One Question,Multiple Answers: Biochemical and Biophysical Screening Methods Retrieve Deviating Fragment Hit Lists

Fragment‐based lead discovery is gaining momentum in drug development. Typically, a hierarchical cascade of several screening techniques is consulted to identify fragment hits which are then analyzed by crystallography. Because crystal structures with bound fragments are essential for the subsequent hit‐to‐lead‐to‐drug optimization, the screening process should distinguish reliably between binders and non‐binders. We therefore investigated whether different screening methods would reveal similar collections of putative binders. First we used a biochemical assay to identify fragments that bind to endothiapepsin, a surrogate for disease‐relevant aspartic proteases. In a comprehensive screening approach, we then evaluated our 361‐entry library by using a reporter‐displacement assay, saturation‐transfer difference NMR, native mass spectrometry, thermophoresis, and a thermal shift assay. While the combined results of these screening methods retrieve 10 of the 11 crystal structures originally predicted by the biochemical assay, the mutual overlap of individual hit lists is surprisingly low, highlighting that each technique operates on different biophysical principles and conditions.     

Modeling and Flow Sheet Simulation of Selected Mechanical Recycling Processes for Li-Ion Batteries

To investigate the mechanical processes of Li-ion battery recycling in more detail, models for the different unit processes are to be developed. Here, model approaches for the cutting mill and the zig-zag-sifter are presented. These models are to be used in dynamic flow sheet simulations, with which the individual unit processes as well as the combination to a small process chain were simulated. Thereby, the dynamic interactions between the process steps were investigated, which can be used later for optimization and regulation of the processes. The particle sizes after the cutting mill process as well as the mass flow between the processes influence the separation behavior of the sifter. These changes in the separation function due to an increasing mass flow out of the mill are shown.     

Characterization of spatial inhomogeneities and dynamic properties of random cross-linked polystyrene networks by dynamic light scattering

The network inhomogeneity and the cooperative motion of the network chains of random cross-linked poly(styrene-co-maleic anhydride) gels were investigated by dynamic light scattering. Measurements were performed for gels in the preparation state as well as in the swelling equilibrium. Network inhomogeneities and cooperative motion were analyzed at varying the cross-linker concentration and the polymer volume fraction. While the cross-linker concentration has only a minor influence on the inhomogeneity and the diffusion constant D_coop, the polymer volume fraction clearly influences both measured properties. The concentration dependence of D_coop can be well described by a power law, as known for semi-dilute polymer solutions. In the preparation state the networks appear homogeneous, exhibiting dynamic contributions to the scattering intensity of 70-90%. Swollen to equilibrium stage, significant heterogeneities emerge, reducing the dynamic contributions to 10-20%.     

Co-oxidation of carotene and crocin by soyabean lipoxygenase isoenzymes

Summary Three lipoxygenases that occur in soya beans were separated chromatographically. L-1 (optimum pH = 9.0), L-2 (pH 6.5), L-3 (pH 6.5). The velocities with which these enzymes co-oxidise-carotene or Crocin in the presence of linoleic acid or linoleyl sulphate weremeasured. The carotenoid turnover was related to each lipoxygenase activity.-carotene/linoleic acid = 55% (L-2), 43% (L-3), 6% (L-1), Crocin/linoleic acid = 17,8% (L-2), 14,3% (L-3), 3.3% (L-1), crocin/linoleyl sulphate = 24% (L-3), 4,2% (L-1).The relationship between the reaction rate of the Crocin bleaching and the concentrations of the enzyme, Crocin and linoleic acid was determined. To explain the differences between the pH-6.5 (L-2, L-3) and the alkaline (L-1) lipoxygenases it is supposed that L-2 and L-3 form specially active radicals that are able to co-oxidise polyenes. Both enzymes possess a hydrophobic bonding position, in the neighbourhood of the active site, for-carotene.

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Co-oxidation von Carotin und Crocin durch Lipoxygenase-Isoenzyme aus der Sojabohne

