• electrospray ionization mass spectrometry;
  • tandem mass spectrometry;
  • hydrolytic cleavage;
  • oxidized insulin B chain;
  • platinum and copper complexes


Interaction of cis-[Pt(en)(H2O)2]2+ and [CuL(H2O)]2+, where L is 2-[bis(2-aminoethyl)amino]ethanol, with oxidized insulin B chain in molar ratio of 1 : 1, 1 : 2 and 1 : 3 at pH 2.5 and 40 °C has been investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The results show that the binding sites of the two complexes with oxidized insulin B chain are terminal NH2, imidazole groups of His5 and His10. The hydrolytic cleavage studies show that the [CuL(H2O)]2+, upon a pendant hydroxyl group of the ligand, selectively cleaves the peptide bonds at Gly8–Ser9, Asn3–Gln4 and Phe1–Val2, and the cis-[Pt(en)(H2O)2]2+ only cleaves the peptide bond at His10–Leu11. This is the first report of cis-[Pt(en)(H2O)2]2+-promoted cleavage of His–X peptide bond. Copyright © 2006 John Wiley & Sons, Ltd.