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We develop a new strategy for single-molecule monitoring of telomerase based on proximity ligation-transcription circuit-powered exponential amplifications.

A novel AIE-active furo[2,3-c]pyridine-based photosensitizer was developed for specific imaging and photodynamic ablation of Gram-positive bacteria in vitro and in vivo.

The photophysical and charge transport properties of five non-planar cyclopenta-fused polycyclic aromatic hydrocarbons including dibenzo[a,m]rubicene (molecule 1) and its derivatives are studied through density functional theory (DFT). The absorption and emission spectra (λab and λem) are calculated at the B3LYP/6-31+G(d,p), PBE0/6-31+G(d,p), BMK/6-31+G(d,p), M062X/6-31+G(d,p) and CAM-B3LYP/6-31+G(d,p) levels in dichloromethane solvent. The results show that the BMK and M062X functionals can reproduce experimental λab and λem more accurately than other functionals, respectively. The charge mobilities can be effectively tuned through introducing silyl groups of different sizes (molecules 2, 3 and 4) and the 1,3-dimethoxy benzene group (molecule 5) to dibenzo[a,m]rubicene. The relationship between the structures of five dibenzo[a,m]rubicene derivatives and a set of relevant electronic properties including the molecular geometries, frontier molecular orbitals, ionization potentials, electron affinities, reorganization energies and transfer integrals have been established. The results show that these molecules possess prominent charge carrier mobilities, although they all possess non-planar geometries. The charge transport properties could be effectively modulated via introducing different substituents to molecule 1. The high hole mobilities indicate that all five molecules facilitate hole transport, which is in accordance with the experimental results. Intriguingly, the electron mobility is enhanced maximally by five times through introducing silyl groups of different sizes from 0.06 cm2 V−1 s−1 (molecule 1) to 0.30 cm2 V−1 s−1 (molecule 4). Particularly, molecules 4 and 5 possess balanced electron and hole mobilities, which could be used as bipolar semiconductors and show promising use in optoelectronic devices.

We develop a new fluorescence method for the sensitive detection of protein tyrosine phosphatase 1B (PTP1B) based on dephosphorylation-directed tricyclic DNA amplification cascades. This method exhibits good specificity and high sensitivity with a detection limit of 0.24 pM. Moreover, it can be applied for kinetics analysis, inhibitor screening, and the accurate detection of PTP1B in a variety of cancer cells.

Three 9-substituted acridines, namely 9-carboxyacridine (CA), 9-methylacridine (MA), and 9-aminoacridine (AA), were designed and synthesized for the development of effective inhibitors for mild steel corrosion in a 15% HCl solution. The corrosion-resistance ability was tested by weight-loss tests, electrochemical techniques, surface-topography analyses (SEM, SECM, and XPS), and contact angle measurements. The results indicated the inhibition performance followed the order of η(AA) > η(MA) > η(CA), and these acridines acted as mixed type inhibitors with a predominant restrained cathode process. The adsorption of the three acridines on a mild steel surface obeyed the Langmuir adsorption isotherm and involved both physisorption and chemisorption modes. Surface analysis and characterization confirmed the existence of an adsorbed film. Quantum chemical calculations were performed to provide mechanistic insights into the roles of the different substituents (−COOH, −CH3, and −NH2) on the corrosion-inhibition behavior of the three acridines. Molecular dynamics (MD) simulations were carried out to explore the configurational adsorption behavior of these 9-substituted acridines on the Fe(110) surface.

Single nucleotide polymorphisms (SNPs) have been proven to be important biomarkers for disease diagnosis, prognosis and disease pathogenesis. Here, taking the advantages of a self-assembled oligonucleotide sandwich structure and robust chemical reactions, we have developed a simple, high-throughput and effective colorimetric analytical technique termed CuAAC-based ligation-assisted assays (CuAAC-LA) for SNP detection using a DNA-BIND 96-well plate. With the 5'-azide and 3'-alkyne groups labelled on two oligonucleotide probes, the target DNA can direct a Cu(i)-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction. Since the small difference in duplex stability caused by a single-nucleotide mismatch was amplified by the steric effects of these reactive groups for the ligation reaction of an unstable duplex, CuAAC-LA exhibited an ultra-sensitive discrimination ability for a mutant type target in the presence of large amounts of wild type targets. As low as 0.05% SNP could be clearly detected, which was better than most previously reported methods by various DNA ligases, indicating that a simple and rapid synthetic method i.e., the DNA template-directed click reaction held the potential to replace the ligase for SNP detection.

