Voltage sensors immobilization

To demonstrate that we could immobilize a voltage sensor, we first turned to Shaker potassium channels, because (i) gating currents, which primarily reflect S4 movement, are easy to measure, and (ii) the channels have tetrameric symmetry. We used a non inactivating variant of Shaker into which we introduced the cysteine mutant A359C, located at the extracellular end of the S4 segment. After exposure to BPMTS each channel has four labelled S4 segments. 

Kiihn FJ, Greef NG 1999 Movement of voltage sensor S4 in domain 4 is tightly coupled to sodium channel fast inactivation and gating charge immobilization. J GenPhysiol 114 167—183... 

An example of a sensor utilizing these three components is illustrated in figure 1.2, which shows a schematic of a typical enzyme electrode for the detection of glucose (also see chapter 17 of this text). The bioactive surface consists of immobilized glucose oxidase (GOD) sandwiched between a polycarbonate and cellulose acetate membrane. The transducer is a platinum electrode and the electronics are those typically found in any polarograph, i.e. an electronic system to measure low currents (on the order of microamperes) at a fixed voltage bias on the platinum electrode. The action of glucose... 

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