymerization is stereoselective, ascribable to a preferable reaction between the optical enantiomorphs of the terminal residue of the growing chain and the NCA of the same chirality. On the other hand, the polymerization initiated by SarNMe2 and MeNH(CH2)2CONMe2 were stereoselective in NO2Ph and HCONEt2, but they were not stereoselective in m-(MeO)2Ph. These findings indicate that the polymerizations initiated by a strong base in highly dipolar solvents are stereoselective. Apparently, the reaction between a chiral, cyclic terminal of growing chain and a chiral, cyclic activated NCA in the activated-NCA mechanism is highly stereoselective. In addition, from a kinetic investigation on on the copolymerization between L- and D-NCAs, the penultimate chiral centers were also suggested to contribute to the stereoselection. Stereoselection by the α-helical conformation of the growing chain and by a chiral, linear terminal amine have been considered so far, and the contribution from the present type of stereoselection must have been overlooked.
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    On the B to A conformation change of the double helix (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 965-982 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have investigated the B to A conformation change of DNA double helices by a new method “soft-mode analysis.” We find theoretically that a mode does soften when the vibration normal modes are perturbed by increasing the electrostatic interaction between the unbalanced charges on atoms in the double helix. The same mode also softens for enhanced van der Waals interactions. The mode softening indicates the onset of conformation change. The enhancing of the electrostatic and van der Waals interaction mimic the effect of decreasing the polar nature of the solvent or water of hydration associated with the B conformation DNA. We discuss qualitatively the concept of soft modes and their relation to conformation change as well as their applicability to macromolecules. We discuss previous work in which the normal vibrational modes have been calculated. We also discuss the displacement which comes from the soft mode and show that it correlates very well with that expected for the B to A conformation charge.
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    Quantitative electron microscope observations of the collagen fibrils in rat-tail tendon (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1015-1031 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An electron microscope study of collagen fibrils from fixed tail tendons of rats has revealed that from some time shortly after birth until maturity, the fibril diameters have a bimodal distribution. The “two” types of fibril are indistinguishable in both transverse and longitudinal section. Unfixed specimens of eight-week-old-tail tendon showed a similar bimodal distribution of diameters though the positions of the peak values compared to fixed specimens of an eight-week-old-tail tendon were shifted upwards by about 30%. It has also been shown quantitatively that the polar collagen fibrils are directed randomly “up” and “down” with respect to their neighbors. Whilst it has been suggested by others that anastomosis is a feature of collagen structure, the results presented here do not support this hypothesis. Fibrillar units ∼ 140 Å in diameter have been observed and the possibilities that these are elastic fibers or the breakdown products of collagen fibrils have been considered.
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    The organization and repair of DNA in the mammalian chromosome. II. A gradient-shape-induced speed dependence affecting DNAs larger than T4 DNA (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1083-1092 
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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 addition of a lytic layer to a preformed linear sucrose gradient induces a temporary (up to half a day) initial gradient of considerable steepness which retards the sedimentation of large (〉T4) DNAs. Centrifugation at sufficiently slow angular velocities permits the temporary initial gradient to disappear and therefore the sedimentation distance increases, yielding a rotor speed dependent effect on sedimentation distance. Gradients which are free of this effect are described and shown to permit mouse leukemia cell DNA to sediment independently of rotor speed (5-30 krpm).
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    Helix coil transitions of d (A)n·d(T)n, d(A-T)n·d(A-T)n, and d(A-A-T)n·d(A-T-T)n; evaluation of parameters governing DNA stability (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1115-1137 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermally induced helix-coil transitions of three A-T DNAs, d(A)n·d(T)n, d(A-T)n·d(A-T)n, and d(A-A-T)n·d(A-T-T)n, were studied. Experimental transition curves of the DNAs were analyzed using the loop entropy model of DNA melting. The calculation of the melting curve of d(A-A-T)n·d(A-T-T)n is presented using the integral equation formalism of Goel and Montroll. The aim of this work was to evaluate thermodynamic parameters which govern DNA stability and to test the theoretical model employed in the analysis. Our results show (1) an excellent over-all agreement between theory and experiment, (2) a loop entropy exponent k = 1.55 ± 0.05 provided the best fit to all the polymer transition curves, (3) the evaluated stacking free energies reflect the relative stability of the DNAs, and (4) the stacking energies of the ApA·TpT dimer evaluated from d(A)n·d(T)n and d(A-A-T)n·d(A-T-T)n differ. The last result is consistent with different conformations for the dimer in these two polymers.
