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| 2. |
- Sjöqvist, Jonas, 1985-, et al.
(författare)
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A combined MD/QM and experimental exploration of conformational richness in branched oligothiophenes
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 16:45, s. 24841-24852
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Tidskriftsartikel (refereegranskat)abstract
- Infrared (IR) absorption and vibrational Raman spectra of a family of branched oligothiophenes have been determined experimentally as well as theoretically. The molecular spectra have been compared to those of the linear analogues, with identification made of spectral features due to structural properties that are valued in organic solar cell applications. The theoretical spectra have been obtained through a newly developed method in which individual conformer spectra, calculated at the time-dependent DFT level in this work, are weighted by statistics extracted from classical molecular dynamics trajectories. The agreement with experiment for the resulting averaged spectra is at least as good as, and often better than, what is observed for Boltzmann-weighted spectra. As the weights are available before the costly step of spectrum calculation, the method has the additional advantage of enabling efficient approximations. For simulating the molecular dynamics of the studied α,β-linked thiophenes and 2-methylthiophenes, high quality parameters have been derived for the CHARMM force field. Furthermore, the temperature dependence of the IR and Raman spectra have been investigated, both experimentally and theoretically.
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| 3. |
- Barcelo, Marta, et al.
(författare)
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Isolation and culture of strawberry protoplasts and field evaluation of regenerated plants
- 2019
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Ingår i: Scientia Horticulturae. - : ELSEVIER. - 0304-4238 .- 1879-1018. ; 256
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Tidskriftsartikel (refereegranskat)abstract
- Protoplasts are an useful biotechnological tool for plant improvement In strawberry, very few studies on protoplast technology have been carried out. In this investigation, a procedure for the isolation and culture of strawberry protoplasts, cv. 'Chandler', has been developed. The effect of several factors affecting the successful isolation of protoplasts and formation of microcalli, e.g. explant source, washing procedure, hormonal composition of the culture medium and protoplast density, were evaluated. For shoot regeneration, microcalli derived from isolated protoplasts were transferred to MS medium supplemented with 0.2 mg l(-1) NAA and either 5 mg l(-1) BA or 3 mgl(-1) TDZ, obtaining a similar regeneration rate, 17%, in both media. Twenty-one independent protoclones were transferred to field conditions for agronomic evaluation. Significant alterations in the growth habit, density of foliage, leaf color and leaf morphology were detected in some lines. Fruit yield was significantly reduced in 15 out of the 21 protoclones evaluated due to a reduction in fruit weight and/or the number of fruits. Ploidy level was unaffected in a sample of 6 lines selected at random; however, a study of genetic stability by using 10 EST-SSR markers showed genetic alterations in all the lines analyzed. Despite the high rate of somaclonal variation detected in the protoclones, some of the lines displayed an agronomical behavior similar to control plants, indicating that this protocol could be useful for genetic improvement in this species.
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| 4. |
- De Groot, Natasja M.S., et al.
