| 1. |
- Edhborg, Fredrik, 1990, et al.
(författare)
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Triplet States of Cyanostar and Its Anion Complexes
- 2023
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Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 127:28, s. 5841-5850
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Tidskriftsartikel (refereegranskat)abstract
- The design of advanced optical materials based on triplet states requires knowledge of the triplet energies of the molecular building blocks. To this end, we report the triplet energy of cyanostar (CS) macrocycles, which are the key structure-directing units of small-molecule ionic isolation lattices (SMILES) that have emerged as programmable optical materials. Cyanostar is a cyclic pentamer of covalently linked cyanostilbene units that form π-stacked dimers when binding anions as 2:1 complexes. The triplet energies, ET, of the parent cyanostar and its 2:1 complex around PF6- are measured to be 1.96 and 2.02 eV, respectively, using phosphorescence quenching studies at room temperature. The similarity of these triplet energies suggests that anion complexation leaves the triplet energy relatively unchanged. Similar energies (2.0 and 1.98 eV, respectively) were also obtained from phosphorescence spectra of the iodinated form, I-CS, and of complexes formed with PF6- and IO4- recorded at 85 K in an organic glass. Thus, measures of the triplet energies likely reflect geometries close to those of the ground state either directly by triplet energy transfer to the ground state or indirectly by using frozen media to inhibit relaxation. Density functional theory (DFT) and time-dependent DFT were undertaken on a cyanostar analogue, CSH, to examine the triplet state. The triplet excitation localizes on a single olefin whether in the single cyanostar or its π-stacked dimer. Restriction of the geometrical changes by forming either a dimer of macrocycles, (CSH)2, or a complex, (CSH)2·PF6-, reduces the relaxation resulting in an adiabatic energy of the triplet state of 2.0 eV. This structural constraint is also expected for solid-state SMILES materials. The obtained T1 energy of 2.0 eV is a key guide line for the design of SMILES materials for the manipulation of triplet excitons by triplet state engineering in the future.
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| 2. |
- Aissaoui, Nesrine, 1983, et al.
(författare)
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FRET enhancement close to gold nanoparticles positioned in DNA origami constructs
- 2017
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Ingår i: Nanoscale. - Cambridge, United Kingdom : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 9:2, s. 673-683
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Tidskriftsartikel (refereegranskat)abstract
- Here we investigate the energy transfer rates of a Förster resonance energy transfer (FRET) pair positioned in close proximity to a 5 nm gold nanoparticle (AuNP) on a DNA origami construct. We study the distance dependence of the FRET rate by varying the location of the donor molecule, D, relative to the AuNP while maintaining a fixed location of the acceptor molecule, A. The presence of the AuNP induces an alteration in the spontaneous emission of the donor (including radiative and non-radiative rates) which is strongly dependent on the distance between the donor and AuNP surface. Simultaneously, the energy transfer rates are enhanced at shorter D-A (and D-AuNP) distances. Overall, in addition to the direct influence of the acceptor and AuNP on the donor decay there is also a significant increase in decay rate not explained by the sum of the two interactions. This leads to enhanced energy transfer between donor and acceptor in the presence of a 5 nm AuNP. We also demonstrate that the transfer rate in the three "particle" geometry (D + A + AuNP) depends approximately linearly on the transfer rate in the donor-AuNP system, suggesting the possibility to control FRET process with electric field induced by 5 nm AuNPs close to the donor fluorophore. It is concluded that DNA origami is a very versatile platform for studying interactions between molecules and plasmonic nanoparticles in general and FRET enhancement in particular.
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| 3. |
- Albinsson, Bo, 1963, et al.
(författare)
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Anti, ortho, and gauche conformers of perfluoro-n-butane: Matrix-isolation IR spectra and calculations
- 1996
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Ingår i: Journal of Physical Chemistry. - 0022-3654. ; 100:9, s. 3418-3429
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen matrix-isolation IR spectra have been obtained for each of the three conformers of n-C4F10 (gauche, ortho, and anti) by trapping a hot conformer mixture on a cold CsI window and subsequent matrix annealing and spectral differencing. They were assigned by comparison with results of HF/6-31G* calculations, and the nature of the normal modes has been analyzed using the total energy distribution procedure. At the fully optimized MP2/6-31G* (frozen core) level, the CCCC dihedral angles and relative energies (kcal/mol) are 54.2 degrees and 0.68 (gauche), 94.8 degrees and 1.63 (ortho), and 165.5 degrees and 0 (anti). Single-point MP2/6-311G* (frozen core) relative energies at these geometries are 0.85, 2.12, and 0 kcal/mol, respectively. Only a minute amount of the ortho conformer is trapped in nitrogen matrix, and none in other matrices that were tried. A variation of the relative intensities of IR peaks of the gauche and anti conformers as a function of the temperature of the gas before deposition yields an ''average'' Delta H value of about 0.9 kcal/mol, with the anti conformer more stable. The temperature range covered was too small to reveal the expected bilinear nature of the van't Hoff plot.
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| 4. |
- Albinsson, Bo, 1963, et al.
(författare)
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Conformers of n-Si5Me12: A comparison of ab initio and molecular mechanics methods
- 1999
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Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 103:14, s. 2184-2196
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Tidskriftsartikel (refereegranskat)abstract
- Optimized geometries of the conformers of permethylated linear pentasilane, n-Si5Me12, were calculated by the HF/3-21G*, MM3, MM2, and MM+ methods, which predict eight, nine, six, and six energetically distinct enantiomeric conformer pairs, respectively, at geometries representing various combinations of the anti (similar to 165 degrees), ortho (similar to 90 degrees), and gauche (similar to 55 degrees) SiSiSiSi dihedral angles in the backbone. The results of the MM2 and MM+ methods, based on the same force field, differ insignificantly. The barriers between conformers appear to be exaggerated by the molecular mechanics methods, particularly MM2. Contour maps showing the groundstate energy as a function of the full range of two backbone SiSiSiSi dihedral angles, with all other geometrical variables optimized, computed by each of the methods (only a limited range of angles near the anti,anti geometry in the case of HF/3-21G*) are compared with each other and with analogous results for a model compound, Si4Me10. Conformer interconversion paths are discussed, and two meso transition states for enantiomer interconversion have been located at the HF/3-21G* level of calculation. At the eight HF/3-21G* optimized geometries, single-point energies (HF/6-31G* and MP2/6-31G*) and vibrational frequencies (HF/3-21G*) were computed. The predicted IR and Raman spectra suggest that about half of the expected conformers will be identifiable by vibrational spectroscopy under conditions of matrix isolation. Relative conformer energies calculated by the MM2 and HF methods are similar and favor the anti dihedral angles over gauche and ortho, in agreement with results of solution experiments. Those calculated by the hIM3 and HF methods are similar to each other and favor both anti and gauche dihedral angles nearly equally over ortho, in agreement with indications provided by gas-phase experiments. A rationalization of these solvent effects is proposed. The energies of the conformers of Si4Me10 and Si3Me12 were used to set up a system of additive increments at the MM2, MM3, HF/3-21G*, HF/6-31G*, and MP2/6-31G* levels of calculation, which can be used to predict conformational energies of longer permethylated oligosilanes. An intrinsic energy value is assigned to each of the a, o, and g dihedral angles, and interaction energy values are assigned to each combination of two dihedral angles. The interaction values follow the expected rules in that equal twist sense is favored for adjacent aa, ag, oo, and gg pairs, whereas opposite twist sense is generally favored for adjacent so and go pairs. The MM3-derived set of increments has been tested against results computed for Si6Me14 and found to perform well.
