Distilbene Derivative as a New Environment-Sensitive Bifunctional Ligand for the Possible Induction of Serum Protein Aggregation: A Spectroscopic Investigation and Potential Consequences

The photophysical properties of a new distilbene fluorophore, DPDB, belonging to the conjugated polyene family is found to be well modulated with the variation of the microenvironment. Compared to the ground state, the excited-state photophysical properties of the fluorophore have been altered to larger extents with the variation of polarity and the hydrogen-bonding nature of solvents. The change in the fluorescence intensity of DPDB shows a nice correlation with the aggregation behavior of different surfactants which have been utilized for the determination of the CMC of surfactants. The distribution of DPDB is found to be higher in nonionic micelles. On the other hand, DPDB specifically binds the subdomain IB cavity of serum albumin with a stronger binding ability with HSA compared to BSA. DPDB behaves like a bivalent (bifunctional) ligand and forms a complex of 2:1 stoichiometry with serum albumins. Dynamic light scattering and circular dichroism measurements indicate that DPDB favors the association of serum albumin molecules, promoting their preaggregation state. Aggregation is an important phenomenon and is known to be initiated by heat, extreme pH conditions, very high ionic strength, surfactants, metal ions, and so forth. This study explores a new avenue in bringing about association phenomena of serum albumins and points out that the binding of such a bifunctional ligand may also become an important factor in inducing the protein association.