Roberts, John D. and Chun, Yu and Flanagan, Cynthia and Birdseye, Teresa R. (1982) A nitrogen-15 nuclear magnetic resonance study of the acid-base and tautomeric equilibriums of 4-substituted imidazoles and its relevance to the catalytic mechanism of α-lytic protease. Journal of the American Chemical Society, 104 (14). pp. 3945-3949. ISSN 0002-7863. doi:10.1021/ja00378a027. https://resolver.caltech.edu/CaltechAUTHORS:20151005-120248113
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Abstract
The pH dependence of the ^(15)N NMR shifts of histamine, imidazole-4-propionic acid, imidazole-4-acetic acid, trans and cis-urocanic acid, and endo-cis-3-(4-imidazoyl)bicyclo[2.2.h1]e pt-5-ene-2-carboxylic acid has been determined at the natural-abundance level of ^(15)N. The chemical-shift changes permit calculation of pK_a values for the acidic species present as well as reasonably accurate positions of the Nl(H)⇌N3(H) tautomeric equilibria for those species having unprotonated imidazole rings. The ^(15)N shifts of cis-urocanic acid and endo-cis-3-(4-imidazoyl)bicyclo [2.2.1] hept-5-ene-2-carboxylic acid demonstrate that carboxylate-N3(H) hydrogen-bonding interactions can cause the N3(H) tautomers to be substantially more stable than the Nl(H) tautomers. The unusual positions of these tautomeric equilibria are quite similar to that found for the histidine of the catalytic triad of α-lytic protease.
| Item Type: | Article | |||||||||
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| Additional Information: | © 1982 American Chemical Society. Received September 23, 1981. Supported by the National Science Foundation and the National Institute of Health. We are very indebted to Dr. Keiko Kanamori for her suggestions and help with this investigation. | |||||||||
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| Issue or Number: | 14 | |||||||||
| DOI: | 10.1021/ja00378a027 | |||||||||
| Record Number: | CaltechAUTHORS:20151005-120248113 | |||||||||
| Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20151005-120248113 | |||||||||
| Official Citation: | A nitrogen-15 nuclear magnetic resonance study of the acid-base and tautomeric equilibriums of 4-substituted imidazoles and its relevance to the catalytic mechanism of .alpha.-lytic protease John D. Roberts, Yu Chun, Cynthia Flanagan, and Teresa R. Birdseye Journal of the American Chemical Society 1982 104 (14), 3945-3949 DOI: 10.1021/ja00378a027 | |||||||||
| Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
| ID Code: | 60763 | |||||||||
| Collection: | CaltechAUTHORS | |||||||||
| Deposited By: | Ruth Sustaita | |||||||||
| Deposited On: | 05 Oct 2015 21:39 | |||||||||
| Last Modified: | 10 Nov 2021 22:38 |
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