Figure 4.

Stochastic sensing on the modular ion channel chip. (A) Time-dependent transportation of analyte from the sample cell to the sensor element in the chip. Single pores of wild-type αHL were incorporated into the sandwiched bilayer as the sensor element. 40 μM βCD was added to the chip from the sample cell (Fig.1B). Agarose layers contained 1 M KCl, 10 mM Tris, and 1.5% ultra-low gelling temperature agarose (pH7.2). Left panel shows current traces recorded after 5, 30 and 40 minutes after addition of βCD. Right panel is the time-dependent block occurrence with βCD; (B) Detection of second messenger IP3 on chips. Mutant αHL, M113R/T145R, was used as the single pore sensor element. Agarose layers contained the same components as in A, with the addition of 0.5 mM MgCl₂. All traces were recorded at +30 mV. Trace (I), control test without analyte; Trace (II), 500 nM IP3 was loaded into the sample cell of the same chip; Trace (III) 0.3 mM ATP was added in a separate control test; and Trace (IV), mixture of 500 nM IP₃ and 0.3 mM ATP was loaded in the chip. All traces were captured after the block occurrence reached the maximum.