Electrochemical behaviour of proteins at graphite electrodes

Brabec, Viktor; Mornstein, Vojtěch

doi:10.1016/0301-4622(80)80048-2

Cited by 147 publications

(92 citation statements)

References 10 publications

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“…The proposed mechanism for the indole with a substituent at C3 position is in Scheme 3. Since all indole derivatives (1) are substituted in C3 position, the oxidation reaction taking place at peak P 1 corresponds to the oxidation at C2 position on the pyrrole ring [14,28].…”

Section: Discussionmentioning

confidence: 99%

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Pathways of Electrochemical Oxidation of Indolic Compounds

2011

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The electrochemical behaviour of indole and a group of indole-containing compounds with a substituent at the C3 position, indol-3-acetamide (IAM), tryptamine, gramine, indole acetic acid (IAA), indole propionic acid (IPA), indole butyric acid (IBA) and tryptophan, was investigated at a glassy carbon electrode, in order to determine their oxidation pathways. Indole undergoes one irreversible pH dependent oxidation, whereas the oxidation process of indole derivatives was more complex, a two step, the oxidation at C2 position on the pyrrole ring followed by the hydroxylation at the C7 position of the benzene moiety of indoles, irreversible pH dependent oxidation.

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Section: Discussionmentioning

confidence: 99%

“…According to [14] and [28], the oxidation on C2 of the pyrrole ring corresponds to a reaction by which the tryptophan, an indole-derivative with a substituent at C3 position, is oxidized to 2-oxyindoles. The oxyindole oxidation can give several products such as 2,4-, 2,5-, 2,6-and 2,7-oxyindoles [16].…”

Section: Differential Pulse Voltammetrymentioning

confidence: 99%

Pathways of Electrochemical Oxidation of Indolic Compounds

2011

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“…We considered alternative assignments for the species, which is oxidized by the tryptophanyl radical during the 50-s phase. However, published absorbance difference spectra (30) and potentials (35) for the oxidation of amino acids do not identify any possible candidate other than tyrosine. Because our recombinant protein contains no cofactor apart from FAD (which is not involved in this reaction), we conclude that the 50-s phase in PL from A. nidulans reflects electron transfer from a tyrosine residue to the tryptophanyl radical.…”

Section: Resultsmentioning

confidence: 99%

Intraprotein electron transfer between tyrosine and tryptophan in DNA photolyase from Anacystis nidulans

Aubert

Mathis²,

Eker³

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

135

122

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Light-induced electron transfer reactions leading to the fully reduced, catalytically competent state of the f lavin adenine dinucleotide (FAD) cofactor have been studied by f lash absorption spectroscopy in DNA photolyase from Anacystis nidulans. The protein, overproduced in Escherichia coli, was devoid of the antenna cofactor, and the FAD chromophore was present in the semireduced form, FADH ⅐ , which is inactive for DNA repair. We show that after selective excitation of FADH ⅐ by a 7-ns laser f lash, fully reduced FAD (FADH ؊ ) is formed in less than 500 ns by electron abstraction from a tryptophan residue. Subsequently, a tyrosine residue is oxidized by the tryptophanyl radical with t1 ͞2 ‫؍‬ 50 s. The amino acid radicals were identified by their characteristic absorption spectra, with maxima at 520 nm for Trp ⅐ and 410 nm for TyrO ⅐ . The newly discovered electron transfer between tyrosine and tryptophan occurred for Ϸ40% of the tryptophanyl radicals, whereas 60% decayed by charge recombination with FADH ؊ (t1 ͞2 ‫؍‬ 1 ms). The tyrosyl radical can also recombine with FADH ؊ but at a much slower rate (t1 ͞2 ‫؍‬ 76 ms) than Trp ⅐ . In the presence of an external electron donor, however, TyrO ⅐ is rereduced efficiently in a bimolecular reaction that leaves FAD in the fully reduced state FADH ؊ . These results show that electron transfer from tyrosine to Trp ⅐ is an essential step in the process leading to the active form of photolyase. They provide direct evidence that electron transfer between tyrosine and tryptophan occurs in a native biological reaction.The role of amino acid radicals as intermediates in electron and hydrogen atom transfer is a topic of growing interest and research activity in enzymology (1, 2). Prominent examples include a catalytically essential tyrosyl radical in ribonucleotide reductase (3, 4), tyrosine Y Z in photosynthetic wateroxidizing enzyme (5-7), and a tryptophan that can be oxidized by a photoexcited flavin semiquinone in DNA photolyase (PL) from Escherichia coli (8-10). It has even been suggested that tryptophan and tyrosine could act as sequential redox components in long-range electron transfer in proteins (11-13). The feasibility of such an electron transfer has been demonstrated in aqueous amino acids solutions (14), in model peptides (12,15,16), and in proteins after artificial oxidation of tryptophan (11, 17), but it has never been demonstrated in a native biological reaction. DNA PLs use blue or near-UV light to repair UV-induced DNA lesions [refs. 18 and 19; either cyclobutane pyrimidine dimers or (6-4) photoproducts] in a variety of organisms, ranging from bacteria to multicellular eukaryotes (reviewed in ref. 20). This enzyme is a single polypeptide of 50-65 kDa. It contains a flavin adenine dinucleotide (FAD) as the essential catalytic cofactor and a second chromophore (either a reduced folate or a 8-OH-5-deazaflavin), which has the sole function of absorbing light and transferring excitation energy to the FAD cofactor (21). The FAD cofactor must be in the ...

