Intrinsic fluorescence from firefly oxyluciferin monoanions isolated in vacuo

Abstract

Fireflies, click beetles, and railroad worms glow in the dark. The color varies from green to red among the insects and is associated with an electronically excited oxyluciferin formed catalytically...

Cryogenic Fluorescence Spectroscopy of Ionic Fluorones in Gaseous and Condensed Phases: New Light on Their Intrinsic Photophysics

“…The above-mentioned studies were performed almost exclusively at room temperature; there are only a few reports of gas-phase fluorescence instruments incorporating cryogenic cooling of the ions (i.e., T < 120 K) through cooling of the ion trap and buffer gas with liquid nitrogen or attachment of the ion trap to a helium refrigerator. ,, The principal advantages of cryogenic cooling of the ions are (i) to increase spectral resolution, through the removal of hot bands, allowing for enhanced fingerprinting , (e.g., for FRET), and (ii) to increase fluorescence quantum yield as a result of decreasing temperature.…”

Cryogenic Absorption and Emission Spectroscopy of the Oxyluciferin Anion In Vacuo

“…Recently, we reported the emission spectrum of gaseous dm-OL − at both 100 K and room temperature. 6 The band maximum was found to be 605 ± 4 nm at room temperature, corresponding to an orange emission color. This band maximum is blue-shifted compared to that found for the ions in aqueous solution (λ max = 634 nm, i.e., red light) 7 and to that from red cephalic luciferases of Phrixothrix heydeni (λ max ≈ 628 nm).…”

“…One of these is the 5,5-dimethyl­oxyluciferin (deprotonated form, dm-OL – , shown in Figure ) where the two methyl substituents prevent the formation of the phenolate-enol tautomer. Recently, we reported the emission spectrum of gaseous dm-OL – at both 100 K and room temperature . The band maximum was found to be 605 ± 4 nm at room temperature, corresponding to an orange emission color.…”

“…Absorption spectra of dm-OL – ions at room temperature are shown in Figure A together with the recently reported emission spectrum . In the fluorescence–excitation experiments, only photons with wavelengths longer than either 600 or 650 nm were sampled by use of long-pass filters to prevent unwanted detection of the laser photons.…”

“…Only emitted photons with wavelengths longer than 600 nm (PMT) or 650 nm (iCCD) were detected through use of long-pass filters. The emission spectra are taken from ref and were obtained with an excitation wavelength of 561 nm (A, B). Simulated absorption (blue) and emission (black) spectra at 100 and 210 K, respectively (C).…”