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Photoelectron spectroscopy of the deprotonated tryptophan anion: the contribution of deprotomers to its photodetachment channels

Gibbard, Jemma A.; Kellow, Catherine S.; Verlet, Jan. R. R.

Photoelectron spectroscopy of the deprotonated tryptophan anion: the contribution of deprotomers to its photodetachment channels Thumbnail


Authors

Profile image of Jemma Gibbard

Dr Jemma Gibbard jemma.gibbard@durham.ac.uk
Royal Society University Research Fellow

Catherine S. Kellow

Jan. R. R. Verlet



Abstract

Photoelectron spectroscopy and electronic structure calculations are used to investigate the electronic structure of the deprotonated anionic form of the aromatic amino acid tryptophan, and its chromophore, indole. The photoelectron spectra of tryptophan, recorded at different wavelengths across the UV, consist of two direct detachment channels and thermionic emission, whereas the hν = 4.66 eV spectrum of indole consists of two direct detachment features. Electronic structure calculations indicate that two deprotomers of tryptophan are present in the ion beam; deprotonation of the carboxylic acid group (Trp(i)−) or the N atom on the indole ring (Trp(ii)−). Strong similarities are observed between the direct detachment channels in the photoelectron spectra of tryptophan and indole, which in conjunction with electronic structure calculations, indicate that electron loss from Trp(ii)− dominates this portion of the spectra. However, there is some evidence that direct detachment of Trp(i)− is also observed. Thermionic emission is determined to predominantly arise from the decarboxylation of Trp(i)−, mediated by the ππ* excited state near λ = 300 nm, which results in an anionic fragment with a negative electron affinity that readily autodetaches.

Citation

Gibbard, J. A., Kellow, C. S., & Verlet, J. R. R. (2024). Photoelectron spectroscopy of the deprotonated tryptophan anion: the contribution of deprotomers to its photodetachment channels. Physical Chemistry Chemical Physics, 26(15), 12053-12059. https://doi.org/10.1039/d4cp00309h

Journal Article Type Article
Acceptance Date Mar 27, 2024
Online Publication Date Apr 5, 2024
Publication Date Apr 21, 2024
Deposit Date Apr 23, 2024
Publicly Available Date Apr 24, 2024
Journal Physical Chemistry Chemical Physics
Print ISSN 1463-9076
Electronic ISSN 1463-9084
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 26
Issue 15
Pages 12053-12059
DOI https://doi.org/10.1039/d4cp00309h
Public URL https://durham-repository.worktribe.com/output/2378867

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