STRUCTURE OF THE ALPHA-FORM OF POLY(D(A)CDOT POLY(D(T)) AND AND RELATED POLYNUCLEOTIDE DUPLEXES
The alpha-form of poly(d(a))cdotpoly(d(T)), observed in fibres at high (.80%) relative humidity, is a 10-fold double-helical structure of pitch 3cdot2 nm. This new X-ray analysis shows that the two strands of the double helix are of the same kind conformationally and both beta-like in containing C-2'-"it endo/"- puckered deoxyribose rings. Nevertheless, the two strands are different enough for the overall morphology of the duplex to resemble that of the heteromerous model for the drier (beta) form of poly(d(A))cdotpoly(d(T)) in which one strand has C-2'-"it endo/" rings and the other C-3'-"it endo/". Since the orientations of the bases in poly(d(A))cdotpoly(d(T)) are persistently different from those of classical B-DNA it is likely that there will be local bending (about 10"rm o") at the junctions between general sequence tracts and the oligo (d(A))cdotoligo(d(T)) tracts that occur in some native DNAs. The conclusions about the structure of alpha- poly(d(A))cdotpoly(d(T)) are reinforced by independent analyses of similar X-ray diffraction patterns from poly(d(A))cdotpoly(d(U)) and poly(d(A))cdotpoly(d(C-T)).
Bibliographic Reference: JOURNAL OF MOLECULAR BIOLOGY, VOL. 197, PP 513-523, 1987
Record Number: 1989126063600 / Last updated on: 1989-05-01
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