Stark Spectroscopy of Lumichrome: A Possible Candidate for Stand-Off Detection of Bacterial Quorum Sensing

Abstract

Lumichrome (7,8-dimethylalloxazine, LC) is a natural photodegradation product and catabolite of flavin coenzymes. Although not a coenzyme itself, LC is used for biosignaling in plants and single-celled organisms, including quorum sensing in the formation of biofilms. The noninvasive detection of in vivo lumichrome would be useful for monitoring this signaling event. For molecules that undergo significant charge redistribution upon light excitation (e.g., intramolecular charge transfer), there are optical detection methods (e.g., secondharmonic generation) that would be well suited to this task. Here, we have used Stark spectroscopy to measure the extent and direction of charge redistribution in photoexcited LC. Stark and low-temperature absorption spectra were obtained at 77 K on LC in ethanol glasses and analyzed using the Liptay analysis to obtain the difference dipole moments and polarizabilities. These data were complemented by a computational analysis of the excited states using density functional theory (DFT) at the TD-B3LYP/6-311+G(2d,p) level of theory.

High-sensitivity electronic Stark spectrometer featuring a laser-driven light source

“…At the maximum field strength of ∼400 kV/cm, the absolute amplitude of the most prominent signal at 735 nm was ∼7.3 × 10 −4 , which, given a noise amplitude of 6 × 10 −6 , corresponds to a S/N of ∼122. For reference, noise amplitudes of this order of magnitude have been achieved in the literature, 4,10,[23][24][25][26][27] although it is not clear as to what extent ensemble averaging contributed to the reduction of noise in these examples. A quadratic fit to a plot of the maximum signal amplitude as a function of applied field strength yields a coefficient of determination (i.e., R 2 ) of unity (data not shown), consistent with the expected quadratic field dependence of the observed signal.…”

“…However, the measured Stark signal is small-generally of the order 10 −3 to 10 −6 -and requires specialized instrumentation. Many excellent articles, [1][2][3][4] reviews, [5][6][7][8] and book chapters [9][10][11] have been dedicated to the topic, which also include details for non-specialists.…”

Subinhibitory antibiotic concentrations promote the horizontal transfer of plasmid-borne resistance genes from Klebsiellae pneumoniae to Escherichia coli

“…In this study, 9 heteroproxies were selected, including 7,8-dimethylalloxazine, phenylalanylproline, B-D-fructosyl-a-D-(6-O-(E))-feruloylglucoside, pterosin J, PS (16,0/16:0), endomorphin 1, hawkinsin, L-Phenylalanyl-L-hydroxyproline, corchoionoside. Of these, 7, 8-dimethylalloxazine is a photodegradation product of riboflavin ( van Galen et al, 2020 ). The downregulation of this metabolite in the presence of meropenem at sub-MIC levels suggests that the decomposition of riboflavin is reduced.…”

Electroabsorption and Stark Fluorescence Spectroscopies of Thioflavin T

“…This is known as the Stark effect, and its application in molecular spectroscopy is called Stark spectroscopy. Because CT states usually have a large dipole moment, Stark spectroscopy may be useful for studying these states. − In addition, Stark spectroscopy is a powerful technique for understanding the changes in photophysics (especially fluorescence QY) induced by external electric fields. , …”