Physicochemical properties of Sendai virus RNA. II. Effect of ionic strength on thermostability of RNA.

The dependence of the melting point (Tm) and width of the melting range (deltaTm) on the ionic strength and pH of the medium was investigated for the double-stranded RNA formed through self-hybridization during the isolation of RNA from Sendai virus. It was shown that Tm is a linear function of the logarithm of the sodium ion concentration in the range of concentrations from 10(-1) to 10(-4) M, with a slope of 11.5 degrees toward the abscissa for each order of magnitude. The width of the melting range increased slightly with a decrease in the ionic strength. A change in the pH of the solutions from 5 to 8 had almost no effect on the melting point or the width of the melting range. The degree of purification of the preparations of RNA and the presence of EDTA in the solutions affected the form of the dependence of the mp on the logarithm of the sodium ion concentration very strongly, especially in the region of low ionic strengths.