摘要:

AbstractWe present here a brief analysis of ultraviolet isotropic absorption and related circular dichroism of then–π* and π–π* transitions for the peptide (amide) chromophore in the 185–240 mμ region. Investigations by ultraviolet absorption and circular dichroism techniques on natural amino acids with aromatic chromophores in their side chains are also reported. By taking into account both the peptide and aromatic transitions we discuss the conformational studies of proteins with aromatic side‐chain effects. Our attention is largely focused on the optical rotatory dispersion and circular dichroism spectra of these proteins in the near ultraviolet region, where characteristic aromatic side‐chain bands occur. The 185–240 mμ region is also discussed when evidence exists of overlapping Cotton effects of aromatic an

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061202

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

年代:1968

数据来源: WILEY

摘要:

AbstractRecent improvements in apparatus permit the examination of circular dichroism (CD) and optical rotatory dispersion (ORD) spectra to 185 mμ. In addition, new solvents which are transparent to 185 mμ have become available for synthetic polypeptides. The spectral region 185–250 mμ is extremely important for the amide (peptide) chromophore, because of the presence at these wavelengths of then–π* and π–π* bands,1and of another transition, the assignment of which remains

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061203

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe adsorption of deoxyribonucleic acid (DNA) in the mercury–electrolyte interface has been investigated. The effect of this adsorption on the differential capacity of the electrical double layer between a polarized mercury surface and an 0.15MNaCl solution containing DNA was measured by means of the alternating current polarography (Breyer polarography). The effective alternating currentĨunder actual conditions (adsorption processes only, small electrolytic resistance, small alternating current frequency, and alternating current amplitude) is directly proportional to the differential double layer capacity. The combination of this method with the application of a stationary mercury drop electrode allows the coverage of the electrode to be followed, continuously in the range 0.2 sec, to about 60 sec. The diffusion is the rate‐controlled step of the adsorption kinetics. Therefore the lowering of the alternating currentĨby the adsorbed DNA is proportional to the surface concentration for partly covered surface and reaches a constant value after the surface becomes fully covered. Adsorption of further layers does not affect the differential capacity. This makes it possible to determine the maximum surface concentration of the DNA. For that it is necessary to determine the diffusion coefficient of DNA. This was done directly by Strassburger and Reinert in our institute. The surface concentrations of the native DNA and the relative surface concentrations of the denatured DNA in dependence on the potential of the polarized mercury surface was estimated. Both surface concentrations show a pronounced dependence on the potential with a minimum of the surface concentration around −0.4 V with respect to the normal calomel electrode. This property may be caused by the structure of the adsorption layer depending on the potential. That means that only several segments at the rigid DNA molecules are adsorbed and the other ones remain in the solution near the surface. The adsorption in the neighborhood of the electrocapillary zero potential at −0.4 V is strongest, and therefore the fraction of the adsorbed segments has a maximum. At these potentials consequently the maximum coverage is already reached at relatively low surface concentrations. Opposite to this is Miller's hypothesis, that native DNA preserves its double helical structure when adsorbed on a negatively charged mercury surface, whereas unfolding occurs on a positively charged mercury surface. Miller's hypothesis is supported by facts that the surface concentration of the denatured DNA should be independent of the potential and should be equal to the surface concentration of the native DNA at a positively charged mercury surface. But an evaluation of Miller's diagrams by no means gives an independence on the potential of the surface concentration of the denatured DNA and no accordance between the surface concentrations of denatured and of native DNA's at the positively charged mercury surface. Moreover Miller compared different DNA samples with different moleculer weights and possibly with different molecular weight distributions. Both the molecular weight and the molecular weight distribution have a pronounced influence on the surface concentration. Therefore this accordance mentioned above is not evident. The critical inspection of Miller's work and the own investigation lead to the conclusion that an unfolding or denaturation of native DNA does not take place in the mercury–electrolyt

