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  • Chemistry  (14,243)
  • 1980-1984  (6,410)
  • 1970-1974  (5,638)
  • 1925-1929  (2,195)
  • 1980  (6,410)
  • 1974  (5,638)
  • 1929  (2,195)
Collection
Keywords
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Years
  • 1980-1984  (6,410)
  • 1970-1974  (5,638)
  • 1925-1929  (2,195)
Year
  • 1
    Electronic Resource
    Electronic Resource
    The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry in rabbits (1974)
    Springer
    Calcified tissue international 16 (1974), S. 145-152 
    Details
    ISSN: 1432-0827
    Keywords: EHDP ; Bone ; Chemistry ; Serum ; Rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry were investigated in adult rabbits. EHDP was administered by subcutaneous injection at doses of 0.25, 2.5 and 10 mg/kg body weight/day for of 28 days. Blood samples were obtained weekly from each rabbit and serum levels of total calcium, ionized calcium, inorganic phosphate and alkaline phosphatase were determined. At the end of the treatment period all rabbits were sacrificed and the tibiae removed for chemical analysis and histological evaluation. The effect of EHDP administration on serum chemistry was both dose- and time-related. The highest of the three doses, 10 mg/kg/day, resulted in a time-related decrease in total serum calcium. This dose also caused a rapid but transient reduction in serum ionized calcium. The effect of EHDP on serum inorganic phosphate was biphasic. Administration of 2.5 mg/kg/day resulted in a time-related elevation in this parameter, whereas the 10 mg/kg/day dose resulted in a time-related hypophosphatemic response. There were no significant drug-related changes in tibial fat-free dry weight, ash weight, total calcium or total phosphorus values. However, administration of 2.5 and 10 mg/kg/day EHDP resulted in increased osteoid tissue as measured histologically. These results are compared with data from other EHDP studies, and discussed in relation to the maturity and growth-state of the experimental animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02008220
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  • 2
    Electronic Resource
    Electronic Resource
    Interstellar molecules (1980)
    Springer
    Journal of molecular evolution 15 (1980), S. 79-101 
    Details
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732663
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  • 3
    Electronic Resource
    Electronic Resource
    The importance of energetic particle precipitation on the chemical composition of the middle atmosphere (1980)
    Springer
    Pure and applied geophysics 118 (1980), S. 128-151 
    Details
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01586448
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  • 4
    Electronic Resource
    Electronic Resource
    Studies in the basic mineralizing system, CaO-P2O5-H2O (1974)
    Springer
    Calcified tissue international 14 (1974), S. 3-14 
    Details
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Mineral ; Phase ; Chemistry ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des diagrammes de phase d'équilibre ont été déterminés pour le système CaO-P2O5-H2O en utilisant des techniques de synthèse hydrothermique au cours de variatio nsde température allant de 300–600° et 2 Kb H2O de pression. De l'hydroxyapatite bien cristallisé a été synthétisé et caractérisé. De faibles variations de paramètres de la maille cristalline, liées à la température de synthèse et composition globale du matériel initial, ont été déterminées. Des conditions chimiques précises sont nécessaires pour obtenir de l'apatite, en tant que seule phase solide en équilibre dans la solution. Les résultats de diagramme de phase d'équilibre sont comparés avec ceux obtenus dans des milieux synthétiques.
    Abstract: Zusammenfassung Es wurden Gleichgewichts-Phasendiagramme für das System CaO-P2O5-H2O bestimmt, indem hydrothermale Synthese-Techniken im Temperaturbereich von 300–600° und bei einem Druck von 2 Kb H2O verwendet wurden. Es wurde gut-kristallisiertes Hydroxyapatit erzeugt und charakterisiert. Es wurden geringe Unterschiede in den Parametern der Zelleinheiten festgestellt, welche von der angewandten Temperatur und der Zusammensetzung des Startmaterials abhingen. Es waren genaue chemische Bedingungen nötig, um Apatit als die einzige feste Phase im Gleichgewicht mit der Lösung zu erhalten. Die Resultate der Gleichgewichts-Phasendiagramme werden mit früheren Untersuchungen mit der Synthesetechnik verglichen.
    Notes: Abstract Equilibrium phase diagrams have been determined for the system CaO-P2O5-H2 using hydrothermal synthesis techniques in the temperature range 300–600° and 2 Kb H2O pressure. Well-crystallized hydroxyapatite has been produced and characterized. Small variations in unit cell parameters dependent on temperature of synthesis and bulk composition of the starting materials have been determined. Precise chemical conditions were required to obtain apatite as the only solid phase in equilibrium with solution. Equilibrium phase diagram results are compared with previous synthetic investigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02060279
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  • 5
    Electronic Resource
    Electronic Resource
    Fluorescence correlation spectroscopy. I. Conceptual basis and theory (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1-27 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a method for determining chemical kinetic constants and diffusion coefficients by measuring the rates of decay of spontaneous concentration fluctuations. The equilibrium of the system is not disturbed during the measurement. We measure the number of molecules of a specified type in a defined open volume as a function of time and compute the time course of the deviations from the thermodynamic mean concentration. The method is based on the principle that the rates of decay of spontaneous microscopic fluctuations are determined by the same phenomenological rate coefficients as those of macroscopic departures from equilibrium which result from external perturbations. Hence, an analysis of fluctuations yields the same chemical rate constants and diffusion coefficients as are measured by conventional procedures. In practice the number of the specified molecules is measured by a property such as absorbance or fluorescence which is specific and sensitive to chemical change. The sample volume is defined by a light beam which traverses the cell. As the molecules appear in or disappear from the light beam, either due to diffusion or chemical reaction, their concentration fluctuations give rise to corresponding fluctuations of the intensity of absorbed or emitted light. This paper presents the theory needed to derive chemical rate constants and diffusion coefficients from these fluctuations in light intensity. The theory is applied to three examples of general interest: pure diffusion in the absence of chemical reaction; the binding of a small rapidly diffusing ligand to a larger slowly diffusing macromolecule; and a unimolecular isomerization. The method should be especially useful in studying highly cooperative systems, relatively noncooperative systems with intermediate states closely spaced in free energy, small systems, and systems not readily subject to perturbations of state.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130102
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular mobility of polypeptides containing proline as determined by 13C magnetic resonance (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 97-114 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular conformations and dynamics of poly(L-prolyl), poly(hydroxyl-L-prolyl), poly(L-prolyl-glycyl), poly(hydroxyl-L-prolyl), and poly(glycyl-glycyl-L-prolyl-glycyl), in aqueous solution, have been studied using 13C pulse Fourier transform nmr spectroscopy. From a measurement of the intensities of major and minor resonances in the spectra of the copolypeptides, it was determined that 15-20% of the glycyl-prolyl and glycyl-hydroxyprolyl peptide bonds are cis. Effective rotational correlation times (τeff), obtained from measurements of spin-lattice relaxation times (T1) of individual backbone and side-chain carbons, demonstrated that backbone reorientation is approximately isotropic for the five polypeptides and is characterized by correlation times of ca. 0.3-0.6 nanoseconds as a result of rapid segmental motion. In a given polypeptide glycyl and pyrrolidine residues were found to have the same backbone correlation times, but backbone carbon τeff values did decrease as the glycyl content of the peptides increased. A semi-quantitative analysis of Cβ, Cγ, and Cδ correlation times suggests that rapid ring motion in both prolyl and hydroxyprolyl involves primarily Cγ and Cβ, with the prolyl ring being more mobile than the hydroxyprolyl ring.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130106
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  • 7
    Electronic Resource
    Electronic Resource
    Comment on “rotational relaxation of macromolecules determined by dynamic light scattering” (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 237-238 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No. Abstract.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130117
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  • 8
    Electronic Resource
    Electronic Resource
    Flexibility of DNA (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 217-226 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for the flexibility of DNA is proposed that is based on discrete variations in the direction of propagation in going from one subunit to the next. Expansion of the local free energy in terms of the local bending gives a Gaussian distribution function. The assumption of the independence of local bends on neighbors lead to very simple formulae for the persistence length and the characteristic ratio. Emphasis, however, is placed on the application of the formulae for molecules of finite size where the persistence length and C∞ are not defined. The formulae are worked out for two models, which should serve as limits for the real physical situation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130115
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  • 9
    Electronic Resource
    Electronic Resource
    Dispersion effect on turbidimetric size measurement (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 735-743 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If dispersion effects are not taken into account, the dimensions of particles in suspension estimated from spectrophotometric data (slope of the log OD versus log λ plot) are too low. By measuring dispersion curves for the medium and for the suspension, a consistent estimate of the size of latex particles of different diameter is obtained from the OD data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130408
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  • 10
    Electronic Resource
    Electronic Resource
    13C nmr study of the helix-coil transition of poly-N5-(3-hydroxypropyl)-L-glutamine (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 765-768 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix-coil transition of poly-N5-(3-hydroxypropyl)-L-glutamine in methanol-water solutions has been observed using 13C nuclear magnetic resonance. Two signals appear in the α-CH region in the course of the transition; this is in contrast with previous proton magnetic resonance experiments carried out on this polymer in the same solvent system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130411
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  • 11
    Electronic Resource
    Electronic Resource
    The V amylose-H2O system: Structural changes resulting from hydration (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 779-790 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray diffraction and stereochemical analyses were used to study the hydrated structure of the helical amylose polymorph having a fiber repeat spacing of 8 Å. Intensity calculations using computer models confirmed six as the number of residues per turn and supported the space group P212121. Both diffraction intensity and stereochemical methods indicate the suitability of residue G3 from the potassium acetate complex of cyclohexaamylose as opposed to residues with longer O(4)-O(1) vectors. Comparison of the present results with those obtained for V amylose dehydrate indicated no major conformational differences between the two helix skeletons. A net helical rotation of approximately 30° accompanied the hydrate-dehydrate transition and the rotational position in the hydrate allowed packing that was less close. Hydration water molecules were not located; noncarbohydrate peaks on the electron density maps were primarily due to Fourier series termination errors.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130413
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  • 12
    Electronic Resource
    Electronic Resource
    A circular dichroism study of the primary structures of three crab satellite DNA's rich in A:T base pairs (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 843-852 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have measured the circular dichroism spectra and have obtained melting curves for samples of purified satellite DNA's from three species of crab, Cancer borealis, Gecarcinus lateralis, and Callinectes sapidus. Although all three satellite DNA's have the same density in neutral CsCl, their circular dichroism spectra and melting and reassociation characteristics are different, as are other properties of these DNA's. The circular dichroism spectra are analyzed to give estimates of nearest-neighbor frequencies. We estimate that about 90% of the Cancer borealis satellite DNA and over 80% of the Gecarcinus lateralis satellite DNA consist of d(AT)n:d(AT)n sequences, while the serially repeating unit of the Callinectes sapidus satellite DNA may not contain any extended d(AT)n:d(AT)n sequences. The results from the circular dichroism spectra for the Cancer borealis, Gecarcinus lateralis, and the Callinectes sapidus satellite DNA's are in agreement with base composition analyses, which give 2.4, 8, and 25% G+C, respectively, for these DNA's.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130417
