[Determination of the degree of base protonation in isionic solutions of DNA from the curve of conductometric titration].

Conductance of the DNA isoionic solution at different degrees of neutralization has been investigated at 25 degrees. There are regions on the conductometric titration curve corresponding to titration of: 1) primary phosphoryl groups 2) guanine 3) adenine 4) adenine and cytosine in half-protonated pairs 5) thymine. The pH intervals corresponding to protonation of bases in isoionic solutions are shifted into alkaline region compared with Na-DNA solutions. It has also been found for molar per cent of unprotonatad bases to equal to that of thymine determined as from conductometric titration curve so from chromatographic analysis of the DNA hydrolysate.