Structures and fragmentations of Cobalt(II)-cysteine complexes in gas phase

William Buchmann (1) , Riccardo Spezia (1) , Guewen Tournois (1) , Thierry Cartailler (1) , Jeanine Tortajada (1)

1 LAMBE - Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement

The electronebulization of a cobalt(II)/cysteine(Cys) mixture in water/methanol (50/50) produced mainly cobalt‐cationized species. Three main groups of the Co‐cationized species can be distinguished in the ESI‐MS spectrum: (1) the cobalt complexes including the cysteine amino acid only (they can be singly charged, for example, [Co(Cys)_n − H]⁺ with n = 1–3 or doubly charged such as [Co + (Cys)₂]²⁺); (2) the cobalt complexes with methanol: [Co(CH₃OH)_n − H]⁺ with n = 1–3, [Co(CH₃OH)₄]²⁺; and (3) the complexes with the two different types of ligands: [Co(Cys)(CH₃OH) − H]⁺. Only the singly charged complexes were observed. Collision‐induced dissociation (CID) products of the [Co(Cys)₂]²⁺, [Co(Cys)₂ − H]⁺ and [Co(Cys) − H]⁺ complexes were studied as a function of the collision energy, and mechanisms for the dissociation reactions are proposed. These were supported by the results of deuterium labelling experiments and by density functional theory calculations. Since [Co(Cys) − H]⁺ was one of the main product ions obtained upon the CID of [Co(Cys)₂]²⁺ and of [Co(Cys)₂ − H]⁺ under low‐energy conditions, the fragmentation pathways of [Co(Cys) − H]⁺ and the resulting product ion structures were studied in detail. The resulting product ion structures confirmed the high affinity of cobalt(II) for the sulfur atom of cysteine.

Mots clés: cysteine; electrospray ionization; tandem mass spectrometry; collision-induced dissociation; cobalt

Domaines: Chimie-Physique [physics.chem-ph]

William Buchmann, Riccardo Spezia, Guewen Tournois, Thierry Cartailler, Jeanine Tortajada. Structures and fragmentations of Cobalt(II)-cysteine complexes in gas phase. Journal of Mass Spectrometry, 2007, 42 (4), pp.517-526. ⟨10.1002/jms.1183⟩. ⟨hal-00137646⟩