Fast impedance spectroscopy: General aspects and performance study for single ion channel measurements

In the present work, we propose a novel technical approach in time domain i mpedance spectroscopy enabling both enhanced time and current resolution by an improved data analysis and hardware setup. We introduce nonstationary t ime-to-frequency conversion methods such as short-time Fourier transform an d wavelet transform resulting in an improved time resolution. The combinati on of a time domain impedance spectrometer with a patch-clamp amplifier ena bles the resolution of gigaohm impedance at low perturbation signal amplitu des. A fast impedance spectroscopy (FIS) setup is presented which is optimi zed for biophysical application of single ion channel measurements in suppo rted biomembranes. The applicability and performance of the technique is fi rst evaluated by simulations. It is then verified by measurements on model circuits which exhibit the characteristic key properties of single ion chan nel measurements. Here, FIS improves the time resolution by about three ord ers of magnitude down to milliseconds. The general aspects derived in this work are also valid in other fields, where the spectral information of a pe rturbation applied on a system and its response is analyzed, e.g., mechanic al impedance spectroscopy and microrheology. (C) 2000 American Institute of Physics. [S0034-6748(00)03905-8].