Publications

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2013
Cordas, Cristina M., Americo G. Duarte, Jose J. G. Moura, and Isabel Moura. "Electrochemical behaviour of bacterial nitric oxide reductase-Evidence of low redox potential non-heme Fe-B gives new perspectives on the catalytic mechanism." Biochimica Et Biophysica Acta-Bioenergetics. 1827.3 (2013): 233-238. Abstract
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2012
Cordas, C. M., P. Raleiras, F. Auchere, I. Moura, and JJG Moura. "Comparative electrochemical study of superoxide reductases." European Biophysics Journal with Biophysics Letters. 41.2 (2012): 209-215. AbstractWebsite

Superoxide reductases are involved in relevant biological electron transfer reactions related to protection against oxidative stress caused by reactive oxygen species. The electrochemical features of metalloproteins belonging to the three different classes of enzymes were studied by potentio-dynamic techniques (cyclic and square wave voltammetry): desulfoferrodoxin from Desulfovibrio vulgaris Hildenborough, class I superoxide reductases and neelaredoxin from Desulfovibrio gigas and Treponema pallidum, namely class II and III superoxide reductases, respectively. In addition, a small protein, designated desulforedoxin from D. gigas, which has high homology with the N-terminal domain of class I superoxide reductases, was also investigated. A comparison of the redox potentials and redox behavior of all the proteins is presented, and the results show that SOR center II is thermodynamically more stable than similar centers in different proteins, which may be related to an intramolecular electron transfer function.

2011
Folgosa, F., C. M. Cordas, J. A. Santos, AS Pereira, JJG Moura, P. Tavares, and I. Moura. "New spectroscopic and electrochemical insights on a class I superoxide reductase: evidence for an intramolecular electron-transfer pathway." Biochemical Journal. 438 (2011): 485-494. AbstractWebsite

SORs (superoxide reductases) are enzymes involved in bacterial resistance to reactive oxygen species, catalysing the reduction of superoxide anions to hydrogen peroxide. So far three structural classes have been identified. Class I enzymes have two ironcentre-containing domains. Most studies have focused on the catalytic iron site (centre II), yet the role of centre I is poorly understood. The possible roles of this iron site were approached by an integrated study using both classical and fast kinetic measurements, as well as direct electrochemistry. A new heterometallic form of the protein with a zinc-substituted centre I, maintaining the iron active-site centre II, was obtained, resulting in a stable derivative useful for comparison with the native all-iron from. Second-order rate constants for the electron transfer between reduced rubredoxin and the different SOR forms were determined to be 2.8 x 10(7) M(-1) . s(-1) and 1.3 x 10(6) M(-1) . s(-1) for SOR(Fe(IIII)-Fe(II)) and for SOR(Fe(IIII)-Fe(III)) forms respectively, and 3.2 x 10(6) M(-1) s(-1) for the SOR(Zn(II)-Fe(III)) form. The results obtained seem to indicate that centre I transfers electrons from the putative physiological donor rubredoxin to the catalytic active iron site (intramolecular process). In addition, electrochemical results show that conformational changes are associated with the redox state of centre I, which may enable a faster catalytic response towards superoxide anion. The apparent rate constants calculated for the SOR-mediated electron transfer also support this observation.

Cordas, C. M., J. Wilton, T. Cardoso, F. Folgosa, AS Pereira, and P. Tavares. "Electrochemical behaviour of Dps-a mini-ferritin." European Biophysics Journal with Biophysics Letters. 40 (2011): 181. AbstractWebsite
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2009
Cordas, C. M., N. M. T. Lourenco, P. Vidinha, CAM Afonso, S. Barreiros, L. P. Fonseca, and J. M. S. Cabral. "New conducting biomaterial based on Ion Jelly (R) technology for development of a new generation of biosensors." New Biotechnology. 25 (2009): S138-S139. AbstractWebsite
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2008
Cordas, C. M., I. Moura, and JJG Moura. "Direct electrochemical study of the multiple redox centers of hydrogenase from Desulfovibrio gigas." Bioelectrochemistry. 74.1 (2008): 83-89. AbstractWebsite

Direct electrochemical response was first time observed for the redox centers of Desulfovibrio gigas [NiFe]-Hase, in non-turnover conditions, by cyclic voltammetry, in solution at glassy carbon electrode. The activation of the enzyme was achieved by reduction with H(2) and by electrochemical control and electrocatalytic activity was observed. The inactivation of the [NiFe]-Hase was also attained through potential control. All electrochemical data was obtained in the absence of enzyme inhibitors. The results are discussed in the context of the proposed mechanism currently accepted for activation/inactivation of [NiFe]-Hases. (C) 2008 Elsevier B.V. All rights reserved.

