Crystal structure of the GalNAc/Gal-specific agglutinin from the phytopathogenic ascomycete Sclerotinia sclerotiorum reveals novel adaptation of a beta-trefoil domain

International audienceA lectin from the phytopathogenic ascomycete Sclerotinia sclerotiorum that shares only weak sequence similarity with characterized fungal lectins has recently been identified. S. sclerotiorum agglutinin (SSA) is a homodimeric protein consisting of two identical subunits of ∼ 17 kDa and displays specificity primarily towards Gal/GalNAc. Glycan array screening indicates that SSA readily interacts with Gal/GalNAc-bearing glycan chains. The crystal structures of SSA in the ligand-free form and in complex with the Gal-β1,3-GalNAc (T-antigen) disaccharide have been determined at 1.6 and 1.97 Å resolution, respectively. SSA adopts a β-trefoil domain as previously identified for other carbohydrate-binding proteins of the ricin B-like lectin superfamily and accommodates terminal non-reducing galactosyl and N-acetylgalactosaminyl glycans. Unlike other structurally related lectins, SSA contains a single carbohydrate-binding site at site α. SSA reveals a novel dimeric assembly markedly dissimilar to those described earlier for ricin-type lectins. The present structure exemplifies the adaptability of the β-trefoil domain in the evolution of fungal lectins

Vom Streben nach einer [vermeintlich] neuen hegemonialen Männlichkeit

Die vorliegende Arbeit hat es zum Ziel, die Filmfigur Chris Gardner im Hinblick auf ihre Anteilnahme an Ausverhandlungen hegemonialer Vorstellungen von Männlichkeit[en] i[n eine]m [als] deutschsprachig[ konstruiert]en Raum zum Zeitpunkt des Kinostarts von Das Streben nach Glück zu untersuchen und [eine] diesbezüglich dominante Fiktion[en] zu dekonstruieren. Um meine theoretischen Grundlagen und meine [als Notwendigkeit verstandene] pro-feministische Positionierung zu explizieren, diskutiere ich im „Theorie“-Teil vier Prämissen: In der ersten Prämisse vermittle ich mein – und somit das der Arbeit insgesamt zugrunde liegende – Verständnis des vielschichtigen – und hier im Anschluss an [poststrukturalistisch informierte] [pro-]feministische Theoretiker_innen als nicht-essentialisiernd konzeptionalisierten – Komplexes Geschlecht/Subjekt/Identität. In der zweiten Prämisse erläutere ich mein Verständnis der Konstitution und Verortung männlicher Subjekte in Relation zu Distinktions- und Dominanzlogiken sowohl in der [als] hetero- wie der [als] homosozial[ konstruiert]en Dimension auf Grundlage des Konzeptes hegemonialer Männlichkeit[en]. In der dritten Prämisse führe ich meine Einschätzung des Diskursstranges „Krise der Männlichkeit“ aus und zeige nicht nur dessen Funktionsweise auf formaler Ebene auf, sondern unternehme auch eine inhaltliche Bestimmung jener Männlichkeits-Bilder, die darin propagiert, sowie re-, aber auch de-konstruiert werden. In der vierten und letzten Prämisse skizziere ich meine [film-]theoretischen Annahmen zur Relevanz von Spielfilm[figuren]rezeption[en] qua kognitiver [Medien-]Schemata für Ausverhandlungen intelligibler Vorstellungen von Männlichkeit[en] und für die [De- bzw. Re-]Legitimierung ihrer hegemonialen Stellung in einem binär kodierten Geschlechterverhältnis. Auf dieser [erkenntnis]theoretischen Grundlage und auf Rezensionen und Kritiken aufbauend rekonstruiere ich im ersten Teil der Analyse – dem gewählten Figurenanalysemodell „die Uhr der Figur“ folgend – [das] dominant-fiktionale Figurenmodell[e] von Chris Gardner zum Zeitpunkt des Kinostarts von Das Streben nach Glück i[n eine]m [als] deutschsprachig[ konstruiert]en Raum. Da hinsichtlich Fragen rund um [eine] dominant-fiktonale Wahrnehmung[en] vor allem eine Auseinandersetzung mit [meist: stillschweigend vorausgesetzten] Bedingungen von [einer] entsprechenden Rezeptionsleistung[en] vielversprechend erscheint, untersuche ich im Anschluss daran die beiden Paratexte Filmplakat und Filmtrailer im Hinblick auf darin vermittelte Informationen, durch die ein bestimmter kognitiver Referenzrahmen zur [vermutlich:] nachfolgenden Filmwahrnehmung geschaffen wird. Im abschließenden Kapitel diskutiere ich symbolische und symptomatische Aspekte von [der] dominant-fiktionalen Figurenrezeption[en] i[n eine]m [als] deutschsprachig[ konstruiert]en Raum unter der Annahme, dass sich entsprechene Wahrnehmungen entlang des [vermeintlich] neuen [vergeschlechtlichten] Wahrnehmungskomplexes [Film-Genus] „sentimentales Melodrama einer krisenhafter Männlichkeit“ vollziehen und Chris Gardner dementsprechend als symbolische Erlösungsfigur der [vermeintlichen] „Krise der Männlichkeit“ lesbar wird

