Kinetic and thermodynamic investigation of the (dien)Pd(II)-polycytidylic acid system

The reaction between (dien)PdCl+ and polycytidylic acid was studied using spectroscopic and stopped-flow methods. In neutral solution, the palladium complex binds at the N3 site of the cytosine base and causes a noncooperative disruption of the ordered helical structure of poly(C). Interaction at the phosphate group of the polynucleotide was also demonstrated by using the dye acridine orange as an indicator. The results of this study show that the mechanism previously proposed for cytidine and CMP can be applied to poly(C), taking into account particular features of the polymer (polyelectrolytic nature, structure, etc.). In particular, electrostatic effects seem to play a major role in the interaction with metal ion complexes like (dien)Pd(II).