Electronic Olfactory Sensor Based on A. mellifera Odorant‐Binding Protein 14 on a Reduced Graphene Oxide Field‐Effect Transistor

An olfactory biosensor based on a reduced graphene oxide (rGO) field‐effect transistor (FET), functionalized by the odorant‐binding protein 14 (OBP14) from the honey bee (Apis mellifera) has been designed for the in situ and real‐time monitoring of a broad spectrum of odorants in aqueous solutions known to be attractants for bees. The electrical measurements of the binding of all tested odorants are shown to follow the Langmuir model for ligand–receptor interactions. The results demonstrate that OBP14 is able to bind odorants even after immobilization on rGO and can discriminate between ligands binding within a range of dissociation constants from K_d=4 μM to K_d=3.3 mM . The strongest ligands, such as homovanillic acid, eugenol, and methyl vanillate all contain a hydroxy group which is apparently important for the strong interaction with the protein.     

A FRET Probe for Cell‐Based Imaging of Ganglioside‐Processing Enzyme Activity and High‐Throughput Screening

Gangliosides are important signaling molecules in the cell membrane and are processed by several enzymes. Deficiencies in these enzymes can cause human lysosomal storage diseases. Building an understanding of the pathways of glycosphingolipid catabolism requires methods for the analysis of these enzymatic activities A GM3‐derived FRET probe was synthesized chemoenzymatically for the detection and quantitation of a range of ganglioside‐degrading enzymes, both in cell lysates and in living cells. This is the first substrate that enables the ratiometric fluorogenic assay of sphingolipid ceramide N‐deacylase and endoglycoceramidase and can detect and localize neuraminidase activity in living cells. It is therefore a valuable tool for building a better understanding of membrane‐confined enzymology. It also enables the robust and reliable assay of ganglioside‐degrading enzymes in a microtiter plate, thus opening the door to screening for novel or engineered biocatalysts or for new inhibitors.     

Mesenchymal‐Mode Migration Assay and Antimetastatic Drug Screening with High‐Throughput Microfluidic Channel Networks

Increasing evidence shows that activated mesenchymal migration is a key process of the metastatic cascade. Cancer cells usually gain such migratory capability through an epithelial‐to‐mesenchymal transition. Herein we present a high‐throughput microfluidic device with 3120 microchambers to specifically monitor mesenchymal migration. Through imaging of the whole chip and statistical analysis, we can evaluate the two key factors of velocity and percentage related to cell migratory capacity at different cell densities in culture. We also used the device to screen antimetastatic drugs for their inhibition of mesenchymal migration and prevention of metastatic malignancy. This device will provide an excellent platform for biologists to gain a better understanding of cancer metastasis.     

A High‐Throughput Assay for Arylamine Halogenation Based on a Peroxidase‐Mediated Quinone–Amine Coupling with Applications in the Screening of Enzymatic Halogenations

Arylhalides are important building blocks in many fine chemicals, pharmaceuticals and agrochemicals, and there has been increasing interest in the development of more “green” halogenation methods based on enzyme catalysis. However, the screening and development of new enzymes for biohalogenation has been hampered by a lack of high‐throughput screening methods. Described herein is the development of a colorimetric assay for detecting both chemical and enzymatic arylamine halogenation reactions in an aqueous environment. The assay is based on the unique UV/Vis spectrum created by the formation of an ortho‐benzoquinone‐amine adduct, which is produced by the peroxidase‐catalysed benzoquinone generation, followed by Michael addition of either a halogenated or non‐halogenated arylamine. This assay is sensitive, rapid and amenable to high‐throughput screening platforms. We have also shown this assay to be easily coupled to a flavin‐dependent halogenase, which currently lacks any convenient colorimetric assay, in a “one‐pot” workflow.     

