Interaction of a novel platinum drug with bovine serum albumin: FTIR and UV-Vis spectroscopy analysis

Platinum complexes have proven to be very effective in cancer treatment. However, severe side effects of these drugs have lead scientists to pursue new platinum complex derivatives. A novel blue platinum compound, called Platinum-Blue (Pt-Blue), is one of the promising candidate platinum compounds to be used for tumor treatment. In this study, the interaction of Pt-Blue with bovine serum albumin (BSA) has been investigated using UV-Vis and FTIR spectroscopy. One of the findings is that the drug-protein interaction type depends on the drug concentration. Though Pt-Blue is attached to the surface of BSA at high concentrations, it interacts with a hydrophobic region of the protein at low concentrations with a binding constant of 1.93 x 10(5) M-1. Spectroscopic results indicate the hydrophobic docking position to be around Trp 213 in domain II, which is surrounded by a number of Asp and Glu. During this interaction, helices such as helix-10, helix-18, helix-19 and helix-24 change orientation and/or partially unfold to make room for the compound. Binding constants at high and low concentrations of Pt-Blue are determined using UV-Vis spectroscopy, which are found to be comparable to cisplatin. FTIR spectroscopy also reveals that the interaction between Pt-Blue and BSA is noncovalent, which makes the candidate drug favorable because it is available for DNA binding while being carried by albumin.