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- MOUSE (2)
- Nanostructure quantification (2)
- Round Robin (2)
- 2-D electrophoresis (1)
- Alzheimer disease (1)
- Amyloid formation (1)
- Array technique (1)
- Asphalt (1)
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Organisationseinheit der BAM
- 3 Gefahrgutumschließungen; Energiespeicher (2)
- 5 Werkstofftechnik (2)
- 5.1 Mikrostruktur Design und Degradation (2)
- 6 Materialchemie (2)
- 6.3 Strukturanalytik (2)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
- 8 Zerstörungsfreie Prüfung (2)
- 3.0 Abteilungsleitung und andere (1)
- 3.2 Gefahrguttanks und Unfallmechanik (1)
A round-robin study has been carried out to estimate the impact of the human element in small-angle scattering data analysis. Four corrected datasets were provided to participants ready for analysis. All datasets were measured on samples containing spherical scatterers, with two datasets in dilute dispersions and two from powders. Most of the 46 participants correctly identified the number of populations in the dilute dispersions, with half of the population mean entries within 1.5% and half of the population width entries within 40%. Due to the added complexity of the structure factor, far fewer people submitted answers on the powder datasets. For those that did, half of the entries for the means and widths were within 44 and 86%, respectively. This round-robin experiment highlights several causes for the discrepancies, for which solutions are proposed.
A Round Robin study has been carried out to estimate the impact of the human element in small-angle scattering data analysis. Four corrected datasets were provided to participants ready for analysis. All datasets were measured on samples containing spherical scatterers, with two datasets in dilute dispersions, and two from powders.
Most of the 46 participants correctly identified the number of populations in the dilute dispersions, with half of the population mean entries within 1.5 % and half of the population width entries within 40 %, respectively. Due to the added complexity of the structure factor, much fewer people submitted answers on the powder datasets.
For those that did, half of the entries for the means and widths were within 44 % and 86 % respectively. This Round Robin experiment highlights several causes for the discrepancies, for which solutions are proposed.
To assess the suitability of asymmetric cyanine dyes for in vivo fluoro-optical molecular imaging, a comprehensive study on the influence of the number of negatively charged sulfonate groups governing the hydrophilicity of the DY-67x family of asymmetric cyanines was performed. Special attention was devoted to the plasma protein binding capacity and related pharmacokinetic properties. Four members of the DY-67x cyanine family composed of the same main chromophore, but substituted with a sequentially increasing number of sulfonate groups (n = 1−4; DY-675, DY-676, DY-677, DY-678, respectively), were incubated with plasma proteins dissolved in phosphate-buffered saline. Protein binding was assessed by absorption spectroscopy, gel electrophoresis, ultrafiltration, and dialysis. Distribution of dye in organs was studied by intraveneous injection of 62 nmol dye/kg body weight into mice (n = 12; up to 180 minutes postinjection) using whole-body near-infrared fluorescence imaging. Spectroscopic studies, gel electrophoresis, and dialysis demonstrated reduced protein binding with increasing number of sulfonate groups. The bovine serum albumin binding constant of the most hydrophobic dye, DY-675, is 18 times higher than that of the most hydrophilic fluorophore, DY-678. In vivo biodistribution analysis underlined a considerable influence of dye hydrophilicity on biodistribution and excretion pathways, with the more hydrophobic dyes, DY-675 and DY-676, accumulating in the liver, followed by strong fluorescence signals in bile and gut owing to accumulation in feces and comparatively hydrophilic DY-678-COOH accumulating in the bladder. Our results demonstrate the possibility of selectively controlling dye-protein interactions and, thus, biodistribution and excretion pathways via proper choice of the fluorophore's substitution pattern. This underlines the importance of structure-property relationships for fluorescent labels. Moreover, our data could provide the basis for the rationalization of future contrast agent developments.
Nanotechnologien werden gegenwärtig als leistungsfähige Oberflächentechniken in erheblichem Umfange industriell genutzt. Dabei spielen dünne Schichten und deren Kenndaten eine wesentliche Rolle, z.B. als Röntgenspiegel oder optische und magnetooptische Datenträger. Die Schichtdicke zählt hierbei zu den technologisch wichtigen Parametern. Abgeleitet von Anwenderinteressen, werden für die Röntgenreflektometrie (XRR bzw. GIXR), Elektronenstrahl-Mikroanalyse (EPMA) und Röntgenfluoreszenzanalyse (XRF) einerseits und die Ellipsometrie andererseits zugeschnittene Schichtdickenmaßverkörperungen (SDM) entwickelt, gefertigt und untersucht. Das Ziel ist die Bereitstellung praxistauglicher, kalibrierter SDM, im weiteren Schichtdickennormale (SDN) genannt. SDN sind Maßverkörperungen, für die der Schichtdickenwert mit einer definierten Messunsicherheit bekannt und auf ein metrologisch anerkanntes Längennormal zurückgeführt ist. Berichtet wird über die Herstellung und messtechnische Charakterisierung der beiden spezifischen Varianten von Maßverkörperungen.
