Organic Fluorophores with Large Stokes Shift for the Visualization of Rapid Protein and Nucleic Acid Assays.

Organic small-molecule fluorophores, characterized by flexible chemical structure and adjustable optical performance, have shown tremendous potential in biosensing. However, classical organic fluorophore motifs feature large overlap between excitation and emission spectra, leading to the requirement of advanced optical set up to filter desired signal, which limits their application in scenarios with simple settings. Here, a series of wavelength-tunable small-molecule fluorescent dyes (PTs) bearing simple organic moieties have been developed, which exhibit Stokes shift up to 262 nm, molar extinction coefficients ranged 30,000-100,000 M-1 cm-1, with quantum yields up to 54.8 %. Furthermore, these dyes were formulated into fluorescent nanoparticles (PT-NPs), and applied in lateral flow assay (LFA). Consequently, limit of detection for SARS-CoV-2 nucleocapsid protein reached 20 fM with naked eye, a 100-fold improvement in sensitivity compared to the pM detection level for colloidal gold-based LFA. Besides, combined with loop-mediated isothermal amplification (LAMP), the LFA system achieved the visualization of single copy level nucleic acid detection for monkeypox (Mpox).

A Novel Cell Membrane-Associated RNA Extraction Method and Its Application in the Discovery of Breast Cancer Markers.

Cell membrane-associated RNA (mem-RNA) has been demonstrated to be cell-specific and disease-related and are considered as potential biomarkers for disease diagnostics, drug delivery, and cell screening. However, there is still a lack of methods specifically designed to extract mem-RNA from cells, limiting the discovery and applications of mem-RNA. In this study, we propose the first all-in-one solution for high-purity mem-RNA isolation based on two types of magnetic nanoparticles, named MREMB (Membrane-associated RNA Extraction based on Magnetic Beads), which achieved ten times enrichment of cell membrane components and over 90% recovery rate of RNA extraction. To demonstrate MREMB's potential in clinical research, we extracted and sequenced mem-RNA of typical breast cancer MCF-7, MDA-MB-231, and SKBR-3 cell lines and non-neoplastic breast epithelial cell MCF-10A. Compared to total RNA, sequencing results revealed that membrane/secreted protein-encoding mRNAs and long noncoding RNAs (lncRNAs) were enriched in the mem-RNA, some of which were significantly overexpressed in the three cancer cell lines, including extracellular matrix-related genes COL5A1 and lncRNA TALAM1. The results indicated that MREMB could enrich membrane/secreted protein-coding RNA and amplify the expression differences of related RNAs between cancer and non-neoplastic cells, promising for cancer biomarker discovery.

Facile Synthesis of Enantiopure Sugar Alcohols: Asymmetric Hydrogenation and Dynamic Kinetic Resolution Combined.

An unprecedented Ir/f-amphox-catalyzed asymmetric hydrogenation of racemic 2,3-syn-dihydroxy-1,4-diones is presented involving dynamic kinetic resolution, which produces (1R,2R,3R,4R)-tetraols. This protocol constitutes an efficient and straightforward approach to accessing sugar alcohols bearing four contiguous stereocenters. The strategy exhibits various advantages over existing methods, including excellent yields (up to 98 %), exceptional stereoselectivities (up to 99:1 dr, 99.9 % ee), operational simplicity and substrate generality. Moreover, the nature of the reaction was revealed as a stepwise transformation by in situ Fourier-transform infrared spectroscopy and isolation of intermediates.

Stereoconvergent, Redox-Neutral Access to Tetrahydroquinoxalines through Relay Epoxide Opening/Amination of Alcohols.

We present an economical catalytic procedure to convert readily available 1,2-diaminobenzenes and terminal epoxides into valuable 1,2,3,4-tetrahydroquinoxalines in a highly enantioselective fashion. This procedure operates through relay zinc and iridium catalysis, and achieves redox-neutral and stereoconvergent production of valuable chiral heterocycles from racemic starting materials with water as the only side product. The use of commercially available reagents and catalysts and a convenient procedure also make this catalytic method attractive for practical application.

