D-Luciferin 6′-methyl ether (also known as 6′-Methoxyluciferin or compound 19a) is a highly effective inhibitor of luciferase obtained from the North American firefly Photinus pyralis (referred to as PpyLuc). It exhibits an IC50 value of 0.1 μM. This compound, which is an analog of D-luciferin, interacts non-specifically with the ATP and luciferin binding sites within the active site of PpyLuc.
CycLuc2 is a cyclic alkylaminoluciferin substrate for firefly luciferase. CycLuc2 emits 4.7-fold more light than aminoluciferin, and 2.6-fold more light than D-luciferin.