摘要:

AbstractPrecipitation of soluble forms of collagen from solutions containing the soluble protein‐polysaccharide (PP‐L) of bovine nasal cartilage, followed by centrifugation at 100,000g, resulted in the formation of coherent elastic pellets whose wet weights increased with the concentration of PP‐L in the initial solution. Dry weights and uronic acid contents of these pellets showed that the amount of water held in the wet pellet was nearly constant for any one kind and concentration of collagen, and ranged from 20 to 100 mg./mg. PP‐L in the pellet. Soluble collagens from four different sources and PP‐L from three kinds of cartilage showed similar effects. Precipitation of soluble collagen in the presence of hyaluronate or dextran yielded pellets of much smaller size than those formed in the presence of PP‐L. The presence of chondroitin sulfate had only a slight effect on wet pellet weights. Wet weights of pellets formed in the presence of PP‐L decreased with increasing ionic strength. A model involving entanglement between insoluble collagen fibrils and the relatively stiff chondroitin sulfate chains of branched PP‐L seems qualitatively capable of accounting fo

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040302

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

年代:1966

数据来源: WILEY

摘要:

AbstractSolutions of calf thymus DNA have been degraded in the presence of vibrating air bubbles in ultrasonic fields of low power which would not normally induce ultrasonic cavitation. The DNA was degraded to a limiting intrinsic viscosity, after which further irradiation by ultrasound had little or no effect. This limiting intrinsic viscosity decreased with increase in the ultrasonic intensity. Previously developed theories have‐been adapted to calculate the maximum velocity gradient associated with the streaming of the solution around such vibrating air bubbles. The tensile force which is induced and which acts on the DNA has been calculated on the basis of current theories of degradation by hydrodynamic shear. These calculations indicate that the degradation of the DNA by ultrasound under conditions of “stable cavitation” is mainly the result of the shearing forces engendered in the solution around the oscillating bu

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040303

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

年代:1966

数据来源: WILEY

摘要:

AbstractA series of oligomers was synthesized of the form:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm Z} \rlap{--} ({\rm Ala} \rlap{--})_n {\rm OEt}$$\end{document}Where Z is the benzyloxycarbonyl group andn= 2, 3, 5, 10. We encountered difficulty in dissolving the decamer in any solvent except strong organic acids. We therefore prepared co‐oligomers of the type:where (a)w=x=y= 1; (b)w= 0,x=y= 3; and (c)w=x=y= 3. A series of model compounds composed of glycineL‐alamine and γ‐methyl‐L‐glutamate were also prepared. We converted manyof the benzyloxycarbonyl oligopeptides into their corresponding acetyl derivatives. Some of these peptides were synthesized by mixed anhydride and active ester techniques while others were prepared via azide coupling techniques using thetert‐butoxycarbonylhydrazide blocking group. All reactions proceeded with retention of c

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040304

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe conformations of oligopeptides derived fromL‐alanine and co‐oligomers ofL‐alanine with γ‐methyl‐L‐glutamate were studied in several solvents via optical rotation and far‐ultraviolet spectroscopy. Calculated values for optical rotation based on model compounds were compared with experimental values for the oligomers. In trifluoroacetic and dichloroacetic acids, the oligomers and co‐oligomers exhibit rotations in close agreement with predicted values based on model compounds. Thus, in these solvents only nonhelical conformations exist. In trifluoroethanol, the experimental points of molar rotation for the pentamer and larger oligomers no longer follow the predicted values. In addition, the benzyloxycarbonyl and acetyl cononamers showb0values of about −150, which demonstrates the presence of stable helical forms for these peptides. We also examined the molar extinction coefficients of oligopeptides in the 190 mμ region and determined the values for nonhelical peptide groups. The molar extinction coefficients per amide bond for the benzyloxycarbonyl and acetyl cononamers show extensive hypo‐chromism, once again indicating the presence of stable helices for these compound

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040305

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe melting temperature of a natural DNA is decreased in the presence of increasing amounts of copper ions, whereas other divalent metal ions stabilize the DNA secondary structure at low ionic strength. At 1.28 × 10−4M, Cu2+produces a decrease ofTmdepending on base composition. At very low Cu2+concentrations (0.5 Cu2+/2 DNA‐P) a stabilization of the DNA conformation appears due to an interaction between Cu2+and phosphate groups of the DNA molecule. In this case the normal trend of GC dependence ofTmexists similar to that with Na+and Mg2+as counterions. If copper ions are in excess, the observed destabilization is stronger for DNAs rich in guanine plus cytosine than for those rich in adenine plus thymine. A sharp decrease ofTmoccurs between 0.5–0.8 Cu2+/2 DNA‐P and 1.5 Cu2+/2 DNA‐P. The breadth of the transition decreases at high Cu2+concentration with further addition of copper ions. Denaturation and renaturation experiments indicate that Cu2+ions exceeding the phosphate equivalents interact with the bases and reduce the forces of the DNA helix conformation. Evidence is presented, that the destabilization effect produced by Cu2+is possibly due to an interaction with guanine sites of the DN

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040306

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

年代:1966

数据来源: WILEY

摘要:

AbstractFor infrared absorption measurements, the following five isotopic polyglycines have been prepared: ordinary polyglycine (—NHCH2CO—)n,N‐deuterated polyglycine (—NDCH2CO—)n,C‐deuterated polyglycine (—NHCD2CO—)n, completely deuterated polyglycine (—NDCD2CO—)n, andN15‐substituted polyglycine (—15NHCH2CO—)n. Infrared spectra have been observed both in the I and II forms of each of these five isotopic polyglycines in the spectral region of 4000–300 cm.−1. On the basis of the comparison of these spectra with each other, a nearly complete set of assignments of the observed bands o

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040307

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

年代:1966

数据来源: WILEY

摘要:

AbstractVarious techniques for recombining the fully reduced A and H chains of insulin were studied. Best results were obtained from water solutions of the reduced chains allowed to oxidize by standing in air at 3 °C. and from metal‐catalyzed oxidation under the same conditions but in 7.6Murea solutions. Average net regeneration of insulin was 6% by weight, based on rat hemidiaphragm analysis for insulin activity. The theoretical yield for a random recombination of the A and B chains was calculated to be 3%. The 50% yield of insulin (from the oxidation of reduced insulin thiosulfate) reported by Jiang et al. could not. be confirm

ISSN:0006-3525    

DOI:10.1002/bip.1966.360040308

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.1966.360040309

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.1966.360040301

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

年代:1966

数据来源: WILEY