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Energy of planar autoassociation of xanthine and spatial structure of poly(riboxanthylic acid)
Author(s) -
Geller M.,
Lesyng B.,
Pohorille A.
Publication year - 1980
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560170212
Subject(s) - chemistry , hydrogen bond , planar , dipole , dissociation (chemistry) , xanthine , hydrogen , interaction energy , bond dissociation energy , atomic physics , computational chemistry , crystallography , molecule , physics , organic chemistry , computer graphics (images) , computer science , enzyme
First‐ and second‐order perturbation theory in a polarization approximation was employed to calculate interaction energies of planar xanthine–xanthine pairs in stable configurations. Electrostatic energy was obtained in the atomic‐dipole approximation. The results provided a basis for formulation of a four‐stranded model of poly(xanthylic acid) that allows two hydrogen bonds per base. The model accounts satisfactorily for the unusual thermal stability and the observed pH transition of the polymer. The latter is due to the gradual dissociation of the N 3 protons accompanying by disrupture of the weak N 3 H ··· O 6 hydrogen bonds. However, the structure is only moderately weakened since the configuration of the coplanar bases remains stabilized by four N 1 H ··· O 2 hydrogen bonds.