Chemiluminescence of 6-aryl-2-methylimidazo[1,2-a]pyrazin-3(7H)-ones in DMSO/TMG and in diglyme/acetate buffer:: support for the chemiexcitation process to generate the singlet-excited state of neutral oxyluciferin in a high quantum yield in the Cypridina (Vargula) bioluminescence mechanism

The chemiluminescence of 6-aryl-2-methylimidazo [1,2-a]pyrazin-3 (7 H) -ones (Cypridina luciferin analogues) in DMSO/ 1,1,3,3-tetramethylguanidine and in diglyme/acetate buffer was investigated. The results indicate that the reaction mechanism that produces a high chemiluminescence quantum yield involves a chemiexcitation process from a neutral dioxetanone intermediate possessing an electron-donating aryl group (sigma(Ar) <-0.6) to the singlet-excited state of neutral acetamidopyrazine. This result may be applied to the reaction mechanism for Cypridina (Vargula) bioluminescence. (c) 2006 Elsevier Ltd. All rights reserved.