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| 5. |
- Albinsson, Bo, 1963, et al.
(författare)
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Conformers of saturated chains: Matrix isolation, structure, IR and UV spectra of n-Si(4)Me(10)
- 1996
-
Ingår i: Chemistry - A European Journal. - 1521-3765 .- 0947-6539. ; 2:5, s. 529-538
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Tidskriftsartikel (refereegranskat)abstract
- Infrared and ultraviolet spectra of the gauche and anti conformers of matrix-isolated permethyl-n-tetrasilane have been obtained separately by taking advantage of thermally induced gauche-to-anti conversion and of wavelength-selective photochemical destruction of either conformer. The resolved UV spectrum of the gauche conformer provides the first piece of experimental evidence in favor of the recently proposed reinterpretation of conformational effects on tetrasilane electronic states. According to this, it is not the energy but the intensity of the lowest singlet excitation that changes dramatically as the SiSiSiSi dihedral angle is varied, as a result of an avoided crossing between sigma sigma* and sigma pi* states. Implications for the general understanding of sigma conjugation in simple terms are discussed. Unconstrained MP2/6-31G* optimization predicts the existence of a third backbone conformer (ortho), with a dihedral angle of about 90 degrees. Its predicted (HF/3-21G*) mid-IR spectrum is indistinguishable from that of the gauche conformer, and the matrix-isolation spectra thus provide no evidence for or against its presence.
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| 6. |
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| 7. |
- Albinsson, Bo, et al.
(författare)
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Distinction between serological responses following tick-borne encephalitis virus (TBEV) infection vs vaccination, Sweden 2017
- 2018
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Ingår i: Eurosurveillance. - 1025-496X .- 1560-7917. ; 23:3, s. 2-7
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Tidskriftsartikel (refereegranskat)abstract
- Tick-borne encephalitis virus (TBEV) is an important European vaccine-preventable pathogen. Discrimination of vaccine-induced antibodies from those elicited by infection is important. We studied anti-TBEV IgM/IgG responses, including avidity and neutralisation, by multiplex serology in 50 TBEV patients and 50 TBEV vaccinees. Infection induced antibodies reactive to both whole virus (WV) and non-structural protein 1 (NS1) in 48 clinical cases, whereas 47 TBEV vaccinees had WV, but not NS1 antibodies, enabling efficient discrimination of infection/vaccination.
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| 8. |
- Albinsson, Bo, 1963
(författare)
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Dual fluorescence from N-6,N-6-dimethyladenosine
- 1997
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Ingår i: Journal of the American Chemical Society. - 1520-5126 .- 0002-7863. ; 119:27, s. 6369-6375
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Tidskriftsartikel (refereegranskat)abstract
- The adenosine derivative N-6,N-6-dimethyladenosine (DMA) shows dual fluorescence in solvents of different polarity. In addition to the ''normal'' fluorescence at 330 nm, another band is observed at 500 nm. The long wavelength emission dominates in aprotic solvents but is dynamically quenched by protic solvents. Steady-state and lifetime measurements show that the emissions originate from two excited state species; the short wavelength emission is from the directly populated excited state which irreversibly isomerizes into the species responsible for the long wavelength emission. It is conceivable to assign the long wavelength emitting species to a twisted intramolecular charge transfer state (TICT). The fluorescence quantum yield of the short wavelength emission is approximately 4 x 10(-4) at room temperature and increases by three orders of magnitude when the temperature is lowered to 80 K in accordance with the behavior of normal nucleic acid bases. In contrast, the long wavelength fluorescence quantum yield is almost temperature independent. The different photophysical processes for DMA are summarized into a kinetic scheme where the temperature quenching of the short wavelength fluorescence is exclusively through isomerization into the long wavelength emitting species. Direct internal conversion to the ground state, commonly believed to be the dominant process for nonradiative deactivation of the DNA bases, makes a negligible contribution for DMA.
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| 9. |
- Albinsson, Bo, 1963, et al.
(författare)
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Electron and energy transfer in donor-acceptor systems with conjugated molecular bridges
- 2007
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 9:44, s. 5847-5864
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Tidskriftsartikel (refereegranskat)abstract
- Electron and energy transfer reactions in covalently connected donor-bridge-acceptor assemblies are strongly dependent, not only on the donor-acceptor distance, but also on the electronic structure of the bridge. In this article we describe some well characterised systems where the bridges are π-conjugated chromophores, and where, specifically, the interplay between bridge length and energy plays an important role for the donor-acceptor electronic coupling. For any application that relies on the transport of electrons, for example molecule based solar cells or molecular scale electronics, it will be imperative to predict the electron transfer capabilities of different molecular structures. The potential difficulties with making such predictions and the lack of suitable models are also discussed. © the Owner Societies.
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| 10. |
- Albinsson, Bo, 1963, et al.
(författare)
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Electron Transfer Through Butadiyne-Linked Porphyrin-Based Molecular Wires
- 2012
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Ingår i: Multiporphyrin Arrays: Fundamentals and Applications. - : Pan Stanford Publishing. - 9789814364287 ; , s. 55-90
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Electron transfer is of fundamental importance in many areas of chemistry and biochemistry [1]. The ability to transfer charge efficiently over distances in the 10 nm range is crucial in various practical devices, such as organic transistors and solar cells both dye-sensitized metal oxide solar cells and bulk-heterojunction blend devices [2]. Furthermore, in the context of the ever-decreasing dimensions of integrated circuits, it is interesting to study charge transport through individual molecules [3]. Organic π -conjugated oligomers and polymers are attractive candidates as molecularwires, because modern synthetic chemistry can be used to create almost any type of π -conjugated backbone, while non-covalent interactions and supramolecular chemistry can be used to modify the backbone conformation. Interactions of conjugated oligomers, both with each other and with the external environment, can also be controlled by self-assembly and non-covalent encapsulation.