High‐Throughput Development of a Hybrid‐Type Fluorescent Glutamate Sensor for Analysis of Synaptic Transmission

Fluorescent sensors are powerful tools for visualizing cellular molecular dynamics. We present a high‐throughput screening system, designated hybrid‐type fluorescence indicator development (HyFInD), to identify optimal position‐specific fluorophore labeling in hybrid‐type sensors consisting of combinations of ligand‐binding protein mutants with small molecular fluorophores. We screened sensors for glutamate among hybrid molecules obtained by the reaction of four cysteine‐reactive fluorescence probes with a set of cysteine‐scanning mutants of the 274 amino acid S1S2 domain of AMPA‐type glutamate receptor GluA2 subunit. HyFInD identified a glutamate‐responsive probe (enhanced glutamate optical sensor: eEOS) with a dynamic range >2400 %, good photostability, and high selectivity. When eEOS was specifically tethered to neuronal surfaces, it reliably visualized the spatiotemporal dynamics of glutamate release at single synapses, revealing synapse‐to‐synapse heterogeneity of short‐term plasticity.     

ADLOC: An Aptamer‐Displacement Assay Based on Luminescent Oxygen Channeling

Functional nucleic acids, such as aptamers and allosteric ribozymes, can sense their ligands specifically, thereby undergoing structural alterations that can be converted into a detectable signal. The direct coupling of molecular recognition to signal generation enables the production of versatile reporters that can be applied as molecular probes for various purposes, including high‐throughput screening. Here we describe an unprecedented type of a nucleic acid‐based sensor system and show that it is amenable to high‐throughput screening (HTS) applications. The approach detects the displacement of an aptamer from its bound protein partner by means of luminescent oxygen channeling. In a proof‐of‐principle study we demonstrate that the format is feasible for efficient identification of small drug‐like molecules that bind to a protein target, in this case to the Sec7 domain of cytohesin. We extended the approach to a new cytohesin‐specific single chain DNA aptamer, C10.41, which exhibits a similar binding behavior to cytohesins but has the advantage of being more stable and easier to synthesize and to modify than the RNA‐aptamer M69. The results obtained with both aptamers indicate the general suitability of the aptamer‐displacement assay based on luminescent oxygen channelling (ADLOC) for HTS. We also analyzed the potential for false positive hits and identified from a library of 18 000 drug‐like small molecules two compounds as strong singlet‐oxygen quenchers. With full automation and the use of commercially available plate readers, we estimate that the ADLOC‐based assay described here could be used to screen at least 100 000 compounds per day.     

3D Printed High‐Throughput Hydrothermal Reactionware for Discovery,Optimization, and Scale‐Up

3D printing techniques allow the laboratory‐scale design and production of reactionware tailored to specific experimental requirements. To increase the range and versatility of reactionware devices, sealed, monolithic reactors suitable for use in hydrothermal synthesis have been digitally designed and realized. The fabrication process allows the introduction of reaction mixtures directly into the reactors during the production, and also enables the manufacture of devices of varying scales and geometries unavailable in traditional equipment. The utility of these devices is shown by the use of 3D printed, high‐throughput array reactors to discover two new coordination polymers, optimize the synthesis of one of these, and scale‐up its synthesis using larger reactors produced on the same 3D printer. Reactors were also used to produce phase‐pure samples of coordination polymers MIL‐96 and HKUST‐1, in yields comparable to synthesis in traditional apparatus.     

High‐Throughput Fabrication,Performance Testing,and Characterization of One‐Dimensional Libraries of Polymeric Compositions

A new general approach for rapid performance‐screening of polymer compositions is provided. Multiple compositions are generated as one‐dimensional libraries in a microextruder with step‐ or gradient‐composition changes in 2–10 g of polymer in < 1 min. To accelerate testing, environmental stress is applied to only local regions, followed by high‐sensitivity spatially resolved characterization. We applied our methodology for weathering of arrays of polymeric compositions and provided ranking of polymer/UV absorber compositions equivalent to traditional weathering data while achieved 20 times faster.

