• Louis J. DeFelice


There are two famous equations in membrane biophysics that we must understand; one is for the average current from a population of opening and closing channels, the other is for fluctuations, or noise, around the average current. If we have a population of N channels (the total number without considering status, i.e., whether or not they are open or closed). The N is therefore a constant for all practical purposes, and we do not consider that channels may enter or leave the membrane; we only require N channels to be available to be opened. The average current is
$$I = Nip$$
where i is the current through an open channel and p is the probability that the channel is open. The probability that the channel is open or the probability of a channel being open is not equivalent to the probability of opening (see Fig. 2.20 and Fig. 2.21). In the following sections, we explore a common formula for p:
$$p = \frac{1} {{1 + e^{ - {\text{a}}(V - {\text{b}})} }}$$


Boltzmann Equation Nuclear Envelope Channel Density Loaded Transporter Charged Macromolecule 
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Copyright information

© Springer Science+Business Media New York 1997

Authors and Affiliations

  • Louis J. DeFelice
    • 1
  1. 1.Vanderbilt University Medical CenterNashvilleUSA

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