Effect of methylation on the pyrimidine-pyrimidine stacking interaction studied by 1H NMR chemical shift

Mutually induced proton chemical shift changes were measured for the mixed solutions of pyrimidine and its methylated forms in deuterium oxide at 35°C. The chemical shift vs. concentration profiles were analyzed using a three-state decomposition model based on competitive self- and hetero-associatio...

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Bibliographic Details
Published inBiophysical chemistry Vol. 54; no. 1; pp. 67 - 73
Main Author Aradi, Ferenc
Format Journal Article
LanguageEnglish
Published Elsevier B.V 01.03.1995
Subjects
1H NMR chemical shift
Hetero-association
Methylation
Pyrimidine
Stacking interaction
1H NMR chemical shift
Stacking interaction
Hetero-association
Methylation
Pyrimidine
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Summary:Mutually induced proton chemical shift changes were measured for the mixed solutions of pyrimidine and its methylated forms in deuterium oxide at 35°C. The chemical shift vs. concentration profiles were analyzed using a three-state decomposition model based on competitive self- and hetero-association dimer equilibria. The equilibrium constants show an increasing association tendency within the series pyrimidine-5-methyl-pyrimidine (0.23 ± 0.02 M −1) < pyrimidine-4,6-dimethyl-pyrimidine (0.32 ± 0.04 M −1) < 5-methyl-pyrimidine-4,6-dimethyl-pyrimidine (0.51 ± 0.04 M −1). The upfield dimer shifts suggest an offset stacked geometry for the structure of associations between the parent molecule of the pyrimidine nucleobases and its methylated derivatives in aqueous solution.
ISSN:0301-4622
1873-4200
DOI:10.1016/0301-4622(94)00115-Z