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  • 13
    Electronic Resource
    Electronic Resource
    Thermodynamic aspects of the gelatinization and swelling of crosslinked starch (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 879-890 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Samples of epichlorohydrin crosslinked potato starch were prepared by using a high ratio of starch to water and alkali concentration below the gelatinization level. This yielded crosslinked samples that were partially crystalline, and where the number of crosslinks could be varied between 1 and 20 crosslinks per 100 anhydroglucose units. The degree of swelling varied regularly with degree of crosslinking, and the molecular weight between crosslinks Mc as derived from swelling data in a good swelling agent compared favorably with Mc derived from chemical analysis.From the heat of gelatinization of the crosslinked starches, as observed in a differential scanning calorimeter, for gelatinization in glycerol, water, and dimethylsulfoxide, a model for the gel state of the crosslinked starch is proposed. It is concluded that the entropy of melting is the determining factor in establishing the temperature of gelatinization.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130504
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  • 14
    Electronic Resource
    Electronic Resource
    The interaction of β-cyclodextrin with dinucleoside phosphates (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 909-917 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism studies of the interaction of β-cyclodextrin with a series of eight dinucleoside phosphates, and with 3′-AMP are reported. From results with ApU and ApA, it is shown that β-cyclodextrin binding is sensitive to dinucleoside stacking in approximately the same way as optical measures of stacking. Some qualitative uses of β-cyclodextrin binding are suggested, based on the fact that the change in the CD spectrum caused by cyclodextrin binding is unique to each of the dinucleosides studied. Hoffman and Bock have previously suggested the use of β-cyclodextrin as a probe of nucleic acid structure. Their work indicated that only binding to adenosine and inosine would have to be considered. The present paper shows that binding to other bases cannot be neglected, and will impose serious restrictions on the use of β-cyclodextrin as a structural probe.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130507
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  • 15
    Electronic Resource
    Electronic Resource
    Synthesis of a novel fluorescent polyriboadenylic acid analog by polynucleotide phosphorylase (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 987-993 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(1,N6-etheno-2-aza-adenylic acid) [poly(2-aza-εA)] was synthesized from 1,N6-etheno-2-aza-adenosine 5′-diphosphate (2-aza-εADP) and Escherichia coli polynucleotide phosphorylase. The values Km = 1.02 mM, V = 1.06 μmol hr-1 enzyme unit-1 were found for the polymerization reaction. In contrast to polyadenylic acid, this novel fluorescent polymer has a random structure in solution. The application of the 2-aza-εADP for localization of polynucleotide phosphorylase was also described.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130513
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  • 16
    Electronic Resource
    Electronic Resource
    Synthesis and optical studies of L-methionine oligopeptides in solution (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1011-1022 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of L-methionine oligomers [BOC-(Met)n-OMe] (n = 2-7) and the corresponding diastereomeric di- and tripeptides were synthesized using the mixed anhydride method. Oligomers prepared in this manner were optically pure and were obtained in reasonable yield. Preliminary optical examination of the peptides suggests that secondary structures may begin forming in the pentamer or hexamer in trifluoroethanol. BOC-(Met)4-OMe and BOC-(Met)5-OMe were also synthesized using an insoluble resin containing BOC-L-methionine as the nitrophenol active ester.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130515
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  • 17
    Electronic Resource
    Electronic Resource
    Sequential oligopeptides. Conformational studies of the oligopeptides and a polypeptide with the repeating sequence L-norvalyl-glycyl-L-proline (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1067-1078 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational studies of a series of oligopeptides (from the tripeptide to the octadecapeptide) with the repeating sequence L-norvalyl-glycyl-L-proline and a polytripeptide with this sequence are reported. By means of chiroptical techniques, unordered conformations are found for all oligopeptides in water, trifluoroethanol, and ethylene glycol and for the water-insoluble polymer in trifluoroethanol. In ethylene glycol the polymer assumes a collagen-like structure. Infrared studies indicate that all the oligomers, in contrast to the polymer, are unordered in the solid state.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130519
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  • 18
    Electronic Resource
    Electronic Resource
    The thermal induced helix - β transition of poly(Nε-methyl-L-lysine) and poly(Nδ-ethyl-L-ornithine) in aqueous solution (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1109-1116 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Uncharged poly(Nε-methyl-L-lysine) (PMLL) and its isomer, poly(Nδ-ethyl-L-ornithine) (PELO), in alkaline solution (pH ca. 12) undergo a helix-to-β transition upon mild heating at 50°C or higher in a manner similar to that of poly(L-lysine) (PLL). The rate of conversion follows the order: PMLL 〈 PELO 〈 PLL. The helix can be regenerated upon cooling near zero degrees, for instance, after more than 12 hr at 2°C. At concentrations less than 0.02% the β form is intramolecular, but at higher concentrations both intra- and intermolecular β forms are generated. Poly(Nδ-methyl-L-ornithine) (PMLO), an isomer of PLL, behaves like poly(L-ornithine); uncharged PMLO in alkaline solution is partially helical and becomes disordered at elevated temperatures.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130604
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  • 19
    Electronic Resource
    Electronic Resource
    Side-chain effect on conformation of ionizable polypeptides in aqueous solution (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1161-1171 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to study the effect of side-chain length on the conformation of polypeptides, conformational changes of various ionic polypeptides with various lengths of side chain, poly-Nε-glutaryl-L-lysine (PGL), poly-Nδ-glutaryl-L-ornithine (PGO), poly-Nε-succinyl-L-lysine (PSL), and poly-Nδ-succinyl-L-ornithine (PGO), were investigated by ORD, potentiometric titration, and dilatometric measurements in aqueous solution. The results of optical rotation and potentiometric titration measurements indicate strongly that the α-helix stability increases in the sequence PSO 〈 PSL ∼ PGO 〈 PGL, which corresponds to increased side-chain length. The volume change associated with the helix-coil transition also increased in the above sequence. This series of polymers seems to be more hydrophobic compared with poly-L-glutamic acid or poly-L-lysine, as suggested from the values of enthalpy and entropy changes for coil-helix transitions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130608
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  • 20
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    Conformational change of poly-Nε-glutary-L-lysine and poly-Nε-succinyl-L-lysine in aqueous salt solutions (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1195-1203 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational changes of poly-Nε-glutaryl-L-lysine (PGL) and poly-Nε-succinyl-L-lysine (PSL) in various salt solutions were studied by use of ORD and potentiometric titration measurements. The addition of alkali metal salts to the fully ionized PGL or PSL solution caused helix formation. The helical content of the polymers increases in the following sequences: at salt concentration 0-2 M, CsCl 〈 KCl 〈 LiCl 〈 NaCl; and at 2-3 M, LiCl 〈 CsCl 〈 KCl ∼ NaCl. The preferential binding of the solvent components with various alkali metal salts of PGL or PSL was measured in LiCl, NaCl, and KCl solutions by means of equilibrium dialysis and differential refractometry. It was found that with increasing salt concentration, the polymers were preferentially hydrated in NaCl and KCl soultions; however the salt was preferentially bound to the polymers in LiCl solution. Such preferential binding was suggested to be closely related to conformational change. The addition of CaCl2 to polymer solutions led to the stabilization of the helical structure of PGL or PSL.
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    Dispersion equation and polarizability of bovine serum albumin from measurements of refractive indices (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1261-1267 
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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: Refractive indices of bovine serum albumin solutions in saline and in 2-chloro ethanol are measured for the spectral region 1770-10000 Å by a reflectance method. A procedure for the determination of a dispersion formula for binary mixtures is developed and applied. The electronic polarizability of bovine serum albumin is determined and is found to be almost independent of the solvent and concentration. Hence it follows that the electronic polarizability of bovine serum albumin is almost independent of the molecular environment.
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    Masthead (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974) 
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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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    Structure of aggregates and helix-coil transition of polypeptides by dielectric measurements. II. Poly-D,L-phenylalanine and poly-β-benzyl-L-aspartate in chloroform-dichloroacetic acid mixturesResults presented at Makromolekulares Kolloqium, Freiburg, Germany, February 1971. (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1309-1316 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dielectric absorption of poly-DL-phenylalanine and poly-γ-benzyl-L-aspartate (PLAB) was measured in very dilute solutions to determine the type of molecular association and to locate the helix-coil transition. Both polypeptides were present as associated helices in chloroform. The mode of aggregation, which was determined by measuring the dipole moment and the critical frequency, did not depend on the polarity of the side chain but rather on that of the solvent.In both polymers, the dissociation of the aggregates in chloroform was observed on addition of small amounts of dichloroacetic acid; further addition of the acid lead to the helix-coil transition.No second region of dielectric absorption that might be related to the kinetics of the transition was found during the helix-coil transition of PBLA.
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    Molecular conformation of polysaccharides in solution. Changes in the optical rotation and in the elution pattern of gel filtration (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1357-1366 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular conformation of some polysaccharides in aqueous solution in evidenced by changes in the optical rotation and in the elution pattern of gel filtration. The changes in the specific rotation against that in water are expressed as a molar conformational value [K]D21: -495° for colominic acid in 1.0 N NaOH solution, and -180° for hyaluronate (HA), +85° for corneal keratin sulfate, and +234° for amylose in 8 M urea solution. The gel filtration of amylose and HA dissolved in 8 M urea solution shows elution patterns distinctly different from those dissolved in water. The phenomena are attributable to a molecular conformational transition of polysaccharide molecules in aqueous solution.
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    Conformation and packing analysis of polysaccharides and derivatives. I: MannanDedicated to Professor E. Husemann on the occasion of her 65th birthday. (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1127-1139 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A previously described procedure for simultaneous optimization of bond lengths and angles was used to test different models for mannan I. Potential hydrogen bonds and the glycosidic angle were included in the optimization. A conformational model with bifurcated intramolecular hydrogen bonds of the type observed in the methyl cellobioside methanol complex showed the best agreement with available exprerimental data. The coordinates of this model were provided by computer calculations. The available X-ray data, however, were not sufficient for selecting this model; rather, ir data were necessary to furnish the needed information. The different conformational models tested all showed an almost constant virtual bond length O(1)-O(4) of the β-pyranose residue. This was in contrast to the previously obtained results for the α-pyranose residues.
