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The channel has a large diameter of 0.8x1.1nm, and is non-selective for small ions. However, it has an upper exclusion size limit corresponding to molecular weights of about 600 Dalton of permeants. Because most metabolites have molecular weights lower than 600 Da and have been shown to pass through porin channels, porins are called general diffusion pores.
The average energy required to produce an ion pair is approximately 33 (or 34) electron volts. ion-selective electrode, n a potentiometric electrode that develops a potential in the presence of one ion (or class of ions), but not in the presence of a similar concentration of other ions.