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The role of the σ‐framework in the properties of the biological purines and pyrimidines: dipole moments and tautomeric equilibria
Author(s) -
Berthod Hélène,
Pullman Alberte
Publication year - 1964
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1964.360020506
Subject(s) - tautomer , chemistry , dipole , computational chemistry , moment (physics) , nucleic acid , cytosine , molecule , stereochemistry , organic chemistry , quantum mechanics , dna , physics , biochemistry
Del Re's method for the study of saturated compounds has been adapted so as to deal with the σ‐framework of conjugated molecules. This modified procedure is used in evaluating the σ‐contribution to the dipole moments of the nucleic bases and of the A‐T and G‐C base pairs and also to the free energy change in the tautomeric, equilibria of the bases. Associated with an appropriate Hückel method for evaluating the π‐contribution, the results obtained predict a small resultant moment for A‐T versus a large moment for G‐C. The energy calculations predict the keto and amino forms of the bases to be the most stable forms and cytosine to be the most easily involved in tautomeric shift to the rare form.