Bioluminophore and Flavin Mononucleotide Fluorescence Quenching of Bacterial Bioluminescence-A Theoretical Study.
Bacterial bioluminescence with continuous glow has been applied to the fields of environmental toxin monitoring, drug screening, and in vivo imaging. Nonetheless, the chemical form of the bacterial bioluminophore is still a bone of contention. Flavin mononucleotide (FMN), one of the light-emitting products, and 4a-hydroxy-5-hydro flavin mononucleotide (HFOH), an intermediate of the chemical reactions, have both been assumed candidates for the light emitter because they have similar molecular structures and fluorescence wavelengths. The latter is preferred in experiments and was assigned in our previous density functional study. HFOH displays weak fluorescence in solutions, but exhibits strong bioluminescence in the bacterial luciferase. FMN shows the opposite behavior; its fluorescence is quenched when it is bound to the luciferase. This is the first example of flavin fluorescence quenching observed in bioluminescent systems and is merely an observation, both the quenching mechanism and quencher are still unclear. Based on theoretical analysis of high-level quantum mechanics (QM), combined QM and molecular mechanics (QM/MM), and molecular dynamics (MD), this paper confirms that HFOH in its first singlet excited state is the bioluminophore of bacterial bioluminescence. More importantly, the computational results indicate that Tyr110 in the luciferase quenches the FMN fluorescence via an electron-transfer mechanism.
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China.
Yanling
Y
Luo
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China. yajun.liu@bnu.edu.cn.
Ya-Jun
http://orcid.org/0000-0001-8761-5339
YJ
Liu
D001419:Bacteria / Q000737:chemistry*; D005486:Flavin Mononucleotide / Q000737:chemistry* / Q000378:metabolism*; D005453:Fluorescence; D008156:Luciferases / Q000737:chemistry*; D008962:Models, Theoretical; D015394:Molecular Structure
D005486:Flavin Mononucleotide; D008156:Luciferases
FMN; bacterial bioluminescence; bioluminophore; density functional calculations; fluorescence