Sub-Microsecond-Scale Dynamics in the Type-1 Ryanodine Receptor Observed with CMOS-Integrated Electrophysiology

Conventional electronics typically limit the available temporal resolution for single ion-channel measurements, making fast channel gating events (<10µs) undetectable. Our group recently developed a platform that allows high-bandwidth conductance measurements by directly interfacing a suspended membrane containing the ion-channel under study on a custom complementary-oxide-semiconductor (CMOS) preamplifier chip. A passivation layer with a 20 µm aperture is deposited on the CMOS-chip surface and a small suspended lipid bilayer is formed within the aperture. This allows us to decrease the total capacitances at the input of the amplifier to less than 3pF, enabling us to measure high conducting ion-channels at bandwidths up to 1MHz. Here we present single ion-channel conductance measurements of the skeletal muscle ryanodine receptor (RyR1) at up to 500kHz bandwidth. We observe microsecond current states which we associate with very fast channel gating events. Further analysis of the recorded data by extended beta-distribution-based analysis reveals closed-state flickering with time scales as short as 50ns. New high-speed CMOS amplifiers provide a new tool for high-bandwidth studies of ion-channel dynamics in vitro.