Herein, the synergistic effect of 1-(2,5-dioxoimidazolidin-4-yl)urea (DMU) and Tween-80 on the corrosion of mild steel in a 1 mol L−1 HCl solution was investigated by weight-loss tests, electrochemical methods and surface analysis (SEM/SECM). The experiments revealed that the combination of DMU and Tween-80 strongly inhibited the corrosion of mild steel as compared to individual inhibitors, and the adsorption mode belonged to the Langmuir isothermal type. Based on the electrochemical results, DMU and DMU–Tween-80 behaved as mixed-type inhibitors, and their best inhibition efficiencies were 77.31% and 96.35%, respectively. The calculated synergistic parameter value was larger than unity, indicating that the enhancement of inhibition efficiency was due to the synergistic effect of DMU and Tween-80. Surface analysis techniques confirmed the presence of inhibitors on the mild steel surface. Quantum chemical parameters based on density functional theory provided a further insight into the mechanism of inhibition. Moreover, molecular dynamics simulations were carried out to explore the configurational adsorption behaviour of DMU on an Fe(110) surface.

The inhibition performance of three pyrido[1,2-a]benzimidazoles, namely, benzo[4,5]imidazo[1,2-a]pyridine (BIP), 2-methylbenzo[4,5]imidazo[1,2-a]pyridine (MBIP), and 2-(trifluoromethyl)benzo[4,5]imidazo[1,2-a]pyridine (TBIP), for steel corrosion in hydrochloric acid solution were researched through a weight loss test, electrochemical techniques, surface morphology (SEM, XPS) studies, and theoretical methods. The experimental results revealed that TBIP, BIP, and MBIP had excellent inhibition performance, and their maximum inhibition efficiencies at 0.25 mmol L−1 were 95.48%, 97.65%, and 98.96%, respectively. The properties of these inhibitors are considered to be mixed-type, and their adsorption mode belongs to the Langmuir isothermal type. The formation and properties of an adsorbed film on a steel surface were investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Quantum chemical calculations provided insightful quantitative information to conclude the correlation between the molecular structures and inhibition performance. Molecular dynamics (MD) simulations were carried out to explore the configurationally adsorption behavior of these pyrido[1,2-a]benzimidazoles on Fe(110) surface, and the binding energy of these three inhibitors followed the order MBIP > BIP > TBIP, which is consistent with the experimental evaluation results.

Pyrene is one kind of interesting polycyclic aromatic hydrocarbon with high charge carrier mobility and chemical stability. The electronic and charge transport properties of six butterfly shaped tetraaryl pyrenes with different electron-donating and electron-withdrawing substituents are explored based on density functional theory. The effects of substituents on the molecular structure, reorganization energy, molecular orbitals, ionization energies, electron affinities, crystal packing, transfer integrals, and charge carrier mobilities are analyzed in detail to clarify the structure–property relationships of the studied molecules. The different crystal packing motifs and diverse intermolecular interactions of the investigated molecules lead to obviously different transfer integrals when different substituents are introduced into the central π-system. The reorganization energies and the frontier molecular orbitals are also modulated by the substituents. These factors result in drastically different charge carrier mobilities of molecules 1 to 6. The hole and electron mobilities of molecule 1 are on the same order of magnitude (μh,ave./μe,ave. is equal to 2.3) due to the balanced transfer integrals, which could be used as an ambipolar semiconductor. Molecule 6 with the thienyl moiety possesses the highest hole mobility due to the largest transfer integrals of holes originating from the strong intermolecular interactions, and may be used as a p-type semiconductor. While the introduced difluorophenyl groups of molecule 4 lead to a lower LUMO level and effective transfer integrals of electrons, achieving an electron mobility of up to 0.01 cm2 V−1 s−1, and showing promising application as an n-type semiconductor.