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    Transient electric birefringence of T-even bacteriophages. IV. T2L0 and T6 with extended tail fibers (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2689-2702 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transient electric birefringence measurements of the bacteriophages T2L0 and T6 were performed under such conditions that the tail fibers are extended. The data obtained are compared to previously reported data for T4B. For all T-even phages the degree of extension of the tail fibers is a function of pH, ionic strength, and temperature. For T4B, much higher ionic strengths are needed than for T2L0 and T6 to accomplish complete tail-fiber extension. The rotational diffusion coefficients of the phages with fully extended fibers are equal to 120 ± 3 sec-1, 132 ± 5 sec-1, 157 ± 4 sec-1 for T2L0, T4B, and T6, respectively. The respective optical anistropies are - (2.66 ± 0.05) × 10-4, and - (3.07 ± 0.15) × 10-4. The differences in the rotational diffusion coefficient and optical anisotropy arise because the conformation of the fully extended tail fibers is different for the three phages. The tail fibers of T2L0 project further into the solution (away from the head) than do those of T4B and T6. The apparent permanent dipole moments of T2L0 and T6 decrease with increasing ionic strength. This decrease is caused by the screening of the surface charges on the phage body by the counter-ions in the solution. The biological relevance of this decrease is illustrated by the fact that the adsorption rate of T6 phages to E. coli B bacteria shows a similar dependence of ionic strength. Evidence is pressented that the tail fibers may move more or less independently of the phage body when an electric field is applied to the suspension.
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    1H nuclear magnetic resonance studies of N-acetyl-L-proline N-methylamide. Molecular conformations, hydrogen bondings, and thermodynamic quantities in various solvents (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1259-1270 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Concentration and temperature dependences of the 1H nmr spectra of N-acetyl-L-proline N-methylamide were observed in various solvents [CCl4, CDCl3, (CD3)2CO, (CD3)2SO, H2O, and D2O]. The fraction of the cis isomer (with respect to the bond between the acetyl carbonyl carbon and prolyl nitrogen atoms) depends greatly on the solvent used; the fraction of the cis isomer is higher in polar solvents than in nonpolar solvents. It depends also on concentration and temperature in nonpolar solvents but not in polar solvents. In nonpolar solvents the trans isomer mostly exists in the γ-turn structure with an intramolecular hydrogen bond and the cis isomer tends to form molecular aggregates by intermolecular hydrogen bonds. In polar solvents both the cis and trans isomers exist in monomeric forms which interact with solvent molecules. The pH dependences of the N-methyl proton resonances indicate that the γ-turn structure of the trans isomer is present also in aqueous solution, though its population is difficult to determine. Apparent enthalpy and entropy changes for the conversion of the trans isomer to cis isomer are evaluated for various solvents. The results are discussed in terms of the intra- and intermolecular hydrogen bondings.
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    On nonequivalent intermolecualar stagger states in collagen fibrils (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1357-1361 
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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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    X-Ray analysis of bovine pancreatic ribonuclease analogs: A difference Fourier at 2.8 Å resolution of (O r n10)-ribonuclease S′ (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1371-1376 
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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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    Synthesis and carbon-13 nuclear magnetic resonance spectra of Cyclo(D-leucyl-L-leucine) and Cyclo(L-leucyl-L-leucine) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1387-1395 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclo(D-Leu-L-Leu) and cyclo(L-Leu-L-Leu) were synthesized, and their carbon-13 nmr spectra at 65 MHz were examined in dimethylsulfoxide and trifluoroacetic acid solutions. The chemical shift data are consistent with a boat or “twisted” boat conformation of the diketopiperazine ring in both solvents. There was no indication of protonation of the cyclic dipeptides by trifluoroacetic acid. Attempts at polymerizing the cyclic dipeptides were unsuccessful.
