Probing the interactions of oxidized insulin chain A and metal ions using electrospray ionization mass spectrometry

This work examines the interactions between a large polypeptide, oxidized insulin chain A (ICA), and several metal ions (Na+, K+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Pd2+) by using tandem mass spectrometry. Fragmentation spectra of the anionic complexes show that each metal ion complex undergoes specific types of interactions, suggesting that different conformations are favored for each complex. The overall results are consistent with the data obtained from ion mobility measurements. Thus, the tandem mass spectrometry approach represents a complementary method for probing the conformations of metal-peptide complexes. The fragmentation spectra obtained from the complexes of the enzyme-digested ICA fragments with metal ions also reflect specific metal-peptide interactions parallel with those for corresponding metal-ICA complexes. (C) 2003 Elsevier Science B.V. All rights reserved.