Rapid Estimation of Membrane Protein Orientation in Liposomes

The topological organization of proteins embedded in biological membranes is crucial for the tight interplay between these enzymes and their accessibility to substrates in order to fulfil enzymatic activity. The orientation of a membrane protein reconstituted in artificial membranes depends on many parameters and is hardly predictable. Here, we present a convenient approach to assess this important property independent of the enzymatic activity of the reconstituted protein. Based on cysteine-specific chemical modification of a target membrane protein with a cyanine fluorophore and a corresponding membrane-impermeable fluorescence quencher, the novel strategy allows rapid evaluation of the distribution of the two orientations after reconstitution. The assay has been tested for the respiratory complexes bo₃ oxidase and ATP synthase of Escherichia coli and the results agree well with other orientation determination approaches. Given the simple procedure, the proposed method is a powerful tool for optimization of reconstitution conditions or quantitative orientation information prior to functional measurements.     

Efficient Screening of Target-Specific Selected Compounds in Mixtures by 19F NMR Binding Assay with Predicted 19F NMR Chemical Shifts

Ligand-based ¹⁹F NMR screening is a highly effective and well-established hit-finding approach. The high sensitivity to protein binding makes it particularly suitable for fragment screening. Different criteria can be considered for generating fluorinated fragment libraries. One common strategy is to assemble a large, diverse, well-designed and characterized fragment library which is screened in mixtures, generated based on experimental ¹⁹F NMR chemical shifts. Here, we introduce a complementary knowledge-based ¹⁹F NMR screening approach, named ¹⁹Focused screening, enabling the efficient screening of putative active molecules selected by computational hit finding methodologies, in mixtures assembled and on-the-fly deconvoluted based on predicted ¹⁹F NMR chemical shifts. In this study, we developed a novel approach, named LEFshift, for ¹⁹F NMR chemical shift prediction using rooted topological fluorine torsion fingerprints in combination with a random forest machine learning method. A demonstration of this approach to a real test case is reported.     

Room-temperature dislocation plasticity in SrTiO3 tuned by defect chemistry

Dislocations have been identified to modify both the functional and mechanical properties of some ceramic materials. Succinct control of dislocation-based plasticity in ceramics will also demand knowledge about dislocation interaction with point defects. Here, we propose an experimental approach to modulate the dislocation-based plasticity in single-crystal SrTiO₃ based on the concept of defect chemistry engineering, for example, by increasing the oxygen vacancy concentration via reduction treatment. With nanoindentation and bulk compression tests, we find that the dislocation-governed plasticity is significantly modified at the nano-/microscale, compared to the bulk scale. The increase in oxygen vacancy concentration after reduction treatment was assessed by impedance spectroscopy and is found to favor dislocation nucleation but impede dislocation motion as rationalized by the nanoindentation pop-in and nanoindentation creep tests.     

Deep red upconversion photoluminescence in Er3+-doped Yb3Ga5O12 nanocrystalline garnet

The nanocrystalline single-phase Er³⁺-doped Yb₃Ga₅O₁₂ garnets have been prepared by the sol-gel combustion technique with a crystallite size of ≈30 nm. The presence of Yb³⁺ in garnet hosts allows their efficient excitation at the ≈977 nm wavelength. The Er³⁺ doping of Yb₃Ga₅O₁₂ garnet host results in deep red Er³⁺: ⁴F_9/2 → ⁴I_15/2 upconversion photoluminescence (UCPL) emission. The dominance of the red UCPL emission over the green Er³⁺: ⁴F_7/2/²H_11/2/⁴S_3/2 → ⁴I_15/2 component was investigated using the measurement of the steady-state and time-dependent Er³⁺ and Yb³⁺ emission spectra in combination with the power-dependent UCPL emission intensity. The proposed upconversion mechanism is discussed in terms of the Er³⁺ → Yb³⁺ energy back transfer process as well as Yb³⁺(Er³⁺) → Er³⁺ energy transfer and Er³⁺ ↔ Er³⁺ cross-relaxation processes. The studied Er³⁺-doped Yb₃Ga₅O₁₂ garnet may be utilized as a red upconversion emitting phosphor.     

Photoelectrochemical and photocatalytic properties of titanium (IV) oxide nanoparticulate layers

Titania nanostructured particles were produced by the sol-gel method in the reverse micelle environment treated thermally and by various extraction steps including supercritical carbon dioxide, subcritical water and their combinations. Thin films comprised of the organized nanoparticles were tested in photoelectrochemical and photocatalytic experiments. The former were configured for the open circuit potential measurements and evaluation of polarization curves and the corresponding photocurrents. Photocatalytic activities of the layered films were assessed by following decomposition of the methyl ester of stearic acid. Attention was also paid to evaluation of the extent of the surface wettability of the layers. The effect of content of residual surface carbon, extent of hydrophilic properties and presence of anatase structure were identified as essential parameters responsible for the enhanced photoactivity of the tested layers. On the other hand also layers treated without any thermal steps revealed certain level of photoactivity that might be of special importance in some specific applications.     