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    Frequency dependence of the proton magnetic relaxation in aqueous solutions of haemoproteins (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1187-1193 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The longitudinal proton magnetic relaxation times T1 were measured for ferri (met)-and carbonmonoxy-bovine haemoglobin and equine myoglobin in 0.1 M KH2PO4 aqueous solutions near pH 6 at 5°C and 35°C from 1.5- to 60-MHz Larmor frequencies. It is concluded that the correlation time τC for the dipole-dipole interaction of electron and nuclear spins is in fact the electron (ferric) spin relaxation time τS being close to 1.5 × 10-10 sec for both metHb and metMb at 5°C. At 35°C the paramagnetic relaxation rates are not determined solely by the relaxation of protons exchanging from the haem pocket with bulk solvent. Hence, τC at 35°C cannot be calculated from the dispersion data obtained at this temperature. The relevance of this for the determination of interspin distances r is discussed.
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    Solvent effects on the orientaion of naphthalene rings in the side chain of poly-γ-1-naphthylmethyl-L-glutamate (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1213-1222 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The orientation of naphthalene rings in the side chain of poly-γ-1-naphthylmethyl-L-glutamate (PNLG) in mixed solvents of dichoroethane (DCE) and hexafluoroisopropanol (HFIP) has been studied together with its conformation by infrared, circular dichroism, and fluorescence spectra. The CD pattern of PNLG varies with the solvent composition while it maintains the α-helical conformation. The fluorescence spectra of PNLG in solution show excimer emission of the naphthalene chromophores. The ratio of intensity of the excimer emission to that of the normal fluorescence decreases as the HFIP component in the solvent increases. It is suggested that the naphthalene rings in the side chain of α-helical PNLG are more rigidly orientated in the solvents of higher HFIP ratio.
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    Optical rotatory properties of L-cystine conformational isomers. Theoretical analysis (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1269-1290 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The near ultraviolet chiroptical properties of L-cystine conformational isomers are examined on a static, “one-electron” model in which the disulfide moiety is the chromophoric group and the atoms of the L-alanyl fragments are treated as perturbers. The zeroth order chromophoric wave functions are calculated on a semiempirical molecular orbital model in which excited states are constructed in the virtual orbital-configuration interaction approximation. The perturbing environment is represented by point charges located at the atomic centers of the L-alanyl fragments. Chromophore-perturber interactions are expressed as charge-multipole moments with only the charge-dipole and charged-quadrupole terms being retained in the calculations. Vicinal contributions to the rotatory strengths of the five lowest energy disulfide transitions are computed for 30 conformational isomers of the L-cystine dizwitterion. The results provide support for the view that vicinal or peripheral effects can account entirely for the observed near ultraviolet (λ 〉 230 nm) chiroptical properties of L-cystine and its derivatives and that these properties are diagnostic of conformational features external to the disulfide moiety.
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    A demonstration of two-component behaviour of the circular dichroic spectra of poly(L-tyrosine, 3-bromo-L-tyrosine) in trimethylphosphate (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1341-1346 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroic spectrum of poly(Tyr,TyrBr) in trimethylphosphate from 180 to 320 nm is found to be a linear function of composition from 25 to 68% TyrBr, and the spectra of the Tyr and TyrBr components are resolved. For Tyr the resolved spectrum is in agreement with available CD spectra of poly(Tyr). These results are interpreted to mean that the side-chain conformations of Tyr and TyrBr are not affected by the other component, and that for Tyr the conformation is the same as in poly(Tyr). It is also concluded that poly(Tyr,TyrBr) is helical with the same helix sense as poly(Tyr). The restrictions on the side-chain conformations are discussed, and it is suggested that the Tyr and TyrBr side chains are all in the same χ1 region.
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    Calculations of the circular dichroism of double-helical nucleic acids. I. Effects involving π → π* transitions (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1377-1389 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism of double-helical nucleic acids was calculated as a function of geometry using the theory of Tinoco and Johnson. This theory does not include contributions of near ultraviolet transitions that are not π → π* in nature. The calculated circular dichroism shows a strong dependence on the distance of base pairs from the helix axis and the tilt of the base pair. Smaller dependences are predicted for the propeller-like twist of a base pair and for variation of the angular increment per base pair. Moderately good agreement between calculated and many experimentally observed spectra could be generated.
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    Collagenase induced changes in the circular dichroism spectrum of collagen (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1427-1434 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The maximum at 220 nm in the circular dichroism spectrum of native collagen solution changed to a negative value after heat denaturation or collagenase hydrolysis. The enzyme induced rate of CD change at 220 nm was shown to be first order in collagen concentration. The specific rate constant k is actually a combined rate constant kfast and kslow in which the ratio kf/ks is 4.1. The initial rates were linear with respect to enzyme concentration, and the Km was found to be 5.5 × 10-7 M. The rate of ultraviolet hyperchromicity at 220 nm on collagen hydrolysis was determined. The kfast was the same as that obtained by CD. The kf/ks ratio was 4.6. Both methods may be readily used to assay for collagenase activity.
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    Crystal and molecular structure of the amylose-DMSO complex (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1461-1482 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal and molecular structure of the complex of amylose with dimethyl sulfoxide has been studied by a combination of stereochemical analysis, potential energy, and X-ray diffraction methods. The complex crystallizes in a pseudotetragonal unit cell with a = b = 19.17 Å and c (fiber axis) = 24.39 Å, with two antiparallel chains per unit cell and space group P212121. The amylose chain is a left-handed 61(1.355) helix with three turns per crystallographic repeat. The O(6) rotational position is approximately gt. Dimethyl sulfoxide is located inside the helix with one DMSO molecule for every three glucose residues. An additional four DMSO molecules and eight water molecules each are located in the large interstices between chains, and it is the interaction of these molecules with the helix that results in the pseudotetragonal chain packing. The interstitial DMSO is the source of the previously reported additional layer lines, which are not consistent with the 8.13-Å amylose repeat distance. The final R factor for the layers with amylose contribution to the structure factors was 0.29, while the overall R factor was 0.35. The stereochemical packing analysis provided suitable phasing models for the subsequent X-ray refinement.
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    On the electric polarization of DNA (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1549-1556 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dielectric dispersion of DNA was studied in the frequency range 100 Hz-100 kHz at four different temperatures (6-30°C). The dielectric increment ε0-ε∞ increased with the rise of temperature. The relaxation time, on the other hand, decreased. Both the increase in dielectric increment and the decrease in relaxation time could not be explained on the basis of the counterion polarization theory. Dipole moment was estimated from Kirkwood theory. It was found to decrease systematically with temperature. Even at 0°C there was a dipole moment of 104D.
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    Intramolecular distances determined by energy transfer. Dependence on orientational freedom of donor and acceptor (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1573-1605 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dependence of Förster long-range resonance energy transfer efficiency on the orientational freedom of donor D and acceptor A molecules attached to a macromolecular substrate is examined. The usefulness of polarized emission measurements in determining the mutual orientation as well as the degree of orientational freedom of D and A and thereby deriving maximum and minimum values for the D-A separation from the transfer efficieny is demonstrated.
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    Water sorption on deoxygenated hemoglobins CC, SC, SS, AS, and AA (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1653-1659 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five human hemoglobins whose genetic relationship to one another involves one set of alleles, hemoglobins CC, SC, SS, AS, and AA, were studied in the deoxygenated form within a McBain gravimetric sorption system at 28°C. Water was used as the adsorbate at relative vapor pressures ranging from 0.11 to 0.39. The results of this study are reported and compared with a similar study on the ferric form of these same five hemoglobins. For both forms of hemoglobin studied, a slight increase was measured in the number of polar sites accessible to H2O vapor for those genotypes in which the substituent in the sixth position from the N terminus of the two β chains had a positively charged side chain, i.e., hemoglobin C. Those samples containing hemoglobin S (less soluble in the deoxy form) show an increased BET monolayer coverage in the deoxy as compared to the ferric form. For each genotype, the deoxygenated form had more polar sites accessible to H2O vapor than its ferric form. This finding is in agreement with an increase in the size of the central cavity as shown by crystallographic analysis.
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    Helix-coil transition in nucleoprotein. Effect of ionic strength on thermal denaturation of polylysine-DNA complexes (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1681-1697 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal denaturation of direct-mixed and reconstituted polylysine-DNA complexes in 2.5 × 10-4 M EDTA, pH 8.0 and various concentrations of NaCl has been studied. For both complexes, increasing ionic strength of the solution raises Tm, the melting temperature of free base pairs. The linear dependence of Tm on log Na+ indicates that the concept of electrostatic shielding on phosphate lattice of an infinitely long pure DNA by Na+ can be applied to short free DNA segments in a nucleoprotein. For a direct-mixed polylysine-DNA complex, the melting temperature of bound base pairs Tm′ remains constant at various ionic strengths. On the other hand, the Tm′ in a reconstituted polylysine-DNA complex is shifted to lower temperature at higher ionic strength. This phenomenon occurs for reconstituted complex with long polylysine of one thousand residues or short polylysine of one hundred residues. It is shown that such a decrease of Tm′ is not due to a reduction of coupling melting between free and bound regions in a complex when the ionic strength is raised. It is also not due to intermolecular or intramolecular change from a reconstituted to a direct-mixed complex. It is suggested that this phenomenon is due to structural change on polylysine-bound regions by ionic strength. It is suggested further that Na+ may replace water molecules and bind polylysine-bound regions in a reconstituted complex. Such a dehydration effect destabilizes these regions and lowers Tm′. This explanation is supported by circular dichroism (CD) results.
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    Theoretical investigation of semiconductive properties in proteins. I. Electrical conductivity, charge carrier mobilities, and free paths in β-polyglycine (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1731-1737 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical values are reported for the specific conductivity, charge carrier mobilities, and delocalized free paths in β-polyglycine using the parallel-chain pleated sheet conformation and the all-valence electron energy band structure obtained previously. The mobilities are found to be much larger along the polypeptide backbones than in the direction of the hydrogen bonds. This indicates a mechanism of conduction in which the former path is favored for electronic delocalization. The preexponential factor of the specific conductivity obtained theoretically agrees well with experimental results.
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    Critical chain length for helix formation in L-methionine oligopeptides (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1747-1750 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism of a series of L-methionine oligopeptides [BOC-(Met)n-OMe] was examined in trifluoroethanol and hexafluoroacetone sesquihydrate. The results indicate that the trimer through the hexamer exists predominantly in disordered conformations in these solvents. An abrupt change in the CD pattern at the heptamer in trifluoroethanol suggests that L-methionine oligopeptides begin forming helices at this chain length.
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    The state of water on hydrated collagen as studied by pulsed NMR (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1767-1776 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The spin-lattice relaxation time (T1) of water adsorbed on collagen fibers was determined at six frequencies and temperatures varying from 25° to -80°C. Care was taken to eliminate the contributions to the signal of protons other than those in the adsorbed water. Quantitative calculations were made on T1 and the results were compared with the experimental data. It is suggested that a maximum of about 0.50-0.55 g water per g collagen forms a hydration layer, which cannot be frozen down to -90°C and exhibits a distribution of motional correlation times. For collagen samples containing a larger quantity of adsorbed water, the additional water molecules behave like ordinary isotropic water, having a single correlation time and a freezing temperature of about -10°C.