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| 11. |
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| 12. |
- Albinsson, Bo, 1963, et al.
(författare)
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ELECTRONIC-TRANSITION MOMENT DIRECTIONS AND IDENTIFICATION OF LOW-ENERGY N-PI-ASTERISK STATES IN WEAKLY PERTURBED PURINE CHROMOPHORES
- 1993
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 115:1, s. 223-231
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of UV linear dichroism on purine and three methyl derivatives partially oriented in poly(vinyl alcohol) matrix gave direct evidence for the assignment of the first singlet npi* state. Intensity distributions and moment directions for the first three pi --> pi* transitions were also determined. The pi --> pi* transitions in purine were found to be polarized at (angles, relative to the pseudo-symmetry long axis, counted positive in the N7 direction): -31-degrees +/- 5-degrees (II at 265 nm), +38-degrees +/- 5-degrees (III at 244 nm), and +36-degrees +/- 10-degrees (IV at 214 nm). The transition energies and moment directions were not markedly perturbed by methyl substitution at the sixth, seventh, or ninth position. Therefore, these methyl substituents could be used as orientational perturbers to resolve a sign ambiguity problem regarding transition moment directions. The orientation were determined by infrared dichroic measurements using both in-plane and out-of-plane polarized vibrational transitions. In addition, the phosphorescence spectra were studied, including phosphorescence anisotropy, phosphorescence lifetimes, and quantum yields, for the purines in an organic glass at 80 K. Based on these measurements, the lowest triplet state is concluded to have effectively pipi* character, and its emission allowedness appears to originate from spin-orbit interactions primarily with singlet sigmapi* states but also with singlet pipi* states via vibronic mixing. The phosphorescence emission spectra of purine and 6-methylpurine are complex, compared to 7-methylpurine and 9-methylpurine, with emission wavelength-dependent lifetimes and excitation spectra. This is ascribed to a prototropic tautomeric equilibrium between the 7H and 9H forms of purine and 6-methylpurine, a ground-state heterogeneity that we believe has caused confusion in earlier studies and, e.g., led to an assignment of the phosphorescence origin of purine.
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| 13. |
- Albinsson, Bo, 1963
(författare)
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ENERGY TRANSFER On the right path
- 2011
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Ingår i: Nature Chemistry. - : Springer Science and Business Media LLC. - 1755-4349 .- 1755-4330. ; 3:4, s. 269-270
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 14. |
- Albinsson, Bo, 1963
(författare)
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Excitation and Excited State Properties of Heterocyclic Chromophores. Indole and Purine Derivatives of Biological Significance
- 1992
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proteins and nucleic acids absorb light in the near-UV due to the presence of aromatic heterocyclic chromophores. In this work linear dichroism (LD) in combination with fluorescence polarization anisotropy (FPA) and magnetic circular dichroism (MCD) is used to investigate electronic excitations and excited states of indole derivatives, purine derivatives, the wye base, 2-phenylindole and 4',6-diamidino-2-phenylindole (DAPI). The UV spectrum of indole, which is the chromophoric core of tryptophan, is resolved into contributions from the lowest nearly degenerate 1A1 --> 1La and 1A1 --> 1Lb transitions, and the moment directions for the four lowest transitions in indole and eight selected methyl and methoxy derivatives are determined. Substitution does not generally perturb the transition moment directions, with exception for the 1A1 --> 1Lb and 1A1 --> 1Bb transitions whose moment directions are significantly altered by a methoxy group in 4- or 6-position. The transition moment directions and the resolved UV-spectra were also determined for purine, a model compound for the purine nucleic acid bases, and the tRNA base wye (Y-base). Purine has a clearly resolved n-->p* transition lowest in energy, followed by two nearly degenerate p-->p* transitions with almost perpendicular moment directions. The phosphorescence spectra of purine and three methyl derivatives were investigated and the emitting triplet was found to have effectively pp* character. In addition, the purines with mobile imidazolic protons (purine and 6-methylpurine) are shown to exist, in an organic glass at 80 K, in two tautomeric forms (7H and 9H) as judged from phosphorescence emission and excitation spectra. A DNA-binding probe 4',6-diamidino-2-phenylindole (DAPI) and its parent chromophore 2-phenylindole were finally investigated using the above mentioned experimental techniques as well as quantum mechanical calculations. Five distinct electronic transitions are found above 200 nm and their moment directions are determined. The theoretical results indicate a weak relation of the two lowest transitions in 2-phenylindole to the 1A1 --> 1Lb and 1A1 --> 1La transitions of indole.
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| 15. |
- Albinsson, Bo, 1963, et al.
(författare)
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Excitation energy transfer in donor-bridge-acceptor systems
- 2010
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 12:27, s. 7338-7351
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Tidskriftsartikel (refereegranskat)abstract
- This perspective will focus on the mechanistic aspects of singlet and triplet excitation energy transfer. Well defined donor-bridge-acceptor systems specifically designed for investigating the distance and energy gap dependencies of the energy transfer reactions are discussed along with some recent developments in computational modeling of the electronic coupling.
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| 16. |
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| 17. |
- Albinsson, Bo, 1963, et al.
