NCAFM2023 Programme Booklet

Monday 1720-1740

USING SINGLE-ELECTRON FORCE MICROSCOPY TO DETERMINE ENZYMATIC ELECTRON TRANSFER DYNAMICS

Catherine Boisvert 1 , José Bustamante 1 , Logan Fairgrieve-Park 1 , Ons Hmam 2 , Antonella Badia 2 , Peter Grütter 1

1 Department of Physics, McGill University, 3600 rue University, Montréal, Québec H3A 2T8, Canada 2 Department of Chemistry, Université de Montréal, 1375 avenue Thérèse-Lavoie-Roux, Montréal, Québec H2V 0B3, Canada Email : catherine.boisvert4@mail.mcgill.ca Enzymes have been of great interest due to their fascinating, yet complex redox properties and their use in green energy production. Specifically, metalloenzymes have great potential in clean H2 utilization and CO2 reduction by means of carbon scrubbing [1]. It is thus imperative to understand the structural properties of metalloenzymes and their internal redox and electron transfer rates, since these quantum properties underpin catalytic activity. To do so, we can use single-electron electrostatic force microscopy (e-EFM), where an oscillating conductive cantilever induces electron tunneling events in structures with discrete electronic states. In this AFM technique, we monitor the frequency shift and dissipation of the cantilever to determine quantum dot density of states, measure single-electron tunneling rates, and observe transitions between quantized nuclear vibronic states at the single-molecule level [2-4]. With these recent quantum imaging developments in AFM, our low-temperature atomic force microscope (LT-AFM) can be used to image single-electron transfers in single- and multi-redox site metalloenzymes. These single-electron transfer events occur between a gold electrode and the metalloenzyme, and the direct electrical connectivity of the system is enabled by using a self-assembled monolayer attached to a suitable-sized functionalized gold cluster that can be coupled to the metal center of the protein pocket [5]. Details surrounding this sample preparation and the various characterization steps will be presented. Moreover, e-EFM on metalloenzymes can be used to determine Franck-Condon factors associated with redox transitions, measure energetic offsets, and map electronic coupling between redox centers [4,6]. This will therefore allow us to understand and engineer the catalytic activity of metalloenzymes in an effort to develop inorganic biomimetic analogues as sustainable energy solutions [1].

Fig. Frequency shift as a function of bias spectroscopy (Ferrocene molecule). Vibronic energy and tunnelling rate can be extracted from the derivative of the frequency shift response [2].

References [1] B.-E. Jugder, J. Welch, K.-F. Aguey-Zinsou, C. P. Marquis, RSC Advances, 2013, 3 , 8142-2013. [2] A. Roy-Gobeil, Y. Miyahara, K. H. Bevan, P. Grütter, Nano Lett, 2019, 19 , 6104-6108. [3] L. Cockins, Y. Miyahara, S. D. Bennett, A. A. Clerk, S. Studenikin, P. Poole, et al., Proc Natl Acad Sci USA, 2010, 107 , 9496-950. [4] K. H. Bevan, A. Roy-Gobeil, Y. Miyahara, P. Grütter, J Chem Phys, 2018, 149 , 104109. [5] J. M. Abad, M. Gass, A. Bleloch, D.J. Schiffrin, J. Am. Chem. Soc, 2009, 131 , 10229–10236. [6] J. Blumberger, Chem Rev, 2015, 115 , 11191-238.

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