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Conformational analysis of the 2′‐deoxyribofuranose ring from proton–proton coupling constants: Analysis of a nucleoside‐carcinogen adduct formed from 2‐acetylaminofluorene utilizing a three‐state model
Author(s) -
Evans Frederick E.,
Levine Robert A.
Publication year - 1987
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.360260704
Subject(s) - chemistry , pseudorotation , adduct , ring (chemistry) , equilibrium constant , coupling constant , moiety , stereochemistry , crystallography , computational chemistry , organic chemistry , physics , particle physics
The conformation of the sugar moiety of 8‐( N ‐fluoren‐2‐ylamino)‐2′‐deoxyguanosine in solution has been examined as a function of temperature by 1 H‐nmr spectroscopy. Analysis of coupling constants shows that lowering the temperature to −50°C in methanol shifts the conformational equilibrium of the sugar ring resulting in a C2′‐ endo conformation at a mole fraction of 0.97. The computed phase angle of pseudorotation and amplitude of pucker are 154° and 36°, respectively, with very little discrepancy between the five calculated coupling constants and coupling constants extrapolated from the temperature profiles. A computer program has been written enabling a three‐state best‐fit analysis. The three‐state analysis indicates an equilibrium between C2′‐ endo , C3′‐ endo , and 04′‐ endo conformations. In aqueous solution, the computed mole fraction of the 04′‐ endo form is 0.18 at 30°C. The conformation associated with the sugar ring and the C4′C5′ bond is compared to that of 2′‐deoxyguanosine.