Abstracts

[background/purpose]Firefly bioluminescence is caused by the reaction of luciferin, a luminescent substrate found in fireflies in nature, with luciferase, a luminescent enzyme.Firefly bioluminescence has a very high luminescence quantum yield due to its high energy efficiency and almost no heat loss.Due to these characteristics, it is applied in a wide range of technologies such as biological imaging.However, since the wavelength of light emitted by natural fireflies is 560 nm, it is absorbed by hemoglobin and other biological substances in the body. Therefore, its light could not visualize deep tissues, making it difficult to put it to practical use as a biological imaging technique. To solve this problem, we have been working on modifying the structure of the luminescent substrate, the luminescent enzyme, or both, to achieve longer wavelengths.In addition, in recent years, analogs with heterocyclic rings, such as TokeOni and seMpai, which are highly water soluble, Akasuke, which emit light with high brightness, and KinPachi, which emit light at the world's longest wavelength, have attracted attention.However, since there are few synthetic examples of analogues with heterocycles, a correlation between luminescence activity has not yet been established. Moreover, the scarcity of synthesized analogs with heterocyclic rings has hindered the establishment of luminescence activity correlations. Therefore, in this study, I synthesized novel luciferin analogs A and B with heterocyclic rings and measured their luminescence to evaluate their luminescence properties.[Results/Discussion]Measurements of luminescence intensity showed that both new luciferin analogs A and B were greatly reduced compared to the natural substrate. As for the emission wavelengths, analog A and B were found to have wavelengths of _λmax = 580 nm and _λmax = 730 nm, respectively. Analog A has a wavelength comparable to that of the natural substrate, D-luciferin, and analog B has a wavelength 170 nm longer than the natural-type substrate.In this presentation, we will discuss the wavelength variation using DFT calculations.