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

Dourado, André H. B.; Queiroz, Rodrigo; Temperini, Márcia L. A.; Sumodjo, Paulo Teng An

doi:10.1016/j.jelechem.2015.09.004

Cited by 10 publications

(12 citation statements)

References 22 publications

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“…The DFT calculations made it possible to investigate the stability of those proposed molecules and to predict their spectra, corroborating the mechanistic suggestion. Some of the oxidized species that are not adsorbed (sulfinic acid) were observed at potentials more positives than 0.70 V (vs. Ag|AgCl|KCl sat ), as suggested in a previous publication (Dourado et al 2016) that proposed that the oxidative desorption took place in this region. The oxidation by the chemical reaction with the surface oxides (Koryta and Pradac 1968a, Pradac and Koryta 1968) would also explain the oxidation, but the mechanism should generate more oxidized species, being necessary to reduce the oxide back to Pt.…”

Section: Oxidationsupporting

confidence: 59%

“…Some studies suggested that the oxidation mechanisms of L-Met and L-Cys on different electrodes are very close (Enache and Oliveira-Brett 2011c, ) since the adsorption of L-Met is believed to be followed by the break of the S-CH 3 bond, generating a thiyl radical -the same observed with thiols -that adsorbs by the oxidation and break of the S-H bond. Because of this, L-Cys is a very interesting molecule to study, demonstrated by the larger amount of studies in the literature (Dourado et al 2016, Enache and Oliveira-Brett 2011c, Feliciano-Ramos et al 2010, Pradac and Koryta 1968, Samec et al 1975.…”

Section: Oxidationmentioning

confidence: 99%

“…The literature about electrochemical dessorption of thiols (Widrig et al 1991 does not present much information on the mechanism since currently only the regeneration of the S-S bond is considered, and if the oxidation is analyzed, not many advances apart from a multielectronic mechanism were related. A recent work (Dourado et al 2016) showed that not just the oxidation of the adsorbed species is rate limited by a desorption step, but also this desorption is observed at less positive potentials than the oxidation of the Pt substrate, indicating that the mechanism proposed by Koryta (1968, Koryta andPardac 1968a) can be questioned. Other kinds of electrodes were also used in recent years, such as Pd (Feliciano-Ramos et al 2010), Ag (Hager and Brolo 2003, Santos et al 2007 and diamond (Enache and OliveiraBrett 2011c).…”

Section: Oxidationmentioning

confidence: 99%

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The long and successful journey of electrochemically active amino acids. From fundamental adsorption studies to potential surface engineering tools.

Dourado

Pastrián

Torresi

2018

An. Acad. Bras. Ciênc.

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Proteins have been the subject of electrochemical studies. It is possible to apply electrochemical techniques to obtain information about their structure due to the presence of five electroactive amino acids that can be oriented to the outside of the peptidic chain. These amino acids are L-and L-Cysteine (L-Cys); their electrochemical behavior being subject of extensive research, but it is still controversial. No spectroscopic investigations have been reported on L-Trp, and due to the short life time of the intermediates, ex situ techniques cannot be employed, leading to a never-ending discussion about possible intermediates. In the L-Tyr and L-His cases, spectroelectrochemical studies were performed and different intermediates were observed, suggesting that some intermediates may be observed under specific conditions, as proposed for L-Cys. This amino acid is the most interesting among the electroactive ones because of the presence of a thiol moiety at its side chain, leading to a wide range of oxidation states. It can adsorb onto surfaces of different crystallographic orientation in stereoselective conformation, modifying the surface for different applications.as a surface engineering tool since it plays the role of as an anchor for the growing of nanocrystals inside proteic templates.

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Section: Oxidationsupporting

confidence: 59%

Section: Oxidationmentioning

confidence: 99%

Section: Oxidationmentioning

confidence: 99%

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The long and successful journey of electrochemically active amino acids. From fundamental adsorption studies to potential surface engineering tools.

Dourado

Pastrián

Torresi

2018

An. Acad. Bras. Ciênc.

Self Cite

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“…However, new insights and species, such as sulfonic acid, sulfoxide and adsorbed sulfoxide, highlight the pH dependence of the mechanism. The same work also confirmed that the adsorbed conformation of L–Cys on Pt is different than the one expected for other metals ,. Pt exhibits a higher affinity to carboxyl group, which seems to influence the mechanism of oxidation of this molecule on Pt as well …”

Section: Introductionsupporting

confidence: 56%

“…Considering a L–Cys (ads) monolayer, 3.0 nm can be too thick, what suggests the formation of multilayer. For a better comprehension, a surface roughness was considered, as in Dourado et al . and Samec et al .…”

Section: Resultsmentioning

confidence: 99%

Kinetics, Assembling, and Conformation Control of L‐Cysteine Adsorption on Pt Investigated by in situ FTIR Spectroscopy and QCM‐D

et al. 2018

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A quartz crystal microbalance method with dissipation (QCM-D) and attenuated total reflection Fourier-transform infrared (ATR-FTIRS) spectroscopy were used to study the adsorption of L-cysteine (L-Cys) on Pt. Through QCM-D, it was possible to verify that the viscoelastic properties of the adsorbed species play an important role in the adsorption, rendering Sauerbrey's equation inapplicable. The modelling of QCM-D data exposed two different processes for the adsorption reaction. The first one had an activation time and is fast, whereas the second is slow. These processes were also resolved by ATR-FTIRS and identified to be water and anion adsorption preceded by L-Cys adsorption. Both techniques reveal that the degree of surface coverage is pH dependent. Spectroscopic data indicate that the conformation of L-Cys changes with pH and that the structures do not fully agree with those proposed in literature for other metallic surfaces. The assembling of the adsorbed monolayer appeared to be very fast, and it was not possible to determine or quantify this kinetics. The conformation is also controlled by applied potential, and the anion adsorption and interfacial water depends on the conformation of the adsorbed molecules.

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Mechanism of Electrochemical L‐Cysteine Oxidation on Pt

2019

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The electrochemical behavior of L-cysteine on Pt electrodes was studied by in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIRS) and online differential electrochemical mass spectrometry (DEMS). The ATR-FTIRS measurements allowed verification of the electrochemical mechanism of the oxidation of this molecule. The time resolution of the technique was crucial for relating each functional group to the faradaic current, suggesting electrochemical and chemical steps for the S atom oxidation. The DEMS experiments do not allow verification of desorbed intermediates due to their high solvation. Nevertheless, this technique was crucial for detecting side reactions, such as the decarboxylation of the adsorbed intermediates observed mainly under highly acidic conditions, in contrast to the conventional Kolbe mechanism.

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

Cited by 10 publications

References 22 publications

The long and successful journey of electrochemically active amino acids. From fundamental adsorption studies to potential surface engineering tools.

The long and successful journey of electrochemically active amino acids. From fundamental adsorption studies to potential surface engineering tools.

Kinetics, Assembling, and Conformation Control of L‐Cysteine Adsorption on Pt Investigated by in situ FTIR Spectroscopy and QCM‐D

Mechanism of Electrochemical L‐Cysteine Oxidation on Pt

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