Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
Abstract:
Photoinduced electron transfer (PET) from excited probes attached to proteins is of considerable current interest. Photochemical processes following 532 nm excitation of triphenyl methane dye, crystal violet (CV+) bound to a protein, bovine serum albumin (BSA), have been investigated in picosecond (ps) to microseconds (μs) time scales by flash photolysis technique. The excited singlet state lifetime of CV+ is found to be increased to 130 ps as compared to 1–5 ps for the unbound dye in low viscosity solvents. From flash photolysis studies in microsecond region, transient absorption in the region 650 nm is observed which is attributed to the dication radical CV√2+ formed by electron transfer from 3CV+* to BSA, contrary to electron transfer from BSA to the excited dye as proposed in a recent report. Supporting spectral evidence for the electron transfer from 3CV+* to BSA is obtained from pulse radiolysis studies.