D-Luciferin Free acid Also known as 4,-5-Dihydro-2-(6-hydroxyl-2-benzo-thiazoyl)-4-thiazole-carboxylic acid. Used with firefly luciterase in bioluminiscence for the determination of ATP. Specifications:MF: C11H8N2O3S2 MW 280.3 CAS#: 2591-17-5 Purity: >99%L-luciferin: <0.5%Protect from light and moistureStorage: -20C