Firefly luciferin is sensitive to light, oxygen, and moisture and must be protected. Light and oxygen can catalyze the oxidation of luciferin to dehydroluciferin. Left in an amber bottle under nitrogen at room temperature, luciferin will begin to decompose to dehydroluciferin after a month (Figure 2), but is stable in an unopened bottle for at least two years in a freezer. Dissolved in water with sufficient oxygen, luciferin will convert to dehydroluciferin in only a few days.
Luciferin should be purchased and stored in the smallest quantity possible to prevent decomposition to dehydroluciferin from multiple freeze-thaw-open cycles. If purchased in bulk, dividing the luciferin reagent into single-use amber vials will help ensure stability. Long-term storage as a frozen solution is not recommended for sensitive applications such as whole-animal studies. To help slow decomposition in frozen solutions, sparge the solution with nitrogen or argon prior to freezing.
Whenever opened, the luciferin bottle must be allowed to come fully to room temperature and then purged with nitrogen or argon before being resealed. If luciferin solutions are to be used within a few hours, few precautions are needed. Solutions that will be used over a day should be sparged with nitrogen or argon. Solutions should not be used over several days, as dehydroluciferin formation will occur.