Zusammenfassung Drei in Sojabohnen vorkommende Lipoxygenasen wurden chromatographisch getrennt: L-1 (pH-Optimum 9,0), L-2 (pH 6,5), L-3 (pH 6,5). Gemessen wurden die Geschwindigkeiten mit denen diese Enzyme-Carotin oder Crocin in Gegenwart von Linolsäure oder Linoleylsulfat co-oxydieren. Die Carotinoid-Umsätze wurden auf die jeweilige Lipoxygenase-Aktivität bezogen.-Carotin/Linolsäure: 55% (L-2), 43% (L-3), 6% (L-1), Crocin/Linolsäure: 17,8% (L-2),14,3% (L-3),3,3% (L-1), Crocin/Linoleylsulfat: 24% (L-3), 4,2% (L-1).Für die Crocin-Bleichung wurde die Abhängigkeit der Reaktionsgeschwindigkeit von der Enzym-, Crocin- und Linolsäure-Konzentration bestimmt.Zur Erklärung der Unterschiede zwischen den pH 6,5- (L-2, L-3) und der alkalischen Lipoxygenase (L-1) wird angenommen: L-2 und L-3 bilden besonders aktiv Radikale, welche die Polyene co-oxydieren können. Beide Enzyme besitzen in der Nähe des aktiven Zentrums eine hydrophobe Bindungsstelle für das-Carotin.

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We are grateful to the Deutsche Forschungsgemeinschaft Bonn-Bad Godesberg for supporting this work.     

Furan fatty acid concentrations in tea infusions prepared from green,black, and herbal teas

Furan fatty acids (FuFAs) are valuable antioxidants with highly effective radical scavenging properties which are widely distributed at low levels in food. Previous research indicated that tea is a valuable source of FuFAs. However, tea is only consumed in form of infusions. To fill this gap, we prepared infusions from different herbal, green, and black teas. Initial measurements with GC-MSMS of tea verified previous findings that 11-(3,4-dimethyl-5-penylfuran-2-yl)-undecanoic acid (11D5) was the prevalent FuFA in tea matrix. Therefore, 11D5 was quantified in tea infusions by means of UHPLC-MSMS equipment after mild alkaline hydrolysis. While herbal tea infusions were low or free of FuFAs, 11D5 was detectable in all samples of green and black tea infusions. Amounts of 11D5 were higher in green tea than in black tea. Moreover, Darjeeling tea infusions were by ~30% richer in 11D5 than black and green teas from other regions. Each cup of green and black tea infusion may provide 20–60 μg 11D5, which is about 5% of the amounts found in tea samples. Spread over the day, regular tea consumption may contribute to the intake of valuable FuFAs.     

Co-Oxidative Transformation of Piperine to Piperonal and 3,4-Methylenedioxycinnamaldehyde by a Lipoxygenase from Pleurotus sapidus

The valuable aroma compound piperonal with its vanilla-like olfactory properties is of high interest for the fragrance and flavor industry. A lipoxygenase (LOX_Psa1) of the basidiomycete Pleurotus sapidus was identified to convert piperine, the abundant pungent principle of black pepper (Piper nigrum), to piperonal and a second volatile product, 3,4-methylenedioxycinnamaldehyde, with a vanilla-like odor through an alkene cleavage. The reaction principle was co-oxidation, as proven by its dependence on the presence of linoleic or α-linolenic acid, common substrates of lipoxygenases. Optimization of the reaction conditions (substrate concentrations, reaction temperature and time) led to a 24-fold and 15-fold increase of the piperonal and 3,4-methylenedioxycinnamaldehyde concentration using the recombinant enzyme. Monokaryotic strains showed different concentrations of and ratios between the two reaction products.     

A Versatile Route to Assemble Semiconductor Nanoparticles into Functional Aerogels by Means of Trivalent Cations

3D nanoparticle assemblies offer a unique platform to enhance and extend the functionality and optical/electrical properties of individual nanoparticles. Especially, a self‐supported, voluminous, and porous macroscopic material built up from interconnected semiconductor nanoparticles provides new possibilities in the field of sensing, optoelectronics, and photovoltaics. Herein, a method is demonstrated for assembling semiconductor nanoparticle systems containing building blocks possessing different composition, size, shape, and surface ligands. The method is based on the controlled destabilization of the particles triggered by trivalent cations (Y³⁺, Yb³⁺, and Al³⁺). The effect of the cations is investigated via X‐ray photoelectron spectroscopy. The macroscopic, self‐supported aerogels consist of the hyperbranched network of interconnected CdSe/CdS dot‐in‐rods, or CdSe/CdS as well as CdSe/CdTe core‐crown nanoplatelets is used to demonstrate the versatility of the procedure. The non‐oxidative assembly method takes place at room temperature without thermal activation in several hours and preserves the shape and the fluorescence of the building blocks. The assembled nanoparticle network provides longer exciton lifetimes with retained photoluminescence quantum yields, that make these nanostructured materials a perfect platform for novel multifunctional 3D networks in sensing. Various sets of photoelectrochemical measurements on the interconnected semiconductor nanorod structures also reveal the enhanced charge carrier separation.