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THE NATURE OF THE IONIZABLE GROUPS IN PROTEINS.
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MedLine Citation:
PMID:  19872424     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
Analysis of the experimental titration curves shows that gelatin contains acid groups with dissociation indices at pH 2.9 to 3.5 corresponding quantitatively with the content in dicarboxylic amino acids; and that the acidic group at pH 9.4 in egg albumin agrees with the amount of tyrosine. The amounts of histidine and lysine present in both these proteins agree quantitatively with basic groups at pH 6.1 and pH 10.4 to 10.6, respectively. However, the quantity of the arginine group (pH 8.1) in these proteins is considerably less than the amount of arginine found on hydrolysis. This deficiency is compensated (quantitatively with gelatin and approximately with egg albumin) by a basic group at pH 4.6. The structure of this "4.6 group" should be similar to aniline and cytosine in consisting of an amino group on a conjugated unsaturated (perhaps cyclic) system. It would appear that the 4.6 group is disrupted on hydrolysis, producing arginine, and may be referred to as "prearginine." The presence of prearginine in proteins, instead of the full amount of arginine, has an important effect on the properties. Otherwise the isoelectric point of gelatin would be 8.0 (instead of 4.7) and of egg albumin 6.6 (instead of 4.8), and the titration curves would be quite different in shape between pH 4 and 10. Deamination of gelatin produces no decrease in prearginine, arginine, or histidine groups, but removes nearly all of the lysine group.
Authors:
H S Simms
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of general physiology     Volume:  11     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1928 May 
Date Detail:
Created Date:  2010-06-23     Completed Date:  2010-06-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985110R     Medline TA:  J Gen Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  629-40     Citation Subset:  -    
Affiliation:
Department of Animal Pathology of The Rockefeller Institute for Medical Research, Princeton, N. J.
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Journal Information
Journal ID (nlm-ta): J Gen Physiol
ISSN: 0022-1295
ISSN: 1540-7748
Publisher: The Rockefeller University Press
Article Information
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Copyright © Copyright, 1928, by The Rockefeller Institute for Medical Research
Accepted Day: 17 Month: 2 Year: 1928
Print publication date: Day: 20 Month: 5 Year: 1928
Volume: 11 Issue: 5
First Page: 629 Last Page: 640
ID: 2141003
PubMed Id: 19872424

THE NATURE OF THE IONIZABLE GROUPS IN PROTEINS
Henry S. Simms
From the Department of Animal Pathology of The Rockefeller Institute for Medical Research, Princeton, N. J.


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