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    Interactions of highly charged colloidal cylinders with applications to double-stranded DNA (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1435-1448 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents new applications of the McMillan-Mayer solution theory to dispersions of highly charged colloidal cylinders in monovalent salt solutions. The thermodynamic solution properties are given in terms of the virial expansions relating to a Donnan membrane equilibrium. General expressions are derived for the second Donnan pressure virial coefficient B2 and for the first two salt distribution coefficients A1 and A2. The effect of electric interactions is represented as an increased effective diameter dB or dA of the colloidal cylinder. This yields the simple excluded volume expressions B2 = πdBL2/4 and A1 = πdA2L/4 for hard cylinders of length L and diameter dB and dA, respectively. The coefficient A2 is derived from the dependence of B2 on the salt concentration.Computations are made for double-stranded DNA in sodium chloride solutions with the DNA model developed in the preceding paper: a uniformly charged cylinder, with size and charge consistent with transport experiments, and surrounded by a Gouy double layer. In 1-0.005M sodium chloride solutions dB is found to vary from 29 Å to about 220 Å, and dA from 30 Å to about 170 Å, with little sensitivity to the uncertainties in the kinetic diameter d ≈ 24 Å and the experimental ζ potentials of DNA. Corresponding results predicted by the classical Donnan theory are 6-167 times too high for B2.Values of A2 are relatively small, in line with the expected rapid convergence of the virial expansion for the salt distribution. This is consistent with a phase transition from random to parallel orientation of the cylinders predicted first by Onsager for hard cylinders on the basis of B2, but not yet observed for DNA in simple salt solutions.
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    Calorimetric investigation of some elastin-solvent systems (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1505-1512 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of ox ligamentum nuchae elastin (native, purified, and soluble) with different solvents (water, ethylene glycol, methanol, and 2,2,2-trifluoroethanol) was investigated by means of differential scanning calorimetry. The unfreezable solvent content and the corresponding solvent to elastin residue molar ratio were determined from the melting endotherms of the freezable solvent present in these systems. The molar ratio obtained in the case of water and ethylene glycol agrees with hypothesis of a direct solvation of the main chain peptide group and is interpreted according to a model previously proposed for polyamides. Quite different molar ratios are obtained in the case of the two monofunctional solvents and no model can be proposed at present to explain their interaction with the protein.
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  • 86
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    Helix-coil stability constants for the naturally occurring amino acids in water. XII. Asparagine parameters from random poly(hydroxybutylglutamine-co-L-asparagine) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1567-1585 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of water-soluble random copolymers containing L-asparagine with N5-(4-hydroxybutyl)-L-glutamine, and the thermally induced helix-coil transitions of these copolymers in water, are described. The incorporation of L-asparagine was found to decrease the helix content of the polymers in water at all temperatures. The Zimm-Bragg parameters σ and s for the helix-coil transition in poly(L-asparagine) in water were deduced from an analysis of the copolymer melting curves in the manner described in earlier papers. The computed values of s indicate that asparagine destabilizes helical sequences at all temperatures in the range 0-60°C.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160715
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  • 87
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    Synthesis and conformational study of poly(0,0′-dicarbobenzoxy-L-β-3,4-dihydroxyphenyl-α-alanine) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1593-1607 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-molecular-weight poly(0,0′-dicarbobenzoxy-L-β-3,4-dihydroxyphenyl-α-alanine) was prepared by the N-carboxyanhydride method. From the results obtained by a study of the optical rotation, nuclear magnetic resonance, and solution infrared absorption, the conformation of poly(0,0′-dicarbobenzoxy-L-β-3,4-dihydroxyphenyl-α-alanine) depended greatly on the solvent taking a right-handed helix with [θ]225 = -13,600 ∼ -18,900 in alkyl halides, a left-handed helix with [θ]228 = 22,100 ∼ 24,800 in cyclic ethers or trimethylphosphate, and a random coil structure in dichloroacetic acid, trifluoroacetic acid, or hexafluoroacetone sesquihydrate. The polypeptide underwent a right-handed helix-coil transition in chloroform/dichloroacetic acid (or trifluoroacetic acid) mixed solvents and a left-handed helix-coil transition in dioxane/dichloroacetic acid (or trifluoroacetic acid) mixed solvents. The results were compared with those of poly(0-carbobenzoxy-L-tyrosine).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160717
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  • 88
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    Unsaturated amino-acid residues as probes for the conformation of polypeptides in solution (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1677-1686 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetyl-(dehydro-Phe) and acetyl-bis(dehydro-Phe) groups have been attached to the ε-amino group of the lysine residues of the copolymer poly(Glu92Lys8) by reacting this last with acetyl-(dehydro-Phe)-azlactone and acetyl-bis(dehydro-Phe)-azlactone, respectively.In the latter case induced CD is observed between 250 and 330 nm, due to the relative dissymmetric disposition of the two dehydro-Phe groups under the chiral field of the polypeptide chain.pH dependence of the induced CD, observed for the copolymer and lacking in the lowmolecular-weight structural model, is related to the α-helical and random coiled conformation of the polypeptide chain.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160806
