Thermal rectification effects of multiple semiconductor quantum dot junctions

Based on the multiple energy level Anderson model, this study theoretically examines the thermoelectric effects of semiconductor quantum dots (QDs) in the nonlinear response regime. The charge and heat currents in the sequential tunneling process are calculated by using the Keldysh Green's function technique. Results show that the thermal rectification effect can be observed in a multiple QD junction system, whereas the tunneling rate, size fluctuation, and location distribution of QD significantly influence the rectification efficiency.Comment: 5 pages, 8figure

Die Bedeutung von Miro1/RHOT1 als Kandidatengen für eine gestörte mitochondriale Funktion und Dynamik bei der Parkinson-Krankheit

Die Parkinson Krankheit (PK) ist eine der häufigsten neurodegenerativen Erkrankungen des Menschen. Bei der Entstehung der Erkrankung spielen verschiedene Faktoren eine Rolle, wobei neben Umweltfaktoren auch verschiedene genetische Faktoren, für die Entstehung der PK verantwortlich sind. So können aktuell ca. 5-10% der Erkrankungen durch monogenetische Formen erklärt werden. Zudem gibt es mind. 28 weitere genetische Risikofaktoren, durch die die Wahrscheinlichkeit, die PK zu entwickeln, erhöht wird. Insgesamt lassen sich durch alle genetischen Faktoren zurzeit etwa 20-30% des Risikos, eine PK zu entwickeln, erklären. Es wird daher intensiv nach weiteren genetischen Ursachen gesucht. Hier gilt das Protein Miro1 als Kandidat, eine Rolle in der Pathogenese der PK zu spielen. Miro1 ist ein Protein der Gruppe der mitochondrialen Rho-GTPasen, das eine entscheidende Rolle im Transport von Mitochondrien in den Neuronen, sowie im Rahmen der Qualitätskontrolle der Mitochondrien spielt. Da bereits aus anderen Studien bekannt war, dass Störungen dieser Funktionen mit der Entstehung der PK assoziiert sind, haben wir im Rahmen einer Kandidatengen-Studie nach Mutationen im Miro1/RHOT1-Gen bei 752 Parkinson-Patienten gesucht. Hierfür wurden die DNA-Proben mittels High Resolution Melting Analysis, Sequenzierung, SNaPshot® und/oder Restriktionsenzymverdau untersucht. Hierbei haben wir insgesamt 10 Single Nukleotid Polymorphism (SNP) beziehungsweise Mutationen nachweisen können. Bei drei dieser SNPs handelt es sich um intronische, nicht-kodierende Basenaustausche und bei 4 weiteren SNPs um synonymous coding SNPs, also Basenaustausche, die die Peptid-Sequenz nicht ändern. Wir haben bei dieser Arbeit jedoch auch drei bisher unbekannt missense Mutationen im Miro1-Gen bei PK-Patienten nachweisen können. Diese drei Mutationen liegen in relevanten strukturellen Bereichen von Miro1 (einer ligand mimic domain an der ersten EF-Hand-Domäne, einer GTPase-Domäne und der Transmembran-Domäne). Diese Mutationen wurden zudem auch durch die Software MutationTaster als krankheitsauslösend eingestuft. Durch den Nachweis von drei bisher unbekannten Mutationen im Miro1/RHOT1-Gen bei PK-Patienten sehen wir die Bedeutung von Miro1/RHOT1 als Kandidatengen für eine gestörte mitochondriale Funktion und Dynamik bei der Parkinson-Krankheit gestärkt. Nachfolgende funktionelle Studien an Patienten-basierten Zellmodellen haben diesen Verdacht zwischenzeitlich bestätigt und weisen auf eine Störung der Calcium-Pufferkapazität der Mitochondrien durch die o.g. Mutationen hin

Non-basic amino acids in the hemagglutinin proteolytic cleavage site of a European H9N2 avian influenza virus modulate virulence in turkeys

