Paired Electrolysis-Enabled Arylation of Quinoxalin-2(1H)-ones.

The first paired electrolysis-enabled arylation of quinoxalin-2(1H)-ones was achieved using cyanoarenes as the arylation reagents. A variety of 3-arylquinoxalin-2(1H)-ones with various important functional groups were obtained in moderate to good yields under metal- and chemical oxidant-free conditions. With a pair of reductive and oxidative processes occurring among the substrates and reaction intermediates, the power consumption can be dramatically reduced.

Ferrocene/air double-mediated FeTiO3-photocatalyzed semi-heterogeneous annulation of quinoxalin-2(1H)-ones in EtOH/H2O.

With both ferrocene and air as the redox catalysts, for the first time, the low-cost natural ilmenite (FeTiO3) was successfully used for photocatalytic bond formations. Under the assistance of a traceless H-bond, and HCHO as the methylene reagent, a variety of imidazo[1,5-a]quinoxalinones were semi-heterogeneously photosynthesized in high yields with good functional group compatibility.

Selectfluor-Mediated Electrophilic Annulation of 2-Alkynyl Biaryls with Diorganyl Diselenides.

A general and efficient method for the synthesis of various selanyl phenanthrenes/polycyclic heteroaromatics through the electrophilic annulation of 2-alkynyl biaryls with diorganyl diselenides under metal-free and mild conditions was established. The sulfanyl phenanthrene was also obtained in moderate yields.

Hairpin loop-enhanced fluorescent copper nanoclusters and application in S1 nuclease detection.

Novel highly fluorescent copper nanoclusters (CuNCs) were prepared by using 24 adenine-thymine pair dsDNA (AT24) with six-base (X6) loops (AT24-X6-hairpin DNA) as an effective template. The AT24 double strand stem serves as a template for CuNC formation, and the six-base sequence loop acts as specific regions to enhance the fluorescence intensity of CuNCs. Relative to the AT24-CuNCs, AT24-X6-hairpin CuNCs have greater fluorescence (5 times enhancement). What's more, the influence of the hairpin loop with different base types and base numbers on the fluorescence of CuNCs was first proposed and investigated. By choosing an AT24 double strand stem, any types of base loops can enhance the fluorescence of CuNCs. However, the fluorescence enhancement would be reduced with an increasing number of hairpin loop sequences. Besides this, the successful detection of S1 nuclease demonstrates its potential to be a new and robust fluorescent probe for sensing applications.

A sensitive assay for trypsin using poly(thymine)-templated copper nanoparticles as fluorescent probes.

A new, simple and sensitive fluorescence strategy was developed for the trypsin assay based on copper nanoparticles (CuNPs) and its different fluorescence response toward trypsin-catalyzed hydrolysis of cytochrome c (Cyt c). Polythymine (poly T)-templated CuNPs served as effective fluorescent probes. Cyt c is well-known to act as a quencher. However, herein, a low concentration of Cyt c was designed specially to act as the substrate of trypsin to avoid the quenching effects by electron transfer from Cyt c to CuNPs. In the presence of trypsin, Cyt c hydrolyzes to small peptides, releasing free cysteine residues. Nonfluorescent coordination complexes were formed upon exposure to free cysteine residues by a metal-ligand bond between Cu atoms and sulfur atoms, leading to a decreased fluorescence response to CuNPs. This novel method for the quantitative determination of trypsin has a linear detection range from 0.25 µg mL(-1) to 1000 µg mL(-1) and a relatively low detection limit of 42 ng mL(-1). To the best of our knowledge, this is the first application of the trypsin-catalyzed hydrolysis reaction of Cyt c to produce quenching effect in bioanalysis, which provided a novel approach for the biochemical sensing strategy.

Terminal protection of small-molecule-linked DNA for sensitive fluorescence detection of protein binding based on nucleic acid amplification.

A novel fluorescence biosensing strategy based on terminal protection triggered nucleic acid amplification reaction upon target binding was developed for the sensitive detection of small molecule-protein interactions. This method relies on the specific interactions between target proteins and their small molecule-linked DNA to produce a ligation probe. Introduction of a target protein into the assay system protected the small molecule-linked DNA from Exonuclease I (Exo I)-mediated digestion and served as the circular template to trigger rolling circle amplification (RCA). The RCA product containing thousands of repeated sequences could hybridize with the TaqMan probes (reporter probes) and were then detected by Exonuclease III (Exo III)-aided recycling amplification reaction, generating remarkable fluorescence signals. This developed strategy transduced small molecule-protein interactions into DNA amplification and detection techniques. Due to the primary RCA followed by the secondary Exo III-aided recycling amplification, the developed method was demonstrated to have very high sensitivity for the detection of a tumor biomarker of folate receptor with a limit of detection of 0.8 pM. The novel strategy holds great promise for the study of small molecule-protein interactions with desirable specificity and sensitivity achieved as a result of terminal protection and nucleic acid amplification.

Sensitive and visual detection of sequence-specific DNA-binding protein via a gold nanoparticle-based colorimetric biosensor.

