Rolle der cytosolischen Glutaredoxine im zellulären Eisenmetabolismus in Eukaryoten

Glutaredoxine kommen in allen phylogenetischen Reichen der Lebewesen vor. Zu dieser Proteinfamilie gehören Dithiol-Glutaredoxine, die ein CPYC Motiv im aktiven Zentrum aufweisen und eine wichtige Rolle bei der Aufrechterhaltung des zellulären Redoxpotentials spielen. Einzeldomänen Monothiol-Glutaredoxine mit einem CGFS Motiv im aktiven Zentrum spielen eine zentrale Funktion bei der Maturierung zellulärer Eisen-Schwefel (Fe/S) Proteine und sind üblicherweise in den Mitochondrien und Chloroplasten lokalisiert. Multidomänen Monothiol-Glutaredoxine sind Fusionsproteine, die aus einer N-terminalen Thioredoxindomäne und einer oder mehreren C-terminalen Monothiol Glutaredoxindomäne(n) bestehen. Diese Unterfamilie der Glutaredoxine kommt im Cytosol und Nukleus fast aller Eukaryoten vor. In der Bäckerhefe S. cerevisiae binden die Multidomänen-Glutaredoxine Grx3 und Grx4 einen Fe/S-Kofaktor und spielen eine essenzielle Rolle bei der Maturierung aller Klassen Eisen-haltiger Proteine und der Regulation der zellulären Eisenhomöostase. Zentrales Ziel der Arbeit war die bessere funktionelle Charakterisierung der Multidomänen Monothiol-Glutaredoxine. Zwei zentrale Fragen standen hierbei im Vordergrund: (1) Welche strukturellen Unterschiede befähigen die ansonsten sehr ähnlichen Glutaredoxine dazu, jeweils spezifische Funktionen zu übernehmen? (2) In wie weit ist die für S. cerevisiae beschriebene Funktion der Multidomänen Glutaredoxine im Eisenmetabolismus höherer Eukaryoten konserviert? Der ersten Frage wurde durch Untersuchungen der Auswirkungen gezielter Mutationen auf die Funktionalität von Grx4 in S. cerevisiae nachgegangen. Diese Analyse zeigte, dass ein Dithiol-Motiv anstelle des Monothiol Motivs im aktiven Zentrum von Grx4 zu einer stark reduzierten Fe/S Clusterbindung und einem moderaten Funktionsverlust dieses Proteins in vivo führt. Hingegen ist ein Prolin im aktiven Zentrum von Grx4 im Gegensatz zu den Einzeldomänen Glutaredoxinen vollkommen kompatibel mit der Bindung eines Fe/S Clusters. Darüber hinaus ist die Thioredoxindomäne von Grx4 absolut essenziell für die Funktion. Wahrscheinlich fungiert diese Domäne als Bindestelle für andere Proteine. Grx3 und Grx4 interagieren direkt mit dem Eisen-regulierten Transkriptionsfaktor Aft1 und inaktivieren Aft1 bei ausreichend verfügbarem Eisen. Es konnte gezeigt werden, dass die Regulation von Aft1 inkompatibel mit einem Dithiol-Motiv im aktiven Zentrum von Grx4 ist und dass Aft1 mit dem C Terminus von Grx4 interagiert. Diese Interaktion ist nicht Eisen-abhängig und ist erhöht, wenn Grx4 keinen Fe/S Cluster gebunden hat. Somit ist nur die Inaktivierung von Aft1 direkt vom Fe/S Cluster von Grx4 abhängig. Insgesamt zeigte diese Arbeit wichtige strukturelle Voraussetzungen für die Funktion der Multidomänen Glutaredoxine im Eisenmetabolismus von S. cerevisiae auf. Zur Beantwortung der zweiten Frage wurden die Auswirkungen der siRNA-vermittelten Depletion von Grx3 in HeLa Zellen untersucht. Grx3-depletierte HeLa Zellen zeigten vergleichbar mit Hefe-Zellen Defekte in der Assemblierung von Fe/S Proteinen des Cytosols und des Zellkerns. Ein Defekt in der Reifung des „Iron Regulatory Protein 1“ (IRP1) führte zum Abbau der Apo-Form dieses Proteins und entsprechenden Auswirkungen auf den Eisenmetabolismus. Im Gegensatz zu Hefe-Zellen zeigten Grx3-depletierte HeLa Zellen keinen Effekt auf die Maturierung mitochondrialer Fe/S Cluster- oder Häm-haltiger Proteine. Trotz des geänderten Eisenmetabolismus wies das Transkriptom von Grx3-depletierten HeLa Zellen keine geänderte Regulation typischer Eisen-regulierter Gene auf. Dazu gehören z.B. Gene, die eine Funktion in den Mitochondrien sowie unter hypoxischen Bedingungen ausüben. Dies und die fehlenden Effekte auf die mitochondrialen Eisen-abhängigen Proteine sind auffällige Unterschiede zu der Hefe. Zusammenfassend konnte eine in allen Eukaryoten konservierte Funktion von Grx3 hinsichtlich der Biogenese von cytosolischen, nicht aber mitochondrialen Fe/S Proteinen nachgewiesen werden