H9N2 avian influenza virus (AIV) is the most widespread low pathogenic (LP) AIV in poultry and poses a serious zoonotic risk. Vaccination is used extensively to mitigate the economic impact of the virus. However, mutations were acquired after long-term circulation of H9N2 virus in poultry, particularly in the hemagglutinin (HA) proteolytic cleavage site (CS), a main virulence determinant of AIV. Compared to chickens, little is known about the genetic determinants for adaptation of H9N2 AIV to turkeys. Here, we describe 36 different CS motifs in Eurasian H9N2 viruses identified from 1966 to 2019. The European H9N2 viruses specify unique HACS with particular polymorphism by insertion of non-basic amino acids at position 319. Recombinant viruses carrying single HACS mutations resembling field viruses were constructed (designated G319, A319, N319, S319, D319 and K319). Several viruses replicated to significantly higher titers in turkey cells than in chicken cells. Serine proteases were more efficient than trypsin to support multicycle replication in mammalian cells. Mutations affected cell-to-cell spread and pH-dependent HA fusion activity. In contrast to chickens, mutations in the HACS modulated clinical signs in inoculated and co-housed turkeys. G319 exhibited the lowest virulence, however, it replicated to significantly higher titers in contact-turkeys and in vitro. Interestingly, H9N2 viruses, particularly G319, replicated in brain cells of turkeys and to a lesser extent in mammalian brain cells independent of trypsin. Therefore, the silent circulation of potentially zoonotic H9N2 viruses in poultry should be monitored carefully. These results are important for understanding the adaptation of H9N2 in poultry and replication in mammalian cells

3D reconstruction of SARS-CoV-2 infection in ferrets emphasizes focal infection pattern in the upper respiratory tract: [Preprint]

The visualization of viral pathogens in infected tissues is an invaluable tool to understand spatial virus distribution, localization, and cell tropism in vivo. Commonly, virus-infected tissues are analyzed using conventional immunohistochemistry in paraffin-embedded thin sections. Here, we demonstrate the utility of volumetric three-dimensional (3D) immunofluorescence imaging using tissue optical clearing and light sheet microscopy to investigate host-pathogen interactions of pandemic SARS-CoV-2 in ferrets at a mesoscopic scale. The superior spatial context of large, intact samples (> 150 mm3) allowed detailed quantification of interrelated parameters like focus-to-focus distance or SARS-CoV-2-infected area, facilitating an in-depth description of SARS-CoV-2 infection foci. Accordingly, we could confirm a preferential infection of the ferret upper respiratory tract by SARS-CoV-2 and emphasize a distinct focal infection pattern in nasal turbinates. Conclusively, we present a proof-of-concept study for investigating critically important respiratory pathogens in their spatial tissue morphology and demonstrate the first specific 3D visualization of SARS-CoV-2 infection

Inhibitors of dihydroorotate dehydrogenase synergize with the broad antiviral activity of 4′-fluorouridine

RNA viruses present a constant threat to human health, often with limited options for vaccination or therapy. Notable examples include influenza viruses and coronaviruses, which have pandemic potential. Filo- and henipaviruses cause more limited outbreaks, but with high case fatality rates. All RNA viruses rely on the activity of a virus-encoded RNA-dependent RNA polymerase (RdRp). An antiviral nucleoside analogue, 4′-Fluorouridine (4′-FlU), targets RdRp and diminishes the replication of several RNA viruses, including influenza A virus and SARS-CoV-2, through incorporation into nascent viral RNA and delayed chain termination. However, the effective concentration of 4′-FlU varied among different viruses, raising the need to fortify its efficacy. Here we show that inhibitors of dihydroorotate dehydrogenase (DHODH), an enzyme essential for pyrimidine biosynthesis, can synergistically enhance the antiviral effect of 4′-FlU against influenza A viruses, SARS-CoV-2, henipaviruses, and Ebola virus. Even 4′-FlU-resistant mutant influenza A virus was re-sensitized towards 4′-FlU by DHODH inhibition. The addition of uridine rescued influenza A virus replication, strongly suggesting uridine depletion as a mechanism of this synergy. 4′-FlU was also highly effective against SARS-CoV-2 in a hamster model of COVID. We propose that the impairment of endogenous uridine synthesis by DHODH inhibition enhances the incorporation of 4′-FlU into viral RNAs. This strategy may be broadly applicable to enhance the efficacy of pyrimidine nucleoside analogues for antiviral therapy

H7 influenza A viruses bind sialyl-LewisX, a potential intermediate receptor between species: [Preprint]