(författare)
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EXCITED-STATE PROPERTIES OF THE INDOLE CHROMOPHORE - ELECTRONIC-TRANSITION MOMENT DIRECTIONS FROM LINEAR DICHROISM MEASUREMENTS - EFFECT OF METHYL AND METHOXY SUBSTITUENTS
- 1992
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Ingår i: Journal of Physical Chemistry. - : American Chemical Society (ACS). - 0022-3654 .- 1541-5740. ; 96:15, s. 6204-6212
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Tidskriftsartikel (refereegranskat)abstract
- From measurements of UV and IR linear dichroism on molecules partially oriented in stretched polyethylene host the transition moment directions for the first four pi-pi* transitions of indole and some indole derivatives were determined. Relative to the pseudosymmetry long axis of indole, the transitions were normally found to be polarized at (angles counted away from the ring nitrogen): +42 +/- 50-degrees (1A1 --> 1L(by) at 287 nm), -46 +/- 5-degrees (1A1 --> 1L(a) at 265 nm), 0 +/- 15-degrees (1A1 --> 1B(by) at 220 nm), and for the 1A1 --> 1B(a) transition occurring around 200 nm, at least at +/- 30-degrees away from this axis. In addition, indication for a weak, essentially short axis polarized transition was found at 235 nm, possibly due to the 1A1 --> 1C transition. An ambiguity problem regarding the sign of the angles was resolved by exploiting the change of orientation properties upon introduction of substituents. Orientation parameters (including diagonalizing angle) were determined by consideration of a large number of in-plane as well as out-of-plane polarized vibrational transitions. The question regarding effects on the excited states by the presence of methyl and methoxy substituents, at varied positions in the indole chromophore, was addressed in terms of the perturbations they caused on the transition moments. Whereas none of the four transitions was found to be very sensitive in this respect to methyl or methoxy groups introduced in 2-, 3-, 5-, or 7-position of indole, the directions of the weak 1A1 --> 1L(by) but also the strong 1A1 --> 1B(by) transition were found to become significantly altered by a methoxy group in 4- as well as 6-position. The conclusions are consistent with recent fluorescence anisotropy data and semiempirical calculations.
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| 18. |
- Albinsson, Bo, 1963, et al.
(författare)
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Functionalized DNA Nanostructures for Light Harvesting and Charge Separation
- 2012
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Ingår i: Coordination Chemistry Reviews. - : Elsevier BV. - 0010-8545. ; 256:21-22, s. 2399-2413
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Forskningsöversikt (refereegranskat)abstract
- Mimicking natural photosynthesis by covalently arranging antenna and charge separation units is a formidable task. Many such beautiful supramolecular complexes have been designed and synthesized with large efforts, some of which are presented in this special issue. The ability to predict relative position of and electronic coupling between the active components in covalent arrays is quite high but there are two obvious drawbacks with the covalent approach. Firstly, as the size grows the complexity of the organic synthesis increases and secondly, sensitivity to light-induced damage becomes a major issue if covalent bonds are broken. Self-assembly of the photoactive components should, in principle, provide a solution to both these issues but generally the ability to predict position and electronic coupling is too low to have the designed properties needed for a functional artificial photosynthetic complex. Here, we present an approach of using DNA as a template for arranging both charge separation units and antenna molecules that govern long-range energy transfer. Of particular interest is the ability of DNA to function as a scaffold for chromophores, either through covalent attachment, or through non-covalent association by means of intercalation or grove binding. Using controlled positioning of dyes, multichromophoric assemblies can be created, capable of long range communication through multi-step energy transfer. This facilitates creation of DNA-based photonic devices for both light harvesting and directed information transfer. The channeled excitation energy can be transformed site specifically to chemical energy by charge separation of DNA linked porphyrins. A two phase system is discussed, in which the DNA is located in buffered solution whereas the hydrophobic porphyrins, responsible for the charge separation reaction, are located in the lipid bilayer of liposomes or supported lipid bilayers.
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| 19. |
- Albinsson, Bo, 1963, et al.
(författare)
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Long-range electron and excitation energy transfer in donor-bridge-acceptor systems
- 2008
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Ingår i: Journal of Photochemistry and Photobiology C: Photochemistry Reviews. - : Elsevier BV. - 1389-5567. ; 9:3, s. 138-155
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Tidskriftsartikel (refereegranskat)abstract
- Donor-bridge-acceptor (D-B-A) systems, either as supermolecules or on surfaces, have been extensively studied with respect to long-range electron (ET) and excitation energy (EET) transfer. In more recent years, the main research objective has been to develop knowledge on how to construct molecular-based devices, with predetermined electron transfer properties, intended for application in electronics and photovoltaics. At present, such construction is in general hampered for several reasons. Most importantly, the property of a D-B-A system is not a simple linear combination of properties of the individual components, but depends on the specific building blocks and how they are assembled. An important example is the ability of the bridge to support the intended transfer process. The mediation of the transfer is characterized by an attenuation factor, beta, often viewed as a bridge specific constant but which also depends on the donor and the acceptor, i.e. the same bridge can either be poorly or strongly conducting depending oil the donor and acceptor. This review gives an account of the experimental exploration of the attenuation factor beta in a series of bis(porphyrin) systems covalently linked by bridges of the oligo(phenyleneethynylene) (OPE) type. Attenuation factors for ET as well as for both singlet and triplet EET are discussed. A report is also given on the dependence of the transfer efficiency on the energy-gap between the donor and bridge states relevant for the specific transfer process. The experimental variation of beta with varying donor and acceptor components is shown fora range of conjugated bridges by representative examples from the literature. The theoretical rationalization for the observed variation is briefly discussed. Based on the Gamow tunneling model, the observed variations in beta-values with varying donors and acceptors for the same bridges is simulated Successfully simultaneously as the observed energy-gap dependence is modelled. (C) 2008 Elsevier B.V. All rights reserved.
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| 20. |
- Albinsson, Bo, 1963, et al.
(författare)
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Matrix-isolation IR and UV spectra of Si3H8 and Si4H10: Isomers and conformers of oligosilanes
- 1996
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Ingår i: Journal of Physical Chemistry. - 0022-3654. ; 100:21, s. 8681-8691
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Tidskriftsartikel (refereegranskat)abstract
- Matrix-isolation IR and UV spectra of Si3H8, i-Si4H10, and the two conformers of n-Si4H10 have been recorded. A quantitative separation of the IR spectrum of n-Si4H10 into contributions from the anti and gauche forms was accomplished by a combination of matrix annealing and selective monochromatic photodestruction experiments. A qualitative separation of their UV spectra was achieved as well. The IR spectra of Si3H8, i-Si4H10, and the two conformers of n-Si4H10 have been assigned by comparison with results of ab initio calculations, which reproduce the frequencies and even the relative intensities quite well. The calculations predict dihedral angles omega of 180 degrees and 57 degrees for the anti and the gauche conformer of n-Si4H10, respectively, and confirm earlier predictions of nearly equal stability for an isolated molecule. In the matrix, the anti conformer is more stable, The conformational effects on the UV spectrum of n-Si4H10 are not those anticipated from simple models of the Sandorfy or ladder C type, in that it is primarily not the energy but the intensity of the low-energy excited singlet states that depends strongly on the SiSiSiSi dihedral angle omega. This result is interpreted in terms of data from 6-in-8 CASSCF 6-31G* calculations, which predict an avoided crossing between a strongly allowed sigma sigma* B state and a very weakly allowed sigma pi* B state as omega changes, with the former lower in energy at 180 degrees and the latter lower at 0 degrees. Consequences for attempts to understand the effects of conformation on optical spectra of polysilanes are noted.