DNA methyltransferase (MTase) is an important epigenetic modification enzyme responsible for DNA methylation, and the dysregulation of DNA MTase activity is associated with various diseases in humans. Herein, we take advantage of the DNA lesion repair mechanism in vivo to develop a new fluorescence approach for the specific and sensitive detection of DNA methyltransferase (DNA MTase) on the basis of the DNA lesion repair-directed cascade isothermal amplification. Due to the high amplification efficiency of the uracil repair-mediated exponential isothermal amplification reaction (EXPAR), the efficient cleavage of endonuclease IV (Endo IV)-induced cyclic catalysis, and the low background signal caused by single uracil repair-mediated inhibition of nonspecific amplification, this approach exhibits high sensitivity with a detection limit of 0.014 U mL-1 for pure Dam MTase and 0.61 × 10-6 mg mL-1 for Dam MTase in E. coli cells and it can be further applied for the screening of DNA MTase inhibitors. More importantly, this approach can be applied to detect other DNA MTases by designing appropriate substrates, showing great potential in biomedical research and clinical diagnosis.

The generation of hydrogen by water splitting through the electrocatalytic approach could become a sustainable way to replace traditional fossil energy. The search for alternatives to the precious metals (Pt, Pd, and Ir) for hydrogen production from water splitting is one of the central issues in the area of renewable energy. Two-dimensional metal carbide and nitride (MXenes) materials have shown some characteristics of promising catalysts for the hydrogen evolution reaction (HER). Herein, we performed density functional calculations to systematically explore the exfoliation properties of more than 50 MAX phases and the HER performances of 30 MXenes to search the universal descriptors for the HER performances of MXenes. The exfoliation properties of MAXs were studied and the results showed that for most MAXs, the lower the binding energy of A elements, the higher the exfoliation energy of 2D MXenes from MAXs. A critical value of exfoliation energy of 0.253 eV A−2 was obtained, whereby MAXs with an exfoliation energy lower than this value favor exfoliation. For the predication of the HER performances of MXenes, two descriptors, namely Ne and Ef, have been proposed in the literature. The present calculations illustrated that these two parameters could not fully address the influence of hydrogen coverage on the Gibbs free energy of hydrogen adsorption (ΔGH*) on MXenes. Further studies indicated that both Ne and Ef relate to the surface-terminated O-p orbital center (ep), whereby the lower ep, the larger Ne and Ef, and the stronger interaction between O* with MXenes substrates. However, it is not favored for HER, if ep is either too large or too small. These results show that the surface-terminated O-p orbital center ep, could be used as a good descriptor for predicting the HER performances of MXenes. The best values of ep were in the range of −4.1 to −3.3 eV, with the corresponding values of Ne and Ef from 0.93 to 1.15 e and 3.15 to 3.78 eV, respectively, and ΔGH* from −0.3 to 0.3 eV. The result for the energy change in the HER process (Volmer–Heyrovsky and Volmer–Tafel mechanisms) of 10 M2CO2, and the minimum energy pathway of Mo2CO2 and Zr2CO2 confirmed that MXenes with a medium ep could deliver optimal HER performance.

