The protonation of the spermine containing calf thymus DNA (molecular mass 15 and 5 MDa) solutions has been studied by means of circular dichroism method. It has been shown that the acid-induced transition from the low-protonated B(+)-form to the double-stranded structure with presumably Hoogsteen complementation of syn-G.C-base-pairs (S-form) in case of high-molecular partially condensed DNA is accompanied by differential scattering of circularly polarized light (DSCPL). The comparative study of protonation of partially and completely condensed low-molecular DNA enabled to obtain a family of DSCPL spectra. It has been demonstrated that the B+----S-transition in partially condensed high-molecular DNA is associated with formation of large intermolecular aggregates (with dimensions about 200 divided by 400 nm) which are destructed by acid-induced DNA denaturation.

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