Wheat straw and lipids: UV-mutagenized Yarrowia lipolytica for the conversion of wheat straw hydrolysate into lipids

ArticleDue to the rising energy demand of our modern society and the finite amounts of petroleum-based fuels, renewable forms of energy have become extremely important. Bio-based fuels like bioethanol and biodiesel represent an already applied and accepted alternative. Biodiesel is currently mainly produced from plant oils. A new and promising alternative, which avoids the use of food crops, is the cultivation of the oleaginous yeast Yarrowia lipolytica, which possesses the capacity to accumulate up to 40% of its biomass in form of lipids. Moreover, this non-conventional yeast is able to metabolize a broad range of carbon-sources, presenting a sustainable alternative to reutilize a wide spectrum of waste substrates. This makes it an auspicious candidate for the generation of non-edible oils for biodiesel production. In this work, we aimed to generate a Y. lipolytica mutant strain with enhanced lipid production when grown on wheat straw hydrolysate as sole carbon source. Therefore, UV mutagenesis was applied and mutants with a high-lipid content were selected by their ability to grow in the presence of the fatty acid inhibitor cerulenin. Further, growth of the mutants on wheat straw hydrolysate was evaluated. The fatty acid composition was analysed by GC-FID and the calculated total lipid content revealed an up to 33% increase compared to the wild type strain. Fermentation optimisation and the combination of various waste substrates as carbon sources are expected to further increase the total lipid yield by the Y. lipolytica mutant strain and serve as initial point for its industrial scale evaluation

Cognitive Ergonomics in Virtual Environments: Development of an Intuitive and Appropriate Input Device for Navigating in a Virtual Maze

For patients suffering from mild cognitive impairments, the navigation through a virtual maze should be as intuitive and efficient as possible in order to minimize cognitive and physical strain. This paper discusses the appropriateness of interaction devices for being used for easy navigation tasks. Information gained from human centered evaluation was used to develop an intuitive and ergonomic interaction device. Two experiments examined the usability of tracked interaction devices. Usability problems with the devices are discussed. The findings from the experiments were translated into general design guidance, in addition to specific recommendations. A new device was designed on the basis of these recommendations and its usability was evaluated in a second experiment. The results were used to develop a lightweight interaction device for navigation in the virtual maz

Neurophysiological Age Differences During Task-Performance in a Stereoscopic Virtual Environment

In today's society, there is an increasing number of workplaces in virtual environments (VE). But, there are only a few reports dealing with occupational health issues or age effects. The question arises how VR generally interferes with cognitive processes. This interference might have relevant implications for workability and work-efficiency in virtual environments. Event-related potentials are known to reflect different stages of stimulus reception, evaluation, and response. We have established an electroencephalographic (EEG) monitoring, focussing on event-related potentials (N100; mismatch negativity, i.e., MMN) to obtain access to attention dependent and pre-attentive processing of sensory stimuli applied in VE. The MMN is known to be correlated with the ability of subjects to react to an unexpected event. The aim of the present study was to investigate cognitive responses to distracting auditory stimuli in two different age groups in a virtual environment (VE) and in a real environment ("real reality”), and to compare characteristic neurophysiological response patterns. Data show that stimulus detection as given by the N100 amplitude and latency does not differ in both age groups and task conditions. In contrast, the pre-attentive processing as given by the MMN is altered in the VR such as the non-VR condition in an age-related manner. A relevant finding of the present study was that the age related differences seen in the non-VR condition were not strengthened in V

„Warm brothers“ on trial: The image of the male homosexual as constructed by homosexuals themselves and by others during the NS period in Austria

