| 1. |
- Fan, Mingzhen, et al.
(författare)
-
The Legionella autoinducer LAI-1 is delivered by outer membrane vesicles to promote interbacterial and interkingdom signaling
- 2023
-
Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 299:12
-
Tidskriftsartikel (refereegranskat)abstract
- Legionella pneumophila is an environmental bacterium, which replicates in amoeba but also in macrophages, and causes a life-threatening pneumonia called Legionnaires’ disease. The opportunistic pathogen employs the α-hydroxy-ketone compound Legionella autoinducer-1 (LAI-1) for intraspecies and interkingdom signaling. LAI-1 is produced by the autoinducer synthase Legionella quorum sensing A (LqsA), but it is not known, how LAI-1 is released by the pathogen. Here, we use a Vibrio cholerae luminescence reporter strain and liquid chromatography-tandem mass spectrometry to detect bacteria-produced and synthetic LAI-1. Ectopic production of LqsA in Escherichia coli generated LAI-1, which partitions to outer membrane vesicles (OMVs) and increases OMV size. These E. coli OMVs trigger luminescence of the V. cholerae reporter strain and inhibit the migration of Dictyostelium discoideum amoeba. Overexpression of lqsA in L. pneumophila under the control of strong stationary phase promoters (PflaA or P6SRNA), but not under control of its endogenous promoter (PlqsA), produces LAI-1, which is detected in purified OMVs. These L. pneumophila OMVs trigger luminescence of the Vibrio reporter strain and inhibit D. discoideum migration. L. pneumophila OMVs are smaller upon overexpression of lqsA or upon addition of LAI-1 to growing bacteria, and therefore, LqsA affects OMV production. The overexpression of lqsA but not a catalytically inactive mutant promotes intracellular replication of L. pneumophila in macrophages, indicating that intracellularly produced LA1-1 modulates the interaction in favor of the pathogen. Taken together, we provide evidence that L. pneumophila LAI-1 is secreted through OMVs and promotes interbacterial communication and interactions with eukaryotic host cells.
|
|
| 2. |
- Gong, Miaoxin, et al.
(författare)
-
Fiber-based stray light suppression in spectroscopy using periodic shadowing
- 2021
-
Ingår i: Optics Express. - 1094-4087. ; 29:5, s. 7232-7246
-
Tidskriftsartikel (refereegranskat)abstract
- Stray light is a known strong interference in spectroscopic measurements. Photons from high-intensity signals that are scattered inside the spectrometer, or photons that enter the detector through unintended ways, will be added to the spectrum as an interference signal. A general experimental solution to this problem is presented here by introducing a customized fiber for signal collection. The fiber-mount to the spectrometer consists of a periodically arranged fiber array that, combined with lock-in analysis of the data, is capable of suppressing stray light for improved spectroscopy. The method, which is referred to as fiber-based periodic shadowing, was applied to Raman spectroscopy in combustion. The fiber-based stray-light suppression method is implemented in an experimental setup with a high-power high-repetition-rate laser system used for Raman measurements in different room-temperature gas mixtures and a premixed flame. It is shown that the stray-light level is reduced by up to a factor of 80. Weak spectral lines can be distinguished, and therefore better molecular species identification, as well as concentration and temperature evaluation, were performed. The results show that the method is feasible and efficient in practical use and that it can be employed as a general tool for improving spectroscopic accuracy.
|
|
| 3. |
- Hendriks, Kasper P., et al.
(författare)
-
Global Brassicaceae phylogeny based on filtering of 1,000-gene dataset
- 2023
-
Ingår i: Current Biology. - : Elsevier. - 0960-9822 .- 1879-0445. ; 33:19, s. 4052-4068
-
Tidskriftsartikel (refereegranskat)abstract
- The mustard family (Brassicaceae) is a scientifically and economically important family, containing the model plant Arabidopsis thaliana and numerous crop species that feed billions worldwide. Despite its relevance, most phylogenetic trees of the family are incompletely sampled and often contain poorly supported branches. Here, we present the most complete Brassicaceae genus-level family phylogenies to date (Bras-sicaceae Tree of Life or BrassiToL) based on nuclear (1,081 genes, 319 of the 349 genera; 57 of the 58 tribes) and plastome (60 genes, 265 genera; all tribes) data. We found cytonuclear discordance between the two, which is likely a result of rampant hybridization among closely and more distantly related lineages. To eval-uate the impact of such hybridization on the nuclear phylogeny reconstruction, we performed five different gene sampling routines, which increasingly removed putatively paralog genes. Our cleaned subset of 297 genes revealed high support for the tribes, whereas support for the main lineages (supertribes) was moder-ate. Calibration based on the 20 most clock-like nuclear genes suggests a late Eocene to late Oligocene origin of the family. Finally, our results strongly support a recently published new family classification, dividing the family into two subfamilies (one with five supertribes), together representing 58 tribes. This includes five recently described or re-established tribes, including Arabidopsideae, a monogeneric tribe accommodating Arabidopsis without any close relatives. With a worldwide community of thousands of researchers working on Brassicaceae and its diverse members, our new genus-level family phylogeny will be an indispensable tool for studies on biodiversity and plant biology.
|
|
| 4. |
- Hynynen, Jonna, 1987, et al.
