1 Stock number stamps contain movable bands with the numbers 0 - 9. 2  Choose between a sturdy metal core frame or sleek, economical plastic frame number stamp.
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 three main groups of ion channels are 1) the voltage-gated channels such as the sodium and potassium channels of the nerve axons and nerve terminals, 2) the extracellular ligand-activated channels which includes channels such as GABA and glycine receptor channels, most of which are regulated by ligands that are neurotransmitters.