Reaction of the Anticancer Organometallic Ruthenium Compound, [(η6-p-Cymene)Ru(ATSC)Cl]PF6 with Human Serum Albumin

The reaction of [(eta(6)-p-cymene)Ru(ATSC)Cl]PF(6) (ATSC = 9-anthraldehyde thiosemicarbazone) with human serum albumin was investigated at different temperatures using fluorescence and infrared spectrophotometry. The binding constant, K, for the reaction was determined using a number of different methods. Using a modified Stern-Volmer equation, K was determined to be 9.09 x 10(4), 12.1 x 10(4), and 13.1 x 10(4) M(-1) at 293 K, 298 K, and 308 K, respectively. A thermodynamic analysis showed that the reaction is spontaneous with DeltaG being negative. The enthalpy of reaction DeltaH = 16.5kJ mol(-1) and the entropy of reaction DeltaS = 152 Jmol(-1)K(-1). The values of DeltaH and DeltaS suggest that hydrophobic forces are dominant in the mode of interaction and that the process is mostly entropy driven.