D.B. Wetlaufer

Experimental circular dichroic (CD) spectra of three proteins have been combined with estimates of the content of peptide-chain structural modes obtained from x-ray diffraction studies of the same proteins. Solution of the simultaneous equations at a series of wavelengths permits the construction of a CD spectrum for each of three structural modes: alpha-helix, beta-structure, and the so-called "random". The CD spectra thus obtained are compared with those obtained from polypeptide models. The alpha-helical spectra from the two approaches are nearly congruent, the beta-structure spectra are in fair agreement, and the third forms agree qualitatively, but are substantially different quantitatively. Comparisons are made between the present approach and earlier approaches to interpreting protein CD spectra. Certain advantages of the present approach are indicated.

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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA Conformation-dependent Cotton Effect in α-Helical Polypeptides and Proteins1,2N. S. Simmons, C. Cohen, A. G. Szent-Gyorgyi, D. B. Wetlaufer, and E. R. BloutCite this: J. Am. Chem. Soc. 1961, 83, 23, 4766–4769Publication Date (Print):December 1, 1961Publication History Published online1 May 2002Published inissue 1 December 1961https://pubs.acs.org/doi/10.1021/ja01484a017https://doi.org/10.1021/ja01484a017research-articleACS PublicationsRequest reuse permissionsArticle Views220Altmetric-Citations169LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

With the glutathione system that leads to rapid regeneration of reduced lysozyme (Saxena, V. P., and Wetlaufer, D. B. (1971) Biochemistry 9, 5015), reduced pancreatic ribonuclease (RNase) regenerated activity in high yield (greater than 90%) but at a considerably lower rate (t1/2 approximately 75 min). Systematic examination of the effects upon regeneration of the concentrations and ratios of reduced and oxidized glutathione (GSH and GSSG) showed the same broad optima for RNase as were earlier found for lysozyme: [GSSG] = 5 X 10(-4) M, [GSH] = 5 X 10(-3) M. Regeneration of reduced RNase by air oxidation was shown to be inhibitable by 10(-4) M EDTA, whereas the glutathione regeneration was unaffected by EDTA. In addition the air-oxidative regeneration showed a strong temperature dependence, in contrast with the glutathione system. The mechanisms of these two kinds of regenerations are therefore different. Six potentially catalytic metal ions were tested in the air-oxidative regeneration of RNase: Cu2+, Co2+, Mn2+, Fe3+, Zn2+, and Ni2+. Of these, only Cu2+ enhanced the rate of regeneration of RNase activity, although both Cu2+ and Co2+ catalyzed thioloxidation of reduced RNase. The rates and yields of RNase regenerations were independent of protein concentration from 3 X 10(-7) M to 1.2 X 10(-5) M in the glutathione system. Preincubation of freshly dissolved reduced RNase under nonoxidizing conditions before adding glutathione did not change the rate or extent of regeneration. Studies of its pH dependence showed that the glutathione regeneration depends on the deprotonation of prototropic groups with 7.5 less than pK less than 8.0. The major ion exchange chromatographic peaks from glutathione and air-oxidative regenerations appeared to be identical with native RNase, by the criteria of specific activity, chromatographic mobility, and circular dichroic spectra. The glutathione system permits regeneration at much higher RNase concentration than the air regeneration, with rates and yields comparable to the greatest reported for air regeneration.