Editing Gap junction (section)

==Properties of connexon pairs==
[[File:Validation of the dye diffusion assay performed with the flattened cochlear preparation.png|right|thumb|Light microscope images do not allow us to see connexons or innexons themselves but do let us see the fluorescing dye injected into one cell moving into neighboring cells when gap junctions are known to be present.<ref>{{cite journal |pmid=19116647 |doi=10.1371/journal.pone.0004088 |pmc=2605248 |volume=3 |issue=12 |title=Gap junction mediated intercellular metabolite transfer in the cochlea is compromised in connexin30 null mice |year=2008 |journal=PLOS ONE |at=e4088 |editor1-last=Schiffmann |editor1-first=Raphael |last1=Chang |first1=Qing |last2=Tang |first2=Wenxue |last3=Ahmad |first3=Shoeb |last4=Zhou |first4=Binfei |last5=Lin |first5=Xi |bibcode=2008PLoSO...3.4088C |doi-access=free}}</ref>]]

A connexon or innexon channel pair:
# Allows for direct electrical communication between cells, although different hemichannel subunits can impart different single channel [[Electrical resistance and conductance|conductances]], from about 30 [[Siemens (unit)|pS]] to 500 pS.
# Allows for chemical communication between cells through the transmission of small [[second messenger]]s, such as inositol triphosphate ({{chem|link=Inositol trisphosphate|IP|3}}) and calcium ({{chem|link=Ca2+|Ca|2+}}),<ref name="mbc">{{Cite book|first=Bruce |last=Alberts |title=Molecular biology of the cell |publisher=Garland Science |location=New York |year=2002 |edition=4th |isbn=978-0-8153-3218-3}}{{Page needed|date=September 2010}}</ref> although different hemichannel subunits can impart different selectivities for particular molecules.
# Generally allows transmembrane movement of molecules smaller than 485 [[Dalton (unit)|daltons]]<ref>{{cite journal |vauthors= Hu X, Dahl G |year=1999 |title=Exchange of conductance and gating properties between gap junction hemichannels |journal=FEBS Lett |volume=451 |issue=2| pages=113–117 |doi=10.1016/S0014-5793(99)00558-X |pmid=10371149 |s2cid=19289550|doi-access=free |bibcode=1999FEBSL.451..113H }}</ref> (1,100 daltons through invertebrate gap junctions<ref>{{cite journal |vauthors=Loewenstein WR |title=Permeability of membrane junctions |journal=Ann. N. Y. Acad. Sci. |volume=137 |issue=2 |pages=441–472 |date=July 1966 |pmid=5229810 |bibcode=1966NYASA.137..441L |doi=10.1111/j.1749-6632.1966.tb50175.x|s2cid=22820528 }}</ref>), although different hemichannel subunits may impart different pore sizes and different charge selectivity. Large biomolecules, including [[nucleic acid]]s and [[protein]]s, are precluded from cytoplasmic transfer between cells through gap junction hemichannel pairs.
# Ensures that molecules and current passing through the gap junction do not leak into the intercellular space.