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The development of biocompatible two-photon fluorophores with a large absorption cross-section is challenging, despite the presence of theoretical guidelines. By rendering asymmetric PRODAN dye centrosymmetric, we designed and synthesized a novel class of two-photon fluorophores (TPZ). Their photophysical properties were investigated and their imaging potentials in cells, tissues and zebrafish were showcased.

By fusion of HBT and hemicyanine, we have designed a novel donor-two-acceptor type fluorophore ( HHC ) as a platform for the detection of different kinds of guests. HHC displays an emission at 580 nm in aqueous solution and two emission bands at 450 nm and 616 nm as a result of the donor-two-acceptor feature with the existance of CTAB. The fluorescence of HHC may be readily modulated by protection/deprotection of its electron-donating hydroxyl group and response different guests. As an example, we introduced p-nitrobenzyl group, which is sensitive to Nitroreductase (NTR), to the hydroxyl group of HHC and constructed a novel selective and sensitive fluorescence probe HHCP for fast detection and intracellular imaging of nitroreductase.

Nitric oxide (NO) donors are versatile tools for nitric oxide biology. The biological response of NO is dependent on the transient concentration and the sustained duration. N-Nitrosated rhodamines are photo-triggered and photo-calibrated NO donors. We recently discovered that suppression of the dihedral angle between the N-nitroso fragment with the rhodamine scaffold facilitates NO release. Inspired by this discovery, we developed a fast-releasing NO donor (NOD575) suitable for biological applications, e.g., the pulmonary arterial smooth muscle cells (PASMCs).

A convenient method was developed for the cyclopropanation of aryl acetates and aryl acetonitrile using vinyl diphenyl sulfonium triflate salt. The newly developed conditions are simple, mild, and compatible with a wide range of functional groups, without the need to apply an inert atmosphere, or alkali bases.

Autophagy is a physiological process governing proteostasis and implicated in many diseases. Enhanced ROS levels was known to be associated with lysosomal autophagy and therefore a lyso-specific ROS probe could find applications in autophagy related studies. Following the probe-design principle of bridging-group modification, we previously developed a ROS probe capable of detect a broader range of reactive species than the existing probes. Additional merits of the probe include ratiometry-capability, minimal probe-product spectral crosstalk, resistance toward autoxidation at lysosomal acidity, and structural simplicity. It is the aim of this manuscript to render this probe lyso-specificity and examine its potentials to monitor autophagy-related ROS generation in HeLa cells treated by H2O2 or 6-OHDA.

Nucleolus is a sub-cellular nuclear structure identified with an optical microscope. Surprisingly, the fluorescent labelling tools for nucleolus remains very scarce compared to other cellular organelles. In recent years, the biorelevance of nucleolus in various diseases receive intensity scrutiny, and therefore high-performance fluorescence stains for nucleolus are warranted. The proximal pH of the cell nucleolus is slightly lower compared to the other nucleoplasmic region. However, differentiation of a minor pH variation with a traditional Henderson-Hasselbalch type pH probe is difficult due to its inferior sensitivity. Harnessing a molecular mechanism for pH-sensing with positive cooperativity, we were able to design Hill-type small-molecular pH probes with a profile. They exhibit a reduced acid-base transition range and better differentiate biorelevant small pH changes. We showcase that such Hill-type pH probes are suitable for selective nucleolus staining. It exhibits fast membrane permeability and applies to live, fixed, and permeated cells. PHN is expected to find applications in nucleolar chemical biological studies.

As one final end of the redox buffer network, endogenous protein vicinal thiols show a higher tendency to cope with redox changes and are more sensitive and prone to free-radical oxidation. Therefore, endogenous vicinal-dithiol-containing proteins (VDPs) are of considerable significance for regulating cellular functions through the reversible dithiols/disulfide inter-conversion reaction. However, compared to the critical role of VDPs, the detection approaches for exploration of the protein vicinal thiols and related VDPs are limited. Especially, no effective strategies had been used for in-situ detection of endogenous protein vicinal in live cells until that we discovered a fluorophore with dithiarsenolane to serve as a useful fluorescent probe for in-situ detection of VDPs in live cells. Thus, the idea of harnessing the power of chemical approaches to determine the protein vicinal dithiols and related VDPs has presented an optional tool for investigating the various functions of VDPs in the biological process and related diseases. In this review, we present different chemical probes-based strategies for the detection of endogenous protein vicinal thiols and related VDPs, especially focusing on the different monoarsenic-based fluorescent probes for real-time visualization of VDPs in live cells. The principle involved in the development of chemical strategies for tracing cellular endogenous VDPs, and problems and challenges in this field are also discussed. Finally, we prospect future research directions in this area.

