The trans labilization of cis-[PtCl₂(¹³CH ₃NH₂)₂] by glutathione can be monitored at physiological pH by [1H,13C] HSQC NMR

In order to monitor the trans labilization of cisplatin at physiological pH we have prepared the complex cis-[PtCl₂(¹³CH ₃NH₂)₂] and studied its interactions with excess glutathione in aqueous solution at neutral pH by two-dimensional [1H,13C] heteronuclear single-quantum correlation (HSQC) NMR spectroscopy. [1H,13C] HSQC spectroscopy is a good method for following the release of ¹³CH ₃NH₂ but is not so good for characterizing the Pt species in solution. In the reaction of cisplatin with glutathione, Pt-S bonds are formed and Pt-NH₃ bonds are broken. The best technique for following the formation of Pt-S bonds of cisplatin is by UV spectroscopy. [1H,13C] HSQC spectroscopy is the best method for following the breaking of the Pt-N bonds. [1H,15N] HSQC spectroscopy is the best method for characterizing the different species in solution. However, the intensity of the peaks in the ¹⁵NH₃-Pt-S region, in [1H,15N] HSQC, reflects a balance between the formation of Pt-S bonds, which increases the signal intensity, and the trans labilization, which decreases the signal intensity. [1H,15N] HSQC spectroscopy and [1H,13C] HSQC spectroscopy are complementary techniques that should be used in conjunction in order to obtain the most accurate information on the interaction of platinum complexes with sulfur-containing ligands.