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Science 14 December 1973:
Vol. 182. no. 4117, pp. 1142 - 1143
DOI: 10.1126/science.182.4117.1142
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Articles

Structure of a Dinucleotide: Thymidylyl-(5'rarr3')-Thymidylate-5' (pTpT)

Norman Camerman 1, J. K. Fawcett 1, and Arthur Camerman 2

1 Department of Biochemistry, University of Toronto, Toronto 181, Canada
2 Departments of Medicine (Neurology) and Pharmacology, University of Washington, Seattle 98195

The crystal and molecular structure of the naturally occurring deoxyribose dinucleotide sodium thymidylyl-(5'rarr3')-thymidylate-5' has been determined by x-ray diffraction. There are four molecules of dinucleotide and 52 water molecules in an orthorhombic unit cell of dimensions (in angstroms) a = 16.06, b = 15.13, c = 15.65, space group P21212. There is a very high degree of conformational consistency between the two halves of the molecule when the dinucleotide is viewed as the combination of two 5'-mononucleotides. The planes of the two thymines are not parallel, but are tilted 38° with respect to each other. An extensive system of hydrogen bonding exists involving the bases, waters, phosphates, and sodiums; no base-base hydrogen bonding occurs. The dinucleotide structural parameters should be of assistance in interpreting DNA fiber diagrams in terms of possible structures.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)