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| 21. |
- Albinsson, Bo, et al.
(författare)
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Multi laboratory evaluation of ReaScan TBE IgM rapid test, 2016 to 2017
- 2020
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Ingår i: Eurosurveillance. - : EUR CENTRE DIS PREVENTION & CONTROL. - 1025-496X .- 1560-7917. ; 25:12, s. 27-36
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Tidskriftsartikel (refereegranskat)abstract
- Tick-borne encephalitis (TBE) is a potentially severe neurological disease caused by TBE virus (TBEV). In Europe and Asia, TBEV infection has become a growing public health concern and requires fast and specific detection. Aim: In this observational study, we evaluated a rapid TBE IgM test, ReaScan TBE, for usage in a clinical laboratory setting. Methods: Patient sera found negative or positive for TBEV by serological and/or molecular methods in diagnostic laboratories of five European countries endemic for TBEV (Estonia, Finland, Slovenia, the Netherlands and Sweden) were used to assess the sensitivity and specificity of the test. The patients' diagnoses were based on other commercial or quality assured in-house assays, i.e. each laboratory's conventional routine methods. For specificity analysis, serum samples from patients with infections known to cause problems in serology were employed. These samples tested positive for e.g. Epstein-Barr virus, cytomegalovirus and Anaplasma phagocytophilum, or for flaviviruses other than TBEV, i.e. dengue, Japanese encephalitis, West Nile and Zika viruses. Samples from individuals vaccinated against flaviviruses other than TBEV were also included. Altogether, 172 serum samples from patients with acute TBE and 306 TBE IgM negative samples were analysed. Results: Compared with each laboratory's conventional methods, the tested assay had similar sensitivity and specificity (99.4% and 97.7%, respectively). Samples containing potentially interfering antibodies did not cause specificity problems. Conclusion: Regarding diagnosis of acute TBEV infections, ReaScan TBE offers rapid and convenient complementary IgM detection. If used as a stand-alone, it can provide preliminary results in a laboratory or point of care setting.
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| 22. |
- Albinsson, Bo, 1963, et al.
(författare)
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Multistep FRET and Nanotechnology
- 2013
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Ingår i: FRET - Förster Resonance Energy Transfer: From Theory to Applications. - : Wiley. ; , s. 607-653
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 23. |
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| 24. |
- Albinsson, Bo, 1963, et al.
(författare)
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Polarized Spectroscopy with Fluorescent Biomolecular Building Blocks
- 2016
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Ingår i: Fluorescent Analogues of Biomolecular Building Blocks: Design and Applications: Design and Applications (eds M. Wilhelmsson and Y. Tor). - Hoboken, NJ, USA : John Wiley & Sons, Inc. - 9781118175866 ; , s. 40-54
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- © 2016 by John Wiley & Sons, Inc. All rights reserved. This chapter considers linear dichroism (LD), magnetic circular dichroism (MCD), and Forster resonance energy transfer (FRET) and how these phenomena are related to and may report on transition moment orientations and on molecular structure. MCD is an asset in combination with LD and fluorescence anisotropy for the deciphering of transition moment directions in biophysically important chromophores, and many examples of applications are found among nucleobases. A property corresponding to the absorption anisotropy (linear dichroism) for emission is the fluorescence anisotropy. The amino acid tryptophan, with indole as its photoactive aromatic chromophore, is the most frequently used natural fluorescent probe in biophysical contexts, due to its relatively high fluorescence quantum yield and well-resolved absorption profile in the near-UV. The single-molecule fluorescence-detected linear dichroism (smFLD) method is a useful complement to smFRET since it can help to avoid misinterpretation of false smFRET signals.
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| 25. |
- Albinsson, Bo, et al.
(författare)
-
Seroprevalence of tick-borne encephalitis virus and vaccination coverage of tick-borne encephalitis, Sweden, 2018 to 2019
- 2024
-
Ingår i: Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin. - : European Centre for Disease Control and Prevention (ECDC). - 1560-7917 .- 1025-496X. ; 29:2
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundIn Sweden, information on seroprevalence of tick-borne encephalitis virus (TBEV) in the population, including vaccination coverage and infection, is scattered. This is largely due to the absence of a national tick-borne encephalitis (TBE) vaccination registry, scarcity of previous serological studies and use of serological methods not distinguishing between antibodies induced by vaccination and infection. Furthermore, the number of notified TBE cases in Sweden has continued to increase in recent years despite increased vaccination.AimThe aim was to estimate the TBEV seroprevalence in Sweden.MethodsIn 2018 and 2019, 2,700 serum samples from blood donors in nine Swedish regions were analysed using a serological method that can distinguish antibodies induced by vaccination from antibodies elicited by infection. The regions were chosen to reflect differences in notified TBE incidence.ResultsThe overall seroprevalence varied from 9.7% (95% confidence interval (CI): 6.6-13.6%) to 64.0% (95% CI: 58.3-69.4%) between regions. The proportion of vaccinated individuals ranged from 8.7% (95% CI: 5.8-12.6) to 57.0% (95% CI: 51.2-62.6) and of infected from 1.0% (95% CI: 0.2-3.0) to 7.0% (95% CI: 4.5-10.7). Thus, more than 160,000 and 1,600,000 individuals could have been infected by TBEV and vaccinated against TBE, respectively. The mean manifestation index was 3.1%.ConclusionA difference was observed between low- and high-incidence TBE regions, on the overall TBEV seroprevalence and when separated into vaccinated and infected individuals. The estimated incidence and manifestation index argue that a large proportion of TBEV infections are not diagnosed.
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| 26. |
- Albinsson, Bo, 1963, et al.
(författare)
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The Electronically Excited-States of 2-Phenylindole
- 1991
-
Ingår i: Chemical Physics. - 0301-0104. ; 151:1, s. 149-157
-
Tidskriftsartikel (refereegranskat)abstract
- The light absorption of 2-phenylindole (2PI) in the UV region (210-350 nm) is investigated by means of linear dichroism in stretched polyethylene film and fluorescence polarization anisotropy in a propylene glycol glass. Experimentally, 2PI is found to have five distinct electronic transitions located above 200 nm for which the transition moments are determined. The conclusions are supported by quantum chemical calculations and the origin of the so-called composite band is discussed. Comparison with the absorption spectrum of the fluorescent DNA binding probe DAPI is also made and 2PI is found to be an appropriate model system for the electronic transitions of DAPI.
