Size limit of molecules permeating the junctional membrane channels

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Science  21 Jan 1977:
Vol. 195, Issue 4275, pp. 294-296
DOI: 10.1126/science.831276


The permeability of the cell-to-cell membrane channels in salivary gland cell junction (Chironomus thummi) was probed with fluorescent-labeled amino acids and synthetic or natural peptides. Molecules up to 1200 daltons pass through the channels with velocities depending on molecular size. Molecules of 1900 daltons or greater do not pass. This passage failure seems to reflect the normal size limit for junctional channel permeation; the channels continue to be permeated by the molecules up to 1200 daltons when these are mixed with the nonpermeant molecules. From this size limit a channel diameter of 10 to 14 angstroms is estimated.