Biopolymers and cell. 1989. Volume 5. № 1. 16 - 22
Lipanov, D. B. Beglov, D. G. Alexeev, I. Ya. Skuratovsky
BUCKLE OF THE A-T PAIR IN THE Bh-FORM OF POLY(dA):POLY(dT) A. A.
Summary
The structures of calcium and sodium salts of poly(dA): poly(dT) have been refined on the basis of X-ray diffraction in fibres using two parameter flexible sugar, and allowing for the possible A-T buckle. The bases of one chain, probably thymines, are tilted in the Na-poly(dA):poly(dT) structure at an angle of about —13°, while the tilt of the other chain bases is negligible. A number of unique features warrant a special designation, Bh, to distinguish poly(dA) : poly(dT) structure from other B-type structures. The refined structural parameters may be significant for the interpretation of data on DNA bends containing sufficiently long dAn:dTn tracts.