An electrostatic model of B-DNA for its stability against unwinding.
In single molecule experiments Smith et al. (Science 271 (1996) 795) have unwound the B-DNA helix by stretching it in an aqueous salt solution. They found that the stretching force required for the transition decreases significantly with lowering of the salt concentration. We show that the observed salt effect is consistent with a uniformly charged cylinder model of DNA surrounded by a Poisson-Boltzmann ionic atmosphere. We also derive a simple connection between the sharpness of the center part of the transition and its cooperativity in terms of an average block size of base pairs that unwinds or rewinds.
Department of Pharmaceutical Chemistry, University of California, San Francisco 94143, USA.
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D010582:Bacteriophage lambda / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004247:DNA / Q000737:chemistry*; D004279:DNA, Viral / Q000737:chemistry; D008956:Models, Chemical; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D012492:Salts; D012996:Solutions; D055672:Static Electricity; D013816:Thermodynamics
D004279:DNA, Viral; D012492:Salts; D012996:Solutions; D004247:DNA