Influenza A viruses (IAVs) can overcome species barriers by adaptation of the receptor binding site of the hemagglutinin (HA). To initiate infection, HAs bind to glycan receptors with terminal sialic acids, which are either N-acetylneuraminic acid (NeuAc) or N-glycolylneuraminic acid (NeuGc), the latter is mainly found in horses and pigs but not in birds and humans. We investigated the influence of previously identified equine NeuGc-adapting mutations (S128T, I130V, A135E, T189A, and K193R) in avian H7 IAVs in vitro and in vivo. We observed that these mutations negatively affected viral replication in chicken cells, but not in duck cells, and positively affected replication in horse cells. In vivo, the mutations reduced virus virulence and mortality in chickens. Ducks excreted high viral loads for a longer time than chickens, although they appeared clinically healthy. To elucidate why chickens and ducks were infected by these viruses despite the absence of NeuGc, we re-evaluated the receptor binding of H7 HAs using glycan microarray and flow cytometry studies. This revealed that mutated avian H7 HAs also bound to α2,3-linked NeuAc and sialyl-LewisX, which have an additional fucose moiety in their terminal epitope, explaining why infection of ducks and chickens was possible. Interestingly, the α2,3-linked NeuAc and sialyl-LewisX epitopes were only bound when presented on tri-antennary N-glycans, emphasizing the importance of investigating the fine receptor specificities of IAVs. In conclusion, the binding of NeuGc-adapted H7 IAV to sialyl-LewisX enables viral replication and shedding by chickens and ducks, potentially facilitating interspecies transmission of equine-adapted H7 IAVs. (249 words) Importance Influenza A viruses cause millions of deaths and illness in birds and mammals each year. The viral surface protein hemagglutinin initiates infection by binding to host cell terminal sialic acids. Hemagglutinin adaptations affect the binding affinity to these sialic acids and therefore the potential host species targeted. While avian and human IAVs tend to bind N-acetylneuraminic acid (a form of sialic acid), equine H7 viruses prefer binding to N-glycolylneuraminic acid (NeuGc). To better understand the function of NeuGc-specific adaptations in hemagglutinin and to elucidate interspecies transmission potential NeuGc-adapted viruses, we evaluated the effects of NeuGc-specific mutations in avian H7 viruses in chickens and ducks, important economic hosts and reservoir birds, respectively. We also examined the impact on viral replication and found a binding affinity to sialyl-LewisX, another terminal epitope. These findings are important as they contribute to the understanding of the role of sialyl-LewisX in avian influenza infection

Engineering a Highly Regioselective Fungal Peroxygenase for the Synthesis of Hydroxy Fatty Acids

The hydroxylation of fatty acids is an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. In this study, we have engineered a highly regioselective fungal peroxygenase for the ω-1 hydroxylation of fatty acids with quenched stepwise over-oxidation. One single mutation near the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward subterminal hydroxylation with a drop in the over-oxidation activity. While crystallographic soaking experiments and molecular dynamic simulations shed light on this unique oxidation pattern, the selective biocatalyst was produced by Pichia pastoris at 0.4 g L−1 in a fed-batch bioreactor and used in the preparative synthesis of 1.4 g of (ω-1)-hydroxytetradecanoic acid with 95 % regioselectivity and 83 % ee for the S enantiomer.This work was supported by the European Union Project grant H2020-BBI-PPP-2015-2-720297-ENZOX2; the Spanish projects PID2019-106166RB-100-OXYWAVE, PID2020-118968RB-100-LILI, PID2021-123332OB-C21 and PID2019-107098RJ-I00, funded by the Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación (AEI)/doi: 10.13039/501100011033/; the “Comunidad de Madrid” Synergy CAM project Y2018/BIO-4738-EVOCHIMERA-CM; the Generalitat Valenciana projects CIPROM/2021/079-PROMETEO and SEJI/2020/007; and the PIE-CSIC projects PIE-202040E185 and PIE-201580E042. P.G.d.S. thanks the Ministry of Science, Innovation and Universities (Spain) for her FPI scholarship (BES-2017-080040) and the Ministry of Science and Innovation for her contract as part of the PTQ2020-011037 project funded by MCIN/AEI/10.13039/501100011033 within the NextGenerationEU/PRTR. D.G.-P. thanks Juan de la Cierva Incorporación contract Ref. No.: IJC2020-043725-I, funded by MCIN/AEI/10.13039/501100011033, and the EU NextGenerationEU/PRTR program. K.Ś. thanks to Ministerio de Ciencia e Innovación and Fondo Social Europeo for a Ramón y Cajal contract (Ref. RYC2020-030596-I). We thank the Synchrotron Radiation Source at Alba (Barcelona, Spain) for assistance with the BL13-XALOC beamline

