Imidazopyrazine Luciferins and Photoproteins

The imidazopyrazine substructure occurs in luciferins from a wide range of organisms living in the sea and in ostracod crustaceans, e.g. Cypridina. The chemistry of the luminescent effect in these systems involves reaction with oxygen to form a stable cyclic dioxetanone, similar to the hrefly luciferin as indicated in (3.108). 

Decarboxylation of this intermediate on reaction with a trigger prodnces the activated oxylnciferin intermediate, which emits light on retnming to the ground state. 

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