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rdf:type |
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lifeskim:mentions |
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pubmed:issue |
3
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pubmed:dateCreated |
1977-7-18
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pubmed:abstractText |
The log kobs vs. pH profiles were determined in the intermediate acidity region for the glycosyl hydrolysis of guanosine and its 8-amino, 8-monomethylamino, 8-dimethylamino and 8-bromo derivatives. The decreased rate of the 8-amino and enhanced rate of the 8-bromo compound compared to guanosine support an A type mechanism: base protonation followed by glycosyl bond cleavage. All three 8-amino guanosines exhibited log kobs - pH profiles clearly showing that both mono and di-base protonated nucleosides undergo hydrolysis. The 700 fold rate acceleration of 8-N(CH3)-guanosine compared to 8-NHCH3-guanosine and the 110 fold rate acceleration of 8-N(CH3)2-adenosine compared to 8-NHCH3-adenosine could be unequivocally attributed to the fixed syn glycosyl conformation of both 8-dimethylamino compounds and relief of steric compression upon hydrolysis in these molecules. The lack of anomerization of all substrates during the course of the reaction supports an A rather than a Schiff-base mechanism.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-14289333,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-4337967,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-4414318,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-4415404,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-4543068,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-4626532,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-4638983,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-4638984,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5009434,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5036169,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5044241,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5059890,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5131788,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5416936,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5418456,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5785205,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-5920516,
http://linkedlifedata.com/resource/pubmed/commentcorrection/17100-6073218
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Mar
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pubmed:issn |
0305-1048
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:volume |
4
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
697-709
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
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pubmed:year |
1977
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pubmed:articleTitle |
Glycosyl conformational and inductive effects on the acid catalysed hydrolysis of purine nucleosides.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.
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