Fluorophores with a minimal push-pull backbone are actively pursued due to their potentials in biological labelling. Herein a series of structurally-thrifty and visible-absorbing fluorophores (SDXs) were successfully constructed following the D′D-π-A design strategy, in which a secondary donor (D′) was introduced in conjugation with the donor (D) to enhance its electron donating capability. For a very small scaffold, SDXs exhibit a surprisingly long-wavelength absorption band in the visible spectral range (λabs = 420 nm) and a strong green fluorescence emission (λem = 530 nm) with a fluorescence quantum yield up to 0.84. Notably, fluorescence of SDXs was quenched in hydrogen-bonding solvents, e.g. MeOH and H2O. This phenomenon renders SDXs feasibility for imaging of cellular non-hydrogen-bonding microenvironment, as demonstrated with BEAS-2B cells. These results proved that the D′D-π-A is a powerful design strategy to construct novel structurally-thrifty fluorophores.

Based on the thioether-rich crown receptor, we describe a naphthalimide based bifunctional fluorescent sensor (FS-G) for simultaneous detection and separation of trace Hg(2+) in water. FS-G exhibited excellent selectivity toward Hg(2+) in aqueous environment and showed 5-fold increase in fluorescence emission intensity upon the addition of Hg(2+). A good linearity was observed between the fluorescence enhancement and the dose of Hg(2+) with a lower detection limit of 33.4ppb. Additionally, adsorption capacity of FS-G is 7.4mgg(-1). FS-G can be easily regenerated when treated with dimercaptosuccinic acid. These results indicate that FS-G has potential applications for detection and removal of trace Hg(2+) in water.

A method for preparation of 1,4,2-dithiazolidine or 1,3-thiazetidine heterocycles was developed by reactions of phenylthioureas with 1,1-dichloro-2-nitroethene. The solvent has a significant influence on the type of product formation. 1,4,2-Dithiazolidines were formed in the aprotic solvent chloroform, while in the protic solvent ethanol, 1,3-thiazetidines were the main products.

Peroxynitrite (OONO(-)) is profoundly implicated in health and disease. The physiological and pathological outcome of OONO(-) is related to its local concentration, and hence, a reliable OONO(-) assay is highly desired. We have developed a FRET-based small-molecule fluorescent probe (PNCy3Cy5), harnessing the differential reactivity of Cy3 and Cy5 toward OONO(-) by fine-tuning. It exhibits high detection sensitivity and yields a ratiometric fluorescent signal. We have exemplified that it can be applied in semiquantitative determination of OONO(-) in living cells. Notably, it specifically localizes in mitochondria, where endogenous OONO(-) is predominantly generated. Thus, PNCy3Cy5 is a promising molecular tool for peroxynitrite biology.

Compared to normal cells, most cancer cells produce ATP by glycolysis under aerobic conditions rather than via the tricarboxylic acid cycle (TCA). This study is intended to determine whether 3B, a novel photosensitizer, can inhibit glycolysis and inflammation in breast cancer cells. We showed that 3B had the ability to repress glucose consumption as well as the generation of ATP, lactate and lactate dehydrogenase. 3B-PDT not only inhibited the expression of IL-1β and IL-6 but also affected the JAK-STAT3 inflammatory pathway in vitro. The present study showed that 3B featured a significant inhibitory effect on the expression of microRNA-155-5p and SOCS1 might serve as a target gene. In vivo studies revealed that 3B inhibited tumor growth and exhibited almost no side effects. Therefore, through the anti-glycolytic effect and breakage of the JAK/STAT3/SOCS1 feedback loop via miR-155-5p, 3B may potentially serve as a potential therapeutic agent against breast cancer.

Developing fluorescent probes for selective and sensitive detection of hypochlorite has received much attention, because hypochlorite is closely related to human health. In this work, a new fluorescent probe based on dipyrromethene boron difluoride (BODIPY) fluorophore using hydrazine as detecting group for hypochlorite was synthesized and fully characterized. The reaction of the probe with sodium hypochlorite is complete within 1 min in phosphate-buffered saline, and the fluorescence of the system significantly enhanced. The probe also exhibits admirable sensitivity and selectivity as well. The results of nuclear magnetic resonance monitoring and high-performance liquid chromatography analysis indicate that the detection process plausibly involves a free radical oxidation mechanism.