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  • 89
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    The dichroic tensor of flexible helices (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2143-2165 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A statistical theory of the linear dichroism of DNA-like chains is presented for two models which are discrete versions of the wormlike coil. In the final form the linear dichroism of the entire chain is related directly to the dichroic properties of a chain segment (base pair). Though the derivations are somewhat complicated, the result [Eq. (28)] is simple and the required statistical parameters can be easily calculated for either model from measured values of the persistence length. In fact, for molecules as stiff as double-stranded DNA, the results can be reduced with good accuracy to the form \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{\Delta \varepsilon (chain)}}{{\Delta \varepsilon (segment)}} = \frac{{P_{\infty} }}{l}\frac{r^{2}}{{\langle r^2 \rangle_0 }} $$\end{document} showing that the “optical persistence” given on the left is directly proportional to the structural persistence, P∞/l. As in previous theories the results are restricted to chains in their Gaussian limit.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360161006
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  • 90
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    Histidine-containing cyclic dipeptides as catalysts in the hydrolysis of carbonic acid p-nitrophenyl esters (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2203-2215 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A histidine-containing cyclic dipeptide, cyclo(D-Leu-L-His), was almost 20 times as efficient a catalyst as imidazole in the hydrolysis of p-nitrophenyl laurate. The effect of dioxane on the hydrolysis showed that hydrophobic interaction between the cyclic dipeptide and the ester is very important. This reaction obeyed the Michaelis-Menten kinetics, and the Michaelis constant Km was as low as 9.98 × 10-5M. Since the linear dipeptide having D-Leu-L-His sequence was nearly inactive in the hydrolysis, the functional groups of cyclo(D-Leu-L-His) in a specific arrangement held by the rigid backbone must have cooperated in the fast hydrolysis. Very weak catalysis by the diasteremeric cyclic dipeptide, cyclo(L-Leu-L-His), in the hydrolysis supported the above view.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360161009
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  • 91
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    Alexander von Humboldt (1769-1859) (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 14-21 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110103
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  • 92
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    Die Olefin-Metathese (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 22-27 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    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/ciuz.19770110104
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    Masthead (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977) 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110201
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    Isomerie. LaborBücher Chemie. Von H. Daecke. Verlag Moritz Diesterweg/Otto Salle Verlag, Frankfurt/M., und Verlag Sauerlander, Aarau 1976. 1. Aufl., XI, 115 S., zahlr. Abb. geb. DM 19,80 (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 28-29 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110108
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    mini-chiuz. Europäische Kooperation in der Didaktik der Naturwissenschaften (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. A4 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110111
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  • 96
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    Struktur und Verhalten von Molekülen im Raum. Von G. Natta und M. Farina. Übersetzt von P Schmid. Verlag Chemie GmbH, Weinheim/B., New York 1976. 1. Aufl., VIII, 248 S., 132 Abb., 8 Tab., brosch. DM 38, - (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 63-63 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110206
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    Rompps Chemie-Lexikon. Von O.-A. Neumüller. Franckh'sche Verlagshandlung, W. Keller & Co, 7. Auflage, Band 1-6, Stuttgart 1972-1977. Geb. DM 160,-pro Band (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 64-64 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110210
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    Mikroorganismen als organische Chemiker (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 75-82 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110303
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    Intensivkurs Mathematik. Programmierte Prüfung für das Selbststudium. [taschentext 54]. Von W. Schmidt. Verlag Chemie GmbH, Weinheim, New York 1976. 1. Aufl., 185 S., 44 Abb., 1 Tab., 4 Ausklapptafeln, geb. DM 16,80 (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 94-94 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110306
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  • 100
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    Chronik (1977)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 197-198 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19770110606
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