Study on the control of excitation and alleviation in chemiluminescence reaction on the basis bioluminescence

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Chemiluminescence compound 2-methyl-6-(4-methoxyphenyl)imidazo[1,2 - α]pyrazin-3(7H)-one (MCLA) was attached to cyclomaltooligosaccharides (cyclodextrins) by the formation of an amide bond. The properties of oxygen-induced chemiluminescence of the synthesized cyclodextrin-bound MCLA were investigated in pH 8.0 aqueous phosphate buffer. The light-emitting efficiency was remarkably dependent n the kibnd of bounhd cyclodextrin, chain length between the MCLA and cyclodextrin, and the binding site in cyclodextrin. The light-emitting efficiencies of cyclomaltooctaose (γ-cyclodextrin)-bound compounds were higher than that of cyclomaltohexaose or cyclomaltoheptaose-bound compounds. Especially a compound in which MCLA attached to the secondary side of γ-cyclodextrin through short chain showed an up to 44 -fold enhancement over that of a non-cyclodextrin compound. In the present case, the efficiency of excited singlet state formation was 23-fold grater than that of the non-cyclodextrin compound and significantly contributed to the grater light-emitting efficiency. Induced circular dichroism spectra indicated the wide entrance of the secondary side of γ-cyclodextrin and short chain allow strong intramolecular affinity of the light-emitting chromophore and the cycrodextrin.