CVD Grown Tungsten Oxide for Low Temperature Hydrogen Sensing: Tuning Surface Characteristics via Materials Processing for Sensing Applications

The intrinsic properties of semiconducting oxides having nanostructured morphology are highly appealing for gas sensing. In this study, the fabrication of nanostructured WO₃ thin films with promising surface characteristics for hydrogen (H₂) gas sensing applications is accomplished. This is enabled by developing a chemical vapor deposition (CVD) process employing a new and volatile tungsten precursor bis(diisopropylamido)-bis(tert-butylimido)-tungsten(VI), [W(N^tBu)₂(NⁱPr₂)₂]. The as-grown nanostructured WO₃ layers are thoroughly analyzed. Particular attention is paid to stoichiometry, surface characteristics, and morphology, all of which strongly influence the gas-sensing potential of WO₃. Synchrotron-based ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron emission microscopy (XPEEM), low-energy electron microscopy (LEEM) and 4-point van der Pauw (vdP) technique made it possible to analyze the surface chemistry and structural uniformity with a spatially resolved insight into the chemical, electronic and electrical properties. The WO₃ layer is employed as a hydrogen (H₂) sensor within interdigitated mini-mobile sensor architecture capable of working using a standard computer's 5 V 1-wirebus connection. The sensor shows remarkable sensitivity toward H₂. The high, robust, and repeatable sensor response (S) is attributed to the homogenous distribution of the W⁵⁺ oxidation state and associated oxygen vacancies, as shown by synchrotron-based UPS, XPS, and XPEEM analysis.     

Comparative study of a simulative bearing design with an experimentally determined data of a prototype bearing

Forschung im Ingenieurwesen - In some specific applications, the need of an optimized rolling bearing, having a similar load carrying capacity as a tapered roller bearing but with...     

From Precursor Chemistry to Gas Sensors: Plasma‐Enhanced Atomic Layer Deposition Process Engineering for Zinc Oxide Layers from a Nonpyrophoric Zinc Precursor for Gas Barrier and Sensor Applications

The identification of bis‐3‐(N,N‐dimethylamino)propyl zinc ([Zn(DMP)₂], BDMPZ) as a safe and potential alternative to the highly pyrophoric diethyl zinc (DEZ) as atomic layer deposition (ALD) precursor for ZnO thin films is reported. Owing to the intramolecular stabilization, BDMPZ is a thermally stable, volatile, nonpyrophoric solid compound, however, it possesses a high reactivity due to the presence of Zn‐C and Zn‐N bonds in this complex. Employing this precursor, a new oxygen plasma enhanced (PE)ALD process in the deposition temperature range of 60 and 160 °C is developed. The resulting ZnO thin films are uniform, smooth, stoichiometric, and highly transparent. The deposition on polyethylene terephthalate (PET) at 60 °C results in dense and compact ZnO layers for a thickness as low as 7.5 nm with encouraging oxygen transmission rates (OTR) compared to the bare PET substrates. As a representative application of the ZnO layers, the gas sensing properties are investigated. A high response toward NO₂ is observed without cross‐sensitivities against NH₃ and CO. Thus, the new PEALD process employing BDMPZ has the potential to be a safe substitute to the commonly used DEZ processes.     

Quadrature frequency resolved spectroscopy of upconversion photoluminescence in GeGaS:Er<Superscript>3+</Superscript>; II. elucidating excitation mechanisms of red emission besides green emission

The paper addresses the quadrature frequency resolved spectroscopy (QFRS) on the red (⁴ F _9/2 → ⁴ I _15/2) upconverted photoluminescence (UCPL) as well as the green (⁴ S _3/2 → ⁴ I _15/2) UCPL of Er³⁺ in GeGaS chalcogenide glasses at the pump wavelength 975 nm. On the basis of the perturbed rate equations for the generally accepted 5-level model of the green and red UCPLs of Er³⁺, we have derived the formulas for the QFRS on the green and red UCPLs of the two differently Er-doped samples. Adopting the respective formulas as model functions for the nonlinear regressions on the QFRS data of both the UCPLs, we have determined the relevant parameters such as relaxation rates at the four excited levels, the excited absorption cross section and energy transfer parameters. Thereby the differences of UCPL dynamics between the green and red UCPLs as well as between the two differently Er-doped Ge₂₅Ga₁₀S₆₅ samples are interpreted in terms of the determined parameters.     

Autonomous Vision-Based Helicopter Flights Through Obstacle Gates

The challenge for unmanned aerial vehicles to sense and avoid obstacles becomes even harder if narrow passages have to be crossed. An approach to solve a mission scenario that tackles the problem of such narrow passages is presented here. The task is to fly an unmanned helicopter autonomously through a course with gates that are only slightly larger than the vehicle itself. A camera is installed on the vehicle to detect the gates. Using vehicle localization data from a navigation solution, camera alignment and global gate positions are estimated simultaneously. The presented algorithm calculates the desired target waypoints to fly through the gates. Furthermore, the paper presents a mission execution plan that instructs the vehicle to search for a gate, to fly through it after successful detection, and to search for a proceeding one. All algorithms are designed to run onboard the vehicle so that no interaction with the ground control station is necessary, making the vehicle completely autonomous. To develop and optimize algorithms, and to prove the correctness and accuracy of vision-based gate detection under real operational conditions, gate positions are searched in images taken from manual helicopter flights. Afterwards, the integration of visual sensing and mission control is proven. The paper presents results from full autonomous flight where the helicopter searches and flies through a gate without operator actions.