Field assisted sintering of Ta–Al2_2O3_3 composite materials and investigation of electrical conductivity

Ta–Al$_2$O$_3$ composite samples with different compositions are prepared using Field Assisted Sintering Technique (FAST). Two different alumina powders are used to investigate the influence of the starting powders particle size on the microstructural features and the resulting electrical conductivity of the prepared composite materials. Percolation threshold of the two material systems is influenced by the metal fraction, as well as the alumina particle size of the starting powder. The percolation threshold for the fine- and the coarse-grained alumina is found to be at 15 vol.-% Ta and 7.5 vol.-% Ta, respectively. Microstructural investigations show significant differences in terms of particle shape of both, Ta and Al$_2$O$_3$ after sintering, most likely being the reason for the different percolation thresholds of the investigated materials. Anisotropy effects resulting from the processing using FAST and the influence on electrical properties are also shown

Field‐Assisted Sintering of Nb–Al2_2O3_3 Composite Materials and Investigation of Electrical Conductivity

Field-assisted sintering technique (FAST) is used for the preparation of Nb–Al$_2$O$_3$ composite materials. The electrical conductivity is investigated depending on the particle size of the used starting powders and under varying volume contents of the refractory metal in the starting powder mixture. The percolation threshold is investigated and found to be influenced not only by the metal fraction but also by the particle size of the alumina used for sample preparation. For the fine- and coarse-grained alumina, a percolation threshold of 17.5 and 10 vol% Nb is estimated, respectively. Furthermore, the microstructure is investigated to gain a basic understanding of the dependency between microstructural features and the resulting material properties on the macroscopic scale. Also, the influence of the sintering process and the resulting microstructure–properties relationship is considered. It could be shown that the electrical properties are anisotropic because of anisotropy effects caused by the FAST process

Synthesis and biological evaluation of a novel MUC1 glycopeptide conjugate vaccine candidate comprising a 4'-deoxy-4'-fluoro-Thomsen-Friedenreich epitope

The development of selective anticancer vaccines that provide enhanced protection against tumor recurrence and metastasis has been the subject of intense research in the scientific community. The tumor-associated glycoprotein MUC1 represents a well-established target for cancer immunotherapy and has been used for the construction of various synthetic vaccine candidates. However, many of these vaccine prototypes suffer from an inherent low immunogenicity and are susceptible to rapid in vivo degradation. To overcome these drawbacks, novel fluorinated MUC1 glycopeptide-BSA/TTox conjugate vaccines have been prepared. Immunization of mice with the 4' F-TF-MUC1-TTox conjugate resulted in strong immune responses overriding the natural tolerance against MUC1 and producing selective IgG antibodies that are cross-reactive with native MUC1 epitopes on MCF-7 human cancer cells

What’s in a name? The challenge of describing interventions in systematic reviews: analysis of a random sample of reviews of non-pharmacological stroke interventions

Objective: To assess, in a sample of systematic reviews of non-pharmacological interventions, the completeness of intervention reporting, identify the most frequently missing elements, and assess review authors’ use of and beliefs about providing intervention information. Design: Analysis of a random sample of systematic reviews of non-pharmacological stroke interventions; online survey of review authors. Data sources and study selection: The Cochrane Library and PubMed were searched for potentially eligible systematic reviews and a random sample of these assessed for eligibility until 60 (30 Cochrane, 30 non-Cochrane) eligible reviews were identified. Data collection: In each review, the completeness of the intervention description in each eligible trial (n=568) was assessed by 2 independent raters using the Template for Intervention Description and Replication (TIDieR) checklist. All review authors (n=46) were invited to complete a survey. Results: Most reviews were missing intervention information for the majority of items. The most incompletely described items were: modifications, fidelity, materials, procedure and tailoring (missing from all interventions in 97%, 90%, 88%, 83% and 83% of reviews, respectively). Items that scored better, but were still incomplete for the majority of reviews, were: ‘when and how much’ (in 31% of reviews, adequate for all trials; in 57% of reviews, adequate for some trials); intervention mode (in 22% of reviews, adequate for all trials; in 38%, adequate for some trials); and location (in 19% of reviews, adequate for all trials). Of the 33 (71%) authors who responded, 58% reported having further intervention information but not including it, and 70% tried to obtain information. Conclusions: Most focus on intervention reporting has been directed at trials. Poor intervention reporting in stroke systematic reviews is prevalent, compounded by poor trial reporting. Without adequate intervention descriptions, the conduct, usability and interpretation of reviews are restricted and therefore, require action by trialists, systematic reviewers, peer reviewers and editors