Divergent, Enantioselective Synthesis of Pyrroles, 3H-Pyrroles and Bicyclic Imidazolines by Ag- or P-Catalyzed [3+2] Cycloaddition of Allenoates with Activated Isocyanides.

The divergent, stereoselective formal [3+2] cycloadditions of allenoates with activated isocyanides catalyzed by silver or phosphine-based catalysts were investigated. Silver catalysis is capable of delivering a range of 3H-pyrroles in high stereoselectivities. These enantioenriched heterocycles can either undergo sequential cyclisation with isocyanoacetates to deliver unprecedented bicyclic imidazolines with excellent yields and stereoselectivity or undergo unusual aromatization pathways leading to polysubstituted pyrroles. On the other hand, a simple mix-and-go procedure using an amino acid-derived phosphine as the catalyst produces pyrroles bearing a benzylic stereocenter with good enantioselectivity.

Catalytic Asymmetric [3 + 2] Cycloaddition Reaction between Aurones and Isocyanoacetates: Access to Spiropyrrolines via Silver Catalysis.

The first enantioselective formal [3 + 2] cycloaddition of aurone analogues with isocyanoacetates was developed via chiral Ag-complex catalysis. A variety of optically enriched spiro-1-pyrrolines were obtained in excellent yields, diastero- and enantioselectivities (up to 99% yield, >20:1 dr, >99% ee). This synthetic approach represents an extremely simple, efficient, and atom-economical method for spiro-1-pyrrolines synthesis.

Transition-metal-free synthesis of polysubstituted pyrrole derivatives via cyclization of methyl isocyanoacetate with aurone analogues.

Presented herein is an unprecedented transition-metal-free cyclization of methyl isocyanoacetate with aurone analogues catalyzed by NaOH. Various 2,3,4-trisubstituted pyrroles were obtained in excellent yields (up to 99%). The high efficiency of this synthetic procedure, coupled with the operational simplicity and atom economy, makes it an attractive method for the synthesis of polysubstituted pyrroles.

[3 + 2] Cycloaddition of Azaoxyallyl Cations with Cyclic Ketones: Access to Spiro-4-oxazolidinones.

The first formal [3 + 2] cycloaddition reaction of in situ generated azaoxyallyl cation with cyclic ketones has been developed using mild reaction conditions. A variety of spiro-4-oxazolidinones was obtained in excellent yields (up to 99%). The high efficiency of this process, coupled with the operational simplicity, makes it an attractive method for the synthesis of spiro-4-oxazolidinones.

Enantioselective Synthesis of Alkylthioetherpyrrolidine Derivatives via [3+2] Cycloaddition of α-Thioacrylates with Isocyanoacetates.

An unprecedented catalytic asymmetric method for the [3+2] cycloaddition of isocyanoacetates with α-thioacrylates/α-phthalimidoacrylates has been developed with excellent enantioselectivities. The generated pyrrolines could be readily further reduced to an array of structurally various and biologically important pyrrolidine derivatives. α-Tosyloxyacrylate with isocyanoacetates as well as tosylmethylisocyanide could be used to produce 2,4-disubstituted pyrroles.

Catalytic divergent synthesis of 3H or 1H pyrroles by [3 + 2] cyclization of allenoates with activated isocyanides.

The cyclization of allenoates with activated isocyanides was reported for the first time. While Ag catalysis led to an unprecedented enantioselective synthesis of 3H pyrroles, a simple procedure using PPh3 produced a wide range of polysubstituted 1H pyrroles with high efficiency.

Highly diastereo- and enantioselective silver-catalyzed double [3+2] cyclization of α-imino esters with isocyanoacetate.

Presented herein is a new complexity-generating method in which both functionalities of α-imino esters undergo stereoselective cyclization with isocyanoacetates to produce directly linked oxazole-imidazolines, which can be transformed into highly functionalized α,ß-diamino esters and imidazolinium salts in high diastereo- and enantiopurity.

