[A compact form of DNA in solution. 2. Peculiarities of acidic titration of double-stranded DNA in PEG-containing water-salt solutions].

The formation of compact double-stranded DNA molecules in PEG-containing watersalt solutions (0.3 M NaCl) may be observed within the pH-range 3-10; i.e. under conditions at which parameters of double-stranded DNA helices are not strongly different from those of B-form. At pH less than 3, when regularity of double helices is significantly changed, the formation of the specific compact particles of DNA in PEG-containing solutions does not take place. Denaturation of the compact form of DNA in PEG-containing solution is accompanied by disappearance of the negative band in CD spectrum. Hyperchromic effect of denaturation of DNA compact form is uninformative because of the influence of the light-scattering by compact DNA molecules.