Peculiar Features in the Crystal Structure of the Adduct Formed between <i>cis</i>-PtI₂(NH₃)₂ and Hen Egg White Lysozyme

The reactivity of <i>cis</i>-diamminediiodidoplatinum­(II), <i>cis</i>-PtI₂(NH₃)₂, the iodo analogue of cisplatin, with hen egg white lysozyme (HEWL) was investigated by electrospray ionization mass spectrometry and X-ray crystallography. Interestingly, the study compound forms a stable 1:1 protein adduct for which the crystal structure was solved at 1.99 Å resolution. In this adduct, the Pt^II center, upon release of one ammonia ligand, selectively coordinates to the imidazole of His15. Both iodide ligands remain bound to platinum, with this being a highly peculiar and unexpected feature. Notably, two equivalent modes of Pt^II binding are possible that differ only in the location of I atoms with respect to ND1 of His15. The structure of the adduct was compared with that of HEWL–cisplatin, previously described; differences are stressed and their important mechanistic implications discussed

Interactions between Anticancer <i>trans</i>-Platinum Compounds and Proteins: Crystal Structures and ESI-MS Spectra of Two Protein Adducts of <i>trans</i>-(Dimethylamino)(methylamino)dichloridoplatinum(II)

The adducts formed between <i>trans</i>-(dimethylamino)­(methylamino)­dichloridoplatinum­(II), [t-PtCl₂(dma)­(ma)], and two model proteins, i.e., hen egg white lysozyme and bovine pancreatic ribonuclease, were independently characterized by X-ray crystallography and electrospray ionization mass spectrometry. In these adducts, the Pt^II center, upon chloride release, coordinates either to histidine or aspartic acid residues while both alkylamino ligands remain bound to the metal. Comparison with the cisplatin derivatives of the same proteins highlights for [t-PtCl₂(dma)­(ma)] a kind of biomolecular metalation remarkably different from that of cisplatin