research @ NanoBioLab
Electron transport proteins
Electron Transfer (ET) is a key reaction mechanism by which biomolecules and related redox co-factors, are involved in fundamental biological phenomena such as respiration, photosynthesis, various catalytic reactions, exchange electrons. Redox biomolecules perform ET very effectively thanks to billion-year natural evolution. Understanding ET in details is important both from a fundamental and applied standpoint. In our research we face biomolecular ET at the level of single molecule with the aim of shedding light on the physico-chemical parameters ruling its efficiency while unraveling the physical mechanisms by which electrons are exchanged between redox proteins and cofactors. Besides gaining knowledge on the role of redox moieties, protein milieu and water-based environment conductivity, our research regards single molecule ET also as an interesting setting for implementing single molecule bioelectronic devices.
Our research activity takes advantage of both direct electrochemical investigations and the technique of scanning tunneling microscopy with potentiostatic control of tip and substrate (ECSTM). Whereas direct electrochemistry measurements enable a ready investigation of mono and sub-monolayers, ECSTM enables the study of redox reactions at an electrode surface at the level of the single molecule. By ECSTM we have demonstrated substrate potential dependent behavior of single redox proteins on gold [1] (e.g. Azurin, Cyt C); we have elucidated the role of the Cu redox site and the mechanism involved in electron transport through that protein as being coherent two-step ET with partial molecular relaxation [2]; we have demonstrated single protein transistor functionality [3]. More recently, the behaviour of redox reactions involving 2e-/2H+ exchange have been elucidated on Q/HQ couple along with pH dependence of its single molecule redox behavior [4].
Key references
1. Orientation-Dependent Kinetics of Heterogeneous Electron Transfer for Cytochrome c Immobilized on Gold: Electrochemical Determination and Theoretical Prediction
C.A. Bortolotti, M. Borsari, M. Sola, R. Chertkova, D. Dolgikh, A. Kotlyar, and P. Facci
J. Phys. Chem. C, 111, 12100 (2007).
2. Unravelling single metalloprotein electron transfer by scanning probe techniques
A. Alessandrini, S. Corni, and P. Facci
J. Phys. Chem. Chem. Phys., 8, 4383 (2006).
3. Single-metalloprotein wet biotransistor
A. Alessandrini, M. Salerno, S. Frabboni, and P. Facci
Appl. Phys. Lett., 86, 133902 (2005).
4. An electrochemical scanning tunneling microscopy study of 2-(6-mercaptoalkyl)hydroquinone molecules on Au(111)
P. Petrangolini, A. Alessandrini, L. Berti, and P. Facci
J. Am. Chem. Soc., 132, 7445 (2010).
Two-step ET mechanism in ECSTM of Q/HQ couple