(författare)
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Critical appraisal of technologies to assess electrical activity during atrial fibrillation : a position paper from the European Heart Rhythm Association and European Society of Cardiology Working Group on eCardiology in collaboration with the Heart Rhythm Society, Asia Pacific Heart Rhythm Society, Latin American Heart Rhythm Society and Computing in Cardiology
- 2022
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Ingår i: Europace. - : Oxford University Press (OUP). - 1099-5129. ; 24:2, s. 313-330
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Forskningsöversikt (refereegranskat)abstract
- We aim to provide a critical appraisal of basic concepts underlying signal recording and processing technologies applied for (i) atrial fibrillation (AF) mapping to unravel AF mechanisms and/or identifying target sites for AF therapy and (ii) AF detection, to optimize usage of technologies, stimulate research aimed at closing knowledge gaps, and developing ideal AF recording and processing technologies. Recording and processing techniques for assessment of electrical activity during AF essential for diagnosis and guiding ablative therapy including body surface electrocardiograms (ECG) and endo- or epicardial electrograms (EGM) are evaluated. Discussion of (i) differences in uni-, bi-, and multi-polar (omnipolar/Laplacian) recording modes, (ii) impact of recording technologies on EGM morphology, (iii) global or local mapping using various types of EGM involving signal processing techniques including isochronal-, voltage- fractionation-, dipole density-, and rotor mapping, enabling derivation of parameters like atrial rate, entropy, conduction velocity/direction, (iv) value of epicardial and optical mapping, (v) AF detection by cardiac implantable electronic devices containing various detection algorithms applicable to stored EGMs, (vi) contribution of machine learning (ML) to further improvement of signals processing technologies. Recording and processing of EGM (or ECG) are the cornerstones of (body surface) mapping of AF. Currently available AF recording and processing technologies are mainly restricted to specific applications or have technological limitations. Improvements in AF mapping by obtaining highest fidelity source signals (e.g. catheter-electrode combinations) for signal processing (e.g. filtering, digitization, and noise elimination) is of utmost importance. Novel acquisition instruments (multi-polar catheters combined with improved physical modelling and ML techniques) will enable enhanced and automated interpretation of EGM recordings in the near future.
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| 5. |
- DeFrancisco, Justin R., et al.
(författare)
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Torsional Bias as a Strategy To Tune Single-triplet Gaps in Organic Diradicals
- 2018
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 122:23, s. 12148-12157
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Tidskriftsartikel (refereegranskat)abstract
- Quinoidal compounds with proaromatic structures possess differing degrees of diradical character, where the open-shell diradical resonance form has restored aromaticity throughout the compound. Methods to tune the diradical character of these compounds have traditionally focused on altering the length and the molecular composition of the pi-conjugated backbones. However, other molecular design strategies to tune the singlet-triplet gap of pi-conjugated quinoidal molecules have not been extensively explored. We previously reported a strikingly small energy gap between the quinoidal and diradical states of a quinoidal small molecule containing methano[10]annulene (TMTQ) that was dictated in large part by the unusual aromaticity of the central annulene ring. Here, we report on two alkylated derivatives of TMTQthat present substantially different torsional biases to the planarity of the TMTQ pi-system. Using a combination of electronic and vibrational spectroscopies, magnetic measurements, and quantum chemical calculations, we demonstrate here how a steric effect rather than pi-electron compositional molecular engineering can dramatically narrow the singlet-triplet gap of a quinoidal compound to as small as -0.52 kcal/mol, determined experimentally. This study offers important insight for the continued development of open-shell diradical molecules that need not rely exclusively on the design of synthesis of new and complex conjugated systems.
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| 6. |
- Garrido-Arandia, Mariá, et al.
(författare)
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Characterisation of a flavonoid ligand of the fungal protein Alt a 1
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Spores of pathogenic fungi are virtually ubiquitous and cause human disease and severe losses in crops. The endophytic fungi Alternaria species produce host-selective phytotoxins. Alt a 1 is a strongly allergenic protein found in A. alternata that causes severe asthma. Despite the well-established pathogenicity of Alt a 1, the molecular mechanisms underlying its action and physiological function remain largely unknown. To gain insight into the role played by this protein in the pathogenicity of the fungus, we studied production of Alt a 1 and its activity in spores. We found that Alt a 1 accumulates inside spores and that its release with a ligand is pH-dependent, with optimum production in the 5.0-6.5 interval. The Alt a 1 ligand was identified as a methylated flavonoid that inhibits plant root growth and detoxifies reactive oxygen species. We also found that Alt a 1 changes its oligomerization state depending on the pH of the surrounding medium and that these changes facilitate the release of the ligand. Based on these results, we propose that release of Alt a 1 should be a pathogenic target in approaches used to block plant defenses and consequently to favor fungal entry into the plant.
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| 7. |
- Gonzalez-Sanchez, Marina, et al.
