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Single-metalloprotein wet biotransistor
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View: Figures


Image of FIG. 1.
FIG. 1.

(A) Schematic representation of the electrochemically gated, single protein transistor. Electrically biased tip and substrate are fed by a bipotentiostat that controls their potential in an electrochemical cell. Azurin is chemisorbed on the insulated tip by a naturally occurring disulfide bridge; the spot in the lower part of the globule represents the location of the Cu ion. (B) TEM image of azurin coated gold tip; . (C) ECSTM image of azurin on Au(111) . (D) Cyclic valtammetry of azurin coated gold tip.

Image of FIG. 2.
FIG. 2.

(A) Six repeated tip potential sweeps (initial conditions: , tunneling , tip ) showing tunneling current peaks compared to the behavior of a bare insulated gold stylus (hollow circles) and to that of a Zn azurin-coated tip (filled triangles). Inset: eight repeated sweeps (initial conditions: , , tip ) on another sample showing also oxidation wave (outlined by arrow). (B) ECSTM image of a mixture of Cu and Zn azurin on Au(111) imaged at , , ; image size . (C) Mechanism of two-step electron transport via redox center. The first electron transfer (I) is from substrate to a protein vacant redox level in the density of oxidized states (DOxS); while this level relaxes vibrationally and before it drops below tip Fermi level, a second electron transfer event (II) takes place that brings an electron from the molecule to the tip. Fermi levels of substrate and tip are separated by , whereas redox levels are apart ( value derived by best fitting two-step model to experimental data). Numerical values correspond to the measurements shown in (A).

Image of FIG. 3.
FIG. 3.

Bias voltage dependence of the trans-characteristics. Curves (displayed with an offset of each to avoid overlap) were obtained at different bias voltage stepped by in the range , starting from the lowest curve (see arrow), using a sweep rate of . Inset: characteristics measured from the set of curves at (“off res”) and at each current maximum position (“in res”), showing a different tunneling barrier transparency.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Single-metalloprotein wet biotransistor