PHYS224 Lecture Notes - Lecture 20: Relative Permittivity, Dna Replication, Electrostatics
14 Feb 2018
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The electrostatics aspect of dna is due to the overall negative charge it holds. Each sugar-base unit contains a phosphate with an overall charge of e. Double stranded dna can be thought of as a single stranded polymer with negative charges every 0. 17nm [1]. Ideally, if dna wasn"t surrounded by water, coulombs law could be used to determine the electrostatic energy as the bases could be represented by point charges, and the distance between them would represent radius r [1]. Dna, however, is submerged in water and ions, so this is not possible [1]. Water being polar, acts as a dielectric that mitigates the strength of the electric field form each charge, or base [1]. The ions cluster around the negative dna charges, which shield the charge [1]. Dna acting as an electrolyte explains its dependence on salt concentration for the biding of simple oligocations and locally cationic surface regions of dna [1].