Die Risstiefenbestimmung in Festen Fahrbahnen ist hinsichtlich der Dauerhaftigkeit der Konstruktion von wesentlichem Interesse. Im Rahmen eines gemeinsamen Forschungsvorhabens mit der DB AG wurden aus der Literatur bekannte Ansätze bewertet und darauf aufbauend ein Verfahren zur bildgebenden Rissdarstellung entwickelt. Rissüberbrückende Bewehrung sowie Kontaktstellen zwischen den Rissflanken wirken als Schallbrücken und erschweren die Risscharakterisierung, wie bei einem Einsatz an einer Betriebserprobungsstrecke festgestellt wurde. Ein aus der Literatur bekanntes Verfahren der einfachen Laufzeitmessung erwies sich für die Tiefenbestimmung von realen verunreinigten Rissen als ungeeignet.
Since several years ultrasonic imaging techniques are used for testing concrete elements. Combined with a reconstruction calculation they lead to an acoustic imaging of scatterers and reflectors from the inside of the concrete element. For several testing problems it is an advantage to use a two dimensional synthetic aperture and to combine it with a three-dimensional reconstruction calculation (3D-SAFT, Synthetic Aperture Focussing Technique).
This enables the analysis of the tested volume by means of B-scans in two directions and C-scans (projections parallel to the surface), respectively. Using the 2D-scanning technique, especially the disturbing influence of the reinforcing rebars can be minimised.
In this contribution the state of the art of this method is demonstrated and analysed. Examples of the application are presented, concerning
Localisation of honeycombing and compaction faults
Characterisation of cracks (especially measuring the crack depth)
Investigation of tendon ducts
The results presented are obtained in the frame of a research initiative Non-destructive Evaluation of Concrete Structures Using Acoustic and Electromagnetic Echo-Methods supported by the German Science Council (FOR 384 of DFG, Deutsche Forschungsgemeinschaft). The methods are assessed and improved in cooperation with the partners participating in the project.
Electron probe microanalysis (EPMA) measurement of thin-film thickness in the nanometre range
(2002)
The thickness of thin films of platinum and nickel on fused silica and silicon substrates has been determined by EPMA using the commercial software STRATAGEM for calculation of film thickness. Film thickness ranged in the order 10 nm. An attempt was made to estimate the confidence range of the method by comparison with results from other methods of analysis. The data show that in addition to the uncertainty of the spectral intensity measurement and the complicated fitting routine, systematic deviation caused by the underlying model should be added. The scattering in the results from other methods does not enable specification of a range of uncertainty, but deviations from the real thickness are estimated to be less than 20%.
Fibre optic sensors for monitoring in safety-relevant structures have to be validated in order to proof their reliability under typical structural load conditions. The reliable use of optical fibre sensors depends strongly on an appropriate and qualitative application. Diagnostics of the physical condition of embedded and surface-applied fibre optic strain sensors are demonstrated on field examples. Distributed strain measurement based on Rayleigh backscattering is used to determine breakage of the fibre, interface adhesion problems and to identify application related strain transfer mechanisms.
High-accuracy film thickness measurements in the range below 100 nm can be made by various complex methods like spectral ellipsometry (SE), scanning force microscopy (SFM), grazing incidence X-ray reflectometry (GIXR), or X-ray fluorescence analysis (XRF). The measurement results achieved with these methods are based on different interactions between the film and the probe. A key question in nanotechnology is how to achieve consistent results on a level of uncertainty below one nanometre with different techniques.
Two different types of thickness standards are realised. Metal film standards for X-ray techniques in the thickness range 10 to 50 nm are calibrated by GIXR with monochromatised synchrotron radiation of 8048 eV. The results obtained at four different facilities show excellent agreement. SiO2 on Si standards for SE and SFM in the thickness range 6 to 1000 nm are calibrated by GIXR with monochromatised synchrotron radiation of 1841 eV and with a metrological SFM. Consistent results within the combined uncertainties are obtained with the two methods. Surfaces and interfaces of both types of standards are additionally investigated by transmission electron microscopy (TEM).
