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Interference of shot noise of open-channel current with analysis of fast gating: patchers do not (Yet) have to care.

Schroeder, Indra and Hansen, Ulf-Peter (2009):
Interference of shot noise of open-channel current with analysis of fast gating: patchers do not (Yet) have to care.
In: The Journal of Membrane Biology, 229 (3), pp. 153-63, ISSN 1432-1424,
[Article]

Abstract

Microsecond gating of ion channels can be evaluated by fitting beta distributions to amplitude histograms of measured time series. The shape of these histograms is determined not only by the rate constants of the gating process (in relation to the filter frequency) but also by baseline noise and shot noise, resulting from the stochastic nature of ion flow. Under normal temporal resolution, the small shot noise can be ignored. This simplification may no longer be legitimate when rate constants reach the range above 1 mus(-1). Here, the influence of shot noise is studied by means of simulated time series for several values of single-channel current of the fully open state and baseline noise. Under realistic optimal conditions (16 pA current, 1 pA noise, 50 kHz bandwidth), ignoring the shot noise leads to an underestimation of the rate constants above 1 mus(-1) by a factor of about 2.5. However, in that range, the scatter of the evaluated rate constants is at least of the same magnitude, obscuring the systematic error. The incorporation of shot noise into the analysis will become more important when amplifiers with significantly reduced noise become available.

Item Type: Article
Erschienen: 2009
Creators: Schroeder, Indra and Hansen, Ulf-Peter
Title: Interference of shot noise of open-channel current with analysis of fast gating: patchers do not (Yet) have to care.
Language: English
Abstract:

Microsecond gating of ion channels can be evaluated by fitting beta distributions to amplitude histograms of measured time series. The shape of these histograms is determined not only by the rate constants of the gating process (in relation to the filter frequency) but also by baseline noise and shot noise, resulting from the stochastic nature of ion flow. Under normal temporal resolution, the small shot noise can be ignored. This simplification may no longer be legitimate when rate constants reach the range above 1 mus(-1). Here, the influence of shot noise is studied by means of simulated time series for several values of single-channel current of the fully open state and baseline noise. Under realistic optimal conditions (16 pA current, 1 pA noise, 50 kHz bandwidth), ignoring the shot noise leads to an underestimation of the rate constants above 1 mus(-1) by a factor of about 2.5. However, in that range, the scatter of the evaluated rate constants is at least of the same magnitude, obscuring the systematic error. The incorporation of shot noise into the analysis will become more important when amplifiers with significantly reduced noise become available.

Journal or Publication Title: The Journal of Membrane Biology
Volume: 229
Number: 3
Divisions: 10 Department of Biology
Date Deposited: 25 Oct 2012 11:52
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