NOISE PERFORMANCE PATCH VOLTAGE CLAMP BILAYER VOLTAGE CLAMP

RfRf VOVO ReRe e - + CpCp V m Op Amp

Equivalent circuit analysis

Over bandwidths (B) important to patch clamping (<100 kHz - 1 MHz,i.e. < 1/2πт e ), we approximate S ep 2

For pipette resistance 2 MΩ and a patch capacitance of 300 fF, 1/2πт e = 265 kHz and “R e -C p ” noise in a 10 kHz bandwidth (8 pole Bessel filter) is nearly 0.3 pA rms On the other hand for a 10 MΩ and Cp = 10 fF, 1/2πт e = 1.6 MHz and R e -C p noise in a 10 kHz bandwidth is < 20 fA rms

Bilayer Analysis for Andy Hibbs C p is the capacitance of the bilayer R e is the access resistance (R access ), to the bilayer = convergence resistance plus small contribution from the bath and electrodes e e is the noise (in amps rms) of R e. F or a 200 μm diameter bilayer R access = 5 kΩ C p = 314 pF. т e =1.6 μs. Bandwidth of 10 kHz (8 pole Bessel filter) give rms noise = 25 pA. Noise improves as bilayer becomes smaller R access varies linearly with radius but Capacitance varies as a 2

100 μm diameter bilayer R access = 10 kΩ bilayer capacitance ~78 pF. Noise in a 10 kHz bandwidth is 8.8 pA rms. 10 μm diameter bilayer R access ↓ 100 kΩ, but capacitance ↓ 0.8 pF. Noise in a 10 kHz bandwidth is then 0.29 pA rms

Conclusion Wideband Low Noise Recording is best done with Patch Pipette Unless one can make a stable gigasealed bilayer in a 1 µm aperture