| 1. |
|
|
| 2. |
- Jimenez, J. L., et al.
(författare)
-
Evolution of Organic Aerosols in the Atmosphere
- 2009
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 326:5959, s. 1525-1529
-
Tidskriftsartikel (refereegranskat)abstract
- Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high-time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Kowalewski, J, et al.
(författare)
-
Extensive NMRD studies of Ni(II) salt solutions in water and water-glycerol mixtures
- 2008
-
Ingår i: Journal of magnetic resonance. - : Elsevier BV. - 1090-7807 .- 1096-0856. ; 195, s. 103-111
-
Tidskriftsartikel (refereegranskat)abstract
- Aqueous solutions of simple nickel(II) salts are a classical test case for theories of the paramagnetic relaxation enhancement (PRE) and its dependence on the magnetic field (nuclear magnetic relaxation dispersion, NMRD), going back to late fifties. We present here new experimental data, extending the NMRD range up to 21 T (900 MHz). In addition to salt solutions in (acidified) water, we have also measured on solutions containing glycerol. The aqueous solution data do not show any significant changes compared to the earlier experiments. The interpretation, based on the general ("slow-motion") theory is also similar to the earlier work from our laboratory. The NMRD-data in mixed solvents are qualitatively different, indicating that the glycerol not only changes the solution viscosity, but may also enter the first coordination sphere of the metal ion, resulting in lower symmetry complexes, characterized by non-vanishing averaged zero-field splitting. This hypothesis is corroborated by molecular dynamics simulations. A strategy appropriate for interpreting the NMRD-data for the chemically complicated systems of this type is proposed.
|
|
| 6. |
|
|
| 7. |
- Laaksonen, A., et al.
(författare)
-
The role of VOC oxidation products in continental new particle formation
- 2008
-
Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:10, s. 2657-2665
-
Tidskriftsartikel (refereegranskat)abstract
- Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March-April 2003, in Hyytiala, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10-50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3-10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.
|
|
| 8. |
|
|
| 9. |
- Almqvist, Jonas, et al.
(författare)
-
Docking and homology modeling explain inhibition of the human vesicular glutamate transporters
- 2007
-
Ingår i: Protein Science. - 0961-8368 .- 1469-896X. ; 16:9, s. 1819-1829
-
Tidskriftsartikel (refereegranskat)abstract
- As membrane transporter proteins, VGLUT1-3 mediate the uptake of glutamate into synaptic vesicles at presynaptic nerve terminals of excitatory neural cells. This function is crucial for exocytosis and the role of glutamate as the major excitatory neurotransmitter in the central nervous system. The three transporters, sharing 76% amino acid sequence identity in humans, are highly homologous but differ in regional expression in the brain. Although little is known regarding their three- dimensional structures, hydropathy analysis on these proteins predicts 12 transmembrane segments connected by loops, a topology similar to other members in the major facilitator superfamily, where VGLUT1-3 have been phylogenetically classified. In this work, we present a three- dimensional model for the human VGLUT1 protein based on its distant bacterial homolog in the same superfamily, the glycerol- 3-phosphate transporter from Escherichia coli. This structural model, stable during molecular dynamics simulations in phospholipid bilayers solvated by water, reveals amino acid residues that face its pore and are likely to affect substrate translocation. Docking of VGLUT1 substrates to this pore localizes two different binding sites, to which inhibitors also bind with an overall trend in binding affinity that is in agreement with previously published experimental data.
|
|
| 10. |
|
|
