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Investigation of the flexibility of DNA using transient electric birefringence
Author(s) -
Hagerman Paul J.
Publication year - 1981
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1981.360200710
Subject(s) - persistence length , chemistry , electric field , ionic bonding , ionic strength , rotational diffusion , chemical physics , anisotropy , diffusion , molecule , relaxation (psychology) , birefringence , molecular physics , dna , monte carlo method , analytical chemistry (journal) , ion , optics , thermodynamics , physics , organic chemistry , aqueous solution , social psychology , psychology , statistics , mathematics , quantum mechanics , biochemistry
In the preceding article, a Monte Carlo analysis was presented which provides a quantitative numerical relationship between the rotational diffusion coefficients, as measured by the decay of optical anisotropy following an electric field pulse, and the flexibility (persistence length) of short, wormlike chains. In the present article, the results of the foregoing analysis are applied to the observed rates of decay of birefringence for a series of sequenced DNA fragments ranging in size from 104 to 910 base pairs. Under the conditions used in this study, the DNA fragments exist as native, duplex molecules. Furthermore, conditions are defined in which the observed relaxation times are not dependent on DNA concentration, field strength, or the duration of the pulse. It is pointed out that the ionic atmosphere associated with a wormlike polyion does not exert any significant (direct) influence on the rotational diffusion of the polyion and, therefore, that the rotational relaxation times are a true measure of the configurations of the DNA molecules in solution. Moreover, excluded‐volume effects are shown not to be significant for the moderately short molecules employed in this study. The major conclusion of this study is that there is no strong ionic strength dependence of the persistence length for ionic strengths above 1 m M and that the persistence length, under conditions where electrostatic contributions are negligible, is approximately 500 Å. For ionic strengths significantly lower than 1 m M , electrostatic contributions to the stiffness of DNA become significant.