Luciferin Regeneration in Firefly Bioluminescence via Proton-Transfer-Facilitated Hydrolysis, Condensation and Chiral Inversion

Firefly bioluminescence is produced via luciferin enzymatic reactions in luciferase. Luciferin has to be unceasingly replenished to maintain bioluminescence. How is the luciferin reproduced after it has been exhausted? In the early 1970s, Okada proposed the hypothesis that the oxyluciferin produced by the previous bioluminescent reaction could be converted into new luciferin for the next bioluminescent reaction. To some extent, this hypothesis was evidenced by several detected intermediates. However, the detailed process and mechanism of luciferin regeneration remained largely unknown. For the first time, we investigated the entire process of luciferin regeneration in firefly bioluminescence by density functional theory calculations. This theoretical study suggests that luciferin regeneration consists of three sequential steps: the oxyluciferin produced from the last bioluminescent reaction generates 2-cyano-6-hydroxybenzothiazole (CHBT) in the luciferin regenerating enzyme (LRE) via a hydrolysis reaction; CHBT combines with L-cysteine in vivo to form L-luciferin via a condensation reaction; and L-luciferin inverts into D-luciferin in luciferase and thioesterase. The presently proposed mechanism not only supports the sporadic evidence from previous experiments but also clearly describes the complete process of luciferin regeneration. This work is of great significance for understanding the long-term flashing of fireflies without an in vitro energy supply.

Firefly-Inspired Approach to Develop New Chemiluminescence Materials

Bioluminescence, wherein marine and terrestrial organisms chemically produce light for communication, is a burgeoning area of research. Herein, we demonstrate a new series of artificial chemiluminescent compounds inspired by the enol-degradation reaction of natural bioluminescent molecules, luciferins. Based on systematic optical experiments, isotope labeling, and theoretical calculations, the chemiluminescent mechanism of these new materials and the relationship of enol-degradation reaction and chemiluminescence are fully discussed. The color and efficiency of the artificial chemiluminescent materials can be easily adjusted, and blue (486 nm), yellow (565 nm), and near-infrared (756 nm) luminescence can thus be obtained. The findings and in-depth understanding herein may accelerate the development of bio/chemiluminescent materials for analytical applications and non-invasive bioluminescence imaging.

A relay strategy for the mercury (II) chemodosimeter with ultra-sensitivity as test strips

A relay strategy has been proposed to design a new Hg(2+) chemodosimeter (TPE-S), by coupling Hg(2+)-promoted deprotection reaction with ketone-enol isomerization, realizing the multistage amplifying effect. Changes in both of color and fluorescence could occur immediately, and TPE-S displayed high selectivity for Hg(2+), other metal ions (Ag(+), Fe(3+), Cu(2+), Pb(2+), Co(2+), Cr(3+), Al(3+), Cd(2+), Mg(2+), Mn(2+), Ba(2+), Fe(2+), Ca(2+), Ni(2+), Zn(2+), Li(+), K(+) and Na(+)) gave nearly no disturbance to the sensing process. When fabricated as test strips similar to pH-indicator papers, immediate color change from colorless to purple could be visually observed by naked-eyes without the aid of any additional equipment, with the detection limit as low as 1 × 10(-7) M (Hg(2+) in aqueous solution). Due to its easy synthesis, high selectivity and sensitivity, combined with the portable test strips, TPE-S could be developed as a convenient and cost-effective tool for the detection of Hg(2+) in on-site inspections.