Novel outpatient treatment strategy for cranial infections – a single-center experience [Abstract]

Oral e-Poster Presentations - Booth 1: Trends & Innovation A, September 26, 2023, 1:00 PM - 2:30 PM Background: Antibiotic therapy of cranial infections is a resource-intensive process. On the background of the recommendation for longer-term antibiotic administration for cranial infections, we established an outpatient intravenous antibiotic administration in our hospital. Methods: The aim of this study was to evaluate the usefulness of outpatient antibiotic therapy in cranial neurosurgery. For this purpose, we included all patients who received a peripherally inserted central catheter (PICC line) for intravenous antibiotic therapy for cranial infections between 01/20 and 9/22. We evaluated the available patient data with regard to the infectiological and neurosurgical issues. All patients received intravenous antibiotics for at least 6 weeks (inpatient and outpatient). Results: In total, we were able to include 30 patients. The median age was 58.12 years (SD +/- 13.39 years). The proportion of female patients was 43%. The mean hospital stay was 18.4 days (SD +/- 4.97 days) for total inpatient treatment. Subsequent mean outpatient antibiotic therapy was admitted for 71.7 days (SD +/- 23.18 days). Outpatient mean IV therapy accounted for 53.88 days (SD +/- 18.56 days). The most common pathogens were Staphylococcus epidermis and cutibacteria. In 9%, microbiological samples were. In all patients, neither radiographic nor laboratory evidence of inflammation was found in the final control. During outpatient intravenous therapy, 12% of patients experienced a difficult patency of the PICC line due to the prolonged administration of antibiotics. This could be corrected radiologically in each case. In addition, one patient, independent of therapy, showed structural epilepsy after the abscess healing. Conclusions: Outpatient IV antibiotic therapy via a PICC line catheter is a safe and feasible method for long-term antibiotic treatment of cranial infections

A new endstation for extreme-ultraviolet spectroscopy of free clusters and nanodroplets

We present a new endstation for the AMOLine of the ASTRID2 synchrotron at Aarhus University, which combines a cluster and nanodroplet beam source with a velocity map imaging and time-of-flight spectrometer for coincidence imaging spectroscopy. Extreme-ultraviolet spectroscopy of free nanoparticles is a powerful tool for studying the photophysics and photochemistry of resonantly excited or ionized nanometer-sized condensed-phase systems. Here we demonstrate this capability by performing photoelectron-photoion coincidence (PEPICO) experiments with pure and doped superfluid helium nanodroplets. Different doping options and beam sources provide a versatile platform to generate various van der Waals clusters as well as He nanodroplets. We present a detailed characterization of the new setup and present examples of its use for measuring high-resolution yield spectra of charged particles, time-of-flight ion mass spectra, anion-cation coincidence spectra, multi-coincidence electron spectra and angular distributions. A particular focus of the research with this new endstation is on intermolecular charge and energy-transfer processes in heterogeneous nanosystems induced by valence-shell excitation and ionization.Comment: 28 pages, 17 figures, submitted to Review of Scientific Instrument

Avalanche of stimulated forward scattering in high harmonic generation

© 2016 [Optical Society of America]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.Optical amplifiers in all ranges of the electromagnetic spectrum exhibit an essential characteristic, namely the input signal during the propagation in the amplifier medium is multiplied by the avalanche effect of the stimulated emission to produce exponential growth. We perform a theoretical study motivated and supported by experimental data on a He gas amplifier driven by intense 30-fs-long laser pulses and seeded with attosecond pulse trains generated in a separated Ne gas jet. We demonstrate that the strong-field theory in the frame of high harmonic generation fully supports the appearance of the avalanche effect in the amplification of extreme ultraviolet attosecond pulse trains. We theoretically separate and identify different physical processes taking part in the interaction and we demonstrate that X-ray parametric amplification dominates over others. In particular, we identify strong-field mediated intrapulse X-ray parametric processes as decisive for amplification at the single-atom level. We confirm that the amplification takes place at photon energies where the amplifier is seeded and when the seed pulses are perfectly synchronized with the driving strong field in the amplifier. Furthermore, propagation effects, phase matching and seed synchronization can be exploited to tune the amplified spectral range within the seed bandwidth.Peer ReviewedPostprint (author's final draft

Temperature-dependent recombination coefficients in InGaN light-emitting diodes : hole localization, Auger processes, and the green gap

We obtain temperature-dependent recombination coefficients by measuring the quantum efficiency and differential carrier lifetimes in the state-of-the-art InGaN light-emitting diodes. This allows us to gain insight into the physical processes limiting the quantum efficiency of such devices. In the green spectral range, the efficiency deteriorates, which we assign to a combination of diminishing electronhole wave function overlap and enhanced Auger processes, while a significant reduction in material quality with increased In content can be precluded. Here, we analyze and quantify the entire balance of all loss mechanisms and highlight the particular role of hole localization