title: Cisplatin Binding to Biological Ligands Revealed at the Encounter Complex Level by IR Action Spectroscopy.
abstract: Cisplatin [cis-diamminedichloroplatinum(II)] was the first platinum-based antineoplastic agent and is still a cornerstone for the treatment of various solid tumors. Reactive events responsible for cisplatin activity are unveiled here at the molecular level. Simple ligands (L) representing ubiquitous functional groups in the biological environment likely to be encountered by administered cisplatin have been allowed to react with cis-[PtCl(NH3)2 (H2O)](+), the primary intermediate from cisplatin hydrolysis. The substitution reactions have been examined by a combined experimental and computational approach and the structural features of the substitution product, cis-[PtCl(NH3)2(L)](+), have been probed by IR multiple-photon dissociation (IRMPD) spectroscopy. Furthermore, IRMPD spectroscopy has been exploited to elucidate the structure of [PtCl(NH3)2(L)(H2O)](+) clusters, also obtained by electrospray ionization (ESI) from the aqueous solution and representing the major focus of this investigation. These ions conform to the encounter complex of cis-[PtCl(NH3)2 (H2O)](+) with the incoming ligand and represent the first direct evidence of a prototypical Eigen-Wilkins encounter complex in solution, lying on the reaction coordinate for ligand substitution and extracted by ESI for mass spectrometric analysis. Activated [PtCl(NH3)2(L)(H2O)](+) ions dissociate by the loss of either H2O or L, the former process implying a ligand substitution event. IRMPD spectroscopy has thus revealed both structural details and reaction dynamics at the level of the isolated encounter complex.
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco, Università degli Studi di Roma La Sapienza, P. le A. Moro 5, 00185, Roma, Italy), Fax.
authors.forename: Davide
authors.identifier: http://orcid.org/0000-0001-8064-3492
authors.initials: D
authors.lastname: Corinti
authors.affiliation: Dipartimento di Farmacia, Università G. D'Annunzio, Via dei Vestini 31, 66100, Chieti, Italy.
authors.forename: Cecilia
authors.identifier: http://orcid.org/0000-0002-3609-290X
authors.initials: C
authors.lastname: Coletti
authors.affiliation: Dipartimento di Farmacia, Università G. D'Annunzio, Via dei Vestini 31, 66100, Chieti, Italy.
authors.forename: Nazzareno
authors.identifier: http://orcid.org/0000-0002-0957-4049
authors.initials: N
authors.lastname: Re
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco, Università degli Studi di Roma La Sapienza, P. le A. Moro 5, 00185, Roma, Italy), Fax.
authors.forename: Barbara
authors.identifier: http://orcid.org/0000-0002-1585-7061
authors.initials: B
authors.lastname: Chiavarino
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco, Università degli Studi di Roma La Sapienza, P. le A. Moro 5, 00185, Roma, Italy), Fax.
authors.forename: Maria Elisa
authors.identifier: http://orcid.org/0000-0002-0991-5034
authors.initials: ME
authors.lastname: Crestoni
authors.affiliation: Dipartimento di Chimica e Tecnologie del Farmaco, Università degli Studi di Roma La Sapienza, P. le A. Moro 5, 00185, Roma, Italy), Fax. simonetta.fornarini@uniroma1.it.
authors.forename: Simonetta
authors.identifier: http://orcid.org/0000-0002-6312-5738
authors.initials: S
authors.lastname: Fornarini
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry; D002945:Cisplatin / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D010984:Platinum / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000970:Antineoplastic Agents; D008024:Ligands; D010984:Platinum; D002945:Cisplatin
keywords: ESI mass spectrometry; antitumor agents; bioinorganic chemistry; ion-molecule reactions; structure elucidation