(författare)
-
Enhanced Electrical Conductivity of Molecularly p-Doped Poly(3-hexylthiophene) through Understanding the Correlation with Solid-State Order
- 2017
-
Ingår i: Macromolecules. - : AMER CHEMICAL SOC. - 0024-9297 .- 1520-5835. ; 50:20, s. 8140-8148
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular p-doping of the conjugated polymer poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4TCNQ) is a widely studied model system. Underlying structure property relationships are poorly understood because processing and doping are often carried out simultaneously. Here, we exploit doping from the vapor phase, which allows us to disentangle the influence of processing and doping. Through this approach, we are able to establish how the electrical conductivity varies with regard to a series of predefined structural parameters. We demonstrate that improving the degree of solid-state order, which we control through the choice of processing solvent and regioregularity, strongly increases the electrical conductivity. As a result, we achieve a value of up to 12.7 S cm(-2) for P3HT:F4TCNQ, We determine the F4TCNQ anion concentration and find that the number of (bound + mobile) charge carriers of about 10(-4) mol cm(-3) is not influenced by the degree of solid-state order. Thus, the observed increase in electrical conductivity by almost 2 orders of magnitude can be attributed to an increase in charge-carrier mobility to more than 10(-1) cm(2) V-1 s(-1). Surprisingly, in contrast to charge transport in undoped P3HT, we find that the molecular weight of the polymer does not strongly influence the electrical conductivity, which highlights the need for studies that elucidate structure property relationships of strongly doped conjugated polymers.
|
|
| 5. |
- Hynynen, Jonna, 1987, et al.
(författare)
-
Influence of crystallinity on the thermoelectric power factor of P3HT vapour-doped with F4TCNQ
- 2018
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 8:3, s. 1593-1599
-
Tidskriftsartikel (refereegranskat)abstract
- Doping of the conjugated polymer poly(3-hexylthiophene) (P3HT) with the p-dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) is a widely used model system for organic thermoelectrics. We here study how the crystalline order influences the Seebeck coefficient of P3HT films doped with F4TCNQ from the vapour phase, which leads to a similar number of F4TCNQ anions and hence (bound + mobile) charge carriers of about 2 × 10 -4 mol cm -3 . We find that the Seebeck coefficient first slightly increases with the degree of order, but then again decreases for the most crystalline P3HT films. We assign this behaviour to the introduction of new states in the bandgap due to planarisation of polymer chains, and an increase in the number of mobile charge carriers, respectively. Overall, the Seebeck coefficient varies between about 40 to 60 μV K -1 . In contrast, the electrical conductivity steadily increases with the degree of order, reaching a value of more than 10 S cm -1 , which we explain with the pronounced influence of the semi-crystalline nanostructure on the charge-carrier mobility. Overall, the thermoelectric power factor of F4TCNQ vapour-doped P3HT increases by one order of magnitude, and adopts a value of about 3 μW m -1 K -2 in the case of the highest degree of crystalline order.
|
|
| 6. |
- Kiefer, Christian, 1983-
(författare)
-
Characterisation of actin cytoskeletal functions and interactions during planar polarity formation in Arabidopsis
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The establishment of cell and tissue polarity is essential for the development of eukaryotic organisms including plants and animals. When cell polarity is uniformly organised within a plane of a single tissue layer, it is referred to as planar polarity. In the model plant Arabidopsis thaliana, the polarly organised formation of root hairs towards the basal (root tip-oriented) ends of epidermal cells provides an ideal model system to study planar polarity formation. The instructive cue which uniformly organises tissue polarity in the Arabidopsis root epidermis is a concentration gradient of the plant hormone auxin. This concentration gradient leads to the polar recruitment of Rho-of-plant proteins to membrane sites where root hairs will form, making them the earliest cellular markers of planar polarity. Despite having identified several of the components required for planar polarity formation and the cellular read-out of it, little is known about how planar polarity is perceived and stably executed on the single cell level. Recently, a role for ACTIN2 in polar hair positioning was described, suggesting that actin may be involved in the cellular read-out of planar polarity.In the work presented here, we further investigate the contribution of the actin cytoskeleton to polar hair positioning. We identify a role for actin upstream of polar Rho-of-plant (ROP) positioning and describe ACTIN7 and ACTIN-INTERACTING PROTEIN1-2 (AIP1-2) as components required for planar polarity formation which interact directly in yeast and in vitro and genetically during planar polarity formation. AIP1-2 expression proves hair cell file-specific and depends on WEREWOLF function, revealing a link between planar polarity and cell fate patterning in the root. In addition we find that ACT7 genetically interacts with SABRE (SAB) and that actin and SAB co-localise at the cell plate and plasma membrane domains during cell division. Furthermore, we show that actin is not only involved in the positioning, but also in the organisation of the polar membrane domain which marks where a root hair will form. Among the components which localise at this site are the phosphoinositide-biosynthetic enzyme PHOSPHATIDYLINOSITOL 4-PHOSPHATE 5-KINASE3 (PIP5K3), the DYNAMIN-RELATED PROTEINs (DRPs) DRP1A and DRP2B, the D6 PROTEIN KINASE (D6PK) and membrane sterols. For several of these components, we report a function in planar polarity formation and in the organisation of the hair initiation site.With this work, we provide deeper insight into the function of the actin cytoskeleton and its interactions during planar polarity formation and identify additional components that contribute to the process. Moreover, we report AIP1-2 placement under control of the cell fate patterning system during establishment of planar polarity. Our results provide stepping stones for future studies aimed at investigating the mechanistic processes that contribute to planar polarity formation in more molecular and cellular detail.
|
|
| 7. |
- Kiefer, Christian S., et al.
