Abstract

European Journal of Mass Spectrometry
Volume 2 Issue 5, Pages 273–285 (1996)
doi: 10.1255/ejms.59

An electrospray mass spectrometric study of organomercury(II) and mercuric interactions with peptides involving cysteinyl ligands

Antonella D’Agostino, Ray Colton and John C. Traeger
School of Chemistry, La Trobe University, Bundoora, Victoria 3083, Australia
Allan J. Canty
Department of Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia

Positive ion electrospray mass spectrometry (MS) has been used to investigate the interaction of Hg²⁺, [MeHg]⁺ and [PhHg]⁺ cations with cysteine (Cys), glutathione (GSH) and a 27-residue polypeptide (Pp) containing one cysteinyl sulfur located at the N-terminus. MS/MS experiments showed that organomercury adduction occurs primarily at the sulfhydryl group, with some evidence for isomeric species in which the organomercury cation is bound to either an amino or a carboxylic group. Following Ellman modification of GSH and Pp, the maximum number of adducted organomercury cations was reduced by 2 and 1, respectively, indicating a 2 : 1 and a 1 : 1 interaction between [RHg]⁺ and the cysteinyl sulfur. Unlike [PhHg]⁺, [MeHg]⁺ showed an almost exclusive affinity for the cysteinyl sulfur of GSH and Pp. Both Cys and GSH reacted with Hg²⁺ to form polynuclear species. Collisional activation mass spectra of the [2Cys + Hg – H]⁺ ion indicated that the Hg(II) was most probably bridged between the two cysteinyl residues, although not necessarily via a conventional –S–Hg–S– linkage.

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