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. Author manuscript; available in PMC: 2021 Apr 1.
Published in final edited form as: J Am Chem Soc. 2020 Mar 23;142(13):6432–6438. doi: 10.1021/jacs.0c01805

Figure 1:

Figure 1:

Measuring protein conductance under potential control. (a) Illustrating the surface potentials generated when two metals with different work functions are connected to a reference electrode. The molecule, M, is assumed to sit in the middle of of the potential gradient generated by the difference in surface potentials of the two metals. (b) STM measurement of protein conductance illustrating streptavidin protein (green) bound to electrodes by thiolated biotin molecules (red). The substrate is held at a potential Vr with respect to a salt-bridged reference electrode. For conductance measurements, a low (10mM) KCl concentration is used in the bridge, leading to a 360 mV difference with respect to the NHE. (c) Typical current-voltage (IV) curve for a single streptavidin molecule. Black data points are scanning up, red data points are scanning down. The green line is a linear fit yielding the conductance for this particular contact geometry. (d) Conductance distributions derived from many such IV curves for biotin/streptavidin on Au, Pd and Pt electrodes as marked. The dashed lines indicate the positions of peaks II and III in the distribution for the case of Au electrodes.