Investigation of the electrochemical behavior of L-cysteine in acidic media

Author(s)

Dourado, Andre H. B. ; Queiroz, Rodrigo ; Temperini, Marcia L. A. ; Sumodjo, Paulo T. A.

• Document type: Journal article
• Source: JOURNAL OF ELECTROANALYTICAL CHEMISTRY; v. 765, p. 5-pg., 2016-03-15.

Abstract

Cysteine is an important organic molecule in electrochemistry. It can be used as an electrode modifier and is responsible for the adsorption of many proteins. Although it is a well-studied molecule, cysteine's behavior and mechanism of oxidation remain unclear in the literature. The current study is focused on investigating the electrochemical behavior of this molecule in acidic media on a Pt electrode using electrochemical techniques and Raman spectroscopy. The adsorption process appears to be similar to the one proposed in the literature (i.e. a monoelectronic oxidation). The adsorbed species appear to strongly interact with one another, and therefore, this adsorption is more suitably described by a Temkin model. The Raman spectra indicate that the adsorption is most likely due to the thiol group on the side chain of the amino acid. In addition, the carboxyl group interacts more with the electrode than the amino group. The oxidation of these adsorbed species is achieved by 5 electrons, and supports the formation of the previously proposed species. Other experiments suggest that the adsorption does not occur in a single step. Using voltammetry and pseudocapacitance adsorption model interpretations, a monoelectronic rate-limiting step was detected, which indicates the existence of a more complex mechanism for the oxidation of cysteine on platinum. (C) 2015 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 13/25592-8 - Study of L-cysteine and L-cystine adsorption on platinum electrodes
• Grantee: André Henrique Baraldi Dourado
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)