Interaction of Urea with Acridinedione Dye-Protein Complex in Aqueous Solution: A Photophysical Approach

Photophysical studies of water soluble Photoinduced Electron Transfer (PET) based dye with urea in the absence and presence of a globular protein, Bovine Serum Albumin (BSA) were carried out in water. Addition of urea results in a fluorescence quenching of the dye such that the local excited (LE) state emission remains largely unaffected, whereas BSA results in a fluorescence quenching accompanied with larger extent of fluorescence enhancement and promotes the formation of a new emissive peak, assigned to the Charge Transfer (CT) nature of the dye. The loss of PET behavior of the dye in water and the subsequent addition of urea or BSA influences the excited state nature of the dye. Urea predominantly governs the LE state nature of the dye and promotes the formation a new microenvironment in the presence of BSA. The binding constant parameters portray that dye is influenced by urea rather than BSA such that ureawater and urea-urea hydrogen-bonding assemblies predominates over hydrophobic nature of the protein. Fluorescence spectral technique is employed as a tool in establishing the nature of interaction between dyes with more than one water soluble Competitive Hydrogen Bonding solute is established in the present study.