(författare)
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Stacked or Folded? : Impact of Chelate Cooperativity on the Self-Assembly Pathway to Helical Nanotubes from Dinucleobase Monomers
- 2023
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 145:32, s. 17805-17818
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled nanotubesexhibit impressive biologicalfunctionsthat have always inspired supramolecular scientists in their effortsto develop strategies to build such structures from small moleculesthrough a bottom-up approach. One of these strategies employs moleculesendowed with self-recognizing motifs at the edges, which can undergoeither cyclization-stacking or folding-polymerizationprocesses that lead to tubular architectures. Which of these self-assemblypathways is ultimately selected by these molecules is, however, oftendifficult to predict and even to evaluate experimentally. We showhere a unique example of two structurally related molecules substitutedwith complementary nucleobases at the edges (i.e., G:C and A:U) for which the supramolecular pathway takenis determined by chelate cooperativity, that is, by their propensityto assemble in specific cyclic structures through Watson-Crickpairing. Because of chelate cooperativities that differ in severalorders of magnitude, these molecules exhibit distinct supramolecularscenarios prior to their polymerization that generate self-assemblednanotubes with different internal monomer arrangements, either stackedor coiled, which lead at the same time to opposite helicities andchiroptical properties.
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| 8. |
- Joshi, Siddarth Koduru, et al.
(författare)
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Space QUEST mission proposal : experimentally testing decoherence due to gravity
- 2018
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Models of quantum systems on curved space-times lack sufficient experimental verification. Some speculative theories suggest that quantum correlations, such as entanglement, may exhibit different behavior to purely classical correlations in curved space. By measuring this effect or lack thereof, we can test the hypotheses behind several such models. For instance, as predicted by Ralph et al [5] and Ralph and Pienaar [1], a bipartite entangled system could decohere if each particle traversed through a different gravitational field gradient. We propose to study this effect in a ground to space uplink scenario. We extend the above theoretical predictions of Ralph and coworkers and discuss the scientific consequences of detecting/failing to detect the predicted gravitational decoherence. We present a detailed mission design of the European Space Agency's Space QUEST (Space-Quantum Entanglement Space Test) mission, and study the feasibility of the mission scheme.
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| 9. |
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| 10. |
- Ortigoza-Escobar, Juan Darío, et al.
(författare)
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Free-thiamine is a potential biomarker of thiamine transporter-2 deficiency: a treatable cause of Leigh syndrome.
- 2016
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Ingår i: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156. ; 139:Pt 1, s. 31-8
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Tidskriftsartikel (refereegranskat)abstract
- Thiamine transporter-2 deficiency is caused by mutations in the SLC19A3 gene. As opposed to other causes of Leigh syndrome, early administration of thiamine and biotin has a dramatic and immediate clinical effect. New biochemical markers are needed to aid in early diagnosis and timely therapeutic intervention. Thiamine derivatives were analysed by high performance liquid chromatography in 106 whole blood and 38 cerebrospinal fluid samples from paediatric controls, 16 cerebrospinal fluid samples from patients with Leigh syndrome, six of whom harboured mutations in the SLC19A3 gene, and 49 patients with other neurological disorders. Free-thiamine was remarkably reduced in the cerebrospinal fluid of five SLC19A3 patients before treatment. In contrast, free-thiamine was slightly decreased in 15.2% of patients with other neurological conditions, and above the reference range in one SLC19A3 patient on thiamine supplementation. We also observed a severe deficiency of free-thiamine and low levels of thiamine diphosphate in fibroblasts from SLC19A3 patients. Surprisingly, pyruvate dehydrogenase activity and mitochondrial substrate oxidation rates were within the control range. Thiamine derivatives normalized after the addition of thiamine to the culture medium. In conclusion, we found a profound deficiency of free-thiamine in the CSF and fibroblasts of patients with thiamine transporter-2 deficiency. Thiamine supplementation led to clinical improvement in patients early treated and restored thiamine values in fibroblasts and cerebrospinal fluid.
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