Cargando…
Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine
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 chromopho...
Autores principales: | , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2018
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6222404/ https://www.ncbi.nlm.nih.gov/pubmed/30110962 http://dx.doi.org/10.3390/molecules23082036 |
_version_ | 1783369199292252160 |
---|---|
author | Matthews, Edward Cercola, Rosaria Dessent, Caroline E. H. |
author_facet | Matthews, Edward Cercola, Rosaria Dessent, Caroline E. H. |
author_sort | Matthews, Edward |
collection | PubMed |
description | 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 CO(2) and H(2)O), 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. |
format | Online Article Text |
id | pubmed-6222404 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-62224042018-11-13 Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine Matthews, Edward Cercola, Rosaria Dessent, Caroline E. H. Molecules Article 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 CO(2) and H(2)O), 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. MDPI 2018-08-14 /pmc/articles/PMC6222404/ /pubmed/30110962 http://dx.doi.org/10.3390/molecules23082036 Text en © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Matthews, Edward Cercola, Rosaria Dessent, Caroline E. H. Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine |
title | Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine |
title_full | Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine |
title_fullStr | Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine |
title_full_unstemmed | Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine |
title_short | Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine |
title_sort | protomer-dependent electronic spectroscopy and photochemistry of the model flavin chromophore alloxazine |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6222404/ https://www.ncbi.nlm.nih.gov/pubmed/30110962 http://dx.doi.org/10.3390/molecules23082036 |
work_keys_str_mv | AT matthewsedward protomerdependentelectronicspectroscopyandphotochemistryofthemodelflavinchromophorealloxazine AT cercolarosaria protomerdependentelectronicspectroscopyandphotochemistryofthemodelflavinchromophorealloxazine AT dessentcarolineeh protomerdependentelectronicspectroscopyandphotochemistryofthemodelflavinchromophorealloxazine |