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The chemical nature of the complex, and studies on the mode of linkage between its two components, are described in the following paper.This paper forms part of a Ph.J. biol. Chem. Deutsch, H. F. Brit. J. Nutr. Gregory, M. E, Ford, J. E. Kon, S. K. Biochem. J. Holdsworth, E. S. J. gen. Phyiol. Levin, R. Brauer, R. W. J. biol. Chem. Skeggs, H. R, Nepple, H. M, Valentik, K. A, Huff, J. W. Wright, L. D. J. biol. Chem. The first part ofthis paper describes some chemical and microbiological properties of the complex, and provides evidence that it is a <a href="http://www.targetmol.com/compound/GS-7340"></a> combination of cyanocobalamin with a glycoprotein.The manner in which these two components are linked together has been investigated in two ways.One was to test whether blocking specific groups on the protein decreased its capacity to combine with cyanocobalamin.The second was to modify the cyanocobalamin molecule and test whether it still combined with unaltered protein.The results of these investigations are presented in the second part of this paper.HCI and glacial acetic acid and hydrolysed   in a sealed tube at for hr.The following amino acids were detected: cystine, aspartic and glutamic acids, arginine, lysine, histidine, serine, glycine, threonine, alanine, tyrosine, valine, methionine, phenylalanine, leucine and isoleucine.Onedimensional chromatograms were made using butanolacetic acidwater and sprayed with reagents specific for certain amino acids.Microbiological estimation of cyanocobalamin in the complex.A portion of the diluted digest was removed and assayed for cyanocobalamin both unheated and heated with the assay medium.A protein concentrate was prepared from sows milk whey by. Compounds related to cyanocobalamin.Onlyone zone, with an R, slightly greater than that of the original vitamin, was obtained.The air in the flasks containing these solutions as a shallow layer, was displaced by oxygen, the flasks were tightly stoppered and incubated at for hr.The effect of specific group inhibitors on the combination of SF with cyanocobalamin.SF, half the added vitamin was bound and the rest remained free.The free vitamin was estimated by the ultrafiltration method described in the preceding paper. The solutions were mixed well and kept at for hr.If the amount of cyanocobalamin in the ultrafiltrate was greater than that obtained from a control containing untreated SF and cyanocobalamin, then the reagent had blocked a group on the protein necessary for its combination with the vitamin.The acetylated SF was examined for binding activity by this method and, after saturation with cyanocobalamin, V.BOUND CYANOCOBALAMIN IN SOWS MILK by electrophoresis and autoradiography as described in the preceding paper. Combination of the altered cyanocobalamin molecule with SF. The combination of the compounds having structures similar to cyanocobalamin with the binding protein. The technique varied slightly depending on whether the substance tested possessed microbiological activity.SF in distilled water.If the various compounds had combined with SF the cyanocobalamin added subsequently would be free and able to pass into the ultrafiltrate.The amount of cyanocobalamin in these ultrafiltrates was compared with that present in the ultrafiltrate from a control experiment using SF and cyanocobalamin.Of the reagents tested, fluorodinitrobenzene and iodine, at the higher concentrations, completely prevented the protein from combining with the vitamin.

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