Cisplatin has long been recognized for its antitumor activity,but produces severe cytotoxicity.DNA is widely accepted as cisplatins primary target.Cisplatins mechanism of action is believed to involve formation of cisplatin-DNA adducts.However,DNA resides in the nucleus of the cell and thus is not very accessible.Non-specific targeting of cytoplasmic components is believed to cause cisplatins cytotoxicity.Researchers have examined cisplatin analogs in attempts to achieve improved antitumor activity and reduced toxicity.RNA also plays critical and essential roles in the life cycle of cells.RNA is present in both the nucleus and cytoplasm,and at higher concentrations than DNA.Thus,RNA may also be a promising target for cisplatin,its analogues,and other drugs.Several tandem mass spectrometry(MS/MS)approaches are employed to characterize the structures of a variety of amino acid-linked platinum complexes(AA-Pt)and their adducts to RNA nucleosides and nucleic acids.Fourier transform ion cyclotron resonance and quadrupole ion trap mass spectrometers,each equipped with an electrospray ionization source,are used to perform MS/MS experiments.Spectroscopic characterization of the AA-Pt complexes and their RNA nucleoside adducts is achieved using wavelength-resolved infrared multiple photon dissociation(IRMPD)action spectroscopy techniques.Complementary electronic structure calculations have been performed to characterize the stable low-energy conformations of these complexes,their relative stabilities,and linear IR spectra to facilitate analysis and interpretation of the measured IRMPD spectra.Energy-resolved collision-induced dissociation(ER-CID)experiments are used to elucidate the effects of adduct formation on glycosidic bond stability for both unmodified RNA nucleosides and their AA-Pt adducts.Top-down and bottom-up sequencing approaches are also used to characterize the binding sites of AA-Pt adducts to various model and functional RNAs.We have also performed high resolution MS analyses and top-down and bottom-up(via use of an RNAase)sequence analyses via MS/MS experiments to elucidate the binding specificity of the AA-Pt complexes and compare these results to experiments for their DNA analogs.In general complete or nearly complete sequence coverage is achieved via top-down analyses of 25-mers or less,whereas bottom-up coverage is sensitive to the selectivity of the RNAase employed and nucleotide sequence.Notably,several of the AA-Pt complexes examined to date exhibit different reactivities and selectivities vs cisplatin,clearly indicating that the reactivity of the Pt center can indeed be tuned by altering the Pt ligand field using AA ligands.