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061204

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe complex dielectric constant of aqueous hemoglobin solution was measured at 9.5 GHz. A microwave technique allowing phase and attenuation settings with an accuracy of 0.3° and 0.03 db was used. The shift of the relaxation wavelength and the hydration values of horse hemoglobin were determined for native and lyophilized hemoglobin solution and erythrocytes suspensions as well. The isotope effect of light and heavy water on these parameters was detected. The influence of buffers was studied. Relative measurements, with the sensitivity increased by a factor of 20, were made with alternating oxygenated and deoxygenated human hemoglobin solutions. The oxygenation of hemoglobin was found to leave the hydrated molecule volume invariant within ±250 Å3, while a shift of the relaxation wavelength of 0.0025 ± 0.0015 cm occurs for a hemoglobin concentration of 107 g/l. The results are discussed in terms of the structure and function interrelationship of hemoglobin and the current picture of water struct

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061205

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe dielectric properties of horse hemoglobin have been investigated in the frequency range for 100 kcps to 15 Mcps at varying degrees of oxygenation. A linear dependence of the specific increment on the degree of oxygenation was found under a variety of experimental conditions, the increment of oxygenated hemoglobin being about 10% larger than that of deoxygenated hemoglobin. A similar difference was obtained with human adult and fetal hemoglobin. No variation of the dielectric parameters as reported by Takashima and Lumry could be detected.

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061206

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe primary structure of alanine transfer RNA reported by Holley and his colleagues contained a number of inconsistencies between the data and the proposed sequence. In order to resolve these inconsistencies, alanine tRNA was isolated from yeast by using countercurrent techniques similar to those employed by Holley. The alanine accepting RNA obtained by this procedure was found by further purification employing reverse phase partition chromatography, to contain two different species of alanine tRNA. One of these, tRNAalaI, could be shown to be similar to Holley's proposed structure with the addition of a guanine between positions 47 and 48 and only 2 dihydrouridines instead of the 2.5 reported by Holley.

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061207

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

年代:1968

数据来源: WILEY

摘要:

AbstractAcridine Orange, at appropriate intermediate concentrations, causes a substantial broadening of the thermal transitions ofBacillus subtilisDNA and of dAT. Experiments in which the two polymers are healed together show that the broadening is the result of the transfer of acridine orange molecules from denatured to native DNA molecules.

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061208

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe circular dichroism of a number of 1:2 complexes between oligoadenylic acid and polyuridylic acid has been measured. The structure of these complexes, as evidenced by their optical properties, is independent of the chain length of the oligonucleotide throughout all ranges of chain lengths from adenosine to high molecular weight polyadenylic acid. A similar structure was found for the complex (Ap)5A:2(Up)5U.

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061209

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

年代:1968

数据来源: WILEY

摘要:

AbstractBy combining the heat of dilution of a poly(γ‐benzylL‐glutamate)–dichloroacetic acid–1, 2‐dichloroethane solution with the corresponding heat of mixing of two solvents, the integrated heat of the coil–helix transition of poly(γ‐benzylL‐glutamate) in the solution was estimated to be a

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061210

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

年代:1968

数据来源: WILEY

摘要:

AbstractFar‐infrared spectra of poly‐L‐alanines having the α‐helical conformation and the β‐form structure were measured. The spectra of glycine–L‐alanine copolymer, silk fibroin, and copoly‐D,L‐alanines with differentD:Lcompositions were also measured. In addition to the bands so far reported, four bands at 190, 107, 120, and 90 cm−1were found for the α‐helix conformation and the two bands at 442 and 247 cm−1were found for the β form. The 442 cm−1band consists of the parallel 432 cm−1and perpendicular 445 cm−1bands. The 247 cm−1band is well defined and has strong dichroism parallel to the direction of stretching. These two bands appear also for silk fibroin and glycine–L‐alanine copolymer. All the far‐infrared bands of copoly‐D,L‐alanines can be interpreted as α‐helix bands, the three peaks at 580, 478, and 420 cm−1being ascribed to theD‐residue incorporated into the right‐handed

ISSN:0006-3525    

DOI:10.1002/bip.1968.360061211

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

年代:1968

数据来源: WILEY