[Effect of DEAE-dextran upon the interaction of polynucleotides in poly (l+c) double complex]

It has been shown that the formation of poly(I+C) double complex is accompanied by appearance of the 244 nm CD band which is absent from the spectrum of the initial components. The amplitude of this CD band is maximum upon equimolar ratio of components. When one mixes the complementary polynucleotides bound to DEAE-dextran (D-d) double comples is not formed. CD spectrum of poly (I+C) double complex is changed considerably upon addition of D-d: CD increases when P/N ratio is 10:1, decreases at P/N 1:1 and comes back to the initial spectrum at P/N 1:5. Thermal dissociation of poly(I+C) when the anionic component was in surplus was similar to poly(I+C) alone (Tm equals 67 degrees) when the polydextran was in excess; the thermal dissociation was lower (Tm equals 43 degrees) than that of poly (I+C). It is discussed the possible mechanism of the D-d and poly (I+C) interaction.