DNA interaction with biologically active metal ions. Cooperativity of metal ion binding at compacting of DNA.

The interaction of Cu2+, Mn2+ and Ca2+ ions with DNA in aqueous and water-ethanol solutions at different metal ion concentrations was studied by IR-spectroscopy. At sufficiently high DNA concentrations, DNA interaction with Cu2+, Ca2+ and Mn2+ ions results in compacting of DNA in the aqueous solutions. This process shows a very high cooperativity.

Dependence of the biological activity and mass spectrometric pattern on the structure peculiarities of the molecule of alkylating drug thiotepa.

Structural and electronic parameters of the chemotherapeutic alkylating drug thiotepa obtained by MNDO and MINDO/3 quantum mechanical calculations are used to explain some physical, chemical and biological properties of this compound. On the basis of the revealed difference between the preferential conformations of the thiotepa molecule in crystal and vacuum, a conclusion is made concerning the precautions in the choice of the appropriate molecular geometry in the search of structure-activity correlations. The theoretical data are also applied to the explanation of some peculiarities of soft ionization mass spectra of thiotepa, in particular its sensitivity to high field effects and the absence of protonation.