Structural analysis of the anti-arthritic drug Auranofin: Its complexes with cysteine, selenocysteine and their fragmentation products

Positive mode electrospray mass spectrometry was used to investigate complexes of cysteine and selenocysteine with the metallo-drug Auranofin and the analogous chlorotriethylphosphine gold. Evidence for all the complexes, with the exception of the Auranofin-selenocysteine complex, was obtained. Several fragmentation products were examined and their proposed structures reported. Structural details of many experimentally observed ions including [Auranofin + H](+), [(CH3CH2)(3)P-Au-cysteine](+) and [(CH3CH2)(3)P-Au-methylselenocysteine](+) were examined by means of hybrid density functional theory at the B3LYP/DZVP level. Structural information and relative free energies are presented for several isomers of each ion considered. (C) 2009 Elsevier B.V. All rights reserved.