Istituto di Biofisica     
Youssef T., Brazard J., Ley C., Lacombat P. P., Martin M. M., Sgarbossa A., Checcucci G., Lenci F. Steady-state and femtosecond photoinduced processes of blepharismins bound to alpha-crystallin. In: Photochemical & Photobiological Sciences, vol. 7 pp. 844 - 853. RSC, 2008.
The interaction of blepharismin (BP) and oxyblepharismin (OxyBP) with bovine alpha-crystallin (BAC) has been studied both by steady-state and femtosecond spectroscopy, with the aim of assessing the possible phototoxicity of these compounds toward the eye tissues. We showed that these pigments form with BAC potentially harmful ground-state complexes, the dissociation constants of which have been estimated to be 6 2 mol L-1 for OxyBP and 9 4 mol L-1 for BP. Irradiation with steady-state visible light of solutions of blepharismins in the presence of BAC proved to induce a quenching of both the pigment and the intrinsic protein fluorescences. These effects were tentatively rationalized in terms of structural changes of alpha-crystallin. On the other hand, femtosecond transient absorption spectroscopy was used to check the occurrence of any type I photoactivity of oxyblepharismin bound to alpha-crystallin. The existence of a particular type of fast photoinduced reaction, not observed in former studies with human serum albumin but present in the natural oxyblepharismin-binding protein, could here be evidenced but no specific reaction was observed during the first few nanoseconds after excitation. Partial denaturation of alpha-crystallin was however found to alter the excited-state behaviour of its complex with oxyblepharismin, making it partly resemble that of free oxyblepharismin in solution
DOI: 10.1039/b800848e
Subject Blepharisma

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