ALTERNATING CONFORMATION CHARACTERIZES THE PHOSPHODIESTER BACKBONE OF POLY(DA-DT) IN SOLUTION

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 254  (17) , 8125-8128
Abstract
A highly homogeneous 145-base-pair fragment of double helical poly(dA-dT) .cntdot. poly(dA-dT) was obtained by micrococcal nuclease digestion of a semisynthetic chromatin prepared from the nucleosome core histones (H2A, H2B, H3, H4) and the synthetic polydeoxyribonucleotide. In contrast to higher MW alternating copolymers, this fragment displayed 2 resolved 31P NMR signals, separated by 24 Hz at 109.3 MHz. The 2 signals were of equal intensity at all temperatures less than the Tm [melting temperature] for the fragment. Analyses of the possible origins for the 2 resonances leads to the conclusion that the phosphodiester backbone of this DNA contains 2 distinct P environments, probably in an alternating array. This may indicate the presence of sequence-dependent local variation in the helical structure of DNA in general.

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