| 1. |
- Andersson, Emma K., et al.
(författare)
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Modulation of Curli Assembly and Pellicle Biofilm Formation by Chemical and Protein Chaperones
- 2013
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Ingår i: Chemistry and Biology. - : Elsevier. - 1074-5521 .- 1879-1301. ; 20:10, s. 1245-1254
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Tidskriftsartikel (refereegranskat)abstract
- Enteric bacteria assemble functional amyloid fibers, curli, on their surfaces that share structural and biochemical properties with disease-associated amyloids. Here, we test rationally designed 2-pyridone compounds for their ability to alter amyloid formation of the major curli subunit CsgA. We identified several compounds that discourage CsgA amyloid formation and several compounds that accelerate CsgA amyloid formation. The ability of inhibitor compounds to stop growing CsgA fibers was compared to the same property of the CsgA chaperone, CsgE. CsgE blocked CsgA amyloid assembly and arrested polymerization when added to actively polymerizing fibers. Additionally, CsgE and the 2-pyridone inhibitors prevented biofilm formation by Escherichia coli at the air-liquid interface of a static culture. We demonstrate that curli amyloid assembly and curli-dependent biofilm formation can be modulated not only by protein chaperones, but also by "chemical chaperones."
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| 2. |
- Asgharian, Hossein, et al.
(författare)
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Jump Spillover in International Equity Markets
- 2006
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Ingår i: Journal of Financial Econometrics. - : Oxford University Press (OUP). - 1479-8409 .- 1479-8417. ; 4:2, s. 167-203
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Tidskriftsartikel (refereegranskat)abstract
- In this article we study jump spillover effects between a number of country equity indexes. In order to identify the latent historical jumps of each index, we use a Bayesian approach to estimate a jump-diffusion model on each index. We look at the simultaneous jump intensities of pairs of countries and the probabilities that jumps in large countries cause jumps or unusually large returns in other countries. In all cases, we find significant evidence of jump spillover. In addition, we find that jump spillover seems to be particularly large between countries that belong to the same regions and have similar industry structures, whereas, interestingly, the sample correlations between the countries have difficulties in capturing the jump spillover effects.
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| 3. |
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| 4. |
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| 5. |
- Bengtsson, Christoffer
(författare)
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Applications of Bayesian Econometrics to Financial Economics
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This PhD thesis consists of four separate papers. What these papers have in common is that Bayesian Econometrics, in combination with Markov chain Monte Carlo (MCMC) methods, is applied to study various problems in financial economics. The first two papers are further related in that they both deal with portfolio selection and estimation risk, as are the last two papers in that they both deal with international aspects of extreme stock returns. The first paper, "The Impact of Estimation Error on Single-Period Portfolio Selection", examines the impact of estimation error on single-period portfolio selection. This is done under slightly more realistic assumptions than those made by Chopra and Ziemba (1993, Journal of Portfolio Management 19, 6-12) in frequently cited paper, but still using their basic approach and simulation methodology, in which simulated estimation error is added to what are assumed to be the true mean vector and covariance matrix of returns. To obtain estimation error sizes that are more consistent with those in actual estimates, a Bayesian approach based on MCMC methods is used. The paper also looks at what effects short selling constraint have on the impact of estimation error. The empirical results differ from those of Chopra and Ziemba (1993), suggesting that the effect of estimation error may have been overestimated in the past. Furthermore, when some short selling is allowed, the paper finds reason to question the traditional viewpoint that estimating the covariance matrix correctly is always less important than estimating the mean vector correctly. The second paper, "A Shrinkage Estimator of the Covariance Matrix for Improved Mean-Variance Optimization", proposes a shrinkage estimator of the covariance matrix of returns which shrinks the usual sample covariance matrix towards a K-factor principal component covariance matrix. In addition, the paper examines the gains from taking into account the uncertainty of the estimated covariance matrix when selecting portfolios. This is done through portfolio resampling based on the posterior distribution of the covariance matrix quantified with MCMC methods. In an empirical contest between estimators, where the objective is to pick portfolios with as low out-of-sample volatility as possible, the proposed estimator is found to perform better than all other competing estimators. In addition, it is found that the out-of-sample volatility can be reduced even further through portfolio resampling. The third paper, "Jump Spillover in International Equity Markets", co-authored with Hossein Asgharian, studies what is referred to as jump spillover effects between a number of international equity indices. In order to identify the latent historical jumps of each index, a univariate stochastic volatility jump-diffusion model is estimated on each index using a Bayesian approach based on MCMC methods. The paper looks at the simultaneous jump intensities of pairs of countries and the probabilities that jumps in large countries cause jumps or unusually large returns in other countries. In all cases, significant evidence of jump spillover is found. In addition, it is found that jump spillover seems to be particularly large and significant between countries that belong to the same regions and have similar industry structures, whereas, interestingly, the sample correlations between the countries have difficulties in capturing the jump spillover effects. The fourth paper, "International Jumps in Returns", examines, just as the previous paper, the international aspects of jumps in returns, but does so in an econometrically more formal manner. The paper proposes a multivariate stochastic volatility jump-diffusion model which is estimated on three groups of major North American, European, and Asian equity indices. The model assumes that returns are affected by both systemic (simultaneous across markets) and idiosyncratic (market specific) jumps. In all three cases, significant evidence of the existence of systemic jumps is found. In the North American markets (the United States and Canada), the majority of jumps are systemic, whereas in the European markets (the United Kingdom, Germany, and France) and the Asian markets (Japan and Hong Kong), the majority of jumps are idiosyncratic. In all cases, the mean sizes of systemic jumps are significantly negative, while the mean sizes of idiosyncratic jumps are not significantly different from zero. Surprisingly, the finding in all cases is that the correlation coefficients between the sizes of systemic jumps are relatively small and not significantly different from zero.
