Spectrofluorometric studies on the binding interaction of bioactive imidazole with bovine serum albumin: A DFT based ESIPT process

Bioactive imidazole derivatives were synthesized and characterized by NMR spectra, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazole has been studied using emission spectroscopy. In hydrocarbon solvent, the tautomer emission predominates over the normal emission and in alcoholic solvent like ethanol; a dramatic enhancement of normal emission is observed which was due to increased solvation. DFT calculation on energy, charge distribution of the rotamers in the ground and excited states of the imidazole derivative were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than in the ground state. The interaction between bioactive imidazole derivative and bovine serum albumin (BSA) was investigated.

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► ESIPT – presence of intramolecular hydrogen bond – driving force for ESIPT.
► FRET – emission band position of donor and acceptor are very close – characteristic of FRET.
► Energy transfer – energy transfer studies – electrostatic interaction between BSA and imidazole.
► Forester's distance – donor-to-acceptor distance is <8 nm – static quenching.
► Synchronous fluorescence spectroscopic studies of BSA – aromatic hydroxyl group in tyrosine – interaction of BSA with imidazole.