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| 27. |
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| 28. |
- Albinsson, Bo, 1963, et al.
(författare)
-
The origin of lignin fluorescence
- 1999
-
Ingår i: Journal of Molecular Structure. - 0022-2860. ; 508:1-3, s. 19-27
-
Tidskriftsartikel (refereegranskat)abstract
- Spruce lignin exhibits fluorescence emission spectra that peaks at approximate to 360 nm on excitation at wavelengths ranging from 240 to 320 nm. This can be explained by non-radiative energy transfer from lignin chromophores, that are excited in the wavelength range 240-320 nm, to an acceptor that emits fluorescent Light at approximate to 360 nm. Examinations of lignin samples and model compounds suggest that small amounts of phenylcoumarone structures in the lignin is a conceivable acceptor. Such structures and stilbene structures are formed from structural elements in lignin of the phenylcoumaran type on various treatments. The photophysical properties of models for phenylcoumarone structures [2-(3,4-dimethoxyphenyl)-7-methoxy-3-methyo[b]-furan, 2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-7-methoxybenzo[b]furan] and stilbene structures (the E and Z forms of 2-hydroxy-3,3',4'-trimethoxystilbene) have been examined and are discussed on the basis of crystal structure determinations. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 29. |
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| 30. |
- Albinsson, Bo, 1963, et al.
(författare)
-
Untapping solar energy resources
- 2020
-
Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 14:9, s. 528-530
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 31. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
All-photonic molecular half-adder
- 2006
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 128:50, s. 16259-16265
-
Tidskriftsartikel (refereegranskat)abstract
- One molecule acts as both an AND and an XOR Boolean logic gate that share the same two photonic inputs. The molecule comprises a half-adder, adding two binary digits with only light as inputs and outputs, and consists of three covalently linked photochromic moieties, a spiropyran and two quinolinederived dihydroindolizines. The AND function is based on the absorption properties of the molecule, whereas the XOR function is based on an off-on-off response of the fluorescence to the inputs that results from interchromophore excited-state quenching interactions. The half-adder is simple to operate and can be cycled many times.
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| 32. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
Efficient non-radiative deactivation and conformational flexibility of meso-diaryloctaalkylporphyrins in the excited triplet state
- 2000
-
Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 104:41, s. 9307-9314
-
Tidskriftsartikel (refereegranskat)abstract
- The excited triplet state deactivation of zinc(II) meso-diaryloctaalkylporphyrins (ZnDAOAP) has been studied over a wide temperature range using transient triplet-triplet absorption spectroscopy together with steady-state and time-resolved phosphorescence techniques, The results from transient absorption measurements show that the depopulation of the initially formed triplet state (T-1A state) is unusually fast at temperatures above 150 K. The efficiency of the deactivation originates from a spin allowed transition to a second tripler state (T-1B state), The transformation process T-1A-->T-1B is therefore the dominating deactivation channel of the T-1A state in this temperature range, and direct intersystem crossing T-1A-->S-0 makes negligible contribution. The subsequent ground-state recovery T-1B-->S-0 is also very efficient in comparison to many other porphyrins. Due to the substantial activation energy found for the transformation process, it most likely involves a conformational distortion of the porphyrin macrocycle. At low temperature, however, the relaxation of the T-1A State occurs by direct intersystem crossing to the ground state.
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| 33. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
Molecular AND logic gate based on electric dichroism of a photochromic dihydroindolizine
- 2005
-
Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 44:46, s. 7591-7594
-
Tidskriftsartikel (refereegranskat)abstract
- (Chemical Equation Presented) Very ANDy: A photochromic molecular switch has been found to act as an AND Boolean logic gate. The switch takes as input both UV light, which causes photo-isomerization of a dihydroindolizine to an open, dipolar form, and an electric field, which aligns this isomer in solution (see scheme). The output of the gate is read as the electric linear dichroism response of the open isomer. The gate can be reset with visible light. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.
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| 34. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
Photoinduced hole transfer from the triplet state in a porphyrin-based donor-bridge-acceptor system
- 2003
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 107:42, s. 8825-8833
-
Tidskriftsartikel (refereegranskat)abstract
- The triplet excited-state deactivation of a gold porphyrin (AuP) in porphyrin-based donor-bridge-acceptor (D-B-A) systems has been studied. The results from room temperature and 80 K measurements are presented. The primary objectives have been to investigate whether electrons/electron holes or excitation energy could be transferred from (AuP)-Au-3 to the appended zinc porphyrin (ZnP) in the dimers. As the bridging chromophores in our D-B-A systems separate the ZnP and AuP moieties by 19 A edge-to-edge, we do not expect a significant contribution to either electron or energy transfer from a direct (through space) exchange mechanism. This gives us the opportunity to scrutinize how the bridging chromophores influence the transfer reactions. The results show that quenching of (AuP)-Au-3 occurs with high efficiency in the dimers that are connected by fully conjugated bridging chromophores, whereas no quenching is observed when the conjugation of the bridge is broken. We also observed that the decay of (AuP)-Au-3 is complex at temperatures below 110 K. In addition to the two previously published lifetimes on the order of some 10-100 mus, we have found a third lifetime on the nanosecond time scale.
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| 35. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
Temperature and viscosity dependence of the triplet energy transfer process in porphyrin dimers
- 2002
-
Ingår i: Photochemical & Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-905X .- 1474-9092. ; 1:2, s. 111-119
-
Tidskriftsartikel (refereegranskat)abstract
- The temperature and viscosity dependence of the triplet energy transfer (TET) process in porphyrin dimers has been studied. A zinc porphyrin (donor) and a free base porphyrin (acceptor) are covalently linked together by rigid bridging chromophores at a center-center distance of 25 Angstrom. Due to the large donor-acceptor distance and the weakness of the spin forbidden transitions involved, neither direct (through space) electron exchange nor Coulombic mechanisms are expected to contribute to the observed TET process. The results from transient absorption measurements at temperatures between room temperature and 80 K show that TET occurs with unexpectedly high efficiency in the systems connected by fully conjugated bridges and a pronounced temperature dependence of the process is observed. Comparison of the TET efficiencies in dimers connected by different bridging chromophores correlates well with a transfer reaction governed by a through bond exchange (superexchange) interaction. However, in high viscosity media the TET process is dramatically slowed down. This is attributed to a conformational gating of the TET process where the electronic coupling varies strongly with the relative orientation of the donor and the bridging chromophore. Further, the zinc porphyrin donor offers two distinct donor species, T-1A and T-1B. At room temperature, the TET rate constant of the T-1A Species is about two orders of magnitude larger than for the T-1B species. The dimers studied are well suited model systems for materials where the rate of the transfer reactions can be changed by external stimuli.
