Highly Enantioselective Catalytic Synthesis of Neurite Growth-Promoting Secoyohimbanes

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The effect of physical back-diffusion of 13CO2 tracer on the coupling between photosynthesis and soil CO2 efflux in grassland

Pulse labelling experiments provide a common tool to study short-term processes in the plant–soil system and investigate below-ground carbon allocation as well as the coupling of soil CO₂ efflux to photosynthesis. During the first hours after pulse labelling, the measured isotopic signal of soil CO₂ efflux is a combination of both physical tracer diffusion into and out of the soil as well as biological tracer release via root and microbial respiration. Neglecting physical back-diffusion can lead to misinterpretation regarding time lags between photosynthesis and soil CO₂ efflux in grassland or any ecosystem type where the above-ground plant parts cannot be labelled in gas-tight chambers separated from the soil. We studied the effects of physical ¹³CO₂ tracer back-diffusion in pulse labelling experiments in grassland, focusing on the isotopic signature of soil CO₂ efflux. Having accounted for back-diffusion, the estimated time lag for first tracer appearance in soil CO₂ efflux changed from 0 to 1.81±0.56 h (mean±SD) and the time lag for maximum tracer appearance from 2.67±0.39 to 9.63±3.32 h (mean±SD). Thus, time lags were considerably longer when physical tracer diffusion was considered. Using these time lags after accounting for physical back-diffusion, high nocturnal soil CO₂ efflux rates could be related to daytime rates of gross primary productivity (R²=0.84). Moreover, pronounced diurnal patterns in the δ¹³C of soil CO₂ efflux were found during the decline of the tracer over 3 weeks. Possible mechanisms include diurnal changes in the relative contributions of autotrophic and heterotrophic soil respiration as well as their respective δ¹³C values. Thus, after accounting for physical back-diffusion, we were able to quantify biological time lags in the coupling of photosynthesis and soil CO₂ efflux in grassland at the diurnal time scale.     

Time-dependent growth of crystalline Au0-nanoparticles in cyanobacteria as self-reproducing bioreactors: 1. Anabaena sp.

In the experiments, multifunctional nanocomposites with fluorescence, superparamagnetism, and bioactivity were synthesized to isolate and detect bacteria. Fluorescent-magnetic nanocomposites (FMNPs) (Fe₃O₄@SiO₂@FITC–SiO₂, core/shell) were first synthesized. Then, FMNPs were conjugated with N-hydroxysuccinimide-activated 4-oxo-4-(prop-2-ynyloxy) butanoic acid (NHS-activated ester) by the linker of 3-aminopropyltriethoxysilane, and alkyne-functionalized fluorescent-magnetic nanocomposites (FMNPs-alkyne) were produced. After 3′-azidopropyl-O-α-d-manno-pyranoside was grafted on the surface of FMNPs-alkyne by click chemistry, the final product—mannose derivatives-grafted fluorescent-magnetic nanocomposites (FMNPs-mannose) were obtained. Common techniques (Nuclear magnetic resonance, ESI mass spectra, etc.) indicated the successful synthesis of the target products. The results of scanning electron microscopy, transmission electron microscopy, and dynamic light scattering showed that FMNPs with one or more magnetic cores have regular structure with a diameter around 100 nm. Fluorescence spectra and fluorescence microscopy indicated that those nanocomposites exhibited strong and stable fluorescence property. FMNPs-mannose have a saturation magnization of 6.88 emu/g at room temperature. FMNPs-mannose were applied to adhere to Escherichia coli ATCC25722 and Staphylococcus aureus ATCC6538. The results showed that FMNPs-mannose were able to specifically adhere to E. coli ATCC25722. However, it had no effect with S. aureus ATCC6538. The obtained FMNPs-mannose will find its application in bacteria detection and separation.     

Electric Field-Assisted Solid Phase Extraction: Devices, Development and Application with a Cationic Model Compound

This work describes novel devices for electric field-assisted solid phase extraction (E-SPE) and an application was carried out on the antimicrobial marbofloxacin (MAR). Conventional syringe-type SPE cartridges were easily adapted to receive two electrodes that were inserted and positioned below and above the sorbent. The adapted cartridges were coupled to a flow extraction system, which consisted of an electrophoresis power supply, a peristaltic pump and a homemade SPE manifold. These devices were used to apply electric fields during the extraction of MAR from fortified buffer and milk samples. The recovery of MAR was improved (2.3 times) or reduced (4.2 times) in comparison to conventional SPE when the top electrode was used as cathode (E-SPE_(?/+)) or anode (E-SPE_(+/?)), respectively. The results demonstrated that usual SPE cartridges can be easily and inexpensively adapted for applying an electric field in SPE. It was also concluded that the electric field applied in a usual SPE cartridge can be employed as a new suitable approach to enhance the extraction efficiency of ionic compounds in a complex sample matrix.     

