87 zyxwvutsr Inorganica Chimica Acta, 124 (1986) 87-96 NMR Studies of the Interaction of cis-Diamminedichloro-platinum(I1) and Corresponding Hydrolysis Products with Adenosine Phosphates M. SARRAZIN, V. PEYROT and C. BRIAND* Laboratoire de Physique Pharmaceutique, Faculte’ de Pharmacie, 2 7 Boulevard Jean Moulin, I3385 Marseille, Cedex 5, France (Received November 20, 1985) Abstract Complexes formed in aqueous solution between cisplatin or hydrolysis species and 5’ adenosine mono- phosphate (AMP) or 5’ adenosine triphosphate (ATP), the latter with and without chloride ions, have been determined using lg5Pt, 31P, 13C and ‘H NMR. The present results lead to the conclusion that the only monodentate complexes with AMP are cis-Pt(NH3),(AMP-N7)Cl at acid pH and cis- Pt(NHs),(AMP-N7)OH at neutral and basic pH. Other bidentate complexes were identified as cis- Pt(NHs)2(AMP-N7), and cis-Pt(NH3)2(AMP-N7)- (AMP-PO). Also discussed herein are the binding of platinum to the phosphate group Py with ATP and at acid pH, and the formation of the [cis-Pt(NH3)*- (ATP-N7)H,O]+ complex. In neutral and basic pH ranges, the phosphate moiety of ATP is the most reactive site. In the presence of an excess of chloride ions, the complexation rates between the ATP and the cisplatin are decreased. Furthermore, in the experimental conditions used neither the ATP nor the AMP have shown binding to Nl. Introduction cis-Diamminedichloroplatinum(II), cis-PtCl,- (NH3)2 (CDDP), a potent antitumor agent, is a square-planar coordination complex; DNA is thought to be the main target molecule [ 1,2]. Some authors have suggested that minor interaction may occur with the phosphate group [3], while others found no association between platinum complexes and the nucleotide chain [4]. Moreover, many studies have been conducted on phosphate buffer [5-81, although Bose et al. have clearly shown that an interaction takes place between phosphate groups and platinum compounds [9]. In order to elucidate the impact of the phosphate moiety [lo] and the influence of its length on the complexation of the adenosine nucleo- tides, we studied the binding of CDDP and its hydro- - *Author to whom correspondence should be addressed. 0020-1693/86/$3.50 lysis products with AMP and ATP at various pH values and NaCl concentrations. Proton, phosphorus, platinum and carbon NMR were used in order to observe the reactions at different binding sites. Materials and Methods Reagents Pure cisplatinum was supplied by Roger Bellon Laboratories. Adenosine 5’-triphosphate and adeno- sine 5’-monophosphate were provided by Boehringer. All other chemicals used were from Merck. All these products were used without further purification. Cisplatinum (6 mg/ml) was hydrolysed in DzO for 5 days at the appropriate pH without any buffer, and added at time zero to AMP or ATP (lo-’ M) at the same pH. Instruments and Techniques NMR spectra at 200.133 MHz (‘H), 81.015 MHz (31P), 43.022 MHz (lg5Pt) and 50.323 MHz (‘“C) were obtained with a Bruker AM 200 instru- ment, with a tunable 10 mm multinuclear probe at ambient temperature**. ‘H spectra were run with 3 ps pulses and a 1.638 s acquisition time. Shifts are given in relation to external TMS. 31P spectra were carried out using 15 ps pulses and an acquisi- tion time of 0.655 s. Chemical shifts were compared to 85% H3P04 used as an external reference. 195Pt spectra were recorded using 10 ~_ls pulses and 0.131 s acquisition time. All chemical shifts were measured from (PtC16)-’ as external standard. 13C spectra were conducted with 8 ps pulses and 0.41 s acquisition time. Chemical shifts were related to TMS used as an external reference. The pH measurements were performed with a Beckman Selection 5000 pH meter. Values were not corrected for DzO isotopic effect. **Service Interuniversitaire de R.M.N., Marseille. 0 Elsevier Sequoia/Printed in Switzerland