Effects of Salt Concentration and pH on the Absorption Spectra of Polynucleotides with Various S-Values

Poly (A) took stable double-stranded form in 0.02 m phosphate buffer pH 5.8 when its S-value was higher than 3.5. Poly (C) also took stable double-stranded form in 0.01 m acetate buffer pH 3.9 containing 0.1 m NaCl if its S-value was higher than 4.8.Poly (I) with S-values higher than 6.5 stably formed triple-stranded form. Poly (A) with S-values over 3S and poly (I) with S-values over 7S were observed to aggregate in the presence of high concentration of salt, but poly (C) and poly (U) did not aggregate under the same condition. Effect of salt concentration differed with different polynucleotides and with different salts.