2-(2′-Pyridyl)benzimidazole as a fluorescent probe for monitoring protein–surfactant interaction

The effectiveness of 2-(2′-pyridyl)benzimidazole (2PBI) as a fluorescent probe of macromolecular interactions is investigated, with the well-known human serum albumin–sodium dodecyl sulfate aggregates as the test system. The second fluorescence band of 2PBI, arising from a proton-transferred state at the surface of negatively charged sodium dodecyl sulfate micelles, is suppressed in the aggregates. The temporal features reflect the change in the relative population of the cationic and normal forms of the fluorophore. Thus, 2PBI is found to be a potentially good fluorophore for the study of complex systems like protein–surfactant aggregates.