(författare)
-
Arabidopsis AIP1-2 restricted by WER-mediated patterning modulates planar polarity
- 2015
-
Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 142:1, s. 151-161
-
Tidskriftsartikel (refereegranskat)abstract
- The coordination of cell polarity within the plane of the tissue layer (planar polarity) is crucial for the development of diverse multicellular organisms. Small Rac/Rho-family GTPases and the actin cytoskeleton contribute to planar polarity formation at sites of polarity establishment in animals and plants. Yet, upstream pathways coordinating planar polarity differ strikingly between kingdoms. In the root of Arabidopsis thaliana, a concentration gradient of the phytohormone auxin coordinates polar recruitment of Rho-of-plant (ROP) to sites of polar epidermal hair initiation. However, little is known about cytoskeletal components and interactions that contribute to this planar polarity or about their relation to the patterning machinery. Here, we show that ACTIN7 (ACT7) represents a main actin isoform required for planar polarity of root hair positioning, interacting with the negative modulator ACTIN-INTERACTING PROTEIN1-2 (AIP1-2). ACT7, AIP1-2 and their genetic interaction are required for coordinated planar polarity of ROP downstream of ethylene signalling. Strikingly, AIP1-2 displays hair cell file-enriched expression, restricted by WEREWOLF (WER)-dependent patterning and modified by ethylene and auxin action. Hence, our findings reveal AIP1-2, expressed under control of the WER-dependent patterning machinery and the ethylene signalling pathway, as a modulator of actin-mediated planar polarity.
|
|
| 8. |
- Kiefer, David, 1989, et al.
(författare)
-
A Solution-Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics
- 2017
-
Ingår i: Advanced Science. - : Wiley. - 2198-3844 .- 2198-3844. ; 4:1, s. 1600203-
-
Tidskriftsartikel (refereegranskat)abstract
- Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution-doped conjugated polymer poly(3-hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer-thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm−1 and Seebeck coefficient from 100 to 60 μV K−1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m−1 K−1 gives rise to a thermoelectric Figure of merit ZT ∼ 10−4 that remains unaltered for an insulator content of more than 60 wt%. Free-standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.
|
|
| 9. |
- Kiefer, David, 1989, et al.
(författare)
-
Double doping of conjugated polymers with monomer molecular dopants
- 2019
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 18:2, s. 149-155
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular doping is a crucial tool for controlling the charge-carrier concentration in organic semiconductors. Each dopant molecule is commonly thought to give rise to only one polaron, leading to a maximum of one donor:acceptor charge-transfer complex and hence an ionization efficiency of 100%. However, this theoretical limit is rarely achieved because of incomplete charge transfer and the presence of unreacted dopant. Here, we establish that common p-dopants can in fact accept two electrons per molecule from conjugated polymers with a low ionization energy. Each dopant molecule participates in two charge-transfer events, leading to the formation of dopant dianions and an ionization efficiency of up to 200%. Furthermore, we show that the resulting integer charge-transfer complex can dissociate with an efficiency of up to 170%. The concept of double doping introduced here may allow the dopant fraction required to optimize charge conduction to be halved.
|
|
| 10. |
- Kiefer, David, 1989, et al.
(författare)
-
Enhanced n-Doping Efficiency of a Naphthalenediimide-Based Copolymer through Polar Side Chains for Organic Thermoelectrics
- 2018
-
Ingår i: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 3:2, s. 278-285
-
Tidskriftsartikel (refereegranskat)abstract
- N-doping of conjugated polymers either requires a high dopant fraction or yields a low electrical conductivity because of their poor compatibility with molecular dopants. We explore n-doping of the polar naphthalenediimide–bithiophene copolymer p(gNDI-gT2) that carries oligoethylene glycol-based side chains and show that the polymer displays superior miscibility with the benzimidazole–dimethylbenzenamine-based n-dopant N-DMBI. The good compatibility of p(gNDI-gT2) and N-DMBI results in a relatively high doping efficiency of 13% for n-dopants, which leads to a high electrical conductivity of more than 10–1 S cm–1 for a dopant concentration of only 10 mol % when measured in an inert atmosphere. We find that the doped polymer is able to maintain its electrical conductivity for about 20 min when exposed to air and recovers rapidly when returned to a nitrogen atmosphere. Overall, solution coprocessing of p(gNDI-gT2) and N-DMBI results in a larger thermoelectric power factor of up to 0.4 μW K–2 m–1 compared to other NDI-based polymers.
|
|
