A large variety of polymers has been proposed for use as materials with low dielectric constants for applications in microelectronics. The chemical structures and selected properties of these ...polymers are discussed in this review. Polyimides, heteroaromatic polymers, poly(aryl ether)s, fluoropolymers, hydrocarbon polymers without any polar groups, films deposited from the gas phase by chemical vapor deposition, plasma enhanced chemical vapor deposition and other techniques are included. Based on the properties described so far, and the requirements for applications as intermetal dielectric material, conclusions regarding the possibilities for further developments are drawn.
Microalgae are thought to offer great potential as expression system for various industrial, therapeutic and diagnostic recombinant proteins as they combine high growth rates with all benefits of ...eukaryotic expression systems. Moreover, microalgae exhibit a phototrophic lifestyle like land plants, hence protein expression is fuelled by photosynthesis, which is CO(2)-neutral and involves only low production costs. So far, however, research on algal bioreactors for recombinant protein expression is very rare calling for further investigations in this highly promising field. In this study, we present data on the expression of a monoclonal human IgG antibody against the Hepatitis B surface protein and the respective antigen in the diatom Phaeodactylum tricornutum. Antibodies are fully-assembled and functional and accumulate to 8.7% of total soluble protein, which complies with 21 mg antibody per gram algal dry weight. The Hepatitis B surface protein is functional as well and is recognized by algae-produced and commercial antibodies.
Cell diversity of the brain and how it is affected by starvation, remains largely unknown. Here, we introduce a single cell transcriptome atlas of the entire
first instar larval brain. We first ...assigned cell-type identity based on known marker genes, distinguishing five major groups: neural progenitors, differentiated neurons, glia, undifferentiated neurons and non-neural cells. All major classes were further subdivided into multiple subtypes, revealing biological features of various cell-types. We further assessed transcriptional changes in response to starvation at the single-cell level. While after starvation the composition of the brain remains unaffected, transcriptional profile of several cell clusters changed. Intriguingly, different cell-types show very distinct responses to starvation, suggesting the presence of cell-specific programs for nutrition availability. Establishing a single-cell transcriptome atlas of the larval brain provides a powerful tool to explore cell diversity and assess genetic profiles from developmental, functional and behavioral perspectives.
Through analysis of the Drosophila ionotropic receptors (IRs), a family of variant ionotropic glutamate receptors, we reveal that most IRs are expressed in peripheral neuron populations in diverse ...gustatory organs in larvae and adults. We characterise IR56d, which defines two anatomically-distinct neuron classes in the proboscis: one responds to carbonated solutions and fatty acids while the other represents a subset of sugar- and fatty acid-sensing cells. Mutational analysis indicates that IR56d, together with the broadly-expressed co-receptors IR25a and IR76b, is essential for physiological responses to carbonation and fatty acids, but not sugars. We further demonstrate that carbonation and fatty acids both promote IR56d-dependent attraction of flies, but through different behavioural outputs. Our work provides a toolkit for investigating taste functions of IRs, defines a subset of these receptors required for carbonation sensing, and illustrates how the gustatory system uses combinatorial expression of sensory molecules in distinct neurons to coordinate behaviour.
Apicomplexans are widespread parasites of humans and other animals, and include the causative agents of malaria (Plasmodium species) and toxoplasmosis (Toxoplasma gondii). Existing anti-apicomplexan ...therapies are beset with issues around drug resistance and toxicity, and new treatment options are needed. The mitochondrial electron transport chain (ETC) is one of the few processes that has been validated as a drug target in apicomplexans. To identify new inhibitors of the apicomplexan ETC, we developed a Seahorse XFe96 flux analyzer approach to screen the 400 compounds contained within the Medicines for Malaria Venture 'Pathogen Box' for ETC inhibition. We identified six chemically diverse, on-target inhibitors of the ETC in T. gondii, at least four of which also target the ETC of Plasmodium falciparum. Two of the identified compounds (MMV024937 and MMV688853) represent novel ETC inhibitor chemotypes. MMV688853 belongs to a compound class, the aminopyrazole carboxamides, that were shown previously to target a kinase with a key role in parasite invasion of host cells. Our data therefore reveal that MMV688853 has dual targets in apicomplexans. We further developed our approach to pinpoint the molecular targets of these inhibitors, demonstrating that all target Complex III of the ETC, with MMV688853 targeting the ubiquinone reduction (Qi) site of the complex. Most of the compounds we identified remain effective inhibitors of parasites that are resistant to Complex III inhibitors that are in clinical use or development, indicating that they could be used in treating drug resistant parasites. In sum, we have developed a versatile, scalable approach to screen for compounds that target the ETC in apicomplexan parasites, and used this to identify and characterize novel inhibitors.
An acceptorless dehydrogenation of heterocycles catalyzed by frustrated Lewis pairs (FLPs) was developed. Oxidation with concomitant liberation of molecular hydrogen proceeded in high to excellent ...yields for N‐protected indolines as well as four other substrate classes. The mechanism of this unprecedented FLP‐catalyzed reaction was investigated by mechanistic studies, characterization of reaction intermediates by NMR spectroscopy and X‐ray crystal analysis, and by quantum‐mechanical calculations. Hydrogen liberation from the ammonium hydridoborate intermediate is the rate‐determining step of the oxidation. The addition of a weaker Lewis acid as a hydride shuttle increased the reaction rate by a factor of 2.28 through a second catalytic cycle.
The acceptorless dehydrogenation of N‐protected indolines and other heterocycles is catalyzed by frustrated Lewis pairs. Mechanistic as well as quantum‐mechanical studies revealed the liberation of molecular hydrogen to be the rate‐determining step. The addition of a weaker Lewis acid as a hydride shuttle increased the reaction rate by a factor of 2.28.
