A efficient and sustainable approach for the synthesis of 3-alkylquinoxalin-2(1H)-ones has been developed through visible-light-mediated decarboxylative alkylation of quinoxalin-2(1H)-ones with phe...

Visible-Light-Initiated Decarboxylative Alkylation of Quinoxalin-2(1H)-ones with Phenyliodine(III) Dicarboxylates in Recyclable Ruthenium(II) Catalytic System

Sustainable routes for quantitative green selenocyanation of activated alkynes

Metal-free visible-light-induced oxidative cyclization reaction of 1,6-enynes and arylsulfinic acids leading to sulfonylated benzofurans

Solid-state nanopores have shown special high potential in a label-free molecular assay, structure identification, and target-index at the single-molecular level, even though frustrating electrical baseline noise is still one of the major factors that limit the spatial resolution and signaling reliability of solid-state nanopores, especially in small target detection. Here we develop a significant and easy-operating noise-reduction approach via mixing organic solvents with high dielectric constants into a traditional aqueous electrolyte. The strategy is generally effective for pores made of different materials, such as the most commonly used conical glass (CGN) or SiNx. While the mechanism should be multisourced, MD simulations suggest the noise reduction may partially arise from the even ionic distribution caused by the addition of higher dielectric species. Among all solvents experimentally tested, the two with the highest dielectric constants, formamide and methylformamide, exhibit the best noise reduction effect for target detection of CGN. The power spectral density at the low-frequency limit is reduced by nearly 3 orders with the addition of 20% formamide. Our work qualifies the reliability of solid-state nanopores into much subtler scales of detection, such as dsDNAs under 100 bp. As a practical example, bare CGN is innovatively employed to perform in-situ tracking of trigger-responsive DNA machine forming oligomers.

Low-Noise Nanopore Enables In-Situ and Label-Free Tracking of a Trigger-Induced DNA Molecular Machine at the Single-Molecular Level.

An environmentally-friendly method for the clean preparation of various quinolin-2-yl substituted ureas in water under mild and toxic reagent-, base-, and organic solvent-free conditions was established. In the large-scale synthesis, the products could be rapidly collected via simple filtration and washing with ethanol. The usage of readily available raw materials, 100% atom economy, high yield, and excellent regioselectivity enhanced the practicability of this protocol.

Clean Preparation of Quinolin-2-yl Substituted Ureas in Water

Both protease overexpression and local pH changes are key signatures of cancer. However, the sensitive detection of protease activities and the accurate measurement of pH in a tumor environment remain challenging. Here, we develop a dual-response DNA probe that can simultaneously monitor protease activities and measure the local pH by translocation through α-hemolysin (αHL). The DNA probe bears a short peptide containing phenylalanine at a pre-designed position. Enzymatic cleavage of the peptide either exposes or removes the N-terminal phenylalanine that can form a complex with cucurbit[7]uril. Translocation of the DNA hybrid through αHL generates current signatures that can be used to quantify protease activities. Furthermore, the current signatures possess a pH-dependent pattern that reflects the local pH. Our results demonstrate that the versatile DNA probe may be further explored for simultaneously measuring multiple parameters of a complex system such as single cells in the future.

A Dual-Response DNA Probe for Simultaneously Monitoring Enzymatic Activity and Environmental pH Using a Nanopore.

We have developed a rapid and selective approach for the detection of melamine based on simple DNA probes and α-hemolysin nanopores. The limit of detection can be as low as 10 pM.

Rapid and selective DNA-based detection of melamine using α-hemolysin nanopores

Cucurbiturils are one type of widely used macrocyclic host compound in supramolecular chemistry. Their peculiar properties have led to applications in a wide variety of research areas such as fluorescence spectroscopy, drug delivery, catalysis, and nanotechnology. However, the solubilities of cucurbiturils are rather poor in water and many organic solvents, which may cause accuracy problems when measuring binding constants with traditional methods. In this report, we aim to develop an approach to measure the binding constants of cucurbituril-based host–guest interactions at the single-molecule level. First, we covalently attach different guest compounds to the side-chain of DNA molecules. Then, excess cucurbiturils are incubated with DNA probes to form the host–guest complexes. Next, the modified DNA hybrids are threaded through α-hemolysin nanopore to generate highly characteristic current events. Finally, statistical analyses of the obtained events afford the binding constants of cucurbiturils with vari...

Measuring Binding Constants of Cucurbituril-Based Host-Guest Interactions at the Single-Molecule Level with Nanopores.

Fine-tuned ion transport across nanoscale pores is key to many biological processes, including neurotransmission. Recent advances have enabled the confinement of water and ions to two dimensions, unveiling transport properties inaccessible at larger scales and triggering hopes of reproducing the ionic machinery of biological systems. Here we report experiments demonstrating the emergence of memory in the transport of aqueous electrolytes across (sub)nanoscale channels. We unveil two types of nanofluidic memristors depending on channel material and confinement, with memory ranging from minutes to hours. We explain how large time scales could emerge from interfacial processes such as ionic self-assembly or surface adsorption. Such behavior allowed us to implement Hebbian learning with nanofluidic systems. This result lays the foundation for biomimetic computations on aqueous electrolytic chips. Description Toward fluidic neuromorphic computing There is considerable interest in strategies that mimic the structure of human brain and could lead to the development of next-generation neuromorphic devices. Many recent studies have focused on solid-state devices, although information in biological systems is conveyed by ions solvated in water, an approach now explored in two papers in this issue (see the Perspective by Noy and Darling). Robin et al. created nanofluidic devices consisting of nanometer-thick two-dimensional slits filled with a salt solution, whereas Xiong et al. present a nanofluidic ionic memristor based on confined polyelectrolyte-ion interactions. The two studies are focused on different aspects of neuromorphic engineering, but both show precise control of ion transport in water across nanoscale channels. These studies show promising directions for creating neuromorphic functions using energy-efficient fluidic memristors that could mimic biological systems down to their fundamental principles. —YS Two nanofluidic devices can reproduce Hebbian learning using ions in water as charge carriers, similar to how neurons work.

Long-term memory and synapse-like dynamics in two-dimensional nanofluidic channels

Angstrom-scale fluidic channels are ubiquitous in nature and play an important role in regulating cellular traffic, signaling, and responding to stimuli. Synthetic angstrom channels are now a reality with the emergence of several cutting-edge bottom-up and top-down fabrication methods. In particular, the use of atomically thin 2D materials and nanotubes as components to build fluidic conduits has pushed the limits of fabrication to the angstrom scale. Here, we provide an overview of recent developments in the fabrication methods for nano- and angstrofluidic channels while categorizing them on the basis of dimensionality (0D pores, 1D tubes, 2D slits), along with the latest advances in measurement techniques. We discuss the ion transport governed by various stimuli in these channels and the variation of ionic mobility, streaming power, and osmotic power with pore size across all the dimensionalities. Finally, we highlight unique future opportunities in the development of smart ionic devices.

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Yi You

Papers

A Dual-Response DNA Probe for Simultaneously Monitoring Enzymatic Activity and Environmental pH Using a Nanopore.

Rapid and selective DNA-based detection of melamine using α-hemolysin nanopores

Measuring Binding Constants of Cucurbituril-Based Host-Guest Interactions at the Single-Molecule Level with Nanopores.

Long-term memory and synapse-like dynamics in two-dimensional nanofluidic channels

Angstrofluidics: Walking to the Limit