Climate change, CO2 reduction, resource efficiency are only 3 current keywords that describe the current industrial-economic situation. In order to influence climate change effectively, the conversion of supply systems with technically usable forms of energy must succeed in the next decade. The international network founded in Baku in 2015 bundles research activities in the broad field of energy supply and energy efficiency.
Discuss current research approaches and results with scientists and experts from renowned universities and follow Azerbaijan's efforts to implement the energy revolution.
In a proof of concept study, metal-coded affinity tags based on click chemistry (MeCAT-Click) were used to analyze the proteome of Escherichia coli (E. coli) in response to heat stress. This allows high labeling efficiency, high detection sensitivity, and multiplex capabilities, which are pivotal for its application to protein quantification. Two approaches are presented for relative quantification of differentially lanthanide-labeled proteins. The first approach uses isotope-labeling, where ESI-MS was utilized to quantify the differentially labeled proteins from different states of E. coli. With this approach, 14 proteins were found with changed abundance, among them five proteins upregulated.
In the second approach, differentially labeled samples were separated by two dimensional gel electrophoresis (2 DE) and scanned by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Comparison of the signal intensities of the different lanthanides was used to quantify different sample states. Based on this information, ESI-MS was used to identify the proteins with different abundance. The sensitivity of LA-ICP-MS allowed us to find one upregulated protein that was nearly invisible by silver staining ("Probable replication endonuclease from retron EC67"). The advantage of this approach is to locate low abundant proteins with differential expression using LA-ICP-MS, which may be overlooked otherwise.
Biological significance: This paper demonstrates the successful application of a novel metal labeling strategy to quantify the proteins from complex biological samples. In comparison with former metal labeling strategies, it reduces the steric hindrance and improves the labeling efficiency during the labeling process, which ensure its successful application. This methodology is compatible with both molecular and elemental mass spectrometry. ESI-MS/MS in combination with software-based search allows the identification and relative quantification of labeled proteins. In addition, LA-ICP-MS helps to locate the labeled proteins in 2-DE gels with superior detection capability, thus, target proteins with low abundance can be precisely followed. Its excellent sensitivity allows one to track the proteins of interest that are barely visible by silver staining.
3-Aminovinylquinoxalines are readily accessible from (hetero)aryl glyoxylic acids or heterocyclic π-nucleophiles by consecutive four- and fivecomponent syntheses in the sense of an activation-alkynylation-cyclocondensation-addition sequence or glyoxylation-alkynylation-cyclocondensation-addition sequence in good yields. The title compounds are highly fluorescent with pronounced emission solvatochromicity and protochromic fluorescence quenching. Time-resolved fluorescence spectroscopy furnishes radiative and nonradiative fluorescence decay rates in various solvent polarities. The electronic structure is corroborated by DFT and TD-DFT calculations rationalizing the observed spectroscopic effects.
Fibre-reinforced plastics (FRP) especially carbon-fibre-reinforced polymer (CFRP) and glass-fibre-reinforced polymer (GFRP) are commonly used materials in high pressure vessels and storage units for automotive and aerospace purposes. Optical fibres are suitable to be integrated or directly applied to the surface of FRP components. Using optical fibres it is possible to monitor the distributed strain profiles and changes within the fatigue life of a pressure vessel to ensure the operational safety. Within artificial ageing experiments we used swept wavelength interferometry (SWI) based distributed strain sensing for the monitoring of commercial high-pressure composite cylinder. This artificial ageing was performed using test conditions of 503bar pressure load (service pressure 300 bar) and 89 °C for 100 h. The polyimide coated optical fibres were glued to the surface externally in circumferential and axial direction. Using distributed strain sensing (DSS) material expansion of over 0.5% were monitored with sub-centimetre spatial resolution. Within the circumferential direction we observed up to 10 % local fluctuation compared to the median strain caused by inhomogeneous material expansion, which could cause local material fatigue. In addition, we determined material degradation manifested itself as localized remaining material expansion and/or contraction. Results have been validated by other non-destructive methods like digital strip projection.
Zur Weiterentwicklung der Probenpräsentation wurde ein Adapter entwickelt, der Emissionsprüfkammer und Bewertungstrichter miteinander verbindet und dadurch eine der direkten Messung vergleichbare Geruchsbewertung ermöglicht. Die analytischen Messungen zeigen, dass es kaum Unterschiede in der Zusammensetzung der Probenluft in der Kammer im Vergleich zum Probenbehälter gibt. Bei den olfaktorischen Messungen kam es jedoch bei der Bewertung der Probenluft mit Hilfe des Adapters zu Minderbefunden. Anschließende Untersuchungen zeigten, dass beim Ausschalten des Geräts Umgebungsluft über den Trichter in den Adapter strömt und zu einer Verdünnung der Probenluft führt. Um dies zu vermeiden, werden derzeit weitere Messungen durchgeführt.
