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Left-handed helices for DNA: studies on poly[d(I-C)]

Ramaswamy, N and Bansal, M and Gupta, G and Sasisekharan, V (1982) Left-handed helices for DNA: studies on poly[d(I-C)]. In: PNAS, 79 (20). pp. 6109-6113.

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Official URL: http://www.pnas.org/content/79/20/6109.abstract

Abstract

Earlier, we showed that, for the D form (n = 8 and h = 3.03 A, where n is number of nucleotide units per turn and h is height per nucleotide unit) of poly[d(A-T)], both right- and left-handed double helical models are stereochemically satisfactory and give good agreement with the observed fiber diffraction data. It was also noted that the conformations of the right- and left-handed D-DNA models are very similar to those of the right- and left-handed B-DNA models. This observation was consistent with the D leads to B transition in the solid phase. As a continuation of our earlier studies, we have carried out similar experiments with poly[d(I-C)]. We could obtain a crystalline D-form pattern (n = 8, h = 3.13 A) of the fiber at 75% relative humidity (r.h.); the hydrated (r.h. approximately equal to 95%) form of the same fiber gave the classical B-form pattern (n = 10, h = 3.40 A). In the present report, we show that both right- and left-handed double-helical models are consistent with the fiber diffraction data of poly[d(I-C)] in the D-form. Theoretical energy calculations also suggest that the right- and left-handed B- and D-DNA models are almost equally stable. Hence, we conclude that the right- and left-handed double-helical models of poly[d(I-C)] in a given form (B or D) are equally likely and that the fiber diffraction data do not permit discrimination.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to National Academy of Sciences.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 28 Aug 2009 15:13
Last Modified: 19 Sep 2010 05:32
URI: http://eprints.iisc.ernet.in/id/eprint/20417

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