Interpretation of 1/f fluctuations in ion conducting membranes.
The main objective of this work is to resolve some uncertainties associated with the analysis of conductance fluctuations that exhibit 1/f spectral density. To this end, we derive mathematical conditions under which a discrete summation of Lorentzian functions best approximates a strictly 1/f density over a given frequency range. The intrinsic errors associated with spectral density estimates are considered and used as a constraint to determine the smallest number of optimally chosen Lorentzians required to fit a 1/f-like spectrum in a statistically acceptable manner. The results provide criteria concerning the extent to which mechanisms generating a strictly 1/f spectra may be distinguished from those generating sums of Lorentzian spectra. It is found, in particular, that 1/f-like fluctuation spectra observed in a variety of biological and model membranes may well arise from the summation of a few Lorentzian components having appropriate amplitudes and corner frequencies. Consideration of physically realistic models of ion conductive channels indicates that 1/f-like conductance fluctuation spectra could originate naturally as a direct consequence of thermodynamic constraints upon the coefficients of Lorentzian components.
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D001692:Biological Transport; D004553:Electric Conductivity; D006096:Gramicidin / Q000494:pharmacology; D007473:Ion Channels; D007477:Ions; D008051:Lipid Bilayers / Q000378:metabolism; D008433:Mathematics; D008566:Membranes / Q000502:physiology*; D008567:Membranes, Artificial
D007473:Ion Channels; D007477:Ions; D008051:Lipid Bilayers; D008567:Membranes, Artificial; D006096:Gramicidin