The development of facilely synthetic materials for highly efficient enrichment of N-linked glycopeptides is essential in glycoproteome analysis. In this work, by utilizing the self-assembling of glutathione (GSH) on silver nanoparticles (Ag NPs), and the formation and dispersion of Ag NPs on a robust TpPa-1 substrate, a newly functionalized covalent organic framework (COF) called TpPa-1@Ag@GSH was synthesized via a simple two step post-synthetic modification. TpPa-1@Ag@GSH and intermediate products were confirmed and evaluated by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy-energy dispersive spectroscopy, Brunauer-Emmett-Teller and thermogravimetric analyses. Benefiting from the judicious selection of the substrate, the abundance of binding sites, relatively high affinity between GSH and N-linked glycopeptides, and the multivalent interactions between N-linked glycopeptides and unoccupied surfaces of Ag NPs, this porous material showed great performance in N-linked glycopeptide enrichment. By enriching N-linked glycopeptides in tryptic digests of human serum immunoglobulin G (human IgG) followed by mass spectrometry analysis, our method was proved to have good sensitivity (1 fmol), high selectivity (1 : 1500, human IgG to bovine serum albumin), high binding capacity (160 mg g-1, IgG/TpPa-1@Ag@GSH), ultra-fast capture ability (only 1 min incubation time), and good reusability (at least 5 times). It was also successfully applied to the enrichment of N-linked glycopeptides from complex biological samples. Our work improved the enrichment selectivity of COFs, reached the most rapid capture ability among off-column enrichment materials, and provided a very facile and easily popularized post-synthetic modification route for COFs in glycoproteome analysis.

Specific and sensitive detection of DNA MTase activity can be achieved by a single-ribonucleotide repair-mediated ligation-dependent cycling signal amplification approach., DNA methylation is a predominant epigenetic modification that plays crucial roles in various cellular processes. DNA methyltransferase (MTase) is responsible for DNA methylation, and its dysregulation may induce aberrant methylation patterns that are closely related to cancers. Conventional methods for DNA MTase assay are usually cumbersome and laborious with poor sensitivity. Alternatively, some signal amplification strategies are employed to improve the sensitivity, but they suffer from poor specificity and consequently limited sensitivity due to the nonspecific amplification. Herein, we develop for the first time a new fluorescence method to specifically and sensitively detect DNA MTase activity on the basis of single-ribonucleotide repair-mediated ligation-dependent cycling signal amplification. In the presence of DNA MTase, the hairpin substrate is methylated and cleaved by endonuclease Dpn I, releasing a 24-nt cleavage product. The 24-nt cleavage product may function as a primer and adjacently hybridize with the ligation probes (LP1 and LP2) to form the template (LP1–LP2) for strand displacement amplification (SDA), initiating the single-ribonucleotide repair-mediated cyclic ligation-dependent SDA to produce a large number of reporter probes. The reporter probe can subsequently hybridize with the signal probe that is modified with FAM and BHQ1 to form a stable double-stranded DNA (dsDNA) duplex with a ribonucleotide mismatch. Ribonuclease HII (RNase HII) can excise the single ribonucleotide, resulting in the cyclic cleavage of signal probes and the generation of an enhanced fluorescence signal. Taking advantage of the high specificity of RNase HII-catalyzed single-ribonucleotide excision and the high amplification efficiency of cyclic ligation-dependent SDA, this assay exhibits the highest sensitivity reported so far with a detection limit of 4.8 × 10–6 U mL–1 and a large dynamic range of 5 orders of magnitude. Moreover, this method can be used for the discrimination of Dam MTase from other DNA MTases, the accurate quantification of Dam MTase activity in E. coli cells, and the screening of Dam MTase inhibitors, providing a new paradigm for biomedical research and clinical diagnosis.

Human T-lymphotropic virus type II (HTLV-II) is an important type-C retrovirus, closely related to a variety of human diseases. Here, we demonstrate for the first time the controllable fabrication of bio-bar codes for dendritically amplified sensing of low-abundant HTLV-II DNA by the integration of terminal deoxynucleotidyl transferase (TdT)-catalyzed template-free polymerization extension with bio-bar-code amplification (BCA). HTLV-II DNA hybridizes with magnetic microparticle (MMP)-modified capture probe 1, forming a stable DNA duplex with a protruding 3'-hydroxylated sequence which may function as a primer to initiate the TdT-catalyzed first-step polymerization extension for the generation of a poly-thymidine (T) sequence. The resultant poly-T products may hybridize with poly-adenine (A) capture probe 2, inducing the self-assembly of multiple capture probe 2-/reporter probe-functionalized Au nanoparticles (AuNPs) onto the MMP. Subsequently, the reporter probes may act as the primers to initiate the TdT-catalyzed second-step polymerization extension, producing large numbers of G-rich DNAzymes for the generation of an enhanced chemiluminescence signal. Taking advantage of the efficient polymerization extension reaction catalyzed by TdT, the high amplification efficiency of BCA, and the intrinsically high sensitivity of G-rich DNAzyme-driven chemiluminescence, this method exhibits ultrahigh sensitivity with a limit of detection of as low as 0.50 aM and a large dynamic range of 9 orders of magnitude from 1 aM to 1 nM. Moreover, this method can be applied for the discrimination of a single-base mismatch and the measurement of HTLV-II DNA in both human serum and human T-lymphocytic leukemia cells, holding great potential in biomedical research and clinical diagnosis.

