Transporting proteins and rhenium(I) tricarbonyl complexes association studies

HECTOR H. MARTINEZ-SAAVEDRA; FACUNDO GARCIA; GUSTAVO T. RUIZ; EZEQUIEL WOLCAN; GERARDO ARGUELLO

Congreso; 16th INTERNATIONAL CONGRESS ON PHOTOBIOLOGY; 2014

A detailed investigation of the interaction of two novel rhenium(I) complexes with two non-specific proteins (human and bovine serum albumins which are key for the transport of drugs in the blood plasma) is reported. Rhenium(I) complexes Bu4N[(bpy)Re(CO)3(dcbpy)] (where Bu = butyl; bpy = 4,4?-bipyridine; dcbpy = 2,2?-bipyridine-5,5?-dicarboxylate) and ClRe(CO)3(Bathocuproinedisulfonatedisodium salt) herein after on this work called Re1 and Re2, respectively; were found to bind strongly with bovine and human serum albumins (BSA and HSA) with intrinsic binding constants, Kb of (5.2±0.3)×105 M−1 and (2.6±0.3)×105 M−1 at 300 K for the  BSA-Re1 and HSA-Re1 interactions, respectively; and (4.5±0.3)×105 M−1 and (4.6±0.3)×105 M−1 at 299 K for the BSA-Re2 and HAS-Re2 interactions, respectively. The interactions of serum albumins with the above complexes were assessed employing fluorescence spectroscopy, circular dichroism and UV?vis absorption spectroscopy. The serum albumins-Re1, Re2 interactions did not cause meaningful conformational changes in the protein or local perturbation in the domain IIA binding pocket. However,  the relative fluorescence intensity of the albumin (BSA or HSA) bound to the Re1 and Re2 complexes decreased, suggesting that perturbation around the Trp 214 residue took place. The analysis of the thermodynamic parameters ΔG, ΔH, ΔS indicated that the hydrophobic interactions played a major role in both BSA- Re1, Re2 and HSA- Re1, Re2 association processes. The binding distances and transfer efficiencies for BSA- Re1, Re2 and HSA- Re1, Re2 binding reactions were calculated according to the Föster theory of non-radiation energy transfer. Experimental evidence suggest that serum albumins  strongly bind Re1 and Re2 complexes, allowing thus possibility to use them in Photodynamic Therapy (PDT)    Acknowledgments: H.H.M.S. acknowledge the CCT-La Plata-Córdoba for the short research scholarship which supported this work and INFIQC for providing facilities