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    Raman studies of nucleic acids. XII. Conformations of oligonucleotides and deuterated polynucleotides (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1821-1845 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser Raman spectra of the trinucleoside diphoshate ApApA and dinucleoside phosphates ApU, UpA, GpC, CpG, and GpU are reported and discussed. Assignments of conformationally sensitive frequencies are-facilitated by comparison with spectra reported here of poly(rA), poly(rC), and poly(rU) in deuterium oxide solutions. The significant spectral differences between ApU and UpA, and between GpC and CpG, reveal that the sequence isomers have nonidentical conformations in aqueous solution. In UpA at low temperature the bases are stacked and the backbone conformation is similar to that found in ordered polynucleotide structures and RNA. In ApU no base stacking can be detected and the backbone conformation differs from that found in UpA, both in the orientation of phosphodiester linkages and in the internal conformation of ribose. At the conditions employed neither ApU nor UpA exhibits base pairing in aqueous solutions. In both GpC and CpG the bases are stacked and the phosphodiester conformations are similar to those encountered for UpA and RNA. However, major differences between spectra of GpC and CpG indicate that the geometries of stacking and ribosyl conformations are different. In GpC the Raman data favor the formation of hydrogen bonded dimers containing GC pairs. Protonation of C in GpC is sufficient to eliminate the ordered conformation detected by Raman spectroscopy. Despite the ordered backbone conformation evident in GpU, this dinucleoside apparently contains neither stacked nor hydrogen bonded bases at the conditions employed here. The Raman data also confirm the stacking interactions in ApApA, poly(rA), and poly(rC) but suggest that the backbone conformation in poly(rC) differs qualitatively from that found in most ordered polynucleotide structures and is thermally more stable. The present results demonstrate the sensitivity of the Raman technique to sequence-related structural differences in oligonucleotides and provide additional spectra-structure correlations for future conformational studies of RNA by laser Raman spectroscopy.
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    Masthead (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974) 
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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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    Assignment of the proton nmr chemical shifts of the T—N3H and G—N1H proton resonances in isolated AT and GC Watson-Crick base pairs in double-stranded deoxy oligonucleotides in aqueous solution (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1943-1964 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The 300-MHz proton nmr spectra (between 11 and 14 ppm) of a series of double-stranded deoxy oligonucleotides of known sequence have been recorded in H2O solution. These resonances have been assigned to the G—N1H and T—N3H protons of specific base pairs from an evaluation of the temperature dependence of the ring NH linewidths and from the selective ring NH chemical shift changes on actinomycin-D binding. The deoxy oligonucleotides exist predominantly in the DNA-B conformation as evaluated from antibiotic binding studies. Ring-current calculations have been utilized to evaluate the up-field shifts of the G—N1H and T—N3H protons in Watson-Crick base pairs due to the ring currents from the pyrimidine and purine rings of nearest neighbor base pairs in regular DNA-B- and RNA-A-type helices. The perturbations on these up-field ring-current contributions that arise from twisting and tilting a base pair adjacent to the ring NH under study have been evaluated and found to change the calculated chemical shift by ±0.6 ppm for twist and tilt distortions of 〈30°C in a single adjacent base pair. A knowledge of the experimentally assigned ring NH chemical shifts of specific base pairs in known sequences of double-stranded deoxy oligonucleotides coupled with the ring-current tables for the DNA-B helical structure permit the assignment of 13.6 ± 0.1 ppm and 14.6 ± 0.2 ppm for the G—N1H proton of an isolated GC base pair and the T—N3H proton of an isolated AT base pair, respectively.
    Additional Material: 8 Ill.
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    Reversion of the B to A transition of DNA induced by specific interaction with the oligopeptide distamycin A (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 823-831 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The effect of the DNA-binding oligopeptide distamycin A on the B to A transition of DNA in ethanol/water solutions has been studied by means of CD. (The overbars indicate that it does not matter which particular form of the corresponding families is considered.) The results show that increasing the concentration of distamycin A reverses the A conformation (in 82% ethanol) to the B conformation due to its strong binding and stabilization of the latter. In accordance with previous data for pure aqueous solutions, a site size of 3.5 base pairs is obtained from the studies in water/ethanolic solutions. From the data on the B to A transition in the presence of distamycin A, we estimated the length of the cooperativity ν0 = 10 base pairs.The results demonstrate that the oligopeptide systems of distamycin, as well as those of netropsin, are effective stabilizers of the DNA B-conformation.
    Additional Material: 6 Ill.
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    NMR evidence for a type I β-turn in (Pro2)-tetrapeptides and interdependence of cis:Trans isomerism, ring flexibility, and backbone conformation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 781-804 
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    Notes: Tetrapeptides with proline in position 2, asparagine or leucine in position 3, and glycine in positions 1 and 4, with end groups free or blocked on the N-terminal side, were studied in their various ionic states in 2H2O and in Me2SO-d6 by 1H- and 13C-nmr. In order to clarify or refine some details, successive substitutions of the residues in these peptides with amino acids enriched to 85% in 13C, or to 85% 13C plus 97% 2H were carried out. The 1H and 13C chemical shifts as well as the 1H-1H, 13C-13C, and 13C-1H coupling constants and the signal intensities show strong similarity of behavior between the tetrapeptides of asparagine and leucine. The main conformational characteristics are (1) the almost total stabilization of the trans conformer in the type I β-turn structure when the peptide is in the zwitterion state dissolved in Me2SO. This is deduced from the 3JC3αH-N3H and the 3JC2′-H3α coupling constants, which both furnish a dihedral angle of φ3 = -90°, and from the positive value of the temperature coefficient of the glycine-4 amide protons, which suggests a type 4 → 1 hydrogen bond; (2) the evolution of cis and trans isomer fractions which change with the ionic state of the peptides in Me2SO, whereas they remain constant in aqueous solution; and (3) the conformation of the pyrrolidine ring as it follows the variations in cis:trans isomer populations together with the side-chain rotamer fractions of the residue in position 3. In the β-turn conformation the isomer cis is less abundant and the pyrrolidine ring is more flexible; this explains the perfect accommodation of the proline residue in position 2 of a bend. The interdependence of these phenomena where interactive forces play a predominant role underlines the importance of cooperative effects in the molecule. The results also suggest that the cis isomer of proline can adapt itself just as well as the trans isomer to position 2 of a type I β-turn.
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    Transport properties of particles with segmental flexibility. II. Decay of fluorescence polarization anisotropy from hinged macromolecules (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 913-930 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: An algorithm is presented for the Monte Carlo simulation of the decay of fluorescence polarization from segmentally flexible molecules. Based on the random walk model of Brownian motion, the treatment explicitly follows the stochastic changes in the diffusion coefficients as the molecule bends. It includes the effects of a linear restoring force opposing the bending and the effects of hydrodynamic coupling between the translational, rotational, and bending motions. One application is presented: the simulation of anisotropy decay curves for hinged rods. A variety of decay curves are obtained, including single- and multiexponential behavior, and the following conclusions are reached: (1) increasing the flexibility is usually, but not always, accompanied by a more rapid rate of depolarization; (2) reducing the size of the fluorescent subunit will usually, but not always, increase the rate of depolarization; and (3) the complex interplay between the effects of molecular shape, relative sizes of the subunits, restoring force, and orientation of the transition dipoles renders it unlikely that any simple method can be used to interpret anisotrophy data without simulation. In particular, it is not possible to determine the extent of bending by fitting the data with the two-exponential approximation used by some investigators in the past.
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    13C-nmr spectroscopy of red algal galactans (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 977-990 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: 13C-nmr spectra of red seaweed galactans, belonging to the agar and carrageenan groups or having the “intermediate” type of structure, were interpreted on the basis of 13C-nmr spectra of model compounds. Signal assignments have been made for most of the known extreme structures of such galactans. 13C-nmr spectroscopy was shown to be a rapid and convenient method of structural analysis, which permits one to determine the type of galactan structure, the absolute configurations of its constituents (galactose and 3,6-anhydrogalactose), and the positions of the sulfate and O-methyl groups in a polysaccharide molecule.
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    Dielectric changes in hyaluronate solutions at microwave frequencies as a function of concentration, system pH, and temperature (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 931-944 
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    Notes: The dielectric response of human umbilical cord hyaluronic acid in various environments has been studied at microwave frquencies using a resonant microwave cavity as a probe. Both the real and imaginary parts of complex dielectric constant and the loss tangent for hyaluronate solutions are obtained by utilizing equations for perturbation of a resonant cavity. Dielectric changes at room temperature have been observed in aqueous solutions of hyaluronic acid as a function of concentration ranging from 0 to 350 mg/ml. The data indicate the existence of ordered phases in hyaluronate solutions at selective concentrations, that is, exhibiting lyotropic-type transitions. Hyaluronate solutions at 1.5 and 3 mg/ml concentrations have been studied at various pH in the range of 6-8 and at constant ionic strength 0.1. A temperature-dependent transition in hyaluronate solution of 120 mg/ml concentration has been observed at physiological temperature. It is shown that this temperature-dependent behavior can be related to the orientational polarizability term in the Debye theory of polar molecules in liquids.
    Additional Material: 8 Ill.
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    A quantitative test of Zimm's model for the rotor-speed-department sedimentation of linear DNA molecules (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 945-964 
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    Notes: In 1974, Zimm described a theory which predicts that the sedimentation coefficient of high-molecular-weight DNA will decrease as the rotor speed of measurement increases. In 1979, this theory was revised, and the new formula predicts speed-dependence effects that are substantially smaller than the predictions of the original version. This report describes the results of subjecting both the original and the revised versions of the theory to quantitative tests using a well-defined sucrose-gradient system and a DNA of known molecular weight (T4c DNA). T4c bacteriophage is a mutant, whose DNA contains the unmodified base cytosine, instead of the glucosylated hydroxymethylcytosine characteristic of the T-even bacteriophages, and has a molecular weight of 115 ± 3 × 106. The DNA of the wild-type phage (T4D+) was also used in some experiments.In addition to the quantitative tests, the experiments test for an effect first observed by Rubenstein and Leighton, which showed that the sedimentation coefficient measured for T2 DNA depended on the composition of the centrifuge tube used for the measurement (tube composition effect). It can be inferred from this observation that an interaction occurs between particle and tube wall during sedimentation, and this leads to a reduction in sedimentation velocity independent of the reduction in S described by Zimm's theory.The results show that in the range of 25,000-50,000 rpm, the original but theoretically incorrect form of the theory quite accurately describes the sedimentation behavior of both T4c and T4D+ DNA, although T4D+ was a special case in some respects. The revised (corrected) form of the theory predicts much less of a speed-dependence effect than that actually observed. The discrepancy between corrected theory and observation suggests that other factors (perhaps arising from the use of the swinging bucket rotor geometry) are causing the additional observed reduction in S20,w. However, the experiments show that the tube composition effect does not seem to be one of these.
