Complexes of l-histidine with Fe2+, Co2+, Ni2+, Cu2+, Zn2+ studied by electrospray ionization mass spectrometry

Unimolecular Reactivity of Uracil–Cu2+ Complexes in the Gas Phase

“…Interaction of doubly charged metal cations with organic ligands L often results in the detection in electrospray spectra of a series of doubly charged [ML n ] 2 + complexes (n ! 1), [9,30,32,[36][37][38][39][40][41][42] but the smallest species [ML] 2 + (n = 1) is often not observed, especially for metals having a high second ionization potential, such as copper [30,32,36] and lead. [9,39,40] Consistently, in the case of the Cu 2 + /uracil system, no…”

The role of copper in cysteine oxidation: study of intra- and inter-molecular reactions in mass spectrometry

“…Cu 2+ is an intermediate acid that prefers binding to intermediate ligands such as N-imidazole (histidine residue) and Cu + is a soft acid that prefers anchoring to soft ligands such as S-thiolate (cysteine residue) and also N-imidazole. 11 In mass spectrometry (MS), where ions are transferred from a liquid to a gas phase, the binding sites of Cu 2+ in proteins are identical 12,13 to those observed in solution, but arginine becomes the preferred anchorage for Cu + . [13][14][15] Cerda and Wesdemiotis noticed that the Cu + affinity for amino acids is increased when soft donor groups such as RSH are present compared to that of protons.…”

On-line electrogeneration of copper-peptide complexes in microspray mass spectrometry

“…In vivo, the anchor sites for Cu ϩ include the thiol moieties of cysteines and those for Cu 2ϩ include the imidazole residues of histidines [1,7,8]. In the gas phase, the binding sites of Cu 2ϩ are quite identical [9] to those observed in solution whereas arginine becomes the preferred anchorage for Cu ϩ [10,11]. Nevertheless, all these interactions are condition-dependent and other groups on a peptide can also be involved in the coordination of copper [12,13].…”