Nanodomain

In molecular biology, a nanodomain, in reference to calcium signaling, is where highly localized Ca signals associated with a single (or very few at most) ion channel(s) that extend over a few tens of nm from the channel pore. Larger signalling distances from the pore (>100 nm) mediated by a larger number of channels, are referred to as microdomains. Nanodomains are related to, but not the same as coupling distance, which explicitly refers to the distance between the calcium-binding proteins (or "sensors") that are located within a few nanometers of an open calcium channel. The coupling distance is particularly important in the temporality of pre-synaptic signalling and if Ca influx is seen in a nanodomain then one would also expect to see tighter coupling distances in order to expose the calcium sensor to high enough concentrations of Ca to cause vesicular exocytosis of neurotransmitters to occur.