    Additional Material: 7 Ill.
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    Proton NMR study of the interaction of cis-dichloro-diamine-platinum(II) with poly(I) and poly(I)·poly(C) (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1299-1309 
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    Notes: The fixation of cis (NH3)2Cl2Pt(II) to poly(I)·poly(C) leads to the formation of two complexed species. One involves coordination to a single base (accounting for about 70% of the total platinum bound over the rb range 0.07-0.25) and the other to two bases which are not adjacent to each other but may be on the same strand and separated by a loop. Reaction of the platinum compound with poly(I) gives in addition to the above two species a minor one (about 15%, independent of rb over the range 0.05-0.30) in which the platinum is bound to two adjacent bases. The availability of such coordination reduces the dominance of the 1:1 species, which, however, remains the major one (ca. 55%).
    Additional Material: 3 Ill.
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    Heavy-atom effects associated with methylmercury (II) binding to rabbit glyceraldehyde-3-phosphate dehydrogenase (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1329-1344 
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    Notes: The complex of CH3Hg(II) with the accessible cysteines of glyceraldehyde-3-phosphate dehydrogenase (GAPD, EC 1.2.1.12) from rabbit muscle has been studied by phosphorescence and optically detected magnetic resonance (ODMR) spectroscopy. The wavelength dependence of the phosphorescence decay kinetics has also been measured. Comparison of CH3Hg(II)-GAPD with GAPD by these methods shows that a specific optically resolved tryptophan site of GAPD is perturbed by the interaction with a nearby mercury atom. The perturbation on the luminescence and ODMR properties is typical of an external heavy-atom effect. Based on the x-ray diffraction structure of the lobster enzyme, it is proposed that the heavy-atom effect results from the interaction of tryptophan-310 with CH3Hg(II) bound to cysteine-281 in the rabbit muscle enzyme.
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    Interaction of spermine with different forms of DNA. A conformational study (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1415-1434 
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    Notes: The energy of interaction of a spermine molecule with the A- and B-forms of DNA has been calculated, assuming that the molecule of spermine is fixed in the narrow groove of the DNA helix with the formation of hydrogen bonds between the amino groups of spermine and the phosphate groups of DNA. The atom-atom potentials method was used. Optimal structures for the A-DNA-spermine and B-DNA-spermine complexes are suggested. It is shown that, in agreement with the experimental data, the interaction of the spermine molecule with the A-DNA is energetically more favorable than that with the B-DNA. Two main factors are responsible for this: (1) the distance between neighboring phosphates of the chain in A-DNA (which is about 1 Å less than that in B-DNA) corresponds better to the distance between the amino groups of the propyl part of spermine; and (2) the orientation of phosphate groups in A-DNA inside the groove is preferable for complex formation with spermine to the outside groove arrangement of the phosphates in B-DNA. These conclusions are further confirmed by the calculations for DNA-propane diamine complexes.
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    Crystal and molecular structure of isoleucinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-](C60H102N6O18) (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1517-1534 
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    Notes: The crystal structure of a synthetic analog of valinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-] (C60H102N6O18), has been determined by x-ray diffraction procedures. The crystals are orthorhombic, space group P212121, with cell parameters a = 11.516, b = 15.705, c = 39.310 Å, and Z = 4. The atomic coordinates for the C, N, O atoms were refined in the anisotropic thermal motion approximation and for the H atoms in the isotropic approximation. Values of standard (R) and weighted (Rw) reliability factors after refinement are 0.073 and 0.056, respectively. The structure is completely asymmetric. The cyclic molecular backbone is stabilized by six intramolecular hydrogen bonds N—H…O=C, five bonds being of the 4→1 type and one being of the 5→1 type. The side chains are located on the molecular periphery. The conformational state of isoleucinomycin in the crystal is intermediate between the corresponding crystalline states of valinomycin and meso-valinomycin. The observed conformation suggests that complexation could proceed via entry of the ion at the face possessing the L-Lac residues, the less crowded face.
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    Conformational analysis of the milk oligosaccharides (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1555-1566 
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    Notes: Possible conformations of lacto-N-tetraose, lacto-N-neotetraose, related disaccharides, and other milk oligosaccharides have been studied by an energy-minimization procedure using empirical potential functions. Lacto-N-tetraose favors a “curved” conformation, while lacto-N-neotetraose favors an approximately “straight” conformation. These two conformations differ mainly in the position of the terminal galactose residue with respect to the rest of the molecule. This difference explains the greater strength of lacto-N-neotetraose compared with lacto-N-tetraose in its ability to inhibit the cross-reaction of blood group P1 fractions with Type XIV pneumococcal antipolysaccharide. Although the favored conformation of lacto-N-tetraose (inactive) agrees with the model proposed by the earlier workers, that for lacto-N-neotetraose (active) differs. The favored conformations for the disaccharides galactose-β(1-4)-N-acetylglucosamine, galactose-β(1-3)-N-acetylglucosamine, and lactose are similar in overall shape, differing only in the nature and orientation of the side groups. This explains their nearly equal inhibitory activity. These theoretical models also explain the increased activity of lacto-N-fucopentaose I over that of lacto-N-tetraose and the relative activities of the substituted lactoses. The present studies suggest that it is the overall shape of the molecule which is important for activity, rather than the terminal β(1-4)-linked galactose residue alone.
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    Influence of methanol on the rotational diffusion of poly(L-lysine) in the helix-coil transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1571-1585 
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    Notes: 13C spin-lattice relaxation times of poly(L-lysine) have been obtained at 67.9 MHz in aqueous solution and in a mixed solvent (40% methanol/60% water). A concomitant determination of the conformation by CD permits the correlation of conformation and rotational diffusion of the polymer. The dependence on pH of the spin-lattice relaxation times of the 13Cα and the side-chain carbon resonances reflects the diffusional motion in the random-coil conformation, in the helix-coil transition, and in the conformation of the α-helix. In the mixed solvent the reorientational correlation time of the Cα-Hα vector increases from τ = 0.37 nsec (random coil) to τ = 12.0 nsec (α-helix). In aqueous solution the correlation time of this vector increases from τ = 0.33 nsec (random coil) to τ ≫ 11 nsec. The reorientation rates of the side-chain methylene groups in the two solvents are markedly different. The reorientation of all methylene groups is reduced in the mixed solvent.
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    Solid-state conformation of copolymers of β-benzyl-L-aspartate with L-alanine, L-leucine, L-valine, γ-benzyl-L-glutamate, or ∊-carbobenzoxy-L-lysine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1603-1615 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The solid-state conformation of copolymers of β-benzyl-L-aspartate [L-Asp(OBzl)] with L-leucine (L-Leu), L-alanine (L-Ala), L-valine (L-Val), γ-benzyl-L-glutamate [L-Glu(OBzl)], or ∊-carbobenzoxy-L-lysine (Cbz-L-Lys) has been studied by ir spectroscopy and circular dichroism (CD). The ir spectra in the region of the amide I and II bands and in the region of 700-250 cm-1 have been determined. The results from the ir studies are in good agreement with data obtained by CD experiments. Incorporation of the amino acid residues mentioned above into poly[L-Asp(OBzl)] induces a change from the left-handed into the right-handed α-helix. This conformational change for the poly[L-Asp(OBzl)] copolymers was observed in the following composition ranges: L-Leu, 0-15 mol %; L-Ala, 0-32 mol %; L-Val, 0-8 mol %; L-Glu(OBzl), 3-10 mol %; and Cbz-L-Lys, 0-9 mol %.
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    Physical aging of dry elastin (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1667-1673 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Dry purified ligamentum nuchae elastin has been investigated for physical aging. The samples were quenched from a temperature (197°C) close to the softening point to a number of measuring temperatures ranging from -20 to +180°C. At each temperature, the small-strain torsional creep properties were determined at a number of elapsed intervals after the quench. Aging effects were found over the whole temperature range, and the creep and aging behavior of elastin turned out to be very similar to that of synthetic polymers.
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    DNA backbone conformation in cis-syn pyrimidine[]pyrimidine cyclobutane dimersPresented at the American Society of Biological Chemists and Biophysical Society Meeting, June 1-5, 1980, New Orleans, Louisiana [(1980) Fed. Proc. 39, 1879]. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1695-1701 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Toroidal elastic supercoiling of DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1705-1713 
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    Notes: Covalently closed circular DNA can exist in different configurations known as circular, toroidal, and interwound. Changes among these forms can be made in several ways, including the insertion of dye molecules between adjacent base pairs, which tends to untwist the double-helical structure. The aim of this paper is to discuss these configurations, and the changes among them, in the context of classical elastomechanics. The concepts of twisting, linkage and writhing are explained. Simple experiments on a twisted linear-elastic rod are described, and it is shown that although the circular and interwound forms may be modeled in this way, the toroidal form does not occur, being mechanically unstable. Theoretical energy calculations by Levitt on bent and twisted DNA show that DNA exhibits a particular kind of nonlinear elasticity in which there is an unusual coupling between bending and twisting. The aim of the paper is to show qualitatively that this special kind of elasticity can stabilize the toroidal form of closed circular DNA.
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    Physicochemical investigation of k-carrageenan in the random state (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1357-1374 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Light-scattering, viscosity, and sedimentation experiments on aqueous solutions of k-carrageenan show that this sulfated polygalactose is an expanded flexible random coil. This expansion is due to long-range interactions that are predominantly electrostatic. Extrapolation of viscosity data to infinite ionic strength provided values for the intrinsic viscosity which were subjected to the Stockmayer-Fixman analysis, giving a value for the Mark-Houwink coefficient under theta-conditions, Kθ, of 0.27. The characteristic ratio, C∞, under these conditions is 7.8, and the conformation factor σ is 2. In a solution of 0.118 ionic strength, where a Mark-Houwink exponent aη of 0.86 is found, the radii of gyration calculated from viscosity data are lower than those found from the angular dependence of scattered light. On the other hand, the radius of gyration found from the sedimentation rate agrees well with the light-scattering radius. The relations between molecular parameters are corrected for the poly-dispersity of the sample.
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    An interaction of albumin with hyaluronic acid and chondroitin sulfate: A study of affinity chromatography and circular dichroism (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1407-1414 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Masthead (1980)
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    Biopolymers 19 (1980) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360190801
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    The translational friction of toroids (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1475-1489 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approximate analytic expression for the translational friction coefficient of a toroid modeled as a continuous shell of frictional elements is derived using the Kirkwood approximation. The accuracy of this expression was determined by comparing the friction coefficients predicted by it to those predicted by extrapolated shell-model calculations using the modified Oseen tensor. To show that these calculations do indeed yield the correct friction coefficients, actual translational friction coefficients were determined by observing settling rates of macroscopic model rings or toroids in a high-viscosity silicone fluid. Our conclusion is that the approximate expression yields friction coefficients that are about 1.5-3% low for finite rings. For thin rings, a comparison is also made with the exact result of Yamakawa and Yamaki [J. Chem. Phys. 57, 1572 (1972); 58, 2049 (1973)] for the translational friction of plane polygonal rings. This comparison shows that the approximate expression yields results which are low by 2-3% unless the rings are extremely thin, in which case the error is larger. In the limit of an infinitely thin ring the approximate expression reduces to the Kirkwood result [J. Polym. Sci. 12, 1 (1954)], which is low by 8.3%. We discuss briefly how this work may be useful in determining the structure of DNA compacted by various solvent-electrolyte systems and polyamines.
