Annulation of 1-(2-Aminoaryl)pyrroles, Ethers with Elemental Sulfur To Give 1,3,6-Benzothiadiazepine Derivatives through Double C-S Bond Formation and C-O Cleavage of Ethers.

An efficient three-component reaction of 1-(2-aminoaryl)pyrroles, ethers, and elemental sulfur for constructing N-heterocycle-fused 1,3,6-benzothiadiazepines under transition-metal-free conditions has been developed. Ethers act as both reactants and solvent in this reaction. The method proceeds efficiently over a broad range of substrates with good functional group tolerance.

Imaging specific newly synthesized proteins within cells by fluorescence resonance energy transfer.

Metabolic azide amino acid labelling followed by the use of bioorthogonal chemistry is an efficient technique for imaging newly synthesized proteins. Recently, AHA-labelling together with the proximity-ligation assay was used to identify newly synthesized proteins of interest (POI) (Tom Dieck et al., Nat. Meth. 2015, 12, 411). Here we build on this study replacing the proximity-ligation assay with FRET to improve the spatial resolution. Herein, we develop a FRET-based strategy for imaging the newly synthesized endogenous POI within cells: a FRET acceptor is installed onto the newly synthesized proteins via click chemistry, and a FRET donor onto the POI via immunocytochemistry. We found that a photobleaching based FRET efficiency imaging mode and a fluorescence lifetime imaging mode showed the distribution of newly synthesized proteins more accurately compared to the direct observation of FRET signals. We demonstrated the capability of this FRET-based imaging method by visualizing several newly synthesized proteins including TDP-43, tubulin and CaMKIIα in different cell lines. This novel analytical imaging method could be used to visualize other specific endogenous proteins of interest in situ.

Pinpoint the Positions of Single Nucleotide Polymorphisms by a Nanocluster Dimer.

Single nucleotide polymorphisms (SNPs) are the most fundamental internal causes for many genetic diseases. However, the location information on SNPs in a specific DNA sequence is not well acquired through current SNPs detection methods, except for accurate DNA sequencing. Here we report a fluorescence enhancement phenomenon in the process of two silver nanoclusters (AgNCs) approaching closely to form a nanocluster dimer (NCD). The fluorescence intensity is sensitive to the distance between two AgNCs; therefore, the NCD lights into different fluorescence intensities upon binding SNPs targets with mismatched bases at different positions. Interestingly, the fluorescence intensities of the NCD decrease linearly when the position of single mismatched base moves gradually from the middle point to the end of the target DNA. The NCD is a single probe acting as a universal platform to pinpoint various SNP positions. With this single probe, we cannot only identify the existence of SNPs but also pinpoint the location of a specific single mismatched base in the adjacent positions. This strategy is feasible to detect specific gene point mutations in clinical samples.

Graphene Oxide as a Novel Evenly Continuous Phase Matrix for TOF-SIMS.

Using matrix to enhance the molecular ion signals for biomolecule identification without loss of spatial resolution caused by matrix crystallization is a great challenge for the application of TOF-SIMS in real-world biological research. In this report, graphene oxide (GO) was used as a matrix for TOF-SIMS to improve the secondary ion yields of intact molecular ions ([M + H]+). Identifying and distinguishing the molecular ions of lipids (m/z >700) therefore became straightforward. The spatial resolution of TOF-SIMS imaging could also be improved as GO can form a homogeneous layer of matrix instead of crystalline domain, which prevents high spatial resolution in TOF-SIMS imaging. Lipid mapping in presence of GO revealed the delicate morphology and distribution of single vesicles with a diameter of 800 nm. On GO matrix, the vesicles with similar shape but different chemical composition could be distinguished using molecular ions. This novel matrix holds potentials in such applications as the analysis and imaging of complex biological samples by TOF-SIMS. Graphical Abstract ᅟ.

Spatiotemporal fluorescence imaging of newly synthesized proteins in normal and cancerous cells with anticarcinogen modulation.

Some anticarcinogen could treat cancers through regulating the synthesis and degradation of proteins. Therefore, the rules of newly synthesized proteins would be used to evaluate the effect of anticarcinogen. In this study, we coupled noncanonical amino acid tagging with click reaction to label the newly synthesized proteins in normal cells and cancerous cells. We studied the influence of six different drugs on the protein synthesis. The results showed the differences of protein synthesis rate and spatial distribution in normal cells and cancerous cells, as well as their different responding to anticarcinogen stimulation. This approach could help us to understand the growth of proteins and distinguish cancerous cells from normal cells, which would benefit the diagnosis and monitoring of cancer, as well as evaluating the curative effect of drugs. Based on this strategy, more significant biological process about newly synthesized biomolecules would be studied in-depth.

PVP-coated graphene oxide for selective determination of ochratoxin A via quenching fluorescence of free aptamer.

In this paper, we developed a simple method to detect fungi toxin (ochratoxin A) produced by Aspergillus Ochraceus and Penicillium verrucosumm, utilizing graphene oxide as quencher which can quench the fluorescence of FAM (carboxyfluorescein) attached to toxin-specific aptamer. By optimizing the experimental conditions, we obtained the detection limit of our sensing platform based on bare graphene oxide to be 1.9 µM with a linear detection range from 2 µM to 35 µM. Selectivity of this sensing platform has been carefully investigated; the results showed that this sensor specifically responded to ochratoxin A without interference from other structure analogues (N-acetyl-l-phenylalanine and warfarin) and with only limited interference from ochratoxin B. Experimental data showed that ochratoxin A as well as other structure analogues could adsorb onto the graphene oxide. As compared to the non-protected graphene oxide based biosensor, PVP-protected graphene oxide reveals much lower detection limit (21.8 nM) by two orders of magnitude under the optimized ratio of graphene oxide to PVP concentration. This sensor has also been challenged by testing 1% red wine containing buffer solution spiked with a series of concentration of ochratoxin A.