摘要:

AbstractComplex formation of poly(glutumic acid) with cupric ions in aqueous solution was investigated by three different methods: optical spectroscopy, optical rotatory dispersion, and electron spin resonance. Formation of a characteristic complex was found to occur in a pH region suitable for the helix‐coil transition. An analysis of the ESH spectrum of the complex is given, and the results of calculation of bonding parameters suggest that the bond between copper and nitrogen atoms had an appreciably covalent character. The change in the secondary structure of the polymer as a result of complex formation is discusse

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040702

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

年代:1966

数据来源: WILEY

摘要:

AbstractOne hundred hypothetical polynucleotides of varying chain length and composition and of random sequence were generated and their chemical degradation simulated by a computer. Included in the study were 20 hypothetical polymers with the composition and chain length of a transfer RNA. A second computer program attempted to reconstruct the sequences from the nucleotide composition and the simulated fragments produced. Approximately 700 reconstructions were attempted from various sets of fragments generated from the 100 polymers. The dependence of the probability of reconstructing the original sequences on the methods of producing and isolating the fragments was studied.

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040703

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe patterns of disulfide bridges in proteins were considered by using the concept of topological information content. It was proposed that the difference between topological informal ion content in the half‐cystine residues of the native state and of the fully reduced form of a protein is related to the problems of the renaturation of the fully reduced and denatured protein. Specifically, when there is no difference between the topological information contents of the two states, the reduced protein is able to recover its native conformation. The concept reported in the present paper is consistent without exception with reported experimental result

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040704

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe sedimentation coefficient of T2 phage DNA has been studied by zone centrifugation in sector‐shaped preparative centrifuge tubes over a concentration range of 0.02–2.0 μg./ml. DNA. These results have been compared to a similar study in the analytical centrifuge of T4 DNA over the range of 0.50–5.75 μg./ml. DNA. A value for the sedimentation coefficient of 60.7 ± 1.8 S. was obtained by the first method and a value of 61.3 ± 1.5 S. by t

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040705

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe base composition of intact, purified, oligonucleotides has been determined by comparing the absorption spectrum of each oligomer with calculated curves. The spectral curve of each oligomer was measured in 7Murea at three pH values and digitized at 1‐mμ intervals. The calculated curves consisted of the sums of the absorption spectra of mononucleotides in 7Murea at the same pH's. A computer was used to make the comparisons and establish the best fit. Results are presented for nine of the ten possible dimer composition isomers; trimers from pancreatic and T1ribonuclease hydrolyzates of TMV‐RNA; poly‐A, poly‐C, and poly‐U; and intact tobacco mosaic

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040706

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

年代:1966

数据来源: WILEY

摘要:

AbstractLight‐scattering measurements were performed for a number of poly‐γ‐benzyl‐L‐glutamate (PBLG) samples in dimethylformamide (DMF) and in chloroform‐formamide (C‐F) at 25°C. Osmotic pressure data for some of these polypeptide samples in DMF at 37°C. were also determined. The scattering radii 〈S2〉1/2in the two solvents were roughly proportional to the sample's weight‐average molecular weightMw. The lengths per monomeric residueh, calculated from the measured 〈S2〉1/2andMwwith the assumption of a rigid rod of uniform density, were about 1.2 A. in DMF and about 1.5 A. in C‐F. The measured values for theMw/Mnratio indicated that the samples used were quite polydisperse in molecular weight. If this effect is taken into account, the above values forhmust be lowered drastically. In fact, application of Holtzer's procedure, which is capable of yieldinghfree of polydispersity effects, gave 0.85 A. forhin DMF and 1.16 A. forhin C‐F. Since, according to the recent conclusion established by Parry and Elliott, the correct conformation of the PBLG molecule in helicogenic solvents must be the α‐helix for whichhis 1.5 A., these results imply that the overall shape of the PBLG helix cannot be a rigid rod, in contradiction to the

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040707

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

年代:1966

数据来源: WILEY

摘要:

AbstractNine samples of poly‐γ‐benzyl‐L‐glutamate (PBLG), ranging inM̄wfrom 19,000 to 410,000, were examined viscomctrically and by ultracentrifugation with dimethylforma‐mide (DMF) at 25°C. as helicogenic solvent. The data for [η] ands0(limiting sedimentation coefficient) as functions ofM̄wwere fitted well by the theories for a rigid prolate ellipsoid of revolution whose major axis increases linearly withM̄w, but whose minor axis is independent ofM̄w. This implies that the overall shape of the PBLG molecule in DMF is represented by a straight cylinder whose cross section is independent of its length. The length per monomeric residuehevaluated from [η] is about 1.3 A., whereas that from s0is about 1.6 A. No adequate explanation for this difference inhcan be found at present. More serious is the fact that these hydrodynamically evaluated values ofhare appreciably larger than, the value obtained from our light‐scattering measurements reported previously. All these values ofhfrom our studies are not consistent with the value characteristic of the α‐helix, for whichhis 1.5 A. The concentration dependence ofs0was found to agree well with the recent theoretical prediction of Peterson for cyli

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040708

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

年代:1966

数据来源: WILEY

摘要:

AbstractMeasurements by the technique of electric birefringence with pulsed sinusoidal electric fields on polyriboadenylic acid (poly‐A) and polyribouridylic acid (poly‐U) indicate that the kinetics of the double‐stranded helix formation of poly (A + U) in the presence of Mg2+is second order and consists of two steps: nucleation and propagation of base pairs from nuclei. The nucleation involves approximately 7 base pairs. It seems that the requirement of 7 base pairs to start the formation of a double‐stranded helix is not peculiar to poly (A + U) but is associated with double‐stranded helices of polynucleotides in general. This implies that it may be associated with spatial requirements of the phosphate‐sugar backbone, rather than with the particular bases linked to the backbone. The decline in rate of poly (A + U) formation observed above a critical temperature is the consequence of changes in the poly‐A conformation setting in at this critical temperature, rather than resulting from an increase in the reversibility of the base‐pair propagation step of double‐stranded helix formation. The dominant role of the conformation of poly‐A in the double‐stranded helix formation of poly (A + U) is further borne out by the pH dependence of the rate which completely parallels the conformation changes known to occur in poly‐A as a function of pH. This indirectly suggests that at neutral pH poly‐A is a single‐stranded helix. The rotary diffusion coefficients attest to the flexibility of this helix, while the stacked nature of the base pairs at low temperatures is revealed by the identical increments in the specific Kerr constant on going from poly‐A to poly (A + U) and from poly (A + U) to poly (A + 2U) helices. Results suggest that Mg2+binds to the phosphate part of the backbone. Poly‐U binds Mg2+more strongly than poly‐A; this difference in binding strength is attributed to differences in conformation (random coil versus helix). It is also borne out by the present results that the degree of order in the structure of poly‐U, even at low temperatures and neutral pH, is at best an order of magnitude smaller than that of poly‐A under similar conditions. Furthermore, the earlier proposed double‐stranded structure of poly‐U is called into question. A hairpinlike structure seems to agree with results of this investigation. Finally, the results support the contention that the ion atmosphere polarization is responsible for orientation of polyelectrolytes in the presence of alternating electric fields in

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040709

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

年代:1966

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040701

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

年代:1966

数据来源: WILEY