ae·quor·in 
(ē-kwôrĭn, ē-kwŏr-)
(ē-kwôrĭn, ē-kwŏr-)n.
A protein secreted by certain bioluminescent jellyfish, used as a reagent in molecular biology to detect calcium concentrations inside cells.
[New Latin Aequorea, jellyfish genus (from Latin aequoreus, of the sea, from aequor, smooth surface, from aequus, smooth) + –IN.]