Conformation of Polyelectrolyte Chains in Dilute Aqueous Solutions Investigated by Conductometry, 1. Influence of the Degree of Polymerization on the Conformation of Flexible Vinylic Polyanions and Rigid Native DNA

Abstract

The temperature dependencies of the conductivities of dilute salt-free aqueous solutions of flexible vinylic polyelectrolytes - sodium poly(acrylate) and sodium poly(styrene sulfonate) - with different degrees of polymerization (DP) were obtained for solutions of rigid native DNA with different degrees of polymerization (i.e. with a different number of base pairs (bp) in the chain) in 0.001 mol . L -1 NaCI as a supporting electrolyte. On the basis of Manning's polyelectrolyte theory, the mean charge spacing b in the polyion chains was calculated from these data. The determined b values were used to estimate the conformational changes of the charged chains. For all studied polyanions, b increased with the shortenning of the regimes. For both vinylmic polyanions, the transition was observed pratically in the same DP region, i.e. 7 10 2 - 10 3 , whereas rigid native double-stranded DNA molecules underwent the conformational change at substantially higher DP values, namely of the order of 10 3 -10 4 . The obtained results shows that the used conductometric approach is appropriate for the estimation of the conformational changes of polyions in dilute aqueous solutions.