The number and nature of endosymbioses involving red algal endosymbionts are debated. Gene phylogenies have become the most popular tool to untangle this issue, but they deliver conflicting results. ...As gene and lineage sampling has increased, so have both the number of conflicting trees and the number of suggestions in the literature for multiple tertiary, and even quaternary, symbioses that might reconcile the tree conflicts. Independent lines of evidence that can address the issue are needed. Here we summarize the mechanism and machinery of protein import into complex red plastids. The process involves protein translocation machinery, known as SELMA, that arose once in evolution, that facilitates protein import across the second outermost of the four plastid membranes, and that is always targeted specifically to that membrane, regardless of where it is encoded today. It is widely accepted that the unity of protein import across the two membranes of primary plastids is strong evidence for their single cyanobacterial origin. Similarly, the unity of SELMA-dependent protein import across the second outermost plastid membrane constitutes strong evidence for the existence of a single red secondary endosymbiotic event at the common origin of all red complex plastids. We furthermore propose that the two outer membranes of red complex plastids are derived from host endoplasmic reticulum in the initial red secondary endosymbiotic event.
Recent work has provided a mechanistic view of protein import into complex red plastids. The process involves a protein translocation machinery, known as SELMA.
In eukaryotes, DNA is exchanged between endosymbiosis-derived compartments (mitochondria and chloroplasts) and the nucleus. Organelle-to-nucleus DNA transfer involves repair of double-stranded breaks ...by nonhomologous end-joining, and resulted during early organelle evolution in massive relocation of organelle genes to the nucleus. A large fraction of the products of the nuclear genes so acquired are retargeted to their ancestral compartment; many others now function in new subcellular locations. Almost all present-day nuclear transfers of mitochondrial or plastid DNA give rise to noncoding sequences, dubbed nuclear mitochondrial DNAs (NUMTs) and nuclear plastid DNAs (NUPTs). Some of these sequences were recruited as exons, thus introducing new coding sequences into preexisting nuclear genes by a novel mechanism. In organisms derived from secondary or tertiary endosymbiosis, serial gene transfers involving nucleus-to-nucleus migration of DNA have also occurred. Intercompartmental DNA transfer therefore represents a significant driving force for gene and genome evolution, relocating and refashioning genes and contributing to genetic diversity.
The biological degradation of plastics is a promising method to counter the increasing pollution of our planet with artificial polymers and to develop eco-friendly recycling strategies. Polyethylene ...terephthalate (PET) is a thermoplast industrially produced from fossil feedstocks since the 1940s, nowadays prevalently used in bottle packaging and textiles. Although established industrial processes for PET recycling exist, large amounts of PET still end up in the environment-a significant portion thereof in the world's oceans. In 2016, Ideonella sakaiensis, a bacterium possessing the ability to degrade PET and use the degradation products as a sole carbon source for growth, was isolated. I. sakaiensis expresses a key enzyme responsible for the breakdown of PET into monomers: PETase. This hydrolase might possess huge potential for the development of biological PET degradation and recycling processes as well as bioremediation approaches of environmental plastic waste.
Using the photosynthetic microalga Phaeodactylum tricornutum as a chassis we generated a microbial cell factory capable of producing and secreting an engineered version of PETase into the surrounding culture medium. Initial degradation experiments using culture supernatant at 30 °C showed that PETase possessed activity against PET and the copolymer polyethylene terephthalate glycol (PETG) with an approximately 80-fold higher turnover of low crystallinity PETG compared to bottle PET. Moreover, we show that diatom produced PETase was active against industrially shredded PET in a saltwater-based environment even at mesophilic temperatures (21 °C). The products resulting from the degradation of the PET substrate were mainly terephthalic acid (TPA) and mono(2-hydroxyethyl) terephthalic acid (MHET) estimated to be formed in the micromolar range under the selected reaction conditions.
We provide a promising and eco-friendly solution for biological decomposition of PET waste in a saltwater-based environment by using a eukaryotic microalga instead of a bacterium as a model system. Our results show that via synthetic biology the diatom P. tricornutum indeed could be converted into a valuable chassis for biological PET degradation. Overall, this proof of principle study demonstrates the potential of the diatom system for future biotechnological applications in biological PET degradation especially for bioremediation approaches of PET polluted seawater.
The human malaria parasite Plasmodium falciparum relies on lipids to survive; this makes its lipid metabolism an attractive drug target. The lipid phosphatidylserine (PS) is usually confined to the ...inner leaflet of the red blood cell membrane (RBC) bilayer; however, some studies suggest that infection with the intracellular parasite results in the presence of this lipid in the RBC membrane outer leaflet, where it could act as a recognition signal to phagocytes. Here, we used fluorescent lipid analogues and probes to investigate the enzymatic reactions responsible for maintaining asymmetry between membrane leaflets, and found that in parasitised RBCs the maintenance of membrane asymmetry was partly disrupted, and PS was increased in the outer leaflet. We examined the underlying causes for the differences between uninfected and infected RBCs using fluorescent dyes and probes, and found that calcium levels increased in the infected RBC cytoplasm, whereas membrane cholesterol was depleted from the erythrocyte plasma membrane. We explored the resulting effect of PS exposure on enhanced phagocytosis by monocytes, and show that infected RBCs must expend energy to limit phagocyte recognition, and provide experimental evidence that PS exposure contributes to phagocytic recognition of P. falciparum-infected RBCs. Together, these findings underscore the pivotal role for PS exposure on the surface of Plasmodium falciparum-infected erythrocytes for in vivo interactions with the host immune system, and provide a rationale for targeted antimalarial drug design.
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