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“…Figure 7 illustrates that tryptophan yields a peak-shaped voltammogram under these conditions which is similar to that observed for MSH while tyrosine yields a flat voltammogram that more closely resembles that of CLIP and 0-endorphin. Previous work has indicated nearly identical shapes for cyclic voltammograms for these two amino acids at lower scan rates [4,91. Thus, at high scan rates it is possible to distinguish between tyrosine and tryptophan and this is true of peptides that contain these amino acids as well.…”

Section: Cyclic Voltammetrymentioning

confidence: 94%

Amperometry and cyclic voltammetry of tyrosine and tryptophan‐containing oligopeptides at carbon fiber microelectrodes applied to single cell analysis

Paras

Kennedy

1997

Electroanalysis

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The amperometric and cyclic voltammetric detection of a-melanocyte stimulating hormone (MSH), 0-endorphin, and corticotropin-like intermediate lobe peptide (CLIP), all proopiocortin (POC) derived peptides secreted from melanocytes of the pituitary intermediate lobe, at carbon fiber microelectrodes was investigated. For amperometry, it was found that all of these peptides could be detected; however, fouling of the electrodes reduced the response of the electrode after successive application of the peptide in flow injection experiments. The fouling wa5 apparently due to oxidation of tyrosine in the peptides as similar results were found for tyrosine but not tryptophan. The effect of fouling could be reversed if the electrode was electrochemically treated by scanning from -1 .OV to +1.OV at 300 V/s for 2 min between application of the peptides. Using cyclic voltammtery at 800 V/s, it was possible to distinguish MSH, which had a peak shaped voltammogram, from the other POC peptides, which had relatively flat voltammetric waves at this scan rate. The scan rate dependence of the peak current for MSH revealed that the voltammetry was adsorption controlled. As a result, in a monitoring application, where voltammograms are continuously obtained with a fixed interval between them, decreasing the interval increases the temporal resolution but decreases the sensitivity for MSH. It was found that when monitoring the current in the potential range of 0.90 to 1 .OOV, the temporal response to MSH was dependent upon the potential window used for scanning. Using high scan rates and a potential window of 0 to 1.2 V, it was possible to monitor exocytosis from single melanocytes and use the voltammogram to demonstrate detection of MSH from the cells.

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Electrochemical behaviour of proteins at graphite electrodes

Cited by 147 publications

References 10 publications

Pathways of Electrochemical Oxidation of Indolic Compounds

Pathways of Electrochemical Oxidation of Indolic Compounds

Intraprotein electron transfer between tyrosine and tryptophan in DNA photolyase from Anacystis nidulans

Amperometry and cyclic voltammetry of tyrosine and tryptophan‐containing oligopeptides at carbon fiber microelectrodes applied to single cell analysis

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