Photoinduced dissociation mass spectroscopy of firefly oxyluciferin anions

- Fragment ion masses of photoexcited oxyluciferin anions were identified.
- Isotope-labeling reveals that the thiazolyl is most susceptible to fragmentation.
- Dominant fragment ion is deprotonated 2-cyano-6-hydroxybenzothiazole.
- In the firefly the dominant fragment ion, if formed, is recycled to d-luciferin.