Estudo voltamétrico de biomarcadores de estresse oxidativo: 3-nitro-, orto- e para-tirosina

Abstract

Reactive nitrogen (RNS) and oxygen species (ROS) are produced in-vivo within cells as products of cellular metabolism. These species play important physiological roles in controlling blood pressure, cell signaling, apoptosis and phagocytosis. However, in-vivo excess of RNS and ROS can cause damage to biological molecules, such as double-helix deoxyribonucleic acid (dsDNA) and proteins, leading to mutations, with direct consequences in many pathological processes. Peroxynitrite (ONOO-) is an RNS that promotes reactions with proteins in tyrosine residues producing 3-nitro-tyrosine (3-NO2-Tyr), which can cause different types of diseases such as acute pulmonary injury, atherosclerosis and some type of cancers. Thus, 3-NO2-Tyr is an important biomarker of in-vivo production of RNs in various tissues. However, ROS provoke oxidative damage in the proteins leading to the production of ortho- (o-Tyr) and para-tyrosine (p-Tyr). Therefore, the objective of this work was to investigate via electrochemical techniques, such as cyclic voltammetry, differential pulse voltammetry and square wave voltammetry, the redox behavior of 3-NO2-Tyr, o-Tyr and p-Tyr using a glassy-carbon electrode, as well as to develop electroanalytical methods for their quantifications. The study revealed the redox mechanisms of biomarkers. In addition, a bibliographic review was carried out to elaboration of a didactic text on amino acids and proteins, as well as on the fundamentals of voltammetric techniques and their applications in biological studies.