W. Saenger, K. Scheit
May 28, 1970
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Journal
Journal of molecular biology
Abstract
Abstract 4-Thiouridine is a constituent of several transfer RNA's. Four molecules of this nucleoside crystallize together with six water molecules in a unit cell of the monoclinic space group C 2. The structure of 4-thiouridine was solved from three-dimensional X-ray data using the heavy-atom technique. Atomic distances but not the angles within the molecule are in the usual range, the heterocyclic system assuming a keto-keto structure and the ribose moiety arranged in a C(3′)- endo conformation. Most striking is the fact that 4-thiouridine is the first pyrimidine nucleoside to be found in the syn conformation. The crystal packing is such that the pyrimidine rings form endless stacks in the a-b plane, paralleled by continuous chains of ribose residues and water molecules. Some thoughts on the definition of the torsion angle about the glycosidic bond are expressed in the Appendix.