Dessent, Caroline Elizabeth Helen orcid.org/0000-0003-4944-0413, Matthews, Edward and Cercola, Rosaria (2018) Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine. MOLECULES. 2036. ISSN 1420-3049
Abstract
Flavin chromophores play key roles in a wide range of photoactive proteins, but key questions exist in relation to their fundamental spectroscopic and photochemical properties. In this work, we report the first gas-phase spectroscopy study of protonated alloxazine (AL∙H+), a model flavin chromophore. Laser photodissociation is employed across a wide range (2.34–5.64 eV) to obtain the electronic spectrum and characterize the photofragmentation pathways. By comparison to TDDFT quantum chemical calculations, the spectrum is assigned to two AL∙H+ protomers; an N5 (dominant) and O4 (minor) form. The protomers have distinctly different spectral profiles in the region above 4.8 eV due to the presence of a strong electronic transition for the O4 protomer corresponding to an electron-density shift from the benzene to uracil moiety. AL∙H+ photoexcitation leads to fragmentation via loss of HCN and HNCO (along with small molecules such as CO2 and H2O), but the photofragmentation patterns differ dramatically from those observed upon collision excitation of the ground electronic state. This reveals that fragmentation is occurring during the excited state lifetime. Finally, our results show that the N5 protomer is associated primarily with HNCO loss while the O4 protomer is associated with HCN loss, indicating that the ring-opening dynamics are dependent on the location of protonation in the ground-state molecule.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Keywords: | flavin, alloxazine, laser spectroscopy, protomer, photodissociation |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Chemistry (York) |
Depositing User: | Pure (York) |
Date Deposited: | 15 Aug 2018 16:10 |
Last Modified: | 25 Oct 2024 00:00 |
Published Version: | https://doi.org/10.3390/molecules23082036 |
Status: | Published |
Refereed: | Yes |
Identification Number: | 10.3390/molecules23082036 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:134639 |