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Updated: Jun 10, 2026

A Step Beyond BRET: Fluorescence by Unbound Excitation from Luminescence (FUEL)
Published on: May 23, 2014
Development of luciferin analogues bearing an amino group and their application as BRET donors
Hideo Takakura1, Kiyoshi Sasakura, Tasuku Ueno
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
We systematically synthesized bioluminogenic substrates bearing an amino group on benzothiazole, quinoline, naphthalene, and coumarin scaffolds. They emit bioluminescence in various colors: red, orange, yellow, and green. An amino-substituted coumarylluciferin derivative, coumarylaminoluciferin (CAL), showed the shortest bioluminescence wavelength among substrates reported so far. Further, the fluorescence of CAL did not exhibit solvatochromism, which suggests that its bioluminescence is not susceptible to environmental factors. We applied CAL as an energy-donor substrate for a bioluminescence resonance energy transfer (BRET) system with click beetle red luciferase (CBRluc), a mutant of firefly luciferase, as the energy-donor enzyme and yellow fluorescent protein (YFP) as the energy-acceptor fluorophore, and obtained a clearly bimodal bioluminescence spectrum. Stable bioluminescence that is not influenced by environmental factors is highly desirable for reliable measurements in biological assays.
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