Abstract: Based on the court records of 1,500 men accused of homosexual conduct from the Viennese Civil Courts and Military Courts from Austria under National Socialist rule, a sample of 434 men was selected randomly and analyzed quantitatively. The article aims to provide the most comprehensive survey hitherto of the self-perceptions of male homosexuals and of the ways they were perceived by others in that period. The descriptions of identities that were used in the selected case histories by the persecuting authorities and as self-definition by the victims were collected and interpreted in accordance with international discussions that have taken place in historical gender and LGBTIQ Studies. Additionally, the social background of the persecuted men and information on the structure and extent of the persecution were analyzed.Abstract: Based on the court records of 1,500 men accused of homosexual conduct from the Viennese Civil Courts and Military Courts from Austria under National Socialist rule, a sample of 434 men was selected randomly and analyzed quantitatively. The article aims to provide the most comprehensive survey hitherto of the self-perceptions of male homosexuals and of the ways they were perceived by others in that period. The descriptions of identities that were used in the selected case histories by the persecuting authorities and as self-definition by the victims were collected and interpreted in accordance with international discussions that have taken place in historical gender and LGBTIQ Studies. Additionally, the social background of the persecuted men and information on the structure and extent of the persecution were analyzed

Stimulation of Cortisol During Mental Task Performance in a Provocative Virtual Environment

Fully immersive and stereoscopic Virtual Environments (VE) represent a powerful multimedia tool for laboratory-based simulations of distinct scenarios including scenarios for evaluating stressful situations resembling reality. Thus far, cortisol secretion as a neuroendocrine parameter of stress has not been evaluated within a Virtual Reality (VR)-based paradigm. In this study 94 healthy volunteers were subjected to a provocative VR-paradigm and a cognitive stress task. Provocative in this context means the VE was designed to provoke physiological reactions (cortisol secretion) within the respective users by purpose. It was tested (a) if a fully dynamic VE as opposed to a static VE can be regarded as a stressor and (b) if such a fully dynamic VE can modify an additional response to a cognitive stressor presented within the VE additionally. Furthermore, possible gender-related impacts on cortisol responses were assessed. A significant cortisol increase was observed only after the combined application of the fully dynamic VE and the cognitive stressor, but not after application of the dynamic VE or the cognitive stressor alone. Cortisol reactivity was greater for men than for women. We conclude that a fully dynamic VE does not affect cortisol secretion per se, but increases cortisol responses to a dual task paradigm that includes performance of a stressful mental task. This provides the basis for the application of VR-based technologies in neuroscientific research, including the assessment of the human Hypothalamus-Pituitary-Adrenal (HPA) axis regulatio

Catalysis by hen egg-white lysozyme proceeds via a covalent intermediate

Hen egg-white lysozyme (HEWL) was the first enzyme to have its three-dimensional structure determined by X-ray diffraction techniques(1). A catalytic mechanism, featuring a long-lived oxo-carbenium-ion intermediate, was proposed on the basis of model-building studies(2). The `Phillips' mechanism is widely held as the paradigm for the catalytic mechanism of beta -glycosidases that cleave glycosidic linkages with net retention of configuration of the anomeric centre. Studies with other retaining beta -glycosidases, however, provide strong evidence pointing to a common mechanism for these enzymes that involves a covalent glycosyl-enzyme intermediate, as previously postulated(3). Here we show, in three different cases using electrospray ionization mass spectrometry, a catalytically competent covalent glycosyl-enzyme intermediate during the catalytic cycle of HEWL. We also show the three-dimensional structure of this intermediate as determined by Xray diffraction. We formulate a general catalytic mechanism for all retaining beta -glycosidases that includes substrate distortion, formation of a covalent intermediate, and the electrophilic migration of C1 along the reaction coordinate

Substrate-Assisted Catalysis Unifies Two Families of Chitinolytic Enzymes

Hen egg-white lysozyme has long been the paradigm for enzymatic glycosyl hydrolysis with retention of configuration, with a protonated carboxylic acid and a deprotonated carboxylate participating in general acid-base catalysis. In marked contrast, the retaining chitin degrading enzymes from glycosyl hydrolase families 18 and 20 all have a single glutamic acid as the catalytic acid but lack a nucleophile on the enzyme. Both families have a catalytic (βα)8-barrel domain in common. X-ray structures of three different chitinolytic enzymes complexed with substrates or inhibitors identify a retaining mechanism involving a protein acid and the carbonyl oxygen atom of the substrate’s C2 N-acetyl group as the nucleophile. These studies unambiguously demonstrate the distortion of the sugar ring toward a sofa conformation, long postulated as being close to that of the transition state in glycosyl hydrolysis.