ISSN:0006-3525    

DOI:10.1002/bip.1972.360111202

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe dichroic ratio spectra of TMV and four of its mutants (YTAMV, GTAMV, HR, and CV4) were determined from 320 to 240 nm. Measurements were also made on particles of ATMV (TMV protein reconstituted with polyadenylic acid) and rods of repolymerized TMV, YTAMV and GTAMV protein, respectively. These cylindrical molecules were oriented in a flow gradient with their degree of orientation being determined from anisotropic light scattering measurements. Taking length distributions into account, the dichroic ratios were then extrapolated to values characteristic of perfect particle alignment.Due to the large number of overlapping absorbing bands in the whole viruses, it is very difficult to separate out specific contributions to the total spectra. Since, however, the spectra for the whole viruses were similar, this would suggest an overall likeness in structure for all the virus particles studied. Because the repolymerized proteins did not have the four RNA chromophoric groups present, their spectra would be more sensitive to protein contributions to the total spectrum. Repolymerized rods of YTAMVP yielded results similar to those for TMVP, while the spectrum for repolymerized rods of GTAMVP was significantly different from that obtained for TMVP.Dichroic ratio spectra of the nucleic acids, as they exist within the whole particles, were also calculated by subtracting protein absorptivities from their respective viral absorptivities. The spectra indicates similar results for the various nucleic acids in all the particles studied.

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111203

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe binding isotherm of 2, 7‐di‐tert‐butyl proflavine on calf thymus DNA has been measured by dialysis equilibrium. The CD spectra of complexes of the dye and DNA have been measured, and the variation of the induced circular dichroism of the dye with the amount of dye bound (r) has been found. The results show that di‐tert‐butyl proflavine binds to DNA in a completely different manner from proflavine itself, since both the visible and ultraviolet CD spectra of complexes of the two dyes with DNA differ markedly. The conformation of the nucleic acid is not affected by the binding of di‐tert‐butyl proflavine. It is possible that these results may allow determination, by using CD spectroscopy, of whether molecules interca

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111204

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

年代:1972

数据来源: WILEY

摘要:

AbstractLaser‐excited Raman spectra of the double‐helical complexes poly A·poly U and poly G·poly C are reported for2H2O and H2O solutions. The spectra are discussed in relation to their use as quantitative reference spectra for determining the dependence of the Raman scattering of RNA on secondary structure. The Raman line at 815 cm−1, due to the phosphodiester group, exhibits the same intrinsic intensity in spectra of poly A·poly U and poly G·poly C and is thus dependent only upon the amount of ordering of the helix and not on the kinds of nucleotides involved. The hypochromic Raman lines in spectra of poly A·poly U are identified and their intensity changes are determined quantitatively over the temperature range 32–85°C. Comparison of the spectra in the 1500–1750 cm−1region reveals that the Raman lines from carbonyl group vibrations of uracil are about sevenfold more intense than those of guanine and cytosine for both paired and unpaired states and will thus dominate the spectra of RNA. The Raman frequencies in this region are also compared with previously reported infrared frequencies and give evidence of being strongly perturbed by base‐stacking interact

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111205

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

年代:1972

数据来源: WILEY

摘要:

AbstractIn order to obtain information on the binding forces involved in the formation of the complex proflavine–DNA by the stronger process I, the stability of the complexes was investigated in the presence of various organic solvents, methanol, ethanol,n‐propanol, isopropanol, formamide, dimethyl sulfoxide,p‐dioxane, glycerol, and ethylene glycol. Quantitative data on binding in terms ofK/nandrwere obtained by means of absorption and fluorescence spectra, as well as by a thermal denaturation technique.All organic solvents used decrease the binding ability of the dye. The effectiveness of the solvents increases with their hydrocarbon content, but can hardly be related to their dielectric constant. The complex formation is effectively suppressed by organic solvent concentrations, in which DNA still preserves its double‐helical conformation. These results demonstrate the importance of hydrophobic forces in the formation of the complex proflavine–DNA in aqueous solution.The similarity in spectroscopic properties of proflavine bound to DNA by process I and the same dye dissolved in an organic solvent make it possible to interpret the observed red shift of the long‐wavelength absorption peak as being due to the interaction of the dye molecules with the less polar environment.The same behavior was found for other dyes capable of intercalation like purified trypaflavine, phenosafranine and ethidium bromide. However, intercalation is not a necessary condition, as it was shown in the case of pinacyanol, which binds only at the sur

