Comparison of the binding behavior of oxaliplatin, cisplatin and analogues to 5′-GMP in the presence of sulfur-containing molecules by means of capillary electrophoresis and electrospray mass spectrometry

Capillary electrophoresis as well as ESI-MS has been applied for investigating the influence of the sulfur-containing amino acids L-Cysteine and L-methionine on the binding behavior of oxaliplatin (trans-R,R-diaminocyclohexane(oxalato)platinum(Il)), cisplatin (cis-diamminedichloroplatinum(II)), carboplatin (cis-diammine-1,1-cyclobutanedicarboxylatoplatinum(II)),cis-diammine(malonato)platinum(II) and cis-diammine(2-hydroxymalonato)platinum(II) to 5'-GMP. The presence Of L-methionine resulted in a different kind of adduct formation which involves ammine release due to the trans-effect of sulfur. In addition, the time-dependent behavior of the reaction with 5'-GMP changed significantly. Due to the high stability of the diaminocyclohexane (DACH) platinum fragment, oxaliplatin showed a completely different behavior in comparison to diammine platinum complexes. Formation of [Pt(DACH)(L-Met-S,N)](+) inhibits coordination of 5'-GMP. Displacement Of L-Met by 5'-GMP does not occur. Differences concerning the mode of action of oxaliplatin are expected. Characterization of the analytes was performed by UV, NMR and mass spectrometry. (C) 2001 Elsevier Science BY All rights reserved.