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    Dynamic light scattering studies of internal motions in DNA. II. Clean viral DNAs (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1451-1474 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Internal Brownian motions of clean φ29 and λ-DNAs have been studied using photon-correlation techniques at both visible (λ0 = 632.8 nm) and uv (λ0 = 363.8 nm) wavelengths. The present dynamic light scattering data, which extend to K2 = 19 × 1010 cm-2, can in every case be satisfactorily simulated by a Rouse-Zimm model polymer with an appropriate choice of the three model parameters. The effects of pH, salt concentration, single-strand breaks, and molecular weight on those model parameters have also been investigated. Intact clean DNAs exhibit surprisingly little variation with pH from 7.85 to 10.25, with salt concentration from 0.01 NaCl to 5.4M NH4Cl, or with molecular weight or GC content. The single-strand breaks have no effect at pH 9.46, but produce dramatic changes in the model parameters at pH 10.0 and 10.25, indicating the introduction of titratable joints at those pHs. The failure of either single-strand breaks or a large change in GC content to alter the model parameters in the neutral pH range is a strong indication that local denaturation is not required for those flexions and torsions that dominate the relaxation of fluctuations in the scattered light. The Langevin relaxation time for the slowest internal mode of a particular Rouse-Zimm model derived from the dynamic light scattering data is compared with pertinent literature data extrapolated to the same molecular weight. The present algorithm for determining model parameters from the light-scattering Dapp vs K2 curve actually yields a Langevin time in fairly good agreement with the literature value. For unknown reasons the light-scattering D0 values generally exceed those obtained from the molecular weight and sedimentation coefficient by about 20%.
    Additional Material: 7 Ill.
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    Ultraviolet Raman spectroscopy of polyribouridylic acid: Excitation profile of the hypochromism induced by order-disorder transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1507-1515 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raman spectra of polyribouridylic acid excited in the uv region, from 363 to 290 nm, are reported. The conformational changes of the polymer from random coil to ordered structure with stacked bases at high and low temperature, respectively, are reflected by important changes in the Raman line intensities; this Raman hypochromism is itself a function of the excitation wavelength - its profile has been determined and shows negative values in the region of 290 nm (near resonance), i.e., hypochromism becomes hyperchromism. Thus the knowledge of the hypochromism excitation profile is important in following order-disorder transition of a polymer using resonance Raman spectroscopy. Theoretical attempts are proposed for explanation, involving not only the relative variations of the molar extinction coefficient on the order-disorder transition of the polymer, but also the damping factors of the vibronic levels. The theoretical curve is found to fit adequately the experimental data over the excitation range, using only the frequency of the O-O transition of uracil and a vibronic linewidth of 2200 cm-1.
    Additional Material: 4 Ill.
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    Interaction of poly(α-L-glutamic acid) and sodium poly(α-L-glutamate) with solvent components in water-2-chloroethanol mixtures (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2177-2190 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preferential interaction of sodium poly(α-L-glutamate) and poly(α-L-glutamic acid) with the solvent components in water/2-chloroethanol mixtures has been determined using density-increment measurements. The degree of preferential interaction was deduced from the density increments at constant molality of 2-chloroethanol and at constant chemical potential of 2-chloroethanol. Sodium poly(α-L-glutamate) and poly(α-L-glutamic acid) are both preferentially hydrated in the whole range of solvent composition. A dehydration process occurs during the 2-chloroethanol-induced coil-to-helix transition of sodium poly(α-L-glutamate). This dehydration process was attributed to the release of some moles of water from the neighborhood of the peptide bond during the nucleation of the helix. After the conformational transition, sodium poly(α-L-glutamate) is solvated by one 2-chloroethanol molecule. The location of water and 2-chloroethanol molecules in the different parts of the residue (more polar and less polar portions) is also discussed.
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    Effects of pD on ring-stacking interactions between dinucleoside phosphates and tryptamine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2223-2245 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complex formation between tryptamine and mononucleotides and dinucleoside phosphates containing adenine and/or cytosine has been studied at five pD's ranging from 1.1 to 7.4 by proton magnetic resonance spectroscopy. Chemical shifts of base ring protons and the ribose anomeric proton in the nucleotides and indole ring protons in tryptamine were monitored and their changes with pD and intermolecular interactions interpreted qualitatively. Stacked complexes were found to exist at all pD's in the range studied. Complex geometries differ depending on pD. An electrostatic interaction between the tryptamine amino group and the nucleotide phosphate group contributes to complex formation above pD 4 but is not strong enough to shift the dinucleoside phosphate equilibrium towards the unstacked conformer.
    Additional Material: 5 Ill.
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    Conformational energy studies on N-methylated analogs of thyrotropin releasing hormone, enkephalin, and luteinizing hormone-releasing hormone (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1943-1973 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Empirical conformational energy calculations have been carried out for N-methyl derivatives of alanine and phenylalanine dipeptide models and N-methyl-substituted active analogs of three biologically active peptides, namely thyrotropin-releasing hormone (TRH), enkephalin (ENK), and luteinizing hormone-releasing hormone (LHRH). The isoenergetic contour maps and the local dipeptide minima obtained, when the peptide bond (ω) preceding the N-methylated residue is in the trans configuration show that (1) N-methylation constricts the conformational freedom of both the ith and (i + 1)th residues; (2), the lowest energy position for both residues occurs around φ = -135° ± 5° and ψ = 75° ± 5°, and (3) the αL conformational state is the second lowest energy state for the (i + 1)th residue, whereas for the ith residue the C5 (extended) conformation is second lowest in energy. When the peptide bond (ωi) is in the cis configuration the ith residue is energetically forbidden in the range φ = 0° to 180° and ψ = -180° to +180°. Conformations of low energy for ωi = 0° are found to be similar to those obtained for the trans peptide bond. In all the model systems (irrespective of cis or trans), the αR conformational state is energetically very high. Significant deviations from planarity are found for the peptide bond when the amide hydrogen is replaced by a methyl group. Two low-energy conformers are found for [(N-Me)His2]TRH. These conformers differ only in the φ and ψ values at the (N-Me)His2 residue. Among the different low-energy conformers found for each of the ENK analogs [D-Ala2,(N-Me)Phe4, Met5]ENK amide and [D-Ala2,(N-Me)Met5]ENK amide, one low-energy conformer was found to be common for both analogs with respect to the side-chain orientations. The stability of the low-energy structures is discussed in the light of the activity of other analogs. Two low-energy conformers were found for [(N-Me)Leu7]LHRH. These conformations differ in the types of bend around the positions 6 and 7 of LHRH. One bend type is eliminated when the active analog [D-Ala6,(M-Me)Leu7]LHRH is considered.
    Additional Material: 11 Ill.
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    Interactions of molecules with nucleic acids. III. Steric and electrostatic energy contours for the principal intercalation sites, prerequisites for binding, and the exclusion of essential metabolites from intercalation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2067-2089 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on steric and electrostatic considerations, the prerequisites for binding to DNA via the intercalation mechanism are proposed. Steric contour energy curves are presented to demonstrate the region inaccessible to an intercalant. They are calculated with a 6-n (n = 14) potential. This method is a soft potential analog of an excluded-volume approach. Electrostatic contours on the steric surface illustrate the relatively positive and negative regions of the binding site. The principal intercalation sites, predicted to fit into B-DNA via a tetramer-duplex unit, and the unconstrained dimer-duplex units, obtained in crystal structures, are examined. These contours illustrate the requirements of size, conformation, and net atomic charges necessary for intercalation and optimum binding. Based on the limited space available for intercalation by the presence of the backbone and the maximum base-pair separation of 8.25 Å, an Essential Metabolite Exclusion Hypothesis is presented.
    Additional Material: 9 Ill.
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    The chiroptical properties of proteins. II. Near-ultraviolet circular dichroism of lysozymeTaken in part from the Ph.D. dissertation of W. J. G. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2191-2208 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the near-uv CD spectrum of lysozyme was carried out in the presence and absence of the inhibitor tri-N-acetylglucosamine, and theoretical chiroptical calculations based on the tetragonal crystal structure of the enzyme and the enzyme-inhibitor complex were performed. The results of these calculations indicate that the near-uv CD spectrum of lysozyme can be adequately explained in terms of negative rotatory strengths arising from the tryptophan 1La (293-300 nm) and the disulfide n-σ* bands (250 rm), and positive rotatory strength contributions from the tryptophan 1Lb bands (291 nm) and the tyrosine 1Lb bands (275 nm). Contributions to the rotatory strength of each band were approximated in terms of specific interactions between chromophores. It was found that the rotatory strength of most of the near-uv transitions arises primarily from coupling interactions involving other side-chain chromophores and amide groups which are in close proximity. Changes which are observed in the lysozyme CD spectrum on binding of tri-N-acetylglucosamine may be explained in terms of changes in the rotatory strength which result from interactions of the 1La transitions of the active-site tryptophans with the acetamide groups of the inhibitor. The reasonable agreement which is found between the experimental and calculated rotatory strengths implies that the crystal conformation of lysozyme must resemble the solution conformation.
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    URL: http://dx.doi.org/10.1002/bip.1980.360191205
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    Relationship between conformation and physicochemical properties of polypeptides. I. Synthesis of homo- and co-oligopeptides by the liquid-phase method (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 173-187 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the following oligo- and co-oligopeptides by the liquid-phase method is described: (L-Met)15 (I), [L-Glu(OBzl)]20 (II), (L-Val)8-Gly (IV), (L-Ile)8-Gly (V), (L-Ile)4-Gly-(L-Ile)4 (VI), (L-Ile)4-Pro-(L-Ile)4 (VII), (L-Met)5-L-Pro-(L-Met)5 (VIII), [L-Glu(OBzl)]7-L-Pro-[L-Glu(OBzl)]7 (IX). The oligomers are covalently bound to bifunctional polyethylene glycol (PEG) and monofunctional PEG-M of Mr 5 × 103-2 × 104. Analytical controls were carried out after each step of synthesis in order to ensure quantitative coupling yields. All products could be obtained in high purity as indicated by amino acid analysis, thin-layer chromatography and chiroptical methods. The solubility of the oligomers was strongly enhanced by the presence of the C-terminal PEG group, enabling conformational investigations in a variety of solvents. A significant relationship between conformation and physicochemical properties of the oligopeptides was observed. Oligomers with tendencies to adopt α-helical (I, II) or unordered structures (VI-IX) showed no pronounced change in solubility or coupling kinetics during chain elongation, whereas the onset of a β-structure (IV, V) was paralleled by a drastic decrease in solubility and reactivity of the terminal amino groups. Most notably, the insertion of a proline or glycine in the middle of a β-forming peptide chain (VI, VII) resulted in a considerable increase in solubility compared to the corresponding homo-oligomers. The impact of the conformational properties of a peptide chain on strategic considerations of peptide synthesis in solution is delineated.
