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Ion mobility action spectroscopy of flavin dianions reveals deprotomer-dependent photochemistry
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
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Antal upphovsmän: 52018 (Engelska)Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 29, s. 19672-19681Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The intrinsic optical properties and photochemistry of flavin adenine dinucleotide (FAD) dianions are investigated using a combination of tandem ion mobility spectrometry and action spectroscopy. Two principal isomers are observed, the more stable form being deprotonated on the isoalloxazine group and a phosphate (N-3,PO4 deprotomer), and the other on the two phosphates (PO4,PO4 deprotomer). Ion mobility data and electronic action spectra suggest that photo-induced proton transfer occurs from the isoalloxazine group to a phosphate group, converting the PO4,PO4 deprotomer to the N-3,PO4 deprotomer. Comparisons of the isomer selective action spectra of FAD dianions and flavin monoanions with solution spectra and gas-phase photodissociation action spectra suggests that solvation shifts the electronic absorption of the deprotonated isoalloxazine group to higher energy. This is interpreted as evidence for significant charge transfer in the lowest optical transition of deprotonated isoalloxazine. Overall, this work demonstrates that the site of deprotonation of flavin anions strongly affects their electronic absorptions and photochemistry.

Ort, förlag, år, upplaga, sidor
2018. Vol. 20, nr 29, s. 19672-19681
Nationell ämneskategori
Fysik
Forskningsämne
fysik
Identifikatorer
URN: urn:nbn:se:su:diva-162058DOI: 10.1039/c8cp03244kISI: 000448132600043PubMedID: 30014081OAI: oai:DiVA.org:su-162058DiVA, id: diva2:1266457
Tillgänglig från: 2018-11-28 Skapad: 2018-11-28 Senast uppdaterad: 2019-03-14Bibliografiskt granskad
Ingår i avhandling
1. Collision- and photon-induced dynamics of complex molecular ions in the gas phase
Öppna denna publikation i ny flik eller fönster >>Collision- and photon-induced dynamics of complex molecular ions in the gas phase
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In this thesis, I report experiments probing collision- and photon-induced molecular dynamics in the gas phase. Excited molecules formed in such interactions may relax by emitting electrons or photons, isomerization or fragmentation. For complex molecular systems, these processes typically occur on timescales exceeding picoseconds following statistical redistribution of the excitation energy across the internal degrees of freedom. However, energy transfer to molecules through ion/atom impact may in some cases lead to prompt atom knockout in Rutherford-type scattering processes on much faster timescales. Another example of such a non-statistical process is photon-induced excited-state proton transfer, a structural rearrangement occurring on the femtosecond timescale.

In this work, I investigate the competition between statistical and non-statistical fragmentation processes for a range of molecules colliding with He at center-of-mass energies in the sub-keV range. I show that heavy atom knockout is an important process for systems containing aromatic rings such as Polycyclic Aromatic Hydrocarbons (PAHs) or porphyrins, while statistical fragmentation processes dominate for less stable and/or smaller systems such as adenine or hydrogenated PAHs. Furthermore, I present the first measurements of the threshold energies for prompt single atom knockout from isolated molecules. The experimental results are interpreted with the aid of Molecular Dynamics (MD) simulations which allow us to extract the energy deposited into the system during a collision, knockout cross sections, fragmentation pathways and the structures of the fragments. The results presented in this work may be important for understanding the response of complex molecules to energetic processes in e.g. astrophysical environments.

Furthermore, I present the results of photodissociation and luminescence experiments probing flavin mono-anions in the gas phase. These are compared against calculations and previously measured spectra in solution. The discrepancies between the present results and the theoretical values suggest that more consideration of the vibronic structure is needed to model the photoabsorption and emission in flavins. Finally, I present the results of photoisomerisation experiments of flavin di-anions where two different isomers have been found and I discuss the proton transfer mechanisms which govern the structural changes.

Ort, förlag, år, upplaga, sidor
Stockholm: Department of Physics, Stockholm University, 2019. s. 70
Nyckelord
PAHs, Porphyrins, Adenine, Flavins, Biomolecules, Collisions, Experiments, Reactions, Non-Statistical Fragmentation, Molecular Dynamics, Photon-Induced Fragmentation, Luminescence, Photoisomerization, Proton Transfer
Nationell ämneskategori
Atom- och molekylfysik och optik
Forskningsämne
fysik
Identifikatorer
urn:nbn:se:su:diva-167001 (URN)978-91-7797-632-5 (ISBN)978-91-7797-633-2 (ISBN)
Disputation
2019-04-25, FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (Engelska)
Opponent
Handledare
Anmärkning

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 1: Manuscript.

Tillgänglig från: 2019-04-02 Skapad: 2019-03-12 Senast uppdaterad: 2019-03-21Bibliografiskt granskad

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Carrascosa, EduardoGiacomozzi, LindaBieske, Evan J.Stockett, Mark H.
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