Structure and stereochemistry of nucleic acid components and their reaction products part 4 crystal structure of the potassium salt of n purin 6 ylcarbamoyl glycine mono hydrate
Parthasarathy, R.; Ohrt, J.M.; Chheda, G.B.
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry 32(9): 2648-2653
The potassium salt of N-(purin-6-ylcarbamoyl)glycine, a hypermodified base in tRNA, was crystallized as a monohydrate (C8H7O3N6K.H2O). The crystals are monoclinic, space group P21/c with cell parameters (at 22 .+-. 3.degree. C): a = 14.063 (3), b = 7.218 (1), c = 14.424 (1) .ANG., .beta. = 129.12 (1).degree. with 4 molecules/unit cell. Three-dimensional data (2242 reflections to the limit 2.theta. = 160.degree. for Cu K.alpha. radiation) were collected on a diffractometer. The structure was solved by the multisolution technique and refined to an R of 0.058. Significant structural features are an internal hydrogen bond involving N(glycine)-H.cntdot.cntdot.cntdot.N(1) adenine, 'distal' conformation of the substituent on N(6), the stacking and extensive overlapping of the ureidopurine moiety in a head-to-tail fashion, in planes 3.2 .ANG. apart and a 7-fold coordination of the K+. All polar hydrogens take part in hydrogen bonding. There is little self association of amino acid or nucleic acid moieties through hydrogen bonding. The stacking of the bases is stabilized by a hydrogen bond between N(9) of one molecule and the carboxyl oxygen belonging to another molecule stacked on top of the first molecule.