A novel exonuclease III (Exo III) protection-based colorimetric biosensing strategy was developed for rapid, sensitive, and visual detection of sequence-specific DNA-binding proteins. This strategy relied on the protection of DNA-cross-linked gold nanoparticle (AuNP) aggregates from Exo III-mediated digestion by specific interactions of target proteins with their binding sequences. Interestingly, we disclosed a new finding that binding of target proteins to their binding sequences in the aggregated AuNP network rendered a stable and long-period protection of DNA. Unlike conventional fluorescence assays merely based on temporal protection of DNA from Exo III digestion, the stable protection afforded a static color transition indicator for DNA-protein interactions with no time-dependent monitoring required in the assay. Therefore, it furnished the developed strategy with improved technical robustness and operational convenience. Furthermore, we introduced thioctic acid as a stable anchor for tethering DNA on AuNPs. This DNA-tethering protocol circumvented the interferences from thiol compounds in common enzymatic systems. The Exo III protection-based colorimetric biosensor was demonstrated using a model target of TATA binding protein, a key transcriptional factor involving in various transcriptional regulatory networks. The results revealed that the method allowed a specific, simple, and quantitative assay of the target protein with a linear response range from 0 to 120 nM and a detection limit of 10 nM.

DNA encapsulating liposome based rolling circle amplification immunoassay as a versatile platform for ultrasensitive detection of protein.

A novel rolling circle amplification (RCA) immunoassay based on DNA-encapsulating liposomes, liposome-RCA immunoassay, was developed for ultrasensitive protein detection. This technique utilized antibody-modified liposomes with DNA prime probes encapsulated as the detection reagent in the sandwiched immunoassays. The DNA prime probes were released from liposomes and then initiated a linear RCA reaction, generating a long tandem repeated sequences that could be selectively and sensitively detected by a microbead-based fluorescence assay. The developed technique offered very high sensitivity due to primary amplification via releasing numerous DNA primers from a liposome followed by a secondary RCA amplification. A biobarcode design was incorporated in the technique, which allowed the strategy to be directly implemented for multiplex assay of multiple proteins. Also, the technique allowed easy preparation of the DNA-carrying antibody reagent and the implementation with simple instrumentation. The technique was demonstrated for the determination of prostate-specific antigen (PSA), a highly selective biomarker associated with prostate cancer. The results revealed that the technique exhibited a dynamic response to PSA over a 6-decade concentration range from 0.1 fg mL(-1) to 0.1 ng mL(-1) with a limit of detection as low as 0.08 fg mL(-1) and a high dose-response sensitivity. The liposome-RCA immunoassay holds great promise as a versatile, sensitive, and robust platform to combine the nucleic acid amplification with immunoassay for ultrasensitive protein detection.

[Effects of Rhizoma zingiberis and Pericarpium citri reticulatae extracts on myocardial ischemia in rats].

OBJECTIVE: To observe the effects of Rhizoma Zingiberis and Pericarpium Citri Reticulatae extracts on acute myocardial ischemia rats and explore the mechanism. METHODS: The model of myocardial ischemia in rats was established by ligating the front descending anterior branch of the coronary artery. With Fufang Danshen Pill as positive control drug,the effects of Rhizoma Zingiberis and Pericarpium Citri Reticulatae extracts on the electrocardiogram (ECG), the extension of myocardial infarction, the hemorheology indexes, lactic dehydrogenase (LDH), creatine kinase (CK), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) in rats were evaluated. RESULTS: Rhizoma Zingiberis and Pericarpium Citri Reticulatae extracts decreased the ST-segment of ECG (P < 0.01), reduced the extension of myocardial infarction (P < 0.05), decreased the contents of CK and LDH in serum (P < 0.01 or P < 0.05), improved hemorheology (P < 0.05), increased SOD and GSH-Px activity and decreased MDA content (P < 0.05). CONCLUSION: Rhizoma Zingiberis and Pericarpium Citri Reticulatae extracts have protective effect on myocardial ischemia in rats, and its mechanism may be related to inhibiting lipid peroxidation.

Aptamer-based rolling circle amplification: a platform for electrochemical detection of protein.

Aptamer-based rolling circle amplification (aptamer-RCA) was developed as a novel versatile electrochemical platform for ultrasensitive detection of protein. This method utilized antibodies immobilized on the electrode surface to capture the protein target, and the surface-captured protein was then sandwiched by an aptamer-primer complex. The aptamer-primer sequence mediated an in situ RCA reaction that generated hundreds of copies of a circular DNA template. Detection of the amplified copies via enzymatic silver deposition then allowed enormous sensitivity enhancement in the assay of target protein. This novel aptamer-primer design circumvented time-consuming preparation of the antibody-DNA conjugate for the common immuno-RCA assay. Moreover, the detection strategy based on enzymatic silver deposition enabled a highly efficient readout of the RCA product as compared to a redox-labeled probe based procedure that might exhibit low detection efficiency due to RCA product distance from the electrode. With the platelet-derived growth factor B-chain (PDGF-BB) as a model target, it was demonstrated that the presented method was highly sensitive and specific with a wide detection range of 4 orders of magnitude and a detection limit as low as 10 fM. Because of the wide availability of aptamers for numerous proteins, this platform holds great promise in ultrasensitive immunoassay.