Sampling and measurement strategies for HT analysis of combinatorial 1D polymeric libraries: (1) spectroscopic monitoring of chemical properties, (2) in‐situ monitoring of mass and viscoelastic properties, (3) scanning spectroscopic analysis, and (4) spectroscopic imaging of a coiled polymeric array.     

High‐Throughput Reaction Optimisation and Activity Screening of Ferrocene‐Based Lewis Acid–Catalyst Complexes by Using Continuous‐Flow Reaction Detection Mass Spectrometry

Optimising synthetic conversions and assessing catalyst performance is a tedious and laborious endeavour. Herein, we present an automated alternative to the commonly applied sequential approaches that are used to increase catalyst discovery process efficiencies by increasing the number of entities that can be tested. This new approach combines conversion of the reactants and determination of product formation into a single comprehensive reaction detection system that can be operated with minimal catalyst and reactant consumption. With this approach, rudimentary reaction conditions can be quickly optimised and the same system can then be used to screen for the optimal homogenous catalyst in a selected solution‐phase synthetic conversion. The system, which is composed of standard HPLC components, can be used to screen catalyst libraries at a repetition rate of five minutes and can be run unsupervised. The sensitive mass spectrometric detection that is implemented in the reaction detection methodology can be used for the simultaneous monitoring of reactants, catalysts and product ions. In the experiments, the three‐component reaction that gives a substituted 2‐imidazoline was optimised. Afterwards, the same method was used to assess a library of ferrocene‐based Lewis acid catalysts for performance in the aforementioned conversion in six different solvents. We demonstrate the feasibility of using this methodology to directly compare the performance results obtained in different solvents by calibrating the solvent‐specific MS responses.     

High‐Throughput Screening in Olefin‐Polymerization Catalysis: From Serendipitous Discovery Towards Rational Understanding

High–throughput‐screening (HTS) tools and methods are used more and more, especially in industry, in the search for new, selective organometallic catalysts. In most cases, the approach is, in essence, empirical, and the strategy is to increase the number of experiments that can be run at a given place in a given time. Highly miniaturized, parallel reaction setups have been implemented for the rapid assessment of whether novel catalysts resulting from the structural amplification of a basic framework are “good” or “bad” with respect to the properties of interest, and, depending on the response, worthy of a subsequent, more‐careful evaluation. In this article, we demonstrate that it is possible to utilize these state‐of‐the‐art HTS platforms with a different strategy: the rapid generation of reliable kinetic data for mechanistic studies in view of a thorough understanding and rational catalyst design. Ziegler–Natta‐type catalytic olefin polymerization will be used throughout as an example.

     

A Quadruplex‐Based,Label‐Free,and Real‐Time Fluorescence Assay for RNase H Activity and Inhibition

We demonstrate a unique quadruplex‐based fluorescence assay for sensitive, facile, real‐time, and label‐free detection of RNase H activity and inhibition by using a G‐quadruplex formation strategy. In our approach, a RNA–DNA substrate was prepared, with the DNA strand designed as a quadruplex‐forming oligomer. Upon cleavage of the RNA strand by RNase H, the released G‐rich DNA strand folds into a quadruplex in the presence of monovalent ions and interacts with a specific G‐quadruplex binder, N‐methyl mesoporphyrin IX (NMM); this gives a dramatic increase in fluorescence and serves as a reporter of the reaction. This novel assay is simple in design, fast in operation, and is more convenient and promising than other methods. It takes less than 30 min to finish and the detection limit is much better or at least comparable to previous reports. No sophisticated experimental techniques or chemical modification for either RNA or DNA are required. The assay can be accomplished by using a common spectrophotometer and obviates possible interference with the kinetic behavior of the catalysts. Our approach offers an ideal system for high‐throughput screening of enzyme inhibitors and demonstrates that the structure of the G‐quadruplex can be used as a functional tool in specific fields in the future.