COMPETITIVE REACTIONS IN SOLUTIONS OF DNA AND WATER-SOLUBLE INTERPOLYELECTROLYTE COMPLEXES

The reaction of competitive binding of two polyanions-DNA and syntheti c fluorescence-tagged poly(methacrylate) (PMA)-with the polycation-qu encher poly (N-ethyl-4-vinyl-pyridinium) (PEVP) was studied by fluores cence quenching technique. It was found that ability of DNA to displac e PMA fr om the water-soluble nonstoichiometric interpolyelectrolyte c omplex (NPEC) formed by PMA and PEVP-NPEC(PMA*-PEVP)-and to form wate r-soluble NPEC(DNA-PEVP) NPEC(PMA-PEVP) + DNA double left right arrow , NPEC(DNA-PEVP) + PMA can be determined by the parameter psi = ($) o ver bar P-PMA/($) over bar P-PEVP, where ($) over bar P-PMA* and ($) over bar P-PEVP,, are the degrees of polymerization of PMA and PEVP, respectively. In the ease of psi < 1 the decrease of psi leads to the shift of the reaction equilibrium to the right, which can be explained by the gain of entropy due to the increase of the total number of pol ymeric particles in the solution. Introduction of alkali metal cations into the reaction mixture results in the shift of the reaction equili brium, and according to the ability to shift the equilibrium to the ri ght the cations can be arranged in the series Na+ > K+ > Li+. The subs titution of native DNA by denatured DNA practically does not affect th e reaction equilibrium in solutions of NaCl and KCl but considerably s hifts it to the right in solutions of LiCl. The data obtained are in a ccordance with the differences in the selectivity of alkali cations bi nding with competitive polyanions. (C) 1995 John Wiley & Sons, Inc.