Redox reactions of ortho-tyrosine and 3-nitro-tyrosine: A comparative study with para-tyrosine

Voltammetric Studies of 3‐Nitro‐tyrosine Electro‐oxidation at Solid Electrodes and its Interaction with DNA

“…SW voltammograms were also performed for a 200 μmol L −1 solution of p‐ Tyr, prepared in phosphate buffer (pH=7.0), at PtE, Figure 2E, and, as expected, the anodic process 1a was detected at E p1a =+0.70 V, associated with the oxidation of the phenolic group [1]. However, the oxidation potential of peak 1a of 3‐NO 2 ‐Tyr occurs at more positive values, ∼170 mV, in relation to p‐ Tyr, Figure 2E, due to the presence of the nitro group (electron‐withdrawing group) [1, 6, 36], in agreement with previous data using GCE [1], PGE [6] and SPCE [36].…”

“…Oxidative stress (OS) can occur in‐vivo , as a consequence of the suppression of the antioxidant system and/or an imbalance in the redox state, producing an excess of reactive nitrogen (RNS) and oxygen (ROS) species, which may cause irreversible oxidative damage to important biomolecules, such as proteins and nucleic acids, leading to many pathological processes [1–3]. Thus, it is extremely important to establish the chemical properties of these altered biomolecules, as well as to use them as biomarkers of OS, distinguishing the healthy from the pathological state [1–3]. 3‐nitro‐tyrosine (3‐NO 2 ‐Tyr), Scheme 1, is generated in the human body due to excess of RNS and can be found freely or in proteins.…”

“…3‐nitro‐tyrosine (3‐NO 2 ‐Tyr), Scheme 1, is generated in the human body due to excess of RNS and can be found freely or in proteins. Its physicochemical properties are quite different compared to tyrosine (Tyr), regarding, for example, solubility, phenol group pka (3‐NO 2 ‐Tyr, pka=7.1 and Tyr, pka=10), redox and spectrophotometric properties [1–6]. The presence of 3‐NO 2 ‐Tyr in the human body has been associated with numerous diseases, such as cancer, diabetes, Alzheimer's, celiac disease and various neurodegenerative diseases [1–6].…”

“…Voltammetric techniques, such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), mainly using solid electrodes, such as carbon, gold or platinum, are widely used to investigate mechanisms of redox reactions of different species [1, 7, 29–32]. Furthermore, the high sensitivity of pulse voltammetric techniques, such as DPV and SWV makes them very suitable for the development of electroanalytical methodologies [7, 29, 32–35].…”

“…Furthermore, the high sensitivity of pulse voltammetric techniques, such as DPV and SWV makes them very suitable for the development of electroanalytical methodologies [7, 29, 32–35]. The redox properties of 3‐NO 2 ‐Tyr have already been investigated at hanging mercury drop electrode (HMDE) [24], on screen printed carbon electrode (SPCE) in physiological medium, using SWV [36], at a pencil graphite electrode (PGE) using DPV [6] and more recently at glassy carbon electrode (GCE) over a wide pH range, using CV, DPV and SWV [1]. To our knowledge, however, no study of the anodic behaviour of 3‐NO 2 ‐Tyr at metallic electrodes, platinum and gold, has been mentioned in the literature up to the date of our study.…”