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111206

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe sequence‐ordered copolymer poly‐(Lys‐Ala‐Ala) was synthesized by polycondensation of theN‐hydroxysuccinimide ester of ε,Z‐Lys‐Ala‐Ala and deprotection of the polymerization product. A fraction of molecular weight 13,000 obtained by ion‐exchange chromatography was investigated. The polymer is freely soluble in water at allpH values, and is completely digested by trypsin and elastase. From CD and ORD data it was concluded that in water at 1°C the ionized form (atpH 6.5) of the polymer is helical. On heating, helix‐coil transition curves were obtained with a midpoint,Tm, depending on salt concentration. In salt‐free waterTm= 12.3°C and in 0.2MNaClTm= 28.5°C. Adding MeOH, causes an increase in the helical content of the polymer (half helicity at 20% MeOH, without salt, at 29°C). Guanidine·HCl was shown to decrease the helicity. At 1°C half helicity. The nonionized polymer helix is more stable (Tm∼90°C). At the high pH, at 60°C, when concentration of the polymer is higher than 1.9 × 10‐2M, a precipitate is formed which redissolves on cooling with the original helicity. This does not occur in the presence of 50% MeOH. By comparison with polylysine it was concluded that replacing two‐thirds of the lysine residues in polylysine by alanine leads to a polymer forming a more stable α‐helix, when fully ionized. This is essentially due to the diminished coulombic repulsion. Uncharged lysine residues are comparable to alanine residues in their helix‐forming tendency since the sequential polymer as well as one‐third ionized polylysine are helical to appro

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111207

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

年代:1972

数据来源: WILEY

摘要:

AbstractFor an ideal one‐dimensional solid, the low‐temperature specific heat,C, is proportional to temperatureT1, for an ideal two‐dimensional solidCis proportional toT2. We have observed such one‐ and two‐dimensional behavior in alpha‐ and beta‐poly(L‐alanine) in the temperature range 1.5–20°K (also intermixed with a three‐dimensional behavior). A specific heat anomaly has also been observed. These measurements are important in evaluating the effective elastic constants, including hydrogen bonding, of the biopolymers. They also provide essential information for vibrational theories of poly(L‐alanine), which up until now have been bas

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111208

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

年代:1972

数据来源: WILEY

摘要:

AbstractA study of the 100‐MHZnuclear magnetic resonace spectra in D2O solution was made of a series of linear dipeptides of the typesL‐phenylalanine‐L‐and‐D‐X, andL‐phenylalanine‐L‐and‐D‐Y, where X comprised a group of amino acid residues with polar side chains (X = glutamine, glutamic acid, arginine, andNε‐acetyllysine) andYcomprised amino acid residues with purely aliphatic side chains (Y= α‐aminobutyric acid and norvaline). It was found that regardless of the side chain length, resonances due to the α‐methylene protons in the X and Y side chains of theL‐Phe‐D‐Y series consistently exhibited upfield shifts greater than any other protons in these side chains, when compared to the corresponding side chain resonances of the nonaromatic dipeptide seriesL‐Ala‐L‐X andL‐Ala‐L‐Y. The magnitudes of these shielding effects were consistently and considerably greater for theL‐Phe‐D‐X series than for theL‐Phe‐D‐Y series. An intramolecular complex–formed by association of armatic π‐electrons with the positive end of the dipole in the polar side chains—was proposed as one plausible interpretation of the enhanced shielding effects. An increase in temperature from 32 to 70–80° was sufficient to

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111209

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe Raman spectra of three globular proteins, beef pancreas chymotrypsinogen A, beef pancreas ribonuclease, and hen egg white ovalbumin have been obtained in the solid state and aqueous solution. X‐ray diffraction and circular dichroism evidence have indicated that these proteins have a low α‐helical content and a large fraction of the residues in the unordered and β‐sheet conformation. The frequencies and intensities of the amide I and amide III lines are consistent with assignments based on the Raman spectra of polypeptides. The intense amide III lines observed in all the spectra would be expected for proteins with a low fraction of the residues in the α‐helical conformation. Several spectra changes occur upon dissolution of the proteins in water and may be associated with further hydration of the proteins. The spectrum of thermally denatured chymotrypsinogen is presented. A 3 cm–1decrease in the frequency of the amide I line of the protein dissolved in D2O upon heating was observed. This observation is consistent with a denaturation mechanism allowing only slight changes in the secondary structure but an increase in solvent penetration upon going from the native to the reversibly den

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111210

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

年代:1972

数据来源: WILEY

摘要:

AbstractEnthalpy changes [as determined by differential scanning calorimetry (DSC)] and optical rotation changes over the helix → coil transition were measured for various gelatin solutions and films. From these studies it has been concluded that: (1) a linear correlation between ΔHand Δ[α] exists for gelatin solutions, independent of the temperature at which gelation occurred; (2) the amount of triple helical structure regained when a melted gelatin solution is quenched can be calculated from DSC data, but the values obtained will be dependent on assumptions about the number and strength of hydrogen bonds; (3) the anomalously high levorotation values found for cold‐dried films of gelatin do not reflect the presence of an extraordinarily large amount of triple helical structure; rather, the large rotations appear to be the result of orientation of helices in the plane of th

ISSN:0006-3525    

DOI:10.1002/bip.1972.360111211

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

年代:1972

数据来源: WILEY