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Effect of protonation on electronic structure of guanosine and 5′‐guanosine monophosphate and on glycosidic (CN) bond rotations
Author(s) -
Jordan Frank
Publication year - 1974
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.1974.360130205
Subject(s) - protonation , chemistry , cndo/2 , guanosine , guanine , computational chemistry , molecular orbital , base (topology) , crystallography , nucleobase , population , stereochemistry , molecule , ion , dna , nucleotide , organic chemistry , biochemistry , mathematical analysis , mathematics , demography , sociology , gene
Semiempirical molecular orbital studies were performed on 5′‐guanosine monophosphate in its various states of base and phosphate ionization (employing the extended Hückel method) and on guanosine protonated on N‐3 and on N‐7 (employing CNDO/2). Semiempirical potential energy calculations (Lennard–Jones and Coulombic) failed to pinpoint the reasons for the recent experimental suggestion that guanine protonation increases the syn population in 2′‐ and 3′‐guanosine monophosphates. Changes in electron densities upon base protonation are much in evidence and are a very sensitive function of the site of base protonation assumed. It is suggested that the CNDO/2‐type calculations when combined with 13 C and 15 N pH‐dependent chemical shifts can lead to assignment of the site of protonation in the DNA bases.