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    Circular dichroism and conformational analysis of the membrane-modifying peptide -N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu-(OBzl)-Gln-OMe with respect to alamethicin (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 203-214 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of the CD spectrum is reported for the synthetic and membrane-modifying nonadecapeptide analog of alamethicin N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu(OBzl)- Gln-OMe. The CD data are evaluated according to three different methods and are discussed with respect to those obtained from natural alamethicin and suitable models such as N-t-Boc-(Aib-L-Ala)7-OPOE, fragments of the synthetic nonadecapeptide, and the hexadecapeptide N-t-Boc-(Aib-L-Ala)5-Pro-Ala-Aib-Aib-Glu(OBzl)-Gln-OMe. The synthetic nonadecapeptide with the longer helical region exhibits membrane activities comparable to those of alamethicin, whereas the hexadecapeptide with the shorter helix is inactive.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360190201
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    Dynamic light scattering in a flow - a new method of particle anisotropy investigation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 231-240 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper deals with the light scattering from particles rotating in a flow with a transverse velocity gradient. It is theoretically substantiated and experimentally proved that the scattered light spectrum contains reliable information of the particle configuration and dimensions. The proposed technique may prove also very promising for the analysis of particle polydispersion.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190203
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    Poly(ε-L-lysine): Synthesis and conformationPart of this work was presented at the International Symposium on Biomolecular Structure held in Madras, India, in January 1978. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 219-229 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of poly(ε-L-lysine) is described. This is a poly(ε-amino acid) in which the ε-amino group of lysine is condensed with the α-carboxyl group to produce a chain backbone that is a variant of the usual one seen in proteins and the side chain is the α-amino group. Conformational studies of poly(ε-L-lysine) and its t-butyloxycarbonyl derivative suggest the likelihood of a chain order that is formally similar to the antiparallel pleated-sheet conformation of proteins.
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    Contribution of electrodiffusion to the dynamics of electrically stimulated changes in mechanical properties of collagen membranesPresented at the Third International Congress of Biorheology, August 28-September 1, 1978, La Jolla, California. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 241-262 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied the kinetics of oscillatory tensile forces in collagen membranes. These forces were generated by sinusoidal electric fields applied across the membrane. Both the magnitude and phase of the measured force changed with frequency over a three-decade range. The membrane-separated electrolyte baths had different ionic strength but identical non-isoelectric pH. Changes in intramembrane ionic strength due to the electric field were calculated over the same frequency range via an electrodiffusion model that was generalized to include convection and electrokinetic coupling. A comparison of the experimental and theoretical phases and amplitudes versus frequency suggests that electrodiffusion is the dominant rate-limiting process in this electromechanochemical transduction. These results are relevant to electrostatic interactions in connective tissues and to membrane-based filtration devices in which membrane permeability may be actively varied and controlled by an applied electric field.
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    Heat capacity changes and partial molal heat capacities of some di- and tripeptides in water (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 263-272 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Integral enthalpies of solution of several dipeptides and tripeptides in water at low concentrations have been determined at 25 and 35°C. These data have been used to derive the changes in heat capacity on dissolution at infinite dilution ΔCp0 at 30°C. Limiting partial molal heat capacities ΔCp20 have been determined by combining ΔCp0 with Cp2 (heat capacity of pure solid peptides). Using the data on ω-amino acids and these peptides, the partial molal heat capacity of a peptide group —CONH— was semiquantitatively estimated.
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    Heat capacities of transfer of some amino acids and peptides from water to aqueous urea solution (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 273-284 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Integral enthalpies of solution at low concentrations of several amino acids and peptides in 2 and 6M urea solutions have been determined at 25 and 35°C. These data have been used to derive the enthalpies of transfer (at 25 and 35°C) and heat capacities of transfer (at 30°C) of these amino acids and peptides from water to aqueous urea solutions. Furthermore, the enthalpies of transfer and heat capacities of transfer per CH2 group and per peptide group —CONH— have also been estimated. These results show that while the enthalpies and heat capacities of transfer per CH2 group are positive and negative, respectively, the reverse is true for —CONH— group. The implications of these results in the mechanism of the denaturation of proteins by urea are discussed.
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    Studies on transfer ribonucleic acids and related compounds. XXVI.Paper XXV: Ohtsuka, E., Miyake, T. & Ikehara, M. (1979) Chem. Pharm. Bull. 27, 341-345. Circular dichroic properties of cyclic oligoribonucleotides and their linear counterparts (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 285-296 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CD spectra of cUpUp, cCpCp, and cGpGp derived from DCC-catalyzed polymerization of the relevant protected ribonucleoside 3′-phosphates are described. Similar studies on Up, U 〉 p, and cUp, as well as cUpUpUp and cUpUpUpUp, are presented. The spectral properties of the cyclic oligomers are compared with those of the corresponding linear oligomers with terminal 3′-phosphates so as to demonstrate that disruption of normal right-handed base stacking is considerable in these RNA loops.
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    Chemical synthesis of (1 → 2)-α-D-mannopyranan (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 297-309 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of 1,2-anhydro-3,4,6-tri-O-benzyl-β-D-mannopyranose proceeds in the presence of Lewis acids, cationic coordination catalysts, and strong bases. Debenzylation of the products yields oligomeric saccharides or low polymers. Polymerization in toluene by means of potassium alkoxide complexed with crown ethers leads to essentially stereoregular (1 → 2)-α-D-mannopyranan. The original derivatives have been characterized by optical rotation, viscosity, molecular weight, gel permeation chromatography, and spectrometry. The free polysaccharides have been characterized by optical rotation, molecular weight, and 1H- and 13C-nmr spectrometry and compared to yeast mannan hydrolysate oligomers.
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    Physical association of two simple alkylators to some DNA sequences (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 311-324 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular mechanics calculations have been used to determine the preferred physical association sites of the known alkylating agent dimethyl aziridinium ion (Az+) and a CH3+ prototype test probe with B-form, tetrameric DNA sequences. Electrostatic interactions are most important in determining these preferential physical association sites. In turn, the intermolecular energy minima depend on the charge distribution assigned to the DNA sequence. However, for three reported DNA charge distributions, only two distinct sets of energy minima were obtained for the CH3+-like ion interacting with (G-C)4, (A-T)4, and [(G-C)·(A-T)]2 deoxyribonucleic acids. These minima correspond to physical association geometries in which the CH3+-like ion is near known alkylation sites. The results of the Az+ … [(G-C)·(A-T)]2 interaction are virtually identical to those found for the CH3+-like ion. Aqueous solvation energetics have little effect on the physical association of Az+ with [(G-C)·(A-T)]2.
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    Chemical reactivity of protonated aziridine with nucleophilic centers of DNA bases (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 325-340 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of molecular orbital calculations, using MINDO/3 and CNDO/2L methods, have been used to characterize the chemical reaction of protonated aziridine with DNA nucleophilic base sites. The N-7 atom of guanine is found to be the preferred alkylation site only when the O-6 atom of guanine is involved in base-pair hydrogen bonding. Otherwise O-6 is the predicted major site of alkylation. This indirectly suggests that protonated aziridine alkylation processes involve base-paired DNA structures, since N-7 guanine is the observed major site of alkylation. Alkylation of N-3 adenine is predicted to be more favorable than chemical attack of the N-7 adenine position. Both of these sites, however, are predicted to be less reactive than N-7 of guanine. These chemical reactivity studies resolve alkylation specifically not achieved in the DNA-alkylator physical association calculations reported in the preceding paper.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190210
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    Conformational analysis of somatostatin and selected analogs in oriented polyoxyethylene by infrared dichroism (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 341-352 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared dichroic studies and deuterium exchange measurements of somatostatin and some of its analogs incorporated in uniaxially oriented polyoxyethylene are described. Band positions and dichroic ratios in the N-H stretching and amide I and II regions are similar to those of flexible and nonordered peptides like valinomycin and poly[Glu(ONa)]. This information, together with fast deuterium exchange rates, suggests that somatostatin exists in a flexible nonordered conformation in polyoxyethylene. One analog, di-S3,14-acetamidomethyl dihydrosomatostatin, was found to exist in both nonordered and β-like conformations.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190211
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    Monte carlo simulation of the solvent structure in crystals of a hydrated cyclic peptide (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 395-418 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Monte Carlo simulation of the structure of the 16 ordered and disordered waters in the unit cell of crystals of the cyclic peptide cyclo(-L-Ala-L-Pro-D-Phe)2 is reported. The water structure has been characterized in terms of the statistically averaged positions of the individual molecules, their root-mean-square movements about these positions, the probability of finding a water in a given spatial position in the crystal (probability maps), and examination of individual configurations of the system. In this way a picture is obtained of the water structure, including water orientations (hydrogen positions), the hydrogen-bonding network, and fluctuations in these structural features, to a degree hitherto unavailable either from experimental or theoretical studies. In addition, the variation in water structure in various peptide environments was studied and correlated with the energetics of the individual water molecules. Variations in the crystalline environment of different water molecules lead to energy differences of as much as 4-5 kcal/mol in their average energies. Similarly, differences are observed in the water-peptide and water-water components of the energy. Two different water potentials were tested. The results were compared with experimental data in terms of mean positions, root-mean-square movements, and the Fourier transform of the simulated water structure. The agreement factor (R factor) calculated from the theoretical water probability distribution was 18.8% compared to the x-ray value of 14.5%, and the value of 28% when the water is omitted.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190214
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
    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.1980.360190301
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    Polymeric model system for protein-bilirubin interaction (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 445-448 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190217
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  • 86
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    Conformational flexibility of peptides containing α,β-unsaturated amino acid residues. I. Conformational analysis of N-acetyl-N′-methylamides of dehydroalanine and N-methyldehydroalanine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 469-475 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy calculations on the N-acetyl-N′-methylamides of dehydroalanine and N-methyldehydroalanine indicate that their conformational behavior is very different from that of the corresponding saturated compounds. The conformational data in the literature from x-ray and nmr investigations on peptides containing α,β-unsaturated residues are discussed on the basis of these theoretical results.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190303
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  • 87