Cordas, C. M., L. T. Guerra, C. Xavier, and JJG Moura. "Electroactive biofilms of sulphate reducing bacteria." Electrochimica Acta. 54.1 (2008): 29-34. AbstractWebsite

Biofilms formed from a pure strain of Desulfovibrio desulfuricans 27774 on stainless steel and graphite polarised surfaces were studied. The polarisation conditions applied were -0.4V vs. SCE for different times. A cathodic current related with the biofilms growth was observed with a maximum intensity of -270 mA m(-2) that remained stable for several days using graphite electrodes. These sulphate reducing bacteria biofilms present electrocatalytic activity towards hydrogen and oxygen reduction reactions. Electrode polarisation has a selective effect on the catalytic activity. The biofilms were also observed by scanning electronic microscopy revealing the formation of homogeneous films on the surfaces. (c) 2008 Elsevier Ltd. All rights reserved.

2006
Cordas, C. M., AS Pereira, C. E. Martins, C. G. Timoteo, I. Moura, JJG Moura, and P. Tavares. "Nitric oxide reductase: Direct electrochemistry and electrocatalytic activity." Chembiochem. 7.12 (2006): 1878-1881. AbstractWebsite
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2004
Auchere, F., R. Sikkink, C. Cordas, P. Raleiras, P. Tavares, I. Moura, and JJG Moura. "Overexpression and purification of Treponema pallidum rubredoxin; kinetic evidence for a superoxide-mediated electron transfer with the superoxide reductase neelaredoxin." Journal of Biological Inorganic Chemistry. 9.7 (2004): 839-849. Abstract
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2003
Cordas, C. M., A. S. Viana, S. Leupold, F. P. Montforts, and L. M. Abrantes. "Self-assembled monolayer of an iron(III) porphyrin disulphide derivative on gold." Electrochemistry Communications. 5.1 (2003): 36-41. AbstractWebsite

A novel iron(III) porphyrin disulphide derivative have been successfully immobilised on gold surfaces by self-assembly. The redox response of the modified electrodes was compared with the obtained for a similar iron porphyrin in solution, confirming the immobilisation of the metalloporphyrin. The gravimetric data obtained by electrochemical quartz crystal microbalance (EQCM) during adsorption allowed an estimation of the electrode coverage, providing further evidence for the formation of the porphyrin SAM. The modified electrodes were also measured by conventional and imaging ellipsometry. The electrocatalytic activity of the two modified electrodes was tested for the reduction of the molecular oxygen. (C) 2002 Elsevier Science B.V. All rights reserved.

Cordas, C. M., A. Tenreiro, and L. M. Abrantes EQCM study on the polytyramine modified electrodes for the preparation of biosensors. Eds. Y. G. Gogotsi, and I. V. Uvarova. Vol. 102. Nanostructured Materials and Coatings for Biomedical and Sensor Applications, 102., 2003. AbstractWebsite
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2002
Abrantes, L. M., C. M. Cordas, and E. Vieil. "EQCM study of polypyrrole modified electrodes doped with Keggin-type heteropolyanion for cation detection." Electrochimica Acta. 47.9 (2002): 1481-1487. AbstractWebsite

The incorporation of a Keggin-type heteropolyanion, the phosphotungstate ([PW12O40](3-)), into polypyrrole has been achieved during the electrochemical preparation of the polymer films in aqueous solution. The redox behaviour of these modified electrodes is described by using cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). The data allowed to estimate the doping level that indicates the extent of the heteropolyanion insertion. It is found that the polymer films, in aqueous solution, exhibit sensibility to cations, namely to Na+. (C) 2002 Elsevier Science Ltd. All rights reserved.