Evidence for nonlinear capacitance in biomembrane channel system.
The electrophysiological properties of voltage-dependent anion channels from mitochondrial membrane have been studied in a bilayer membrane system. It was observed that the probability of opening of the membrane channel depends on externally applied voltage and the plot is a bell-shaped curve symmetric around probability axis. A scheme of conformational energy levels under varying externally applied voltage was formulated. Assuming that the probability follows Boltzmann distribution, we arrive at an expression of change in energy containing a separate term identical to the energy of a capacitor. This fact indicates the possibility of existence of an added capacitance due to the channel protein. Further it was shown that the aforesaid channel capacitor could be a function of voltage leading to nonlinearity. We have offered a general method of calculating nonlinear capacitance from the experimental data on opening probability of a membrane channel. In case of voltage-dependent anion channel the voltage dependence of the capacitor has a power 0.786. The results have been interpreted in view of the structural organization of the channel protein in the membrane. Our hypothesis is that the phenomenon of capacitor behaviour is a general one for membrane channels.
Ghosh
S
S
Department of Biophysics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India. subho@del3.vsnl.net.in
Bera
A K
AK
Das
S
S
D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers; D008930:Mitochondria, Liver / Q000502:physiology; D008954:Models, Biological; D017711:Nonlinear Dynamics; D051381:Rats
D007473:Ion Channels; D008051:Lipid Bilayers