Alkaline phosphatase (ALP) is an important diagnostic indicator for various human diseases including bone diseases, liver dysfunction, diabetes, breast and prostatic cancers. However, the conventional methods for ALP assay are usually cumbersome and time-consuming with low sensitivity. Here, we develop a new fluorescent method for ultrasensitive detection of ALP activity on the basis of primer dephosphorylation-initiated isothermal circular exponential amplification. We design two dual-functional hairpin probes (HP1 and HP2), which function as both the templates for exponential amplification reaction (EXPAR) and the generators for signal output. In the presence of ALP, the 3'-phosphorylated primer is dephosphorylated and subsequently hybridizes with the 3' protruding end of HP1 to initiate the first strand displacement amplification (SDA), producing trigger 1 and fluorescence signal. The released trigger 1 is complementary to the 3' protruding end of HP2 for the initiation of the second SDA, producing trigger 2 and fluorescence signal. Notably, trigger 2 is complementary to the 3' protruding end of HP1 and may subsequently initiate two consecutive SDAs, enabling circular EXPAR to generate an amplified fluorescence signal. This method exhibits high sensitivity with a detection limit of 2.0 × 10-10 U μL-1 and a large dynamic range of 5 orders of magnitude from 1.0 × 10-9 to 1.0 × 10-4 U μL-1, and it can measure ALP at the single-cell level. Importantly, this method can be applied for the measurement of kinetic parameters and the screening of potential inhibitors, providing a powerful tool for ALP-related biomedical research and clinical diagnosis.

We developed a simple and rapid method for terminal deoxynucleotidyl transferase (TdT) assay on the basis of the polymerization-directed exonuclease-assisted construction of a single quantum dot (QD)-based fluorescence resonance energy transfer (FRET) nanosensor. This method is very sensitive with a detection limit as low as 1 × 10-6 U μL-1, and it can be used for the screening of TDT inhibitors and accurate quantification of TdT activity even in 5 cancer cells.

A simple colorimetric sensing method for the detection of Hg2+ was developed by combining enzymatic catalysis with DNA-based hybridization chain reactions (HCRs). Firstly, thymine (T)-rich capture DNA (cDNA) was immobilized on a gold electrode via Au–S bonding. In the presence of Hg2+, thymine (T)-rich probe DNA (pDNA) hybridized with cDNA via T–Hg2+–T base pairs. Then the HCRs were realized using pDNA as an initiator and two biotin-labeled hairpin DNAs (H1 and H2) as fuel strands. Finally, numerous avidin-labeled horseradish peroxidase (HRP) enzymes were immobilized on long nicked ds-DNA strands, which can catalyze the H2O2-mediated oxidation of 3,3,5,5-tetramethylbenzidine dihydrochloride hydrate (TMB) to cause a dramatic color change. Under optimal conditions, the absorbance of TMB was linear with the logarithm of Hg2+ concentrations in the range of 1 fM to 1 pM, with a detection limit of 0.33 fM. This strategy exhibited good selectivity and high sensitivity, which might be a potential tool for the practical detection of Hg2+ in environmental monitoring.

