The Flexibility of A-Form DNA |
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| Authors: | Elliot Charney Holly-Ho Chen Donald C Rau |
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| Institution: | 1. Laboratory of Chemical Physics;2. Department of Chemistry , George Mason University , 4400 University Drive, Fairfax , Virginia , 2203;3. Laboratory of Biochemical Metabolism , NIDDK National Institutes of Health , Bethesda , Maryland , 20892 |
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| Abstract: | Abstract We have determined the rise per base pair and persistence length of A-form DNA in trifluoroethanol solutions for fragments 350–900 base pairs in length that best describe rotational diffusion coefficients determined by transient electric birefringence. The 2.6 A spacing between base pairs found in crystal and fiber A-form structures is preserved in solution. The persistence length is about 1500 A, or about three times longer than for B-form DNA. There is no apparent electrostatic contribution to the persistence length in the salt concentration range 0.2–2.0 mM Na cacodylate. This suggests an even closer association between DNA and its neutralizing counterions than predicted by condensation theory, perhaps due to a sheath of trifluoroethanol excluded water surrounding the A-form helix. |
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