Deciphering ACE2-RBD binding affinity through peptide scanning: A molecular dynamics simulation approach.

Rapid discovery of target information for protein-protein interactions (PPIs) is significant in drug design, diagnostics, vaccine development, antibody therapy, etc. Peptide microarray is an ideal tool for revealing epitope information of PPIs. In this work, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) spike receptor-binding domain (RBD) and the host cell receptor angiotensin-converting enzyme 2 (ACE2) were introduced as a model to study the epitope information of RBD-specific binding to ACE2 via a combination of theoretical calculations and experimental validation. Through dock and molecular dynamics simulations, it was found that among the 22 peptide fragments that consist of RBD, #14 (YNYLYRLFRKSNLKP) has the highest binding strength. Subsequently, the experiments of peptide microarray constructed based on plasmonic materials chip also confirmed the theoretical calculation data. Compared to other methods, such as phage display technology and surface plasmon resonance (SPR), this method is rapid and cost-effective, providing insights into the investigation of pathogen invasion processes and the timely development of peptide drugs and other fields.

Multiplexed discrimination of SARS-CoV-2 variants via plasmonic-enhanced fluorescence in a portable and automated device.

Portable assays for the rapid identification of lineages of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to aid large-scale efforts in monitoring the evolution of the virus. Here we report a multiplexed assay in a microarray format for the detection, via isothermal amplification and plasmonic-gold-enhanced near-infrared fluorescence, of variants of SARS-CoV-2. The assay, which has single-nucleotide specificity for variant discrimination, single-RNA-copy sensitivity and does not require RNA extraction, discriminated 12 lineages of SARS-CoV-2 (in three mutational hotspots of the Spike protein) and detected the virus in nasopharyngeal swabs from 1,034 individuals at 98.8% sensitivity and 100% specificity, with 97.6% concordance with genome sequencing in variant discrimination. We also report a compact, portable and fully automated device integrating the entire swab-to-result workflow and amenable to the point-of-care detection of SARS-CoV-2 variants. Portable, rapid, accurate and multiplexed assays for the detection of SARS-CoV-2 variants and lineages may facilitate variant-surveillance efforts.

A nano-magnetic size selective cfDNA extraction platform for liquid biopsy with enhanced precision.

As an emerging biomarker, cell-free DNA (cfDNA) carries crucial genetic information for the diagnosis of hereditary disease and cancer. However, test accuracy was severely compromised by the low abundance of cell-free DNA in peripheral blood, frequently diluted by genomic DNA released from white blood cells, resulting in sample rejection, test inaccuracy, and restricted clinical utility. Herein we report a novel strategy for the efficient recovery of cfDNA with significant removal of genomic DNA contamination during the cfDNA extraction process, based on a nano-magnetic size selective cfDNA extraction platform. With this platform, over 90% cfDNA recovery rate was achieved with minimal genomic DNA contamination. For non-invasive prenatal testing, an increase of fetal fraction from 10.10% to 29.94% medially was observed in 11 maternal plasma samples, with two false-negative samples identified by the proposed workflow. Enrichment of cfDNA in plasma sample of cancer patient demonstrated âˆ¼ 100% increase of circulating tumor DNA (ctDNA) percentage by panel sequencing of specific mutation sites. The approach is simple, automatable and cost-efficient, can improve liquid biopsy precision and reduce sequencing depth through significant enrichment of target abundance. The nano-magnetic platform demonstrated its potential application in liquid biopsy, since it exhibited numerous advantages in avoiding false negative results, reducing sequencing cost, improving data quality, and rescuing contaminated samples.

Asymmetric hydrogenation of 1,4-diketones: facile synthesis of enantiopure 1,4-diarylbutane-1,4-diols.

