Radio frequency rectification on membrane bound pores

Abstract

Probing the interaction of biological systems with radio frequencies holdsgreat promise for research and drug screening applications. While a commonassumption is that biological systems do not operate at radio frequencies, we findthat currents due to ion transport through channels and pores in cell membranesare in the pA to nA range. These values translate via the average current⟨I⟩ = ⟨n⟩e/τd = ⟨n⟩ef to frequencies in the range of 1 MHz–1 GHz, where⟨n⟩ is the average number of ions transported andτd is the dwell time of the ions in the channel. It is thus desirable to have circuitry availablewhich facilitates radio frequency spectroscopy of ion transport. This will yield real-time invitro information on ion channel operation. Here we present measurements on the localinteraction of a radio frequency signal with single ion channels and pores. We find radiofrequency rectification and pumping on the channels and pores embedded in suspendedbilipid membranes, recorded in direct current measurements. This electromagneticmodulation can be used to probe the dynamics of ion channel conformational changes.