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Structure of a B-DNA Dodecamer at 16 K

Drew, Horace R. and Samson, Sten and Dickerson, Richard E. (1982) Structure of a B-DNA Dodecamer at 16 K. Proceedings of the National Academy of Sciences of the United States of America, 79 (13). pp. 4040-4044. ISSN 0027-8424.

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The crystal structure of the B-DNA dodecamer C-G-C-G-A-A-T-T-C-G-C-G, previously solved and refined at room temperature (290 K), has been analyzed at 16 K (-257 degrees C). The end-to-end winding of the helix does not vary with temperature but remains constant at 10.1 base pairs per turn. Negatively charged phosphate groups throughout the structure do move closer together on cooling, however, probably because of increase in the dielectric constant of water as the temperature is lowered. This has the two-fold effect of reducing the spacing between neighboring double helices from 24.0 to 22.9 angstrom and of narrowing the helix grooves within any isolated molecule. Overall lattice displacements as deduced from crystallographic temperature factors are very much decreased in the 16 K structure, yet displacements at phosphates continue to exceed those of deoxyribose sugars by B = 9 angstrom^2 and those of base pairs by B = 22 angstrom^2, even at this very low temperature at which practically all thermal motion has been eliminated. These differences, formerly interpreted as evidence for thermal vibration, must now be attributed to static disorder.

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Additional Information:Copyright © 1982 by the National Academy of Sciences Communicated by Paul D. Boyer, March 12, 1982 We thank Albert V. Fratini and Mary L. Kopka for permission to discuss their 9-Br dodecamer results in advance of publication. Development of the low-temperature diffractometer was made possible by National Science Foundation Grant DMS74-19029A1, and the research was supported by National Science Foundation Grants PCM79-13959 and PCM81-41389, National Institutes of Health Grants GM-24393 and GM-30543, and Damon Runyon-Walter Winchell Cancer Fund Fellowship DRG-507 to H.R.D. This is paper no. 5 of a series; papers nos. 1-4 are refs. 10-13. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Subject Keywords:low-temperature crystallography; molecular disorder vs. vibration; crystalline librational disorder; DNA at ultralow temperature
Issue or Number:13
Record Number:CaltechAUTHORS:DREpnas82
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5823
Deposited By: Archive Administrator
Deposited On:03 Nov 2006
Last Modified:02 Oct 2019 23:26

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