Dynamics of Gestalt Polymer Chains in Gel and Separation Mechanism of DNA under Gel Electrophoresis

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The object of this study was to clarify dynamics of gestalt polymeric chains in gels, and to clarify the mechanism of molecular weight dependent separation in gel electrophersis of DNA. We also attempted to establish the optimum electropheric condition that enabled us to separate enormously large DNA more than 10^6 basepairs (bp). First, we examined dielectric relaxation of gest polyisoprene, PI, that exhibits the dielectric normal mode prucess, dissolved in much longer PI matrix, in polybutadiene (PB) matrix, and also in crosslinked PB matrix with varying molecular weight M. Then, we found that when gest chains were too short to entangle with the gel matrix, their relaxation time was proportinal to M^2, and this could be explained by Rouse-Zimm theory. On the other hand, when the gest chains was so long as to entangle with the gel, the relaxation time was proporinal to M^3, and this well suited with Doi-Edowards theory that is invalid in monodisperse systems.Then, we proposed a new electric field that has a sinusoidal field with amplitude E_s and frequency f superposed on a steady biase field E_b ; Biased Sinusolidal Field. We found that in a condition of E_b < E_s, DNAs longer than 20 x 10^3 bp had minimum in mobilityat a particular M-dependent frequency, which was called pin-down frequency, f_p. We also confirmed the relation of f_p alpha M^<-1>C_<gel>^<-1>E_S^0E_b^1 from experiments with various agarose gel concentration C_<gel>. Biased reptation model explained molecular weight dependence of mobility in steady field electrophoresis qualitatively, but not quantitatively. More realistic model describing dynamics of large DNA in gel electrophoresis is required for more detailed discussion.