CONICET | Buscador de Institutos y Recursos Humanos

One of the most importantmodifications of the oxidative damage of proteins is the covalent bond betweentwo tyrosines (Tyr), yielding the tyrosine dimer or dityrosine (Tyr2).This linkage can occur between two Tyr residuesin the same molecule, or between two molecules,1 the latter leadingto a high molecular weight product.2Tyr2 is increasingly used as amarker of aging, stress and pathogenesis. It was identified in manypathological manifestations.3The phenol groups of Tyr2are much more acidic than that of Tyr and the corresponding pKa value was determined to be7.25. The two acid-base forms have well differentiated spectral features, withabsorbance maxima of 283 and 315 nm for the acid and basic form, respectively.This means that when Tyr2 is formed in vivo a new chromophore appears in the proteins, which is able toabsorb, unlike natural amino acids, at wavelengths significantly present insolar radiation and artificial sources of light.The fluorescenceof Tyr2 is an unspecificmarker of oxidative damage in proteins.4,5In this work we have studied the emissionproperties of the acid and the basic forms of Tyr2 in aqueous solution. Steady-state and time-resolved fluorescenceexperiments were carried out and lifetimes, quantum yields and emission spectrawere obtained under different experimental conditions.6We have usedthe emission properties of Tyr2 to investigatethe photosensitized oligomerization of proteins via the formation of Tyr2. As a modelsystem, we have studied the oligomerization of human serum albumin photoinducedby pterin under UV-A irradiation.2 1. R. Kanwar, D. Balasubramanian.Exp. Eye Res. 773, 68(1999).2. L. O. Reid, et. al.Biochemistry, 4777, 55(2016).3. D. Balasubramanian, R. Kanwar. Mol.Cel. Biochem. 234, 27 (2002).4. R. Amado,et. al.MethodsEnzymol.377,107(1984).5. D. A. Malencik, et. al. Anal. Biochem.202, 242 (1966).6. L. O. Reid et.al. DyesPigm. 67, 147 (2017).