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Molecular‐weight dependence of the low‐frequency dielectric properties of aqueous solutions of gel‐fractionated DNA
Author(s) -
Molinari Robert J.,
Cole Robert H.,
Gibbs Julian H.
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.1981.360200510
Subject(s) - chemistry , dielectric , aqueous solution , counterion , dispersion (optics) , relaxation (psychology) , polyelectrolyte , analytical chemistry (journal) , debye , chromatography , ion , organic chemistry , materials science , optics , polymer , social psychology , psychology , physics , optoelectronics
Combined three‐ and four‐terminal AC bridge measurements have been made at frequencies from 10 Hz to 100 KHz on samples of DNA with different molecular weight in aqueous solution under varying conditions of DNA concentrations and added salt. A method is described for the separation of large quantities of DNA fractionated according to size. A complicated pattern of dependence of the specific dielectric increment on concentration is found, and the difficulties of comparing the results from sample to sample are discussed. The dielectric properties of the fractionated samples of DNA in aqueous solution are reported for solutions sufficiently dilute that specific dielectric increment is independent of concentration. The specific dielectric increment of the solutions (with concentration measured in moles of DNA molecules/liter) is found to increase as the square of the molecular weight. The results are compared with results of polyelectrolyte theories which deal explicitly with counterion fluctuations and interactions. The frequency dependence of the dispersion is much broader than for simple Debye relaxation. It is satisfactorily fitted by the empirical Cole–Cole circular are function and the breadth of the dispersion is found to be, if anything, less for the fractionated samples than for native DNA in solution.