We develop a new fluorescence method for real-time monitoring of thymine DNA glycosylase (TDG) activity through cyclic enzymatic repairing-mediated dual-signal amplification. This method exhibits excellent sensitivity with a detection limit of 5.6 × 10−7 U μL−1, and it can be used to determine kinetic parameters and quantify TDG activity from even single cancer cells.

We develop a new method for ultrasensitive detection of folate receptors (FRs) using a target-triggered isothermally exponential amplification reaction (EXPAR)-based DNAzyme biosensor. This method exhibits excellent specificity and high sensitivity with a detection limit as low as 0.23 fM and a large dynamic range of 6 orders of magnitude from 1 fM to 1 nM. It might be further applied for the detection of various small molecule-binding proteins by simply changing the linked small molecule moiety of the hairpin probes.

We develop a single quantum dot (QD)-based nanosensor for sensitive detection of DNA methylation at both CpG and non-CpG sites., DNA methylation is an important epigenetic modification in human genomes. Herein, we develop a single quantum dot (QD)-based nanosensor for sensitive detection of DNA methylation at both CpG and non-CpG sites using tricyclic ligation chain reaction (LCR)-mediated QD-based fluorescence resonance energy transfer (FRET). We design two sets of DNA probes (X and Y, X′ and Y′) for methylated DNA assay. In the presence of thermostable DNA ligase, probes X and Y may adjacently hybridize with the methylated DNA to obtain the ligated XY products which may function as the templates for probes X′ and Y′ to generate the X′Y′ products. The resultant X′Y′ products may in turn act as the templates to ligate probes X and Y for the generation of XY products, consequently inducing tricyclic LCR amplification under thermal denaturation conditions to generate a large number of XY products. The subsequent hybridization of XY products with the capture and reporter probes results in the formation of sandwich hybrids which may assemble on the 605QD surface to obtain 605QD–oligonucleotide–Cy5 nanostructures, inducing efficient FRET from the 605QD to Cy5 and the emission of Cy5. This nanosensor can detect DNA methylation at single 5-methylcytosine (5-mC) resolution with a detection limit of as low as 1.0 aM and a large dynamic range of 7 orders of magnitude. Moreover, this nanosensor can distinguish as low as a 0.01% methylation level, and it can detect DNA methylation in human lung cancer cells as well, holding great potential for accurate epigenetic evaluation and early cancer diagnosis.

A luminescent zinc complex has been encapsulated in the ordered, 3.2 nm wide hexagonal channels of a nanoporous MCM-41 host. A marked 19 nm blue-shift of the major absorption band maximum is found for the zinc complex in ethanol solution relative to the complex loaded in MCM-41, which is correlated with an increased band gap in the former. A 17 nm blue-shift of the emission peak is also observed, which is estimated to be related to the decrease of polarity around the zinc ions.

A telomere-triggered isothermal exponential amplification-based DNAzyme biosensor is developed for highly sensitive detection of telomerase in cancer cells even at the single-cell level. This biosensor can be further applied for the screening of telomerase inhibitors for anticancer drug development.

A carbonyl reductase gene (yueD) from Bacillus sp. ECU0013 was heterologously overexpressed in Escherichia coli, and the encoded protein (BYueD) was purified to homogeneity and characterized. The NADPH-dependent reductase showed a broad substrate spectrum towards different aromatic ketones, and α- and β-ketoesters. Although the enantioselectivity was high to moderate for the reduction of α-ketoesters, all the tested β-ketoesters and aromatic ketones were reduced to the corresponding chiral alcohols in enantiomerically pure forms. Furthermore, the practical applicability of this enzyme was evaluated for the reduction of ethyl 4-chloro-3-oxobutanoate (1a). Using Escherichia coli cells coexpressing BYueD and glucose dehydrogenase, 215 g L(-1) (1.3 M) of 1a was stoichiometrically converted to ethyl (R)-4-chloro-3-hydroxybutanoate ((R)-1b) in an aqueous-toluene biphasic system by using a substrate fed-batch strategy, resulting in an overall hydroxyl product yield of 91.7% with enantiomeric purity of 99.6% ee.