摘要:

AbstractA series of high molecular weight copolypeptides ofL‐proline and sarcosine have been synthesized. Experimental evidence is presented which indicates that the products are true copolymers rather than mixtures of homopolymers. In contrast to poly‐L‐proline I, a copolymer ofL‐proline‐sarcosine I containing approximately 50% sarcosine is soluble in water. Two molecular conformations of the copolymers, similar to those found for polyproline, have been characterized by means of infrared spectroscopy and optical rotatory dispersion. The residue rotation ofL‐proline has been obtained from the copolymers a

ISSN:0006-3525    

DOI:10.1002/bip.360010202

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

年代:1963

数据来源: WILEY

摘要:

AbstractOptical properties of complexes of plant sulfated polysaccharides with basic dyes have been examined. Spectral shifts in the dye have been used as the basis for quantitative analysis of anionic sites in these compounds. The κ‐ and λ‐carrageenans have been shown to give characteristically different titration curves. Other, similar, plant extractives have been shown to fall into one or the other of these two classes. Cotton effects in the region of the absorption spectrum of the dye have been discovered, indicating the presence of long range order and asymmetry in the λ‐C2carrageenan. The relation of the optical effects to each other and to the structure of the polymer is discussed briefly in terms of recent developments in the theory of meta

ISSN:0006-3525    

DOI:10.1002/bip.360010203

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

年代:1963

数据来源: WILEY

摘要:

AbstractA statistical thermodynamic treatment of thermally induced helix–coil transitions is formulated with the matrix method for an (ensemble) of system(s) in which one strand of a double helix consists of a homopolymeric polynucleotide and the other strand comprises a number of complementary oligonucleotides. Each oligonucleotide is considered to be completely bound to the longer chain when in the helical configuration and completely free from it when in the randomly coiled configuration. The case of partial binding; i.e., “dangling,” is treated in a later paper. Taken into account in both cases are intrachain “stacking” interactions between nearest neighbor residues and interchain hydrogen bonding.An approximate treatment of the characteristic equation of the formulation indicates that the reciprocal of the transition temperature (1/T0) is a linear function of the reciprocal of the degree of polymerization (D.P.) of the oligonucleotides. In the same approximation, 1/T0is also a linear function of the negative logarithm of the absolute activity of the oligonucleotides. Transition curves obtained by exact calculation on a computer are presented for various degrees of polymerization of both the oligo‐ and polynucleotides. These curves show a sharpening of the transition with increasing D.P. of the long chain and the aforementioned reciprocal D.P. depende

ISSN:0006-3525    

DOI:10.1002/bip.360010204

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

年代:1963

数据来源: WILEY

摘要:

AbstractThe reaction of soluble RNA with formaldehyde was measured as a function of time. The rate of this reaction can be treated as a combination of simple first‐order rates, such as those observed for the reaction of mononucleotides with formaldehyde. The equilibrium position of the reaction of formaldehyde with soluble RNA in the absence of Mg++is consistent with the equilibrium constants observed for mononucleotides. There is no evidence for the occurrence of crosslinking under the conditions used. All the nucleotides of sRNA are available for reaction with formaldehyde in the absence of Mg++, even though a considerable amount of secondary structure remains under these conditions. The presence of Mg++stabilizes the secondary structure considerably, protecting about two‐thirds of the nucleotides from reaction. The rate of reaction of formaldehyde with sRNA is six times slower than that for mononucleotides. This slowing down of the reaction is interpreted as being due to the weak involvement of the reactive groups in secondary structure, while strong involvement in secondary structure, as in the presence of Mg++, prevents reaction complet

ISSN:0006-3525    

DOI:10.1002/bip.360010205

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

年代:1963

数据来源: WILEY

摘要:

AbstractFrom x‐ray diffraction data, a pseudohexagonal unit cell witha=b= 14.94 A. andc= 7.93 A. has been obtained for partially dried precipitate of amylose and tertiary butyl alcohol. Geometrical considerations establish a helical amylose configuration which has seven glucose residues per helix tur

ISSN:0006-3525    

DOI:10.1002/bip.360010206

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

年代:1963

数据来源: WILEY

摘要:

AbstractThe dielectric dispersion of polyglutamic acid (PGA) was studied in the pH range of 4–9.8. Three different dispersion curves were obtained. Above pH 6.0, where PGA has a random coil configuration, the dielectric dispersion is characterized by a large dielectric increment (ca. 450) and a relaxation time of 10–12.7 × 10−6sec. Between pH 6.0 and 5.0, where PGA is in a transitional state with small viscosity, a dispersion curve with very small dielectric increment and also small relaxation time was observed. Below pH 5.0, where PGA has a helical configuration, the dispersion is characterized by a relaxation time of 10–12 × 10−6sec. and a dielectric increment of about 120. The dipole moment of coil and helical forms of PGA were calculated by using Allgen's equation, and qualitative discussions of these dielectric properties ar

ISSN:0006-3525    

DOI:10.1002/bip.360010207

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

年代:1963

数据来源: WILEY

摘要:

AbstractA method is proposed for the determiantion of nucleotide sequences in nucleic acids. Briefly, the procedure involves the formation of derivatives specific for either the 3′ or 5′ end of nucleic acid. This is followed by a partial enzymatic hydrolysis to yield specific fragments. The functions of the chemically modifying derivative are (a) to serve as a reference point which positions each base according to its distance from the modified end, (b) to provide a convenient means of separating oligomers with derivatives from those without derivatives, (c) to permit the use of additional parameters of fractionation of oligomers with derivative ends. The features of this method include: construction of long sequences from shorter fragments, unequivocal positioning of fragments, independence from quantitative procedures, economical use of nucleic acid polymer, determination of sequences from both ends simultaneously, application to DNA and RNA. Data are presented on the action of pancreatic ribonuclease on bis‐2,4 dinitrophenyl hydrazone derivatives of yeast ribonucleic acid and polyuridylic

ISSN:0006-3525    

DOI:10.1002/bip.360010208

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

年代:1963

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.360010209

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

年代:1963

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.360010201

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

年代:1963

数据来源: WILEY