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STRUCTURE OF A THYMINE‐THYMINE ADDUCT FORMED BY MENADIONE PHOTOSENSITIZATION
Author(s) -
Katz Henry,
Stallings William,
Glusker Jenny P.
Publication year - 1993
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1993.tb02925.x
Subject(s) - thymine , chemistry , ring (chemistry) , crystallography , adduct , molecule , stereochemistry , monoclinic crystal system , methyl group , hydrogen bond , cyclohexane conformation , crystal structure , group (periodic table) , dna , biochemistry , organic chemistry
— The structure of one of the dithymine adducts formed by near‐UV photosensitization of aqueous oxygenated thymine in the presence of 2‐methyl‐ 1, 4‐naphthoquinone is reported. The compound, 6′β‐hydroxy‐5′β‐1 ‐ [5‐methylpyrimidinyl‐ 2,4‐dione]‐5′‐6′‐dihydrothymine has one thymine ring (ring I) linked through the 1‐nitrogen atom to the C5′ atom of a second thymine, which has been hydroxylated af C6′ (ring II). Crystals are monoclinic, space group 12/c, and the structure was refined to R obs = 0.036 for 2072 unique reflections with intensities I greater than 2.33s̀(I). Ring I is planar, whereas ring II is not. Ring I and the OH group on ring II are cis to ring II. The planar ring I and the OH group are attached, respectively, in an equatorial and axial manner to ring II (which is in the sofa conformation). The planar rings I of close‐lying pairs of molecules stack parallel to each other. The structure is held together by a hydrogen‐bonding system consisting of the water molecules, the NH groups, two of the C=O groups and the OH group. The chemical formula and relative configurations at C5′ and C6 are established by this analysis.