Molecular Evolution of Multiple Arylalkylamine N-Acetyltransferase (AANAT) in Fish

Arylalkylamine N-acetyltransferase (AANAT) catalyzes the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to arylalkylamines, including indolethylamines and phenylethylamines. Multiple aanats are present in teleost fish as a result of whole genome and gene duplications. Fish aanat1a and aanat2 paralogs display different patterns of tissue expression and encode proteins with different substrate preference: AANAT1a is expressed in the retina, and acetylates both indolethylamines and phenylethylamines; while AANAT2 is expressed in the pineal gland, and preferentially acetylates indolethylamines. The two enzymes are therefore thought to serve different roles. Here, the molecular changes that led to their specialization were studied by investigating the structure-function relationships of AANATs in the gilthead seabream (sb, Sperus aurata). Acetylation activity of reciprocal mutated enzymes pointed to specific residues that contribute to substrate specificity of the enzymes. Inhibition tests followed by complementary analyses of the predicted three-dimensional models of the enzymes, suggested that both phenylethylamines and indolethylamines bind to the catalytic pocket of both enzymes. These results suggest that substrate selectivity of AANAT1a and AANAT2 is determined by the positioning of the substrate within the catalytic pocket, and its accessibility to catalysis. This illustrates the evolutionary process by which enzymes encoded by duplicated genes acquire different activities and play different biological roles

Phenotypic effects of mutations observed in the neuraminidase of human origin H5N1 influenza A viruses

Global spread and regional endemicity of H5Nx Goose/Guangdong avian influenza viruses (AIV) pose a continuous threat for poultry production and zoonotic, potentially pre-pandemic, transmission to humans. Little is known about the role of mutations in the viral neuraminidase (NA) that accompanied bird-to-human transmission to support AIV infection of mammals. Here, after detailed analysis of the NA sequence of human H5N1 viruses, we studied the role of A46D, L204M, S319F and S430G mutations in virus fitness in vitro and in vivo. Although H5N1 AIV carrying avian- or human-like NAs had similar replication efficiency in avian cells, human-like NA enhanced virus replication in human airway epithelia. The L204M substitution consistently reduced NA activity of H5N1 and nine other influenza viruses carrying NA of groups 1 and 2, indicating a universal effect. Compared to the avian ancestor, human-like H5N1 virus has less NA incorporated in the virion, reduced levels of viral NA RNA replication and NA expression. We also demonstrate increased accumulation of NA at the plasma membrane, reduced virus release and enhanced cell-to-cell spread. Furthermore, NA mutations increased virus binding to human-type receptors. While not affecting high virulence of H5N1 in chickens, the studied NA mutations modulated virulence and replication of H5N1 AIV in mice and to a lesser extent in ferrets. Together, mutations in the NA of human H5N1 viruses play different roles in infection of mammals without affecting virulence or transmission in chickens. These results are important to understand the genetic determinants for replication of AIV in mammals and should assist in the prediction of AIV with zoonotic potential

Soft matter roadmap

Soft materials are usually defined as materials made of mesoscopic entities, often self-organised, sensitive to thermal fluctuations and to weak perturbations. Archetypal examples are colloids, polymers, amphiphiles, liquid crystals, foams. The importance of soft materials in everyday commodity products, as well as in technological applications, is enormous, and controlling or improving their properties is the focus of many efforts. From a fundamental perspective, the possibility of manipulating soft material properties, by tuning interactions between constituents and by applying external perturbations, gives rise to an almost unlimited variety in physical properties. Together with the relative ease to observe and characterise them, this renders soft matter systems powerful model systems to investigate statistical physics phenomena, many of them relevant as well to hard condensed matter systems. Understanding the emerging properties from mesoscale constituents still poses enormous challenges, which have stimulated a wealth of new experimental approaches, including the synthesis of new systems with, e.g. tailored self-assembling properties, or novel experimental techniques in imaging, scattering or rheology. Theoretical and numerical methods, and coarse-grained models, have become central to predict physical properties of soft materials, while computational approaches that also use machine learning tools are playing a progressively major role in many investigations. This Roadmap intends to give a broad overview of recent and possible future activities in the field of soft materials, with experts covering various developments and challenges in material synthesis and characterisation, instrumental, simulation and theoretical methods as well as general concepts