DISSOCIATION OF DOUBLE-STRANDED POLY(I).POLY(C) BY CIS-DIAMMINE-DICHLORO-PT(II)

The covalent binding of cis-Pt(NH3)2Cl2 on the double stranded poly(I) · poly(C) induced an irreversible dissociation of the two strands. This dissociation was evidenced mainly by poly(I)-Agarose affinity chromatography which allowed to recover free strands of cis-Pt(NH3)2Cl2-poly(I) from a cis-Pt(NH3)2Cl2-poly(I) · poly(C) complex, by density equilibrium centrifugation where free poly(C) could be isolated, and by acid titrations of the metalpoly(I) · poly(C) complexes. The separation of the two strands of the polyribonucleotide upon cis-Pt(NH3)2Cl2 fixation was shown not to exceed 90-95%. A dissociation curve of the polynucleotide double helix as a function of the amount of bound cis-Pt(NH3)2Cl2 was determined and was shown to be of a characteristic cooperative effect. The fixation of the platinum compound to poly(I) · poly(C) seemed also to be cooperative. © 1979.