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| 36. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
The gold porphyrin first excited singlet state
- 2002
-
Ingår i: Photochemistry and Photobiology. - 0031-8655 .- 1751-1097. ; 76:1, s. 47-50
-
Tidskriftsartikel (refereegranskat)abstract
- Gold porphyrins are often used as electron-accepting chromophores in artificial photosynthetic constructs. Because of the heavy atom effect, the gold porphyrin first-excited singlet state undergoes rapid intersystem crossing to form the triplet state. The lowest triplet state can undergo a reduction by electron donation from a nearby porphyrin or another moiety. In addition, it can be involved in triplet-triplet energy transfer interactions with other chromophores. In contrast, little has been known about the short-lived singlet excited state. In this work, ultrafast time-resolved absorption spectroscopy has been used to investigate the singlet excited state of Au(III) 5,15-bis(3,5-di-t-butylphenyl)-2,8,12,18,-tetraethyl-3,7,13,17-tetrameth ylporphyrin in ethanol solution. The excited singlet state is found to form with the laser pulse and decay with a time constant of 240 fs to give the triplet state. The triplet returns to the ground state with a lifetime of 400 ps. The lifetime of the singlet state is comparable with the time constants for energy and photoinduced electron transfer in some model and natural photosynthetic systems. Thus, it is kinetically competent to take part in such processes in suitably designed supermolecular systems.
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| 37. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
The photophysical properties of the adenine chromophore
- 1999
-
Ingår i: Journal of Physical Chemistry B. ; 103:44, s. 9782-9789
-
Tidskriftsartikel (refereegranskat)abstract
- The efficient nonradiative deactivation process of the excited adenine chromophore is studied in this paper. By comparing the photophysical properties and temperature dependence of several alkylated adenine derivatives, a mechanism for the thermally activated internal conversion process is suggested, Several alkylamino derivatives of adenine show dual fluorescence, and the solvent dependence of the excited states is investigated. It is concluded that the long wavelength emission originates from a CT state involving the alkylamino group and purine chromophore as donor and acceptor, respectively. The experimental observations are supported by quantum mechanical calculations, and the results are summarized into a model for the photophysical properties of the adenine chromophore. In this model, the two excited states associated with the dual emission from the alkylamino derivatives are populated from a common Franck-Condon state followed by independent decay to the ground state.
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| 38. |
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| 39. |
- Bharmoria, Pankaj, et al.
(författare)
-
Far-red triplet sensitized Z-to-E photoswitching of azobenzene in bioplastics
- 2022
-
Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 13, s. 11904-11911
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first example of direct far-red triplet sensitized molecular photoswitching in a condensed phase wherein a liquid azobenzene derivative (Azo1) co-assembled within a liquid surfactant-protein film undergoes triplet sensitized Z-to-E photoswitching upon far-red/red light excitation in air. The role of triplet sensitization in photoswitching has been confirmed by quenching of sensitizer phosphorescence by Z-Azo1 and temperature-dependent photoswitching experiments. Herein, we demonstrate new biosustainable fabrication designs to address key challenges in solid-state photoswitching, effectively mitigating chromophore aggregation and requirement of high energy excitations by dispersing the photoswitch in the trapped liquid inside the solid framework and by shifting the action spectrum from blue-green light (450-560 nm) to the far-red/red light (740/640 nm) region.
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| 40. |
- Bharmoria, Pankaj, 1985, et al.
(författare)
-
Recyclable optical bioplastics platform for solid state red light harvesting via triplet-triplet annihilation photon upconversion
- 2022
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 10:40, s. 21279-21290
-
Tidskriftsartikel (refereegranskat)abstract
- Sustainable photonics applications of solid-state triplet-triplet annihilation photon upconversion (TTA-UC) are limited by a small UC spectral window, low UC efficiency in air, and non-recyclability of polymeric materials used. In a step to overcome these issues, we have developed new recyclable TTA-UC bioplastics by encapsulating TTA-UC chromophores liquid inside the semicrystalline gelatin films showing broad-spectrum upconversion (red/far-red to blue) with high UC efficiency in air. For this, we synthesized a new anionic annihilator, sodium-TIPS-anthracene-2-sulfonate (TIPS-AnS), that combined with red/far-red sensitizers (PdTPBP/Os(m-peptpy)(2)(TFSI)(2)), a liquid surfactant Triton X-100 reduced (TXr) and protein gelatin (G) formed red/far-red to blue TTA-UC bioplastic films just by air drying of their aqueous solutions. The G-TXr-TIPS-AnS-PdTPBP film showed record red to blue (633 to 478 nm) TTA-UC quantum yield of 8.5% in air. The high UC quantum yield has been obtained due to the fluidity of dispersed TXr containing chromophores and oxygen blockage by gelatin fibers that allowed efficient diffusion of triplet excited chromophores. Further, the G-TXr-TIPS-AnS-Os(m-peptpy)(2)(TFSI)(2) bioplastic film displayed far-red to blue (700-730 nm to 478 nm) TTA-UC, demonstrating broad-spectrum photon harvesting. Finally, we demonstrated the recycling of G-TXr-TIPS-AnS-PdTPBP bioplastics by developing a downstream approach that gives new directions for designing future recyclable photonics bioplastic materials.
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| 41. |
- Börjesson, Karl, 1982, et al.
(författare)
-
A Bioinspired Self Assembled Dimeric Porphyrin Pocket that Binds Electron Accepting Ligands
- 2012
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 48:12, s. 1793-1795
-
Tidskriftsartikel (refereegranskat)abstract
- A binding pocket consisting of two zinc porphyrins self assembled by Watson-Crick base pairing is presented. The porphyrin binding pocket is located in the confined environment of a lipid membrane whereas the DNA is located in the water phase. Bidentate electron accepting ligands are shown to coordinate in-between the two porphyrins.
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| 42. |
- Börjesson, Karl, 1982, et al.
(författare)
-
A membrane anchored DNA-based energy/electron transfer assembly
- 2008
-
Ingår i: Nucleic acids symposium series (2004). - 1746-8272. ; :52, s. 691-691
-
Tidskriftsartikel (refereegranskat)abstract
- In this work the trapping and conversion of visible light energy into chemical energy is examined using a supramolecular assembly. This consists of a light absorbing antenna and a porphyrin redox centre both covalently attached to a DNA strand, which in turn is bound to a lipid membrane. The excitation energy is finally trapped as a benzoquinone radical anion that could potentially be used in subsequent chemical reactions.
