Electrostatic potential distribution positively charged membranes

The electric properties of biological membranes and proteins depend on the potential distribution and the electrostatic interaction energy of their charges (see e.g.. Refs [1 ]). The potential distribution J/(r) at position r around fixed point charges with a distribution p(r) in a uniform medium of relative permittivity is described by the Poisson equation,... 

The porin monomers associate to form trimeric channels as is shown in Fig. 8-20B. They all have a central water-filled, elliptical channel that is constricted in the center to an "eye" -0.8 x 1.1 nm in size. In this restriction zone the channel is lined with polar residues that provide the substrate discrimination and gating. For example, in OmpF and FhoE there are many positively and negatively charged side chains that form the edge of the eye (Fig. 8-20C). The electrostatic potential difference across the outer membrane is small, but apparently determines whether the porins are in an open or a closed state. The voltage difference has opposite effects on OmpF and FhoE, apparently as a result of the differing distribution of charged... 

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