Exploiting Soft and Hard X-Ray Absorption Spectroscopy to Characterize Metallodrug/Protein Interactions: the Binding of [trans-RuCl₄(Im)(dimethylsulfoxide)][ImH] (Im = imidazole) to Bovine Serum Albumin

Abstract

The reaction of bovine serum albumin (BSA) with [ trans-RuCl 4(Im)(dimethylsulfoxide)][ImH] (Im = imidazole) (NAMI-A), an experimental ruthenium(III) anticancer drug, and the formation of the respective NAMI-A/BSA adduct were investigated by X-ray absorption spectroscopy (XAS) at the sulfur and chlorine K-edges and at the ruthenium K- and L 3-edges. Ruthenium K and L 3-edge spectra proved unambiguously that the ruthenium center remains in the oxidation state +3 after protein binding. Comparative analysis of the chlorine K-edge XAS spectra of NAMI-A and NAMI-A/BSA, revealed that the chlorine environment is greatly perturbed upon protein binding. Only modest changes were observed in the sulfur K-edge spectra that are dominated by several protein sulfur groups. Overall, valuable information on the nature of this metallodrug/protein adduct and on the mechanism of its formation was gained; XAS spectroscopy turns out to be a very suitable method for the characterization of this kind of systems.

Overview of the Metallometabolomic Methodology for Metal-Based Drug Metabolism

“…However, ruthenium K and L 3 -edge spectra unambiguously verified that the ruthenium center remained in the oxidation state of +3 upon protein binding. Sulfur K-edge spectra remained the same during the binding, whereas chlorine K-edge spectra indicated changes in the chlorine chemical environment during the NAMI-A binding to albumin, attributed to the release of two chlorides [30] and the subsequent replacement by two water molecules [34].…”

“…Trans-RuCl 4 (Im)(DMSF)(ImH) (NAMI-A; Im = imidazole; DMSF = dimethylsulfoxide) entered clinical trials in the year of 2000 as an antimetastatic agent, whereas trans-RuCl 4 (In) 2 (InH) (In = indazole) (KP1019) entered in 2003 as an agent against colon carcinomas. Ascone and coworkers reported an XANES investigation of the binding environment of bovine serum albumin to NAMI-A [30]. The relative binding affinities of NAMI-A to human serum albumin and other biomolecules (such as DNA) confirmed the preferential interaction of NAMI-A to proteins over nucleotides [31].…”

Synchrotron Radiation Spectroscopic Techniques as Tools for the Medicinal Chemist: Microprobe X-Ray Fluorescence Imaging, X-Ray Absorption Spectroscopy, and Infrared Microspectroscopy

“…Emerging drugs (in phase I clinical trials) such as the potential Ru(III) chorido-indazole anti cancer drug (KP1019) and the anti-metastatic agent, NAMI-A, [87][88] have been analysed in cell culture media, blood serum and cultured mammalian cells to understand the transformations that occur to the metal centre. Lay and coworkers [89] isolated Ru(III)-BSA complexes by gel-filtration chromatography, freeze-dried the product and analysed it by XAS.…”

Spectroscopic Study of the Interactions of Ruthenium-Ketoconazole Complexes of Known Antiparasitic Activity with Human Serum Albumin and Apotransferrin

“…The interactions of metallodrugs with macromolecular blood components have been recognized as crucial for their biodistribution and efficacy. 17-21 In particular, ruthenium complexes of known anticancer activity have been shown to interact with human serum albumin (HSA), 20,22,23 and with apotransferrin (ATf). 24,25 We have shown that such protein-drug interactions also take place with ruthenium-chloroquine complexes with antimalarial activity.…”