Photoinduced dissociation mass spectroscopy of firefly oxyluciferin anions

Abstract

dissociation mass spectroscopy of firefly oxyluciferin anions, International Journal of Mass Spectrometry (2013), http://dx.doi.org/10.1016/j.ijms. 2013.11.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.  Isotope-labelling reveals that the thiazolyl is most susceptible to fragmentation. Dominant fragment ion is deprotonated 2-cyano-6-hydroxybenzothiazole.  In the firefly the dominant fragment ion, if formed, is recycled to D-luciferin. *Highlights (for review)Page 3 of 27 A c c e p t e d M a n u s c r i p t AbstractThe oxyluciferin molecule in its anionic form is responsible for light emission from fireflies and some railroad worms and click beetles. Here we have studied the breakdown of the ions after photoexcitation by 550-nm light, and identified the atom composition of eight fragment ions based on mass spectrometric experiments on isotope-labelled compounds. A sector instrument with an electrospray ion source and a pulsed laser system was used for the experiments. After Dissociation of the oxyluciferin anion into this fragment ion was calculated to require 1.86 eV, which is less than the energy of one photon (2.25 eV). Experiments done on 5,5-dimethyloxyluciferin revealed a similar fragmentation pattern.

What Exactly Is the Light Emitter of a Firefly?

“…Second, the f value of the neutral form is lower than that of the ionic form in both toluene and water such that the ionic form is necessary for high luminous efficiency. Third, the dominant fragment dissociated from oxyluciferin in firefly exists as an ion; therefore, it originates from the ionic form of oxyluciferin.…”

Action spectroscopy of isomer-selected luciferin anions

“…Last, we comment on our failure to observe photofragmentation for any of the luciferin systems. A photodissociation mass spectrometry study on OxyLH − (and DMOxyL − ), including with synthetic isotopologues, found the dissociation threshold for the dominant fragment to be ≈1.86 eV, [48] substantially lower than the VDE and presumably also the adiabatic detachment energy. The major ion fragment at m/z =175 (com-pared with m/z =249 for parent OxyLH − ) should be detectable in our tandem IMS experiment.…”

Intrinsic fluorescence from firefly oxyluciferin monoanions isolated in vacuo

“…17 Absorption cannot be measured directly but often relies on photodissociation, so-called action spectroscopy. 18,19 Interestingly, the most abundant photo-induced fragment ion is deprotonated 2-cyano-6-hydroxybenzothiazole, 20 the same intermediate in the postulated regeneration of luciferin from oxyluciferin in vivo in insects. A single water molecule was found to significantly blueshift the absorption (by about 0.23 eV).…”