摘要:

AbstractDNA in its native and denatured form and yeast RNA complex individual aromatic hydrocarbon molecules but single‐stranded poly A does not. The degree of complexing appears to depend on molecular dimensions; it is appreciable for phenanthrene, pyrene, and benzpyrene but very small or undetectible for coronene, tetracene, pentacene, and 20‐methylcholanthr

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe G–F transformation of actin was studied in terms of an interaction between different counterions and actin. macroion by means of electrometric measurements. Due to the polyelectrolyte‐structure of the actin molecule, the electrostatic interactions must play a predominant role. In this sense the influence of the counterion radius has been investiga

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe study of polyelectrolytes in solution by small‐angle x‐ray scattering techniques involves special problems, raised by the presence of several species: solvent, macroions, counterions, and possibly the ions of an additional electrolyte. A theoretical treatment of this problem is developed, based upon geometric concepts; the treatment applies to globular and to rodlike particles for the case of x‐ray experiments carried out on an absolute scale. The equation obtained involves several parameters: mass and radius of gyration for globular particles; mass per unit length and axial radius of gyration for rodlike particles; partial specific volumes of the neutral macromolecular component of the counterions and of the added electrolyte; solvation of the macromolecular species; fraction of the counterions osmotically free. The equation is used to interpret a series of experiments performed with the Li, Na, and Cs salts of DNA in solution in water containing variable amounts of the chlorides of each cation. The effects of concentration are first eliminated by extrapolating to infinite dilution the experiments carried out at different concentrations; then the effects of the solvation are eliminated by extrapolating to pure water the results obtained at different electrolyte concentration. The parameters still involved at this stage are the mass per unit length, the partial specific volumes of the DNA and of the counterions, and the fraction of the counterions osmotically free. If the partial specific volumes are chosen in agreement with other data of the literature, and if the fraction of the counterions osmotically free is assumed to be 0.30 for the three salts, as suggested by other workers, the structure of the DNA molecules turns out to be the same for three cations, and to agree with the Watson‐Crick model. These results are confirmed by the study of the liquid–crystalline gels, obtained at higher concentration, that lead to a direct determination of the mass per unit length of the rods. Moreover the solvation of the DNA molecules is determined as is shown to be different for each of the three cations. These results are in excellent agreement with those obtained by other t

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe nucleation of a helical sequence from a random chain of the polypeptide molecule as well as the nucleation of a random‐coil sequence from the helical conformation of the molecule are considered simultaneously in evaluating the partition function of the system. This partition function is then used for a comparative analysis of the theories of Zimm and Bragg, Gibbs and DiMarzio, and Lifson and Roig. It is shown that while all three account properly for the essential nature of the nucleation phenomenon the first considers in detail the random‐coil nucleation, the second emphasizes the details of the helix nucleation, while the third neglects the fine details of both in a symmetric

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractPoly‐α‐(1 → 6)‐anhydro‐D‐glucopyranose has been synthesized by the phosphorus pentafluoride‐catalyzed polymerization of l,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose and subsequent debenzylation. Physical characterization establishes its high polymeric

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractPoly‐L‐tyrosine absorbs strongly at 1515 cm.−1, and a band at this frequency has been found in a number of proteins and has been assigned to the tyrosine residue. The assignment was confirmed by examination of spectra of deuterated proteins, which usually exhibit a residual band at 1513 cm.−1. In proteins, this band correlates linearly with known tyrosine content, but the point corresponding to poly‐L‐tyrosine itself does not fall on the correlation line. The possibility and limitations of using the infrared method for tyrosine determinations i

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractNuclear magnetic resonance spectra of acridine have been measured in aqueous methanol solutions over a wide concentration range in the presence and absence of dissolved DNA. In solutions containing DNA the acridine spectra show a marked line broadening and intensity decrease at temperatures lower than 50°C. These line‐shape changes can be associated with two types of binding interactions: (1) a tight, irrotational binding of the acridine at low acridine:phosphate ratios and (2) a weaker, rotationally less restrictive binding at high acridine concentrations. At temperatures above 50°C. a marked line narrowing is noted for the acridine spectrum and is attributed to an increase in mobility of the bound acridine as the DNA complex undergoes a helix–coil transition. A loose association of acridine molecules with the purine and pyrimidine bases in heat‐denatured DNA is indicated by chemical shift changes in the acridine spectrum. The NMR measurements also show that the presence of acridine in denatured DNA solutions greatly reduces renaturation of

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractIn order to provide preliminary data for the interpretation of the spectrophotometric titration properties of RNA, the spectral changes accompanying the ionization of poly‐(uridylic acid) have been determined, as have the ionization constants as a function of salt concentration and the enthalpies and entropies of ionization. The spectral propertics and ionization constants of poly (uridylic acid) have been compared with those of 2′(3′) Uridine monophosphate and of uridine; significant, differences have been established. The results obtained are consistent with the hypothesis that uracil residues in poly U are stacked only in concentrated salt solu

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe optical rotatory dispersion of horse heart ferricytochrome c and of a ferri heme undecapeptide have been determined under various conditions. Analysis of the Soret region makes it possible to characterize three different states of ferricytochrome c. the native state (superposition of a negative and a positive Cotton effect); an intermediate state (single positive Cotton effect whose magnitude Δ[M] is equal to 55,000); a denatured state (single positive Cotton effect whose magnitude Δ[M] is equal to 115,000) in which compared to both the native and intermediate states a more or less important decrease in helix content is observed. The optical rotatory dispersion spectra of the Soret region of the monomeric ferri heme undecapeptide is similar to that of denatured ferricytochrome c. The multiplicity of Cotton effects observed under certain conditions for the hemopeptide is a consequence, resulting from a polymerization, of intermolecular interactions. The comparison of the optical rotatory dispersion spectra of ferricytochrome c and the ferri heme undecapeptide indicates that in the intermediate state interactions remain between the heme group and the portion of the poly pep tide chain absent in the hemopeptide. These interactions disappear in the denatured stat

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractA method for covalently binding proteins to carboxyl‐containing polymers is described.N‐Ethyl‐5‐pheriylisoxazolium‐3′‐sulfonate is used to form active esters of the carboxyls, which then condense with amine groups on the protein to yield amides. Conjugates of α‐chymotrypsin with such polymers have been obtained, with nearly full retention of enzymatic activity in s

ISSN:0006-3525    

DOI:10.1002/bip.1967.360050611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY