XII Iberian Meeting of Electrochemistry XVI Meeting of the ...

XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PB 03
Non-Usual Features of Haem Proteins at Pyrolytic G raphite
Electrodes
Patrícia M. Paes de Sousa, Sofia R. Pauleta, M. Lurdes Simões Gonçalves,
Graham W. Pettigrew, Isabel Moura, José J. G. Moura, Margarida M. Correia
dos Santos
1 Requimte, Centro de Química Fina e Biotecnologia, Departamento de Química, Faculdade de
Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
patricia.sousa@dq.fct.unl.pt
Direct electrochemistry of redox proteins has been reported in an increasing number
of cases, opening the way to thermodynamic and detailed mechanistic studies. To be
successful, proteins must directly exchange electrons with the electrode and at the same
time preserve their native properties [1]. Among the various types of electrode surfaces,
pyrolytic graphite (PG) is extensively used, often in connection with protein film
voltammetry [1]. In this useful strategy the proteins are adsorbed onto a freshly polished
PG electrode, frequently just by painting the surface with a couple of micro litres of a
concentrated protein sample.
In this work, we show that the interaction of haem containing proteins with pyrolytic
graphite electrodes induces altered forms of the proteins, which have a redox potential
300 mV lower than the potential observed when analysed at other electrode surfaces
[2,3]. Moreover, these altered forms present (electro)catalytic activity towards hydrogen
peroxide. This effect had been previously proposed for small Met-His c-type
cytochromes [4,5], but we demonstrate that this phenomenon is independent of the axial
coordination of the haem, and is also observed for a multihaem enzyme.
Therefore, the interpretation of the electrochemical signals obtained for haem
containing proteins at this type of electrodes should be carefully done in order to avoid a
misinterpretation of the results, especially when studying enzymes, in which the altered
forms may present catalytic activity towards the same substrate.
References
[1] Léger, C.; Bertrand, P. Chem. Rev., 2008, 108, 2379.
[2] Correia dos Santos, M. M.; Paes de Sousa, P. M.; Simões Gonçalves, M. L.; Krippahl, L.;
Moura, J. J.G.; Lojou, É.; Bianco, P. J. Electroanal. Chem., 2003, 541, 153.
[3] Santos, M.; Correia dos Santos, M. M.; Simões Gonçalves, M. L.; Costa, C.; Romão, J. C.;
Moura, J. J. G. J. Inorg. Biochem., 2006, 100, 2009.
[4] Ye, T.; Kaur, R.; Senguen, F. T.; Michel, L. V.; Bren, K. L.; Elliott, S. J. J. Am. Chem. Soc.,
2008, 130, 6682.
[5] De Biase, P. M.; Paggi, D. A.; Doctorovich, F.; Hildebrandt, P.; Estrin, D. A.; Murgida, D. H.;
Marti, M. A. J. Am. Chem. Soc., 2009, 131, 16248.
September, 811, 2010. ISEL - Lisbon 69