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Amyloid β aggregation is an important factor in Alzheimer's disease. Since calcium homeostasis plays an important role in amyloid β aggregation, it is crucial to study the interaction between calcium ions and amyloid β directly at the surface of the lipid membrane. With supercritical angle techniques, the signal of interest at the surface is easily separated from the bulk solution, making them a powerful tool for aggregation study. In this work, the influence of calcium ions on amyloid β aggregation over different aggregation time periods is investigated with supercritical angle Raman and fluorescence spectroscopy and microscopy. Note that calcium ions have a larger influence on amyloid β1–42 than on the 40 amino acid variant. We found that a small layer of calcium ions significantly protects the lipid membrane against the protein insertion process. [ABSTRACT FROM AUTHOR]

The physical and chemical analysis of aerosols using reliable and physically traceable methods is important for the thorough investigation of airborne particles to support a better understanding of their origin as well as their health and climate impacts. Within the European Metrology Research AeroMet project, the aim of Physikalisch-Technische Bundesanstalt's (PTB) X-ray spectrometry group is to develop and establish traceable and reliable X-ray methods to measure the elemental mass deposition per unit area, the elemental composition, and the chemical binding state of particulate matter supported by a flat substrate. This approach can substantially contribute to support quantitative analytical methods during on-site measurement campaigns where portable instrumentation is employed by qualifying suitable calibration samples for commercial analytical X-ray instruments and by investigating samples collected during the field campaign., The legal definition and enforcement of air quality regulations require an accurate and reliable monitoring of airborne particulate matter (PM). The monitoring needs to be evaluated at different levels to [...]

The aggregation of α-synuclein (α-Syn) is believed to be one of the key steps driving the pathology of Parkinson's disease and related neurodegenerative disorders. One of the present hypotheses is that the onset of such pathologies is related to the rise of α-Syn levels above a critical concentration at which toxic oligomers or mature fibrils are formed. In the present study, we find that α-Syn aggregation in vitro is a spontaneous process arising at bulk concentrations as low as 1 nM and below in the presence of both hydrophilic glass surfaces and cell membrane mimicking supported lipid bilayers (SLBs). Using three-dimensional supercritical angle fluorescence (3D-SAF) microscopy, we observed the process of α-Syn aggregation in situ. As soon as α-Syn monomers were exposed to the surface, they started to adsorb and aggregate along the surface plane without a prior lag phase. However, at a later stage of the aggregation process, a second type of aggregate was observed. In contrast to the first type, these aggregates showed an extended structure being tethered with one end to the surface and being mobile at the other end, which protruded into the solution. While both types of α-Syn aggregates were found to contain amyloid structures, their growing mechanisms turned out to be significantly different. Given the clear evidence that surface-induced α-Syn aggregation in vitro can be triggered at bulk concentrations far below physiological concentrations, the concept of a critical concentration initiating aggregation in vivo needs to be reconsidered.

To investigate water movement in environmental systems, stable water isotopes (2H and 18O) are commonly used tracers. Analyzing the isotopic composition of water bonded to substances like soil or plant tissue necessitates its extraction prior to analysis. One such method, direct vapor equilibration, is popular due to its cost-effectiveness and straightforward sample processing. However, sample analysis requires a significant manual labor, thereby limiting the number of samples that can be analyzed. This limitation is compounded by the fact that stored samples undergo isotopic composition changes over time, and in addition manual measurements may lack objectivity. To address these challenges, we have developed a device that automates the analysis process. Our vapor autosampler for vapour samples, named VapAuSa, features a modular design with up to 350 ports for direct vapor equilibration samples. These ports sequentially connect the prepared samples to the analyzer, enabling continuous automatic measurements. Within the accompanying software, measurement criteria can be specified, facilitating objective analysis. VapAuSa measurements have a similar uncertainty compared to manual analysis of identical samples (VapAuSa δ 2H = +/− 4.5 ‰ δ 18O = +/− 0.58 ‰ vs. manual δ 2H = +/− 5.7 ‰ δ 18O = +/− 0.37 ‰). However, the increased sample throughput minimizes storage-induced isotopic changes. Moreover, VapAuSa triples sample throughput per week while reducing direct labor time to just 10 % of manual processing. [ABSTRACT FROM AUTHOR]

Beneficial and negative effects of species interactions can strongly influence water fluxes in forest ecosystems. However, little is known about how trees dynamically adjust their water use when growing with interspecific neighbours. Therefore, we investigated the interaction effects between Fagus sylvatica (European beech) and Picea abies (Norway spruce) on water-use strategies and aboveground structural characteristics. We used continuous in situ isotope spectroscopy of xylem and soil water to investigate source water dynamics and root water uptake depths. Picea abies exhibited a reduced sun-exposed crown area in equally mixed compared with spruce-dominated sites, which was further correlated to a reduction in sap flow of −14.5 ± 8.2%. Contrarily, F. sylvatica trees showed +13.3 ± 33.3% higher water fluxes in equally mixed compared with beech-dominated forest sites. Although a significantly higher crown interference by neighbouring trees was observed, no correlation of water fluxes and crown structure was found. High time-resolved xylem δ2H values showed a large plasticity of tree water use (−74.1 to −28.5‰), reflecting the δ2H dynamics of soil and especially precipitation water sources. Fagus sylvatica in equally mixed sites shifted water uptake to deeper soil layers, while uptake of fresh precipitation was faster in beech-dominated sites. Our continuous in situ water stable isotope measurements traced root water uptake dynamics at unprecedented temporal resolution, indicating highly dynamic use of water sources in response to precipitation and to neighbouring species competition. Understanding this plasticity may be highly relevant in the context of increasing water scarcity and precipitation variability under climate change. [ABSTRACT FROM AUTHOR]

Methodological advancements have been made in in situ observations of water stable isotopes that have provided valuable insights into ecohydrological processes. The continuous measurement capabilities of laser-based analyzers allow for high temporal resolutions and non-destructive minimally invasive study designs of such in situ approaches. However, isotope analyzers are expensive, heavy, and require shelter and access to electrical power, which impedes many in situ assays. Therefore, we developed a new inexpensive technique to collect discrete water vapor samples in the field via diffusion-tight inflatable bags that can later be analyzed in the lab. In a series of structured experiments, we tested different procedural settings, bag materials, and closure types for diffusion tightness during storage as well as for practical handling during filling and extraction. To facilitate reuse of sampling bags, we present a conditioning procedure using ambient air as primer. In order to validate our method, direct measurements through hydrophobic in situ probes were compared to repeated measurements of vapor sampled with our bags from the same source. All steps are summarized in a detailed standard operating procedure (SOP). This procedure represents the preparation and measurement of calibration and validation vapor standards necessary for processing of unknown field-collected vapor samples in the foreseen application. By performing pertinent calibration procedures, accuracy was better than 0.4 ‰ for δ18 O and 1.9 ‰ for δ2 H after 1 d of storage. Our technique is particularly suitable when used in combination with minimally invasive water vapor sampling in situ probes that have already been employed for soils and tree xylem. It is an important step towards minimally invasive monitoring of stable isotope distributions and also time series in virtually undisturbed soils and trees without the need to have an analyzer in the field. It is therefore a promising tool for many applications in ecohydrology and meteorology. [ABSTRACT FROM AUTHOR]