title: Photosensitized effects of Rose Bengal on structure and function of lens protein "alpha-crystallin".
abstract: The conformational changes of the bovine lens protein "alpha-crystallin" have been investigated in the presence of the photosensitizer Rose Bengal (RB), in the dark as well as after visible light irradiation. Absorption and fluorescence emission spectra of RB [5 x 10(-6) M] and Fourier transform-IR spectra of alpha-crystallin [5 mg mL(-1)] were significantly altered upon RB alpha-crystallin complex formation. RB was found to bind to alpha-crystallin in a molecular pocket characterized by a low polarity, with Trp most likely involved in this interaction. The binding constant (K(b)) has been estimated to be of the order of 2.5 (mg/mL)(-1). The intrinsic fluorescence of alpha-crystallin was quenched through both dynamic and static mechanisms. Light-induced photosensitized effects showed structural modifications in alpha-crystallin, including tertiary and secondary structure (an increase in unordered structure) alterations. Notwithstanding those photoinduced structural variations detected in alpha-crystallin when complexed with RB, the protein still retains its ability to play the role of chaperone for beta-crystallin.
authors.affiliation: National Institute of Laser Enhanced Sciences (NILES), Cairo University, Giza, Egypt.
authors.forename: Tareq
authors.initials: T
authors.lastname: Youssef
authors.forename: Mohamed
authors.initials: M
authors.lastname: Kassem
authors.forename: Tarek
authors.initials: T
authors.lastname: Abdella
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Harith
authors.forename: Francesco
authors.initials: F
authors.lastname: Lenci
mesh_terms: D000818:Animals; D002417:Cattle; D003624:Darkness; D005456:Fluorescent Dyes / Q000494:pharmacology; D008027:Light; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012395:Rose Bengal / Q000378:metabolism / Q000494:pharmacology*; D017550:Spectroscopy, Fourier Transform Infrared; D038201:alpha-Crystallins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D038201:alpha-Crystallins; D012395:Rose Bengal