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    Synthesis and ordered structure of amphipatic block copolymers with a saccharide and a peptide block (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 493-507 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amphipatic block copolymers (OβEb) with a hydrophilic saccharide block and a hydrophobic polypeptide block were synthesized. In these copolymers the saccharide block is the glyco-amino acid Oβ from ovomucoid and the peptide block (Eb) is a poly(γ-benzyl-L-glutamate) block. Copolymers OβEb exhibit, in the solid state and in Me2SO concentrated solutions, mesomorphic lamellar structures where the polypeptide chains are in an α-helical conformation. Depending on the molecular weight of the polypeptide block, three types of lamellar structures are obtained, and they differ by the mode of organization of the polypeptide chains in their lamellae and by the T or Y conformation of the saccharide block.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190305
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    Spectroscopic and equilibrium dialysis studies of poly(α-L-glutamic acid)-Cu(II) complexes in the pH range 4-7For the preceding paper of the Macromolecule-Metal Ion Complex series, see Macromolecules 12 (1979) in press. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 477-491 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of complex between the Cu2+ ion and poly(α-L-glutamic acid) [poly(Glu)] in 150 mM NaCl solutions was studied by uv-visible absorption and equilibrium dialysis methods at the mixing ratios of Glu residues to Cu2+, R, of 32, 16, and 8 and in the pH range 4-7. The results showed that more than 90% of Cu2+ ions bind to the poly(Glu) at pH 〉 4.9, but the bound Cu(II) begins to dissociate with a decrease in pH. The absorption spectra of bound Cu(II) varied with pH and R in a complicated manner. Three different component spectra were disclosed from the analysis of the pH dependence of the bound spectra. We concluded that poly(Glu)-Cu(II) complexes fall into three classes in the pH range 4-7, with the proportions of these complexes varying with both pH and R. The three complexes predominate either in the helix or extended-coil region, in the helix-coil transition region, or in the helix-aggregate region. The stability constant and binding mode of each Cu(II)-Glu complex were estimated from the dialysis data. With these results, the possible structure of each complex is discussed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190304
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    Nearest-neighbor and next-nearest-neighbor effects in the proton NMR spectra of the oligoribonucleotides ApGpX and CpApX (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 557-573 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variable-temperature proton nmr spectra of the oligoribonucleotides in the series CpApX and the series ApGpX, X = A, G, C, U, together with the parent dimers CpA and ApG have been measured. A complete analysis of all the nonexchangeable base proton resonances and ribose H-1′ proton resonances was made. The presence of trends in the shielding abilities of the various bases at both the nearest-neighbor and next-nearest-neighbor positions were identified. The observed shieldings could be used to predict the chemical shifts of protons in related systems. Based on the empirical results from ribodinucleoside monophosphates, the temperature-dependent behavior of the J1′2′ coupling constants of the triribonucleotides suggested that the compounds in the CpApX series stacked from the 5′-end to the 3′-end, while those in the ApGpX series stacked from the 3′-end to the 5′-end.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190309
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    Monte carlo computation of the supercoiling energy, the sedimentation constant, and the radius of gyration of unknotted and knotted circular DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 619-637 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Closed random Gaussian polygonal chains of N (6 〈 N 〈 150) bonds of equal length b and thickness d have been generated on a computer. The knot type, the writhing number w, the radius of gyration, and the average of the inverse of the distance between two apices have been determined for each chain. For all the studied knot types - 0, 31, 41, 51, and 52 - the probability density of finding a given w is Gaussian. The Gaussian is centered about 0 for the amphichiral knots. Therefore, for long circular DNAs, the contribution to the supercoiling energy, which depends on w only, may be considered as purely entropic and may be expressed as ARTw2/N, in agreement with previous semiempirical considerations. The parameter A increases with chain thickness, it decreases as N gets larger but rapidly reaches a plateau. Comparison with experimental data from the literature would suggest that the ratio of the writhing to the constraint increases with ionic strength. The ratio of sedimentation constant of the supercoiled DNA to the sedimentation constant of the nicked DNA varies as N1/4 (w/N)2, and therefore depends on the writhing density and on the length of the DNA.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190312
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    Application of band centrifugation to the study of the assembly of alfalfa mosaic virus (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 575-595 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A band-centrifugation method for the analysis of an assembly reaction of a simple virus from its RNA and protein is described. The experiment was carried out by sedimenting a band of viral RNA through a solution of depolymerized coat protein. The resulting radial distribution of the reaction products, followed as a function of time, was analyzed by a computer simulation of the series of reaction. This method is based on a numerical solution of the continuity equation for the sedimentation-diffusion process [Claverie, J.-M., Dreux, H. & Cohen, R. (1975) Biopolymers 14, 1685-1700; Cohen, R. & Claverie, J.-M. (1975) Biopolymers 14, 1701-1716]. A numerical method for the simulation of the chemical reaction is derived. From the simulated reaction series, equilibrium constants emerge for the successive addition of protein subunits to the growing nucleoprotein particle.The method is applied to the assembly of alfalfa mosaic virus. If the reaction between RNA and protein is carried out in 0.32M CsCl, pH 7.0, two stages during particle growth are resolved, each characterized by an equilibrium constant K. The determined values for K range from 5 × 105 to 3 × 106 l. mol-1. The existence of these two stages may have a structural implication in the assembly, as they likely represent an elongation and a termination stage. If the reaction is carried out under more favorable conditions (0.25M CsCl, pH 7.0), a kinetic constant of at least 105 l. mol-1 sec-1 is derived for each reaction step. Under these conditions the assembly appears to be completed within 1 min, which is too fast to detect distinct stages by band sedimentation.
    Additional Material: 7 Ill.
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    Characterization of molecular motions in 13C-labeled aortic elastin by 13C-1H magnetic double resonance (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 597-617 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Purified insoluble elastin samples labeled with [1-13C]valine, [1-13C]alanine, and [1-13C]-lysine were prepared from chick aorta in culture. The molecular mobility at the labeled sites was investigated using 13C-1H magnetic double-resonance spectroscopy. Linewidths, T1, and nuclear Overhauser effect (NOE) values of the labeled carbons alone were obtained from dipolar decoupled difference spectra. Analysis of these parameters together with signal intensity measurements showed that essentially all the valyl residues, ca. 75% of the alanyl residues, and ca. 60% of the lysyl residues were characterized by rapid backbone motions having τ = 65 nsec. Resonances due to the remaining alanyl and lysyl residues were detected in cross-polarization experiments, which enhance the signals of motionally restricted carbons. Since lysyl and alanyl residues are found in the crosslink regions of elastin, whereas valyl residues are not, we conclude that crosslinks rather than secondary structures in the extensible region of the protein are the main source of motional restrictions in the protein. Elastin chain mobility was monitored by linewidth measurements over the range -90 to +70°C. When the swelling solvent (0.15M NaCl) was fixed at 0.6 g/g of elastin, a rapid monotonic reduction in chain mobility was observed as the temperature was lowered from 50 to 5°C. Liquidlike mobility was completely lost at 5°C. In contrast, the same sample in contact with excess solvent retained its liquidlike molecular mobility until -13°C, where it abruptly became rigid. The molecular mobility of this sample was temperature insensitive in the physiologically interesting range, 20-40°C, as a consequence of the opposing influences of temperature and swelling. Taken together these nmr data indicate that under physiological conditions, elastin is a network of mobile chains whose motions are strongly influenced by protein-solvent interactions.
    Additional Material: 8 Ill.
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    Measurement of preferential solvation of some glucans in mixed solvent systems by gel-permeation chromatography (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 639-653 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preferential solvation of the glucans amylose, pullulan, and dextran in binary dimethyl-sulfoxide/water (DMSO/H2O) solvent mixtures has been measured using gel-permeation chromatography. The preferential solvation behavior of the three glucans in DMSO/H2O solvent mixtures is indistinguishable in the experiments reported. In solvent mixtures with mol ratio DMSO/H2O less than 1:2, all three glucans are solvated preferentially by H2O. The maximum extent of preferential solvation by H2O is about 2.5 mol H2O/mol of glucose residues. When the DMSO/H2O mol ratio exceeds 1:2, DMSO solvates the glucans preferentially to a maximum extent of about 1 mol DMSO/mol of glucose residues. An interpretation of the change in preferential solvation with mixed solvent composition is suggested in terms of the known characteristics of the binary solvent system, and the relationship of preferential solvation, reported here, to the absolute solvation of the glucan chains is discussed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190313
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    Electrical conductivity of single crystals of lysozyme (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 669-679 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dc electrical conductivity of large single crystals of hen egg-white lysozyme has been measured. The samples were grown from aqueous solution and dried in air with silica gel. The temperature dependence of the conductivity obeyed the relation σ = σ0 exp(- ΔE/kT), with ΔE = 1.2 eV. The ΔE value agreed with most of the previous results for various proteins in the form of lyophilized powder. On the other hand, log σ0, being between 7 and 11, was much larger than the previously reported values and differed among the samples. An irreversible decrease in σ0, without affecting ΔE, was observed on heating the samples above 85°C. It was shown that the set of results can be explained if the charge carriers responsible for the observed conduction are regarded as protons, originating from residual water molecules. Photoresponse of the samples to uv radiation below 305-315 nm was also observed. Reproducible and reliable results were obtained relatively easily in the present experiments, which is thought to be the main advantage of using single-crystalline samples.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190315
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    Transport properties and hydrodynamic centers of rigid macromolecules with arbitrary shapes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 751-766 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general formalism, which includes translation-rotation coupling, is proposed for calculating translational and rotational transport properties, as well as intrinsic viscosities, of rigid macromolecules with an arbitrary shape. This formalism is based on Brenner's theory of translational-rotational dynamics and on methods for the calculation of hydrodynamic properties that have been already presented, and can be regarded as a generalization of the one proposed by Nakajima and Wada. The calculated transport properties depend on the origin as predicted by Brenner's theory, but in a disagreement with him, the center of resistance and the center of diffusion do not coincide. As one can define several hydrodynamic centers, which in practice turn out to be located at different points, the influence of the choice of the center on the calculated transport properties is discussed. An analysis of the translation-rotation coupling effects in translational diffusion reveals that they arise exclusively from hydrodynamic interactions and are rather small in some cases of interest. Finally, we present a study of the rotational diffusion of rigid bent rods with a fixed length-to-diameter ratio. The diffusion coefficients obtained can be useful to estimate changes with respect to a straight rod.
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    mini-chiuz (1974)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 8 (1974), 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.19740080107
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    Das Geheimnis des Lapis lazuli (1974)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 8 (1974), S. 65-71 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19740080302
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    mini-chiuz (1974)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 8 (1974), S. A40 
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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.19740080307
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    Bindungen zwischen Metallen (1974)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 8 (1974), S. 112-120 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19740080404
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    Mathematik fur Naturwissenschaftler und Ingenieure. Bd. 1. Von A. Jeffrey, Verlag Chemie GmbH, Weinheim/Bergstr. 1973. 1. Aufl., 396 S., zahlr. Abb. und Tab., geb. DM39 (1974)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 8 (1974), S. 125-125 
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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.19740080408
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