Theory of D-(−)-Luciferin and Dehydroluciferin in Acidic or Basic Solution

Abstract

In order to understand the molecular mechanism of firefly bioluminescence, the observed absorption spectra of D-(−)-luciferin (LH₂) and dehydroluciferin (L) in acidic or basic solution are reproduced by the LCAO-ASMO-SCF-CI calculation on π-electrons.
It is thus found that the first absorption band of LH₂ in basic solution is ascribable to the intramolecular charge-transfer from benzothiazole to thiazoline ring, and that this absorption band is considerably affected by the reaction field due to solvent medium. On this basis, we discuss the formation process of the excited state of oxyluciferin (oxy-L) caused by the oxidation of LH₂, together with CIEEL (Chemically Initiated Electron Exchange Luminescence) mechanisms proposed by several investigators.