Ion mobility action spectroscopy of flavin dianions reveals deprotomer-dependent photochemistry

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

Electron-transfer processes in fast ion-atom collisions

The subject of this thesis is experimental studies of electron-transfer processes in ion-atom collisions at velocities significantly higher than typical orbital velocities of electrons in bound states of atoms or molecules. The experimental technique applied combines the high beam intensity of heavy-ion storage rings with a supersonic gas-jet target equipped with a recoil-ion-momentum spectrometer. In singleelectron capture to fast protons from helium atoms, we have for the first time achieved a complete separation of the kinematic and Thomas transfer mechanisms and are able to perform a quantitative comparison with the many theoretical results on a much more detailed level than what was previously possible. For the process of transfer ionization in proton-helium collisions we have determined the velocity dependence of the Thomas transfer ionization cross section to be the expected vp-11 when the projectile velocity, vp, is sufficiently high. Further, we have determined the velocity-dependent probability for shake-off of the second electron from helium provided that the first one is transferred in a kinematic capture process. Finally, we have considered collisions between protons and hydrogen molecules. Here we have found a strong variation in the cross section for transfer and excitation processes when the angle between the direction of the incoming projectile and the internuclear axis of the target molecule is varied. The variation can be explained as a result of quantum mechanical interference related to the two indistinguishable atomic centers of the molecule

District heating in the future - thoughts on the business model

In this study, we apply a combination of methods for understanding how business models need to change to meet changing business conditions in the future (time horizon 2050). The process of applying the value proposition canvas and the business model canvas for understanding the future business models to the case of district heating has been documented. The energy transition necessitates a combination of new and existing solutions. District heating is one existing and enabling technology. The sector is, however, facing several challenges that will impact the way that business must be conducted in the future. We provide new knowledge about the characteristics of the future district heating business model and illustrate that technical development must be accompanied by business development otherwise the competitiveness of new technology is reduced. Main results show that a high level of digitalisation, enabling customers to make choices that are efficient to the district heating system, is a key future feature. Additionally, co-creation with a small group of dedicated customers will drive the sector's ongoing development. The results from the study are replicable and of relevance to other sectors undergoing large change

On the effect of a single solvent molecule on the charge-transfer band of a donor-acceptor anion

Many biochromophore anions located within protein pockets display charge-transfer (CT) transitions that are perturbed by the nearby environment, such as water or amino acid residues. These anions often contain the phenolate moiety as the electron donor and an acceptor group that couples to the donor via a π-conjugated system. Here we show using action spectroscopy that single molecules of water, methanol, and acetonitrile cause blue shifts in the electronic transition energy of the bare m-nitrophenolate anion by 0.22, 0.22, and 0.12 eV, respectively (uncertainty of 0.05 eV). These shifts are similar to CC2-predicted ones and are in accordance with the weaker binding to the phenolate end of the ion by acetonitrile in comparison with water and methanol. The nitro acceptor group is almost decoupled from the phenolate donor, and this ion therefore represents a good model for CT excitations of an anion. We found that the shift caused by one acetonitrile molecule is almost half of that experienced in bulk acetonitrile solution, clearly emphasizing the important role played by the microenvironment. In protic solvents, the shifts are larger because of hydrogen bonds to the phenolate oxygen. Finally, but not least, we provide experimental data that serve to benchmark calculations of excited states of ion–solvent complexes.S.B.N. acknowledges support from The Lundbeck Foundation and The Danish Council for Independent Research Natural Sciences (10-082088). M.W. and A.R. acknowledge support from ERC Advanced Grant DYNamo (ERC-2010-AdG 267374), Spanish Grants (FIS2010-21282- C02-01 and PIB2010US- 00652), Grupo Consolidado UPV/EHU del Gobierno Vasco (IT578-13), and European Commission Projects CRONOS (Grant 280879-2 CRONOS CP-FP7) and POCAONTAS (FP7-PEOPLE-2012-ITN, Project 316633). M.W. acknowledges support from the MICINN “Juan de la Cierva” Program.Peer Reviewe