R. Parthasarathy, J. Ohrt, G. Chheda
Sep 15, 1976
Citations
0
Influential Citations
4
Citations
Journal
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry
Abstract
The potassium salt of N-(purin-6-ylcarbamoyl)glycine, a hypermodified base in t-RNA, was crystallized as a monohydrate (CsHvOaN6K. H20). The crystals are monoclinic, space group P21/c with cell parameters (at 22+_3°C): a= 14.063 (3), b=7.218 (1), c= 14.424 (1) ,~, fl= 129.12 (1) ° with four molecules per unit cell. Three-dimensional data (2242 reflexions to the limit 20-160 ° for Cu K~ 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: (i) an internal hydrogen bond involving N(glycine)-H...N(1) adenine, (ii) 'distal' conformation of the substituent on N(6), (iii) the stacking and extensive overlapping of the ureidopurine moiety in a head-to-tail fashion, in planes 3.2 A apart and (iv) a sevenfold coordination of the potassium ion. 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.