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| 43. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Characterization and use of tricyclic fluorescent nucleic acid base analogues
- 2008
-
Ingår i: Nucleic acids symposium series (2004). - 1746-8272. ; :52, s. 3-4
-
Tidskriftsartikel (refereegranskat)abstract
- The two recently developed nucleic acid probe molecules tC and tC(O) both have unique properties compared to other molecules in the family of fluorescent base analogues.(1-5) These tricyclic base analogues both form very stable base pairs with guanine and give minimal perturbations to the native structure of DNA.(2) We have found that tC(O) is the brightest fluorescent base analogue reported(4) and that tC also is very bright and has a fluorescence quantum yield that is virtually insensitive to its surrounding microenvironment within the nucleic acid(3). These base analogues have so far been used in FRET-studies of a DNA-polymerase system(6) and in initial anisotropy-studies of DNA-containing systems(4).
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| 44. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Conjugated anthracene dendrimers with monomer-like fluorescence
- 2014
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:38, s. 19846-19850
-
Tidskriftsartikel (refereegranskat)abstract
- Two generations of highly emissive conjugated anthracene dendrimers containing up to 9 anthracene units are presented. In these dendrimers, anthracene-like absorption and emission properties are preserved due to the relatively weak electronic coupling between the anthracene units, while evidence of fast crosstalk within the molecular framework is still observed.
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| 45. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Functionalized Nanostructures: Redox-Active Porphyrin Anchors for Supramolecular DNA Assemblies
- 2010
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 4:9, s. 5037-5046
-
Tidskriftsartikel (refereegranskat)abstract
- We have synthesized and studied a supramolecular system comprising a 39-mer DNA with porphyrin-modified thymidine nucleosides anchored to the surface of large unilamellar vesicles (liposomes). Liposome porphyrin binding characteristics, such as orientation, strength, homogeneity, and binding site size, was determined, suggesting that the porphyrin is well suited as a photophysical and redox-active lipid anchor, in comparison to the inert cholesterol anchor commonly used today. Furthermore, the binding characteristics and hybridization capabilities were studied as a function of anchor size and number of anchoring points, properties that are of importance for our future plans to use the addressability of these redox-active nodes in larger DNA-based nanoconstructs. Electron transfer from photoexcited porphyrin to a lipophilic benzoquinone residing in the lipid membrane was characterized by steady-state and time-resolved fluorescence and verified by femtosecond transient absorption.
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| 46. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Membrane-Anchored DNA Assembly for Energy and Electron Transfer
- 2009
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 131:8, s. 2831-2839
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we examine the trapping and conversion of visible light energy into chemical energy using a supramolecular assembly. The assembly consists of a light-absorbing antenna and a porphyrin redox center, which are covalently attached to two complementary 14-mer DNA strands, hybridized to form a double helix and anchored to a lipid membrane. The excitation energy Is finally trapped In the lipid phase of the membrane as a benzoquinone radical anion that could potentially be used In subsequent chemical reactions. In addition, In this model complex, the hydrophobic porphyrin moiety acts as an anchor into the liposome positioning the DNA construct on the lipid membrane surface. The results show the suitability of our system as a prototype for DNA-based light-harvesting devices, In which energy transfer from the aqueous phase to the interior of the lipid membrane Is followed by charge separation. © 2009 American Chemical Society.
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| 47. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Nucleic Acid Base Analog FRET-Pair Facilitating Detailed Structural Measurements in Nucleic Acid Containing Systems
- 2009
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 131:12, s. 4288-4293
-
Tidskriftsartikel (refereegranskat)abstract
- We present the first nucleobase analog fluorescence resonance energy transfer (FRET)-pair. The pair consists of tC O , 1,3-diaza-2- oxophenoxazine, as an energy donor and the newly developed tC nitro , 7-nitro-1,3-diaza-2-oxophenothiazine, as an energy acceptor. The FRET-pair successfully monitors distances covering up to more than one turn of the DNA duplex. Importantly, we show that the rigid stacking of the two base analogs, and consequently excellent control of their exact positions and orientations, results in a high control of the orientation factor and hence very distinct FRET changes as the number of bases separating tC O and tCnitro is varied. A set of DNA strands containing the FRET-pair at wisely chosen locations will, thus, make it possible to accurately distinguish distance- from orientation-changes using FRET. In combination with the good nucleobase analog properties, this points toward detailed studies of the inherent dynamics of nucleic acid structures. Moreover, the placement of FRET-pair chromophores inside the base stack will be a great advantage in studies where other (biomacro)molecules interact with the nucleic acid. Lastly, our study gives possibly the first truly solid experimental support to the dependence of energy transfer efficiency on orientation of involved transition dipoles as predicted by the Forster theory. © 2009 American Chemical Society.
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| 48. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Photon up-conversion and molecular solar thermal energy storage: New materials and devices
- 2014
-
Ingår i: 2014 IEEE Photonics Conference, IPC 2014. ; , s. 445-446
-
Konferensbidrag (refereegranskat)abstract
- In a future society with limited access to fossil fuels, technologies for efficient on demand delivery of renewable energy are highly desirable. In this regard, methods that allow for solar energy storage and on demand solar driven energy generation are particularly relevant since the sun is the most abundant energy source.
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| 49. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Photon up-converting devices for solar fuels
- 2014
-
Ingår i: SPIE Newsroom. - : SPIE-Intl Soc Optical Eng. - 1818-2259.
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Employing a molecular solution capable of triplet-triplet annihilation in a layered microfluidic device enables the solar spectrum to be locally modified toward the UV, increasing solar energy system efficiency.
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| 50. |
- Börjesson, Karl, 1982, et al.
(författare)
-
Photon upconversion facilitated molecular solar energy storage
- 2013
-
Ingår i: Journal of Materials Chemistry. - 1364-5501 .- 0959-9428. ; 1, s. 8521-8524
-
Tidskriftsartikel (refereegranskat)abstract
- Photon upconversion is used to facilitate the production of a solar fuel. This is done by collocating a triplet–triplet annihilation upconversion system in a microfluidic device with a molecular solar thermal energy storage system. Incoherent truncated white light is used to drive the reaction and the green part of the spectrum is upconverted to blue light, which in turn is absorbed by the solar fuel.
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