Theoretical study on bioluminescent mechanism and process of Siberian luminous earthworm Fridericia heliota

Abstract

Fridericia heliota (F. heliota) is a kind of bioluminescent earthworm discovered in Siberia. As a novel ATP-dependent bioluminescent system, its luciferin and oxyluciferin structures have been elucidated by Yampolsky group recently. Based on reliable experimental evidences, this group outlined the bioluminescent mechanism of F. heliota, which represents a momentous breakthrough in the research of earthworm bioluminescence (BL). Understandably, the experimentally proposed mechanism does not embody the details of the related chemical reactions and light emission. For the first time, the theoretical investigation in the present paper concretely described the entire process of F. heliota BL from luciferin to light emission at the molecular and electronic-state level. The calculated results indicated that the F. heliota BL initiates from the oxygenation of luciferin induced by a single electron transfer (SET) and produces the light emitter through the thermolysis of a dioxtanone intermediate via a mechanism of gradually reversible charge-transfer initiated luminescence (GRCTIL). This study not only supports and improves experimentally proposed BL mechanism, but also enriches the details of the BL process. It will be helpful for understanding F. heliota BL as well as oligochaete BL in nature.