Fluorescence of tyrosine dimers: properties and applications in the study of the cross-linking of proteins

LARA O. REID; M. LAURA DÁNTOLA; ANDRÉS H. THOMAS

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

One of the most important modifications of the oxidative damage of proteins is thecovalent bond between two tyrosines (Tyr), yielding the tyrosine dimer ordityrosine (Tyr2). This linkage can occur between two Tyr residues in the samemolecule, or between two molecules,1 the latter leading to a high molecularweight product.2 Tyr2 is increasingly used as a marker of aging, stress andpathogenesis. It was identified in many pathological manifestations.3The phenol groups of Tyr2 are much more acidic than that of Tyr and thecorresponding pKa value was determined to be 7.25. The two acid-base forms havewell differentiated spectral features, with absorbance maxima of 283 and 315 nmfor the acid and basic form, respectively. This means that when Tyr2 is formed invivo a new chromophore appears in the proteins, which is able to absorb, unlikenatural amino acids, at wavelengths significantly present in solar radiation andartificial sources of light. The fluorescence of Tyr2 is an unspecific marker ofoxidative damage in proteins.4,5In this work we have studied the emission properties of the acid and the basicforms 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.6 We have used theemission properties of Tyr2 to investigate the photosensitized oligomerization ofproteins via the formation of Tyr2. As a model system, we have studied theoligomerization of human serum albumin photoinduced by pterin under UV-Airradiation.2Contact: athomas@inifta.unlp.edu.arReferences1. 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. Dyes Pigm. 67, 147 (2017).