R. C. Valentine

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRegulation of glutamine synthetase. XII. Electron microscopy of the enzyme from Escherichia coliR. C. Valentine, B. M. Shapiro, and E. R. StadtmanCite this: Biochemistry 1968, 7, 6, 2143–2152Publication Date (Print):June 1, 1968Publication History Published online1 May 2002Published inissue 1 June 1968https://pubs.acs.org/doi/10.1021/bi00846a017https://doi.org/10.1021/bi00846a017research-articleACS PublicationsRequest reuse permissionsArticle Views959Altmetric-Citations637LEARN 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

Abstract Interferon could be titrated by the amount of interference induced in fragments of chorio-allantoic membranes challenged with influenza A virus. Over a ten-fold range, inverse proportion between interferon concentration and haemagglutinin titre reached by the challenge virus was observed. Interferon proved stable at 2°C for 2 weeks. Marked inactivation took place after 1 h at 60°C. Interferon was not measurably sedimented by 100 000 g for ½ h. It was held back by gradocol filters of a. p. d. 0.6 μ. It was not dialyzable. Interferon was active against influenza A, Sendai, Newcastle disease and vaccinia viruses. It was not neutralized by anti-MEL rabbit serum and only slightly inhibited by pooled human serum rich in complement-fixing antibody to influenza A soluble antigen.

A series of bisbiotinyl diamines was synthesized with between 9 and 25 bonds between the carboxyl groups of the two biotin residues. It was found that only one of the two biotin residues could combine with avidin when there were fewer than 12 bonds between the biotin residues. Compounds with longer chains behaved in a bifunctional manner and gave rise to linear polymers of avidin, which were characterized by electron microscopy and by gel filtration. The polymers formed with the shorter-chain reagents (12, 13 or 14 bonds) were relatively unstable and could be depolymerized by weakly bound analogues of biotin. The polymers of longer-chain reagents were not depolymerized under these conditions and were only slowly affected by added biotin. When the chain length of the reagent reached 23 bonds the polymers became much shorter, suggesting that the reagent was now able to link two subunits within the same avidin molecule. From the morphology of the polymers it could be concluded that the four subunits of the avidin molecules were arranged with 222 symmetry and that they were grouped in two pairs at opposite ends of the short axis of the molecule whose dimensions were 55Ax55Ax41A.