title: Red edge excitation shift emission spectroscopic investigation of serum albumins and serum albumin-bilirubin complexes.
abstract: The microenvironments around the intrinsic and extrinsic fluorophores in bovine and human serum albumins as well as their complexes with bilirubin have been visualized by red edge excitation shift (REES) emission spectroscopic investigation. The two albumins and their bilirubin complexes in aqueous buffered solutions (pH 7.5) do not exhibit any appreciable shift in their emission maxima, upon gradual change in excitation wavelength towards the red edge of their respective absorption band. The addition of Triton X-100 triggers REES emission in both the fluorophores. The observations suggest that the microenvironment around the flurophores are not so rigid, and even the extrinsic flurophore bilirubin having two carboxylic acid groups acts as a hydrophobic non-polar molecule when bound to albumins. The ligand binding domains (receptor sites) are large enough and incorporation of Triton X-100 makes the fluorophore environments rigid and subtle polarity may also be induced. Whereas small polar molecules like CHCl3, ANS and L-trp fail to induce REES emission in either of the fluorophores.
authors.affiliation: Department of Biochemistry and Biophysics, University of Kalyani, West Bengal, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Patra
authors.forename: M K
authors.initials: MK
authors.lastname: Pal
mesh_terms: D000818:Animals; D001663:Bilirubin / Q000737:chemistry*; D002417:Cattle; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D017830:Octoxynol; D012709:Serum Albumin / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D012996:Solutions; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013501:Surface-Active Agents; D014867:Water
chemical_list: D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D012709:Serum Albumin; D012996:Solutions; D013501:Surface-Active Agents; D014867:Water; D012710:Serum Albumin, Bovine; D017830:Octoxynol; D001663:Bilirubin