Time-resolved chemiluminescence of firefly luciferin generated by dissolving oxygen in deoxygenated dimethyl sulfoxide containing potassium tert-butoxide

Chemiluminescence (CL) of firefly luciferin (Ln) consisting of red and green emission peaks can be generated by dissolving oxygen (O(2)) gas in deoxygenated dimethyl sulfoxide containing potassium tert-butoxide (t-BuOK) even without the enzyme luciferase. In this study, the characteristics of CL of Ln are examined by varying the concentrations of both Ln ([Ln]) and t-BuOK ([t-BuOK]). The time courses of the green and the red luminescence signals are also measured using a 32-channel photo sensor module. Interestingly, addition of 18-crown-6 ether (18-crown-6), a good clathrate for K(+), to the reaction solution before exposure to O(2) changes the luminescence from green to red when [t-BuOK] = 20 mM and [18-crown-6] = 80 mM. Based on our experimental results, we propose a two-pathway model where K(+) plays an important role in the regulation of Ln CL to explain the two-color luminescence observed from electronically excited oxyluciferin via dioxetanone.