Interactions of serum albumins with antitumor agent benzo [a] phenazine—a spectroscopic study

We present an investigation on the site specific interaction of antitumor agent benzo [a] phenazine (BAP) with serum albumins (HSA and BSA) and related photo-physical properties using absorption, emission and lifetime measurements. The absorption and emission measurements reveal that the binding of biomolecule benzo [a] phenazine took place near tryptophan moiety present in sub-domain IIA in serum albumins (HSA and BSA). In the selective excitation of benzo [a] phenazine at 365 nm, it was observed that the ground state of serum albumin quenches the excited benzo [a] phenazine through charge transfer exciplexation. The fluorescence decay analysis of serum albumins in the presence of benzo [a] phenazine shows decrease in lifetime, which confirms that photo-induced electron transfer takes place from serum albumins (HSA and BSA) to BAP. Also a suitable mechanism was proposed for the observed photo-induced electron transfer processes. Binding average distance (r) between the donor (serum albumins) and acceptor (benzo [a] phenazine) calculated using FRET theory confirmed their high probability of binding interaction.