The Estimation of Rapid Rate Constants from Current-Amplitude Frequency Distributions of Single-Channel Recordings |
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Authors: | PJ White MS Ridout |
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Institution: | (1) Department of Cell Physiology, Horticulture Research International, Wellesbourne, Warwick CV35 9EF, UK, GB;(2) Department of Biometrics, Horticulture Research International, East Malling, West Malling, Kent ME19 6BJ, UK, GB |
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Abstract: | A method is described for estimating rapid rate constants from the distributions of current amplitude observed in single-channel
electrical recordings. It has the advantages over previous, similar approaches that it can accommodate both multistate kinetic
models and adjustable filtering of the data using an 8-pole Bessel filter. The method is conceptually straightforward: the
observed distributions of current amplitude are compared with theoretical distributions derived by combining several simplifying
assumptions about the underlying stochastic process with a model of the filter and electrical noise. Parameters are estimated
by approximate maximum likelihood. The method was used successfully to estimate rate constants for both a simple two-state
kinetic model (the transitions between open and closed states during the rapid gating of an outward-rectifying K+-selective channel in the plasma membrane of Acetabularia) and a complex multistate kinetic model (the blockade of the maxi cation channel in the plasma membrane of rye roots by verapamil).
For the two-state model, parameters were estimated well, provided that they were not too fast or too slow in relation to the
sampling rate. In the three-state model the precision of estimates depended in a complex way on the values of all rate parameters
in the model.
Received: 4 October 1996/Revised: 2 September 1997 |
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Keywords: | :Acetabularia— Blockade — Channel kinetics — Gating — K+ channel — Maxi cation channel — Rye (Secale cereale L ) — Verapamil |
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