ISSN:0006-3525    

DOI:10.1002/bip.1969.360080202

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe laser‐excited Raman vibrational spectrum of poly‐L‐alanine has been obtained. The Raman spectrum is compared with the infrared spectrum and vibrational frequencies calculated from normal coordinate analysis. The symmetric modes of the α‐helix appear with strong intensity in the Raman spectrum. A large number of skeletal modes are obtained in this Raman spectrum for the fi

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080203

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe laser‐excited Raman spectra have been obtained of poly‐L‐proline in the solid and aqueous solution. In the solid state, the Raman spectra are of the form II which is the left‐handed helical form with the peptide bonds in the trans configuration. Dissolution of this form in water produced only minor changes in the Raman spectra. The differences in frequencies produced by dissolving the polymer are associated with vibrational modes of the pyrrolidine ring as indicated by comparison with the Raman spectrum ofL‐proline. The similarity of the Raman spectra dictates that, the conformations of poly‐L‐proline chain are similar in the solid and aqu

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080204

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

年代:1969

数据来源: WILEY

摘要:

AbstractA comparative study on sonicated calf thymus DNA was made by using electron microscopy and sedimentation methods. The length distribution, established by electron microscopy by using Kleinschmidt's technique, is related to the sedimentation curve obtained with the same solution. The relation permits a determination of the sedimentation constant corresponding to a given length up to 8000 Å and vice versa

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080205

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe reversibility of the thermal denaturation of a low‐sulfur fraction of solubilized wool keratin (SCMKA) has been studied under a variety of conditions of time, protein concentration, and pH. Two types of irreversibility for the transition have been encountered. One of these is associated with an aggregation of the protein on denaturation to give a product which may contain elements of a β conformation. This type of irreversibility is favored by high protein concentration, and the original conformation may in fact be regained if the aggregated structure is broken down by a solvent such as 8Murea and the urea subsequently removed by dialysis. The other type of irreversibility appears to be due to racemization of the protein. It does not seem to be dependent on protein concentration and is apparent only at temperatures beyond the actual transition range (∼40–65°C) at pH values below 11, At pH 12, however, racemization appears to proceed slowly even at 4°C. The thermal transition at pH 9 and pH 10 has been shown to be multistage in nature. Over the pH range 9–12 there is a progressive decrease in thermal stability with increase of pH. Addition of NaCl at pH 10 leads to an increase in thermal stability of th

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080206

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe π‐electron polarizability of conjugated base molecules such as uracil and adenine are calculated semiempirically by using molecular orbital theories. The Hüekel method and the self‐consistent‐field (SCF) theory are used in the present calculation. The theoretical values obtained by the Hüekel method are consistently larger than the experimental results. The values obtained by the SCF theory are in good agreement with observed values. It is clearly demonstrated that the SCF method is better than the Hükel method for the calculation of polarizability. The polarizability of the adenine–uracil pair is calculated as the sum of the polarizabilities of adenine and uracil and also calculated by solving the eigenvalue problem for the A–U pair as an entity. The second method gives considerably larger polarizability than the first method. Discussions are presented and it is demonstrated that the second method is the correct way to calculate the polarizability of

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080207

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

年代:1969

数据来源: WILEY

摘要:

AbstractWe report studies of the optical properties of the proflavine–DNA complex, using absorbance and circular dichroism spectroscopy. From comparison of the absorption spectra of proflavine complexed with calf thymus and T2 DNA, we conclude that stacking of the dyes external to the double helix is comparatively much weaker with T2 DXA, probably because of its glucosylation. Several sources are found for the circular dichroism induced in proflavine when it is complexed with DNA. There is a relatively weak circular dichroism induced when the dye is infinitely dilute on the DNA lattice; this presumably arises from the environmental asymmetry of the binding site. Stronger circular dichroism effects are induced by interaction of intercalated and stacked dyes; studies with T2 DNA, for which stacking seems to be blocked, permit a tentative resolution of effects due to the two modes of binding. One recurring theme of these studies is the observation that the optical properties are quite dependent on environment. The most dramatic example is a strong variation with salt concentration of the amplitude of the circular dichroism induced in the isolated (intercalated) monomer by the surrounding DNA. This suggests that the structure of the intercalated complex is quite sensitive to external condition

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080208

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe binding ofn‐butanol, benzyl alcohol, and trifluoroethanol to polyproline I (all peptide bonds incisconfiguration) and II (all peptide bonds intransconfiguration) has been demonstrated. It was found by infrared spectroscopy that hydrogen bonds are formed between the CO groups of the polymer and the OH groups of the alcohols. Their strength increases fromn‐butanol via benzyl alcohol to trifluoroethanol. The binding of benzyl alcohol could also be followed by optical rotatory dispersion due to the fact that the electronic transitions of the benzyl ring are rendered optically active by the binding to the poly

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080209

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe thermally induced conformational changes of poly‐N5‐(3‐hydroxypropyl)‐L‐glutamine in water and in methanol–water (3:7 v/v) have been analyzed in terms of the Lifson‐Roig theory. The transitions in both solvents can be described by usingv= 0.017. The thermodynamic parameters for the random coil‐to‐helix transition of one amino acid residue at room temperature were found to be: in water, ΔH= − 130 cal/mole and ΔS= − 0.45 e.u.; in methanol–water (3:7 v/v), ΔH= − 170 cal mole and ΔS= − 0.45 e.u. The size distribution of helical segments is broad, and the results of numerical calculations are presented for three degrees of polymeri

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080210

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe statistical mechanics of the effect of a small number of randomly occurring defects on the melting of a polypeptide chain is developed by using a perturbation of Boltzmann factors technique. The method is illustrated by an example where a second‐component impurity contributes more to the energy of the hydrogen‐bonded superstructure of the polypeptide chain than does the dominant amino acid residue, resulting in the overall destabilization of the helical conformat

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080211

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

年代:1969

数据来源: WILEY