Chemometrics comes to court: evidence evaluation of chem–bio threat agent attacks

Forensic statistics is a well‐established scientific field whose purpose is to statistically analyze evidence in order to support legal decisions. It traditionally relies on methods that assume small numbers of independent variables and multiple samples. Unfortunately, such methods are less applicable when dealing with highly correlated multivariate data sets such as those generated by emerging high throughput analytical technologies. Chemometrics is a field that has a wealth of methods for the analysis of such complex data sets, so it would be desirable to combine the two fields in order to identify best practices for forensic statistics in the future. This paper provides a brief introduction to forensic statistics and describes how chemometrics could be integrated with its established methods to improve the evaluation of evidence in court. The paper describes how statistics and chemometrics can be integrated, by analyzing a previous know forensic data set composed of bacterial communities from fingerprints. The presented strategy can be applied in cases where chemical and biological threat agents have been illegally disposed. Copyright © 2015 John Wiley & Sons, Ltd.     

A Visualizable Chain‐Terminating Inhibitor of Glycosaminoglycan Biosynthesis in Developing Zebrafish

Heparan sulfate (HS) and chondroitin sulfate (CS) glycosaminoglycans (GAG) are proteoglycan‐associated polysaccharides with essential functions in animals. They have been studied extensively by genetic manipulation of biosynthetic enzymes, but chemical tools for probing GAG function are limited. HS and CS possess a conserved xylose residue that links the polysaccharide chain to a protein backbone. Here we report that, in zebrafish embryos, the peptide‐proximal xylose residue can be metabolically replaced with a chain‐terminating 4‐azido‐4‐deoxyxylose (4‐XylAz) residue by administration of UDP‐4‐azido‐4‐deoxyxylose (UDP‐4‐XylAz). UDP‐4‐XylAz disrupted both HS and CS biosynthesis and caused developmental abnormalities reminiscent of GAG biosynthesis and laminin mutants. The azide substituent of protein‐bound 4‐XylAz allowed for rapid visualization of the organismal sites of chain termination in vivo through bioorthogonal reaction with fluorescent cyclooctyne probes. UDP‐4‐XylAz therefore complements genetic tools for studies of GAG function in zebrafish embryogenesis.     

De Novo 3D Structure Determination from Sub‐milligram Protein Samples by Solid‐State 100 kHz MAS NMR Spectroscopy

Solid‐state NMR spectroscopy is an emerging tool for structural studies of crystalline, membrane‐associated, sedimented, and fibrillar proteins. A major limitation for many studies is still the large amount of sample needed for the experiments, typically several isotopically labeled samples of 10–20 mg each. Here we show that a new NMR probe, pushing magic‐angle sample rotation to frequencies around 100 kHz, makes it possible to narrow the proton resonance lines sufficiently to provide the necessary sensitivity and spectral resolution for efficient and sensitive proton detection. Using restraints from such spectra, a well‐defined de novo structure of the model protein ubiquitin was obtained from two samples of roughly 500 μg protein each. This proof of principle opens new avenues for structural studies of proteins available in microgram, or tens of nanomoles, quantities that are, for example, typically achieved for eukaryotic membrane proteins by in‐cell or cell‐free expression.     

Effect of water on the catalytic oxidation of catechols

A dinuclear copper(II) complex derived from a new water-soluble pentadentate Schiff base backbone ligand has been prepared and characterized in solution and in the solid state. The complex has been found to accelerate the aerobic oxidation of 3,5-di- tert-butylcatechol (DTBC) into 3,5-di- tert-butylquinone (DTBQ) by 5 orders of magnitude, compared to the background reaction in aqueous methanol (k(cat)/k(non) = 160,000) at 30 degrees C. The transformation of the model substrate is considerably slower in pure methanol (k(cat)/k(non) = 60,000) under otherwise identical conditions. In-depth investigation of the catalytically active species revealed different structures for the copper(II) complex in methanol and in methanol/water mixtures.     

Quantitative determination of drug encapsulation in poly(lactic acid) nanoparticles by capillary electrophoresis

Capillary electrophoretic (CE) methods were used for the quantitative determination of model drugs [salbutamol sulphate (SS), sodium cromoglycate (SCG) and beclomethasone dipropionate (BDP)] in poly(D,L-lactic acid) (PLA) nanoparticles, which were prepared by the nanoprecipitation method. Zeta potential and size distribution of the nanoparticles were determined by electrophoretic mobility determinations and photon correlation spectroscopy, respectively. Interactions between the drugs, the PLA nanoparticles and the fused-silica capillary were investigated by electrokinetic capillary chromatography (EKC). A quantitative CE method was developed for salbutamol sulphate and sodium cromoglycate, and the linearity and repeatability of migration times, peak areas and peak heights were determined. Microemulsion electrokinetic chromatography was used for the quantitative determination of beclomethasone dipropionate. According to this study, the applied electromigration techniques were suitable for the interaction, drug entrapment and dissolution studies of pharmaceutical nanoparticles. The results suggest that even quantitation of the drug located inside the nanoparticles was possible. Encapsulation of the more hydrophilic model drugs (SS, SCG) in the PLA nanoparticles was less efficient than in the case of BDP.