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| 7. |
- Bengtsson, Christoffer, et al.
(författare)
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Asymmetric Synthesis of 2,4,5-Trisubstituted (2)-Thiazolines
- 2013
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:30, s. 9916-9922
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Tidskriftsartikel (refereegranskat)abstract
- (2)-Thiazolines are interesting heterocycles that display a wide variety of biological characteristics. They are also common in chiral ligands used for asymmetric syntheses and as synthetic intermediates. Herein, we present asymmetric routes to 2,4,5-trisubstituted (2)-thiazolines. These (2)-thiazolines were synthesized from readily accessible/commercially available ,-unsaturated methyl esters through a Sharpless asymmetric dihydroxylation and an ON acyl migration reaction as key steps. The final products were obtained in good yields with up to 97% enantiomeric excess.
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| 8. |
- Bengtsson, Christoffer, et al.
(författare)
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Design, synthesis and evaluation of triazole functionalized Ring-fused 2-pyridones as antibacterial agents
- 2012
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Ingår i: European Journal of Medicinal Chemistry. - : Elsevier. - 0223-5234 .- 1768-3254. ; 54, s. 637-646
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Tidskriftsartikel (refereegranskat)abstract
- Antibacterial resistance is today a worldwide problem and the demand for new classes of antibacterial agents with new mode of action is enormous. In the strive for new antibacterial agents that inhibit pilus assembly, an important virulence factor, routes to introduce triazoles in position 8 and 2 of ring-fused bicyclic 2-pyridones have been developed. This was made via Sonogashira couplings followed by Huisgen 1,3-dipolar cycloadditions. The method development made it possible to introduce a diverse series of substituted triazoles and their antibacterial properties were tested in a whole cell pili-dependent biofilm assay. Most of the twenty four candidates tested showed low to no activity but interestingly three compounds, one 8-substituted and two 2-substituted, showed promising activities with EC50’s between 9-50 μM.
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| 9. |
- Bengtsson, Christoffer, 1979-, et al.
(författare)
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Rapid Construction of a Chloromethyl-Substituted Duocarmycin-like Prodrug
- 2023
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Ingår i: Molecules. - 1431-5157 .- 1420-3049. ; 28:12
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Tidskriftsartikel (refereegranskat)abstract
- The construction of duocarmycin-like compounds is often associated with lengthy synthetic routes. Presented herein is the development of a short and convenient synthesis of a type of duocarmycin prodrug. The 1,2,3,6-tetrahydropyrrolo[3,2-e]indole-containing core is here constructed from commercially available Boc-5-bromoindole in four steps and 23% overall yield, utilizing a Buchwald-Hartwig amination followed by a sodium hydride-induced regioselective bromination. In addition, protocols for selective mono- and di-halogenations of positions 3 and 4 were also developed, which could be useful for further exploration of this scaffold.
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| 10. |
- Bengtsson, Christoffer, et al.
(författare)
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Regioselective Halogenations and Subsequent Suzuki-Miyaura Coupling onto Bicyclic 2-Pyridones
- 2010
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Ingår i: The Journal of organic chemistry. - : American Chemical Society. - 1520-6904 .- 0022-3263. ; 75:3, s. 972-5
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Tidskriftsartikel (refereegranskat)abstract
- A selective synthesis of 6-bromo-8-iodo dihydro thiazolo ring-fused 2-pyridones is described. These halogenated 2-pyridones are selectively arylated by sequential Suzuki-Miyaura couplings. This approach can advantageously be used to synthesize focused libraries of substituted ring-fused 2-pyridones, a class of compounds with novel antibacterial properties.
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