Eine weitere Versuchsreihe wurde durchgeführt, um den Messaufwand bei der Bewertung der empfundenen Intensität zu reduzieren. Die entwickelte „größer-oder-kleiner/gleich“ Abfrage kann hier hilfreich sein. Die Untersuchungen im Luftqualitätslabor und im Rahmen eines Ringversuches mit verschiedenen Laboren, zeigen, dass die Abfrage in fast allen Fällen zu den gleichen Ergebnissen führt, wie die normgerechte aber aufwendigere Ermittlung der empfundenen Intensität mithilfe des Vergleichsmaßstabes.
Sensitive, accurate and fast absolute quantification of intact proteins is reported using metal coded affinity tags (MeCATs) combined with gel electrophoresis (GE) separation, inductively coupled plasma mass spectrometry (ICP-MS) detection and label-specific isotope dilution analysis quantification. Two different approaches were investigated concerning the introduction of the sample into ICP-MS, mineralization of the gel and direct laser ablation (LA) of the spot. Three major advantages are remarkable in the proposed method. First, not only heteroatom-containing proteins but also all labeled proteins in the sample can be absolutely quantified preparing an isotopically enriched tracer. On the other hand, highly sensitive determination in the amol range can be performed, considerably reducing the analysis time due to the straightforward measurements by ICP-MS. Furthermore, the studied method allows accurate quantifications with different sample-to-spike ratios and using stock spikes stored for months. After the first characterization using standard proteins, human serum albumin (HSA) and transferrin (Tf) were determined in human serum to test the applicability of the method to biological samples. The results show satisfactory quantifications for the studied proteins despite the difference in concentration and the similarity in migration distances.
The β-secretase or β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the enzyme responsible for the formation of amyloid-β peptides, which have a major role in Alzheimer pathogenesis. BACE1 has a transmembrane sequence (TMS), which makes it unique among related proteases. We noticed that the BACE1 TMS contains an uncommon sulfur-rich motif. The sequence MxxxCxxxMxxxCxMxC spans the entire TMS, resembles metal ion binding motifs, and is highly conserved among homologues. We used a synthetic 31-mer model peptide comprising the TMS to study metal ion binding and oligomerization. Applying diverse biochemical and biophysical techniques, we detected dimer and trimer formation of the TMS peptide with copper ions. Replacement of the central Cys466 by Ala essentially abolished these effects. We show that the peptide undergoes a redox reaction with copper ions resulting in a disulfide bridge involving Cys466. Further, we find peptide trimerization that depends on the presence of monovalent copper ions and the sulfhydryl group of Cys466. We identified Cys466 as a key residue for metal ion chelation and to be the core of an oligomerization motif of the BACE1-TMS peptide. Our results demonstrate a novel metal ion controlled oligomerization of the BACE1 TMS, which could have an enormous therapeutic importance against Alzheimer disease.
Bioconversion of Mono- and Sesquiterpenoids by recombinant human Cytochrome P450 Monooxygenases
(2008)
Cytochrome P450 monooxygenases play an important role in the biosynthesis and metabolism of terpenoids. We explored the potential of recombinant human liver cytochrome P450 monooxygenases CYP1A2, CYP2C9, and CYP3A4, heterologously expressed in Escherichia coli, to convert mono- and sesquiterpenoids to human metabolites. This natural product group is a diverse class of secondary metabolites and includes several industrially and pharmaceutically interesting compounds. Incubation of cedrol with CYP3A4 resulted in a bioconversion of 74% (±8.9%) after 1 h of the unknown metabolites 2-hydroxycedrol and 4-hydroxycedrol, which have been structurally elucidated by 1H and 13C NMR and GC-MS. We conclude that recombinant human cytochrome P450 enzymes can be useful tools in a combinatorial biosynthesis strategy for the production of new natural products and for in vitro metabolization studies.
Der Frequenzbereich der Terahertzwellen liegt im elektromagnetischen Spektrum zwischen den Mikrowellen und dem infraroten Licht – also etwa im Bereich von 0,1 bis 10 Terahertz (THz). Der VDI-Statusreport „Terahertzsysteme und Anwendungen“ stellt die unterschiedlichen Konzepte für Terahertzsysteme vor und zeigt Anwendungsbeispiele, bei denen die Terahertztechnik erfolgreich eingesetzt wird. Umfangreiche Literaturangaben ermöglichen eine intensivere Beschäftigung mit allen Themen des VDI-Statusreports.