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Kinetics of the hydrolysis of guanosine 5'-phospho-2-methylimidazolide.

Kinetics of the hydrolysis of guanosine 5'-phospho-2-methylimidazolide.

Authors :
Kanavarioti A
Source :
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life [Orig Life Evol Biosph] 1986; Vol. 17 (1), pp. 85-103.
Publication Year :
1986

Abstract

We have studied the hydrolysis of guanosine 5'-phospho-2-methylimidazolide, 2-MeImpG, in aqueous buffered solutions of various pH's at 75 degrees C and 37 degrees C. At 75 degrees C and pH < or = 1.0, two kinetic processes were observed spectrophotometrically: the first and more rapid one is attributed to the hydrolysis of the phosphoimidazolide P-N bond; the second and much slower one, to the cleavage of the glycosidic bond. At 37 degrees C, pH 2.0, the spectrophotometrically determined rate constant of P-N bond hydrolysis was confirmed by using high pressure liquid chromatography, HPLC. With the latter technique it was possible to separate reactants and products and also to extend the pH-rate profile into the neutral region where rates are slower and, therefore, difficult to measure spectrophotometrically. The pH-rate profiles at both temperatures exhibit similar behavior. At pH < 2 the pseudo-first-order rate constant increases with decreasing pH; in the region 2 < pH < 7 there is a plateau followed by a decrease for pH > 7. These data are consistent with a reactivity order zwitterion > anion for P-N bond hydrolysis. It is noteworthy that P-N bond hydrolysis in phosphoimidazolides is very slow compared to other phosphoramidates. This may be one of the reasons why this compound showed extraordinary ability in forming long oligomers under template-directed conditions.

Details

Language :
English
ISSN :
0169-6149
Volume :
17
Issue :
1
Database :
MEDLINE
Journal :
Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life
Publication Type :
Academic Journal
Accession number :
11536569
Full Text :
https://doi.org/10.1007/BF01809815