Covalent and non-covalent binding in vanadium-protein adducts

The ESI-MS and EPR results obtained during the study of systems containing vanadium-protein adducts have been explained integrating the spectrometric and spectroscopic responses with molecular modelling simulations. The representative systems formed by the potential antibacterial drug [VIVO(nalidixato)2(H2O)] with lysozyme and cytochrome c were fully characterized, interpreting the ESI-MS and EPR signals as the result of covalent and non-covalent binding. This behaviour should be considered for all metal-protein systems, and instrumental techniques-if necessary-should be coupled with modelling to achieve full characterization of the types of binding.