Owing to the biological significance and great synthetic value of 1,4-diarylbutane-1,4-diols and their derivatives, increasingly considerable attention has been paid to developing effective synthetic methods for chiral 1,4-diarylbutane-1,4-diols. We herein report an efficient asymmetric hydrogenation of 1,4-diaryldiketones catalyzed by a chiral iridium complex bearing f-amphox as ligand, furnishing a series of 1,4-diarylbutane-1,4-diols in excellent yields (up to >99%) with exceptional enantioselectivities (up to >99.9% ee) and diastereoselectivities (up to >100 : 1 dr).

Synthesis of 1,4,5,6-tetrahydropyridazines and pyridazines via transition-metal-free (4 + 2) cycloaddition of alkoxyallenes with 1,2-diaza-1,3-dienes.

We developed an economical and practical protocol for the synthesis of 1,4,5,6-tetrahydropyridazines. A diverse range of alkoxyallenes and 1,2-diaza-1,3-dienes undergo (4 + 2) cycloaddition to generate the desired products in excellent yields. The high efficiency, wide substrate scope and good functional group tolerance of this process, coupled with operational simplicity, render the method synthetically attractive. The utility of the cycloaddition is also demonstrated by the preparation of various pyridazines from 1,4,5,6-tetrahydropyridazines.

Chiral N-heterocyclic carbene catalyzed staudinger reaction of ketenes with imines: highly enantioselective synthesis of N-Boc beta-lactams.

N-heterocyclic carbenes (NHCs) were demonstrated to be efficient catalysts for the Staudinger reaction of ketenes with N-tosyl, N-benzyloxycarbonyl, or N-tert-butoxycarbonyl imines. Chiral NHC 8b, conveniently prepared from L-pyroglutamic acid, catalyzed the reactions of arylalkylketenes with a variety of N-tert-butoxycarbonyl arylimines to give the corresponding cis-beta-lactams in good yields with good diastereoselectivities and excellent enantioselectivities (up to 99% ee). Two possible catalytic pathways, initiated by the addition of NHC to ketenes or imines, were discussed.

Synthesis of Spiro-dihydroquinoline and Octahydrophenanthrene Derivatives via Palladium-Catalyzed Intramolecular Oxidative Arylation.

A method for intramolecular sp2 C-H oxidative arylation of unactivated cyclic olefins has been developed to access spiro-dihydroquinoline and octahydrophenanthrene derivatives in a straightforward and efficient manner. Bearing picolinamide as a directing group, the alkenyl anilines cyclized to afford spiro-dihydroquinolines in moderate to excellent yields via direct oxidative arylation, while the alkenyl benzylamines furnished the octahydrophenanthrene derivatives in moderate yields via sequential oxidative arylation and double acetoxylation.

Palladium-catalyzed oxidative arylacetoxylation of alkenes: synthesis of indole and indoline derivatives.

A method for the oxidative arylacetoxylation of alkenes has been developed to synthesize indole and indoline derivatives from readily accessible substrates. The cinnamyl tethered anilines with picolinamide as a directing group provided 3-substituted indoles via intramolecular oxidative arylacetoxylation, and the 2-methyl substituted cinnamyl anilines furnished indoline derivatives with 3-position quaternary stereocenters in good to excellent yields via sequential intramolecular oxidative arylacetoxylation, hydrolysis and oxidation steps.

Enantioselective Synthesis of Tetrahydropyridines/Piperidines via Stepwise [4 + 2]/[2 + 2] Cyclizations.

A phosphine-catalyzed novel enantioselective [4 + 2]-annulation reaction between allene ketones and 1-azadienes has been developed, and tetrahydropyridines were obtained in good yields and with excellent enantioselectivities. Subsequent exposure of tetrahydropyridines to benzyne leads to a [2 + 2]-cyclization, creating optically enriched polycyclic piperidines with a quaternary stereogenic center and a cyclobutene moiety. The reported stepwise [4 + 2]/[2 + 2]-cycloadditions represent a new approach to access enantiomerically enriched nitrogen-containing six-membered ring systems.