Herein, we report a heterogenous catalyst (Pd@FSM) by immobilization of a novel Pd2+ sensor as promoter over mesoporous silica. Pd@FSM with a high palladium loading of ca. 11 mg g−1 exhibited superior catalytic activity for Suzuki–Miyaura cross-couplings and a catalyst loading of 0.05 mol% is typically sufficient to achieve excellent reaction yields. Notably, the reaction is typically carried out in water without removing atmospheric oxygen. The catalyst is conveniently recycled and remains highly active even after being recycled 5 times. During this process, loss of palladium from the solid support of the catalyst is negligible. Furthermore, the catalyst can be stored in air for at least three months without loss of its catalytic activity. This work provides a new approach to developing heterogeneous palladium catalysts by combing materials and fluorescent sensors.

A new artificial fluoro-cofactor was developed for the replacement of natural cofactors NAD(P), exhibiting a high hydride transfer ability. More importantly, we established a new and fast screening method for the evaluation of the properties of artificial cofactors based on the fluorescence assay and visible color change. Published version

Bright and photostable fluorophores play a key role in the imaging of specific intracellular molecules. Here we report a facile approach to improve the brightness of naphthalimide fluorophores in water. We synthesized a series of nonplanar and rigid compounds (FM1, FM2, and FM3) by fusing a seven-membered heterocycle onto a naphthalimide skeleton. Compared with classic naphthalimide (FM0), these novel fluorophores exhibited much higher quantum yield values (Φ = 0.60–0.66), and higher molar extinction coefficients in aqueous solution, which elicited superior brightness to FM0. They also showed good photostability, pH-independence, and two-photon microscope (TPM) imaging ability. This new strategy of structural nonplanarity and rigidification provides an efficient way to improve the quantum efficiencies of traditional dyes.

Based on the NCL reaction, we report a novel “off–on” fluorescent probe BQ for the sensing of Cys/Hcy by a FRET strategy. Owing to the quenching effect of azo-based naphthalimide, BQ showed nonfluorescence. Upon the interaction of Cys/Hcy, a dramatic increase of the fluorescence signal was observed, with a high selectivity toward Cys/Hcy over GSH. Additionally, the discrimination of Cys from Hcy also could be achieved through the different rates of the transthioesterification reaction between thiols and BQ, especially when the concentration of Cys and Hcy was below 100 μM. The Cys/Hcy could be specifically labeled by the BODIPY fluorophore of BQ after the NCL reaction. Living cell imaging experiments demonstrated that BQ can selectively label Cys/Hcy and distinguish Cys/Hcy from other bioreagents including GSH in living systems.

Plants can develop multifaceted system resistance as a result of infection with pathogens, insects, and some specific microbes or after treatment with specific chemicals.1 Among them, systemic acquired resistance (SAR) and induced systemic resistance (ISR)2 are the two most important types. To activate them, a large number of chemical inducers have been exploited based on the SA pathway. However, the JA pathway was rarely investigated for new plant activators. In this study, starting from JA and its analogs, based on the molecular three-dimensional shape and pharmacophore similarity comparison (SHAFTS), a new lead compound, pyrrolidone, as a new scaffold of plant activators was predicted and a series of 1-phenyl-5-pyrrolidone-3-carboxylic acid derivatives were designed and synthesized. The bioactivity was evaluated, and most of the compounds showed satisfactory activity; especially, compounds 7–11 showed almost no in vitro activity but excellent efficacy against tested diseases, and the prediction of the virtual screening results was also confirmed, which promoted the application of SHAFTS in the development of pesticides.

In this paper, we report a sensitive fluorescent sensor (FSCHP) for detection and removal of toxic metal ions (Cd2+, Hg2+ and Pb2+) in aqueous samples. FSCHP is a 2,2-dipicolylamine (DPA) modified naphthalimide fluorophore followed by immobilization to the surface of silica microsphere and support high affinity for Cd2+, Hg2+ and Pb2+. Metal adsorption by FSCHP was featured by an enhancement in its fluorescence intensity. The limit of detection of 36 nM for Cd2+, 48 nM for Hg2+, and 39 nM for Pb2+, was measured respectively. Moreover, FSCHP can also be used as adsorbent for the separation of toxic metal ions in the contaminated aqueous solution with high adsorptivity, and can be regenerated by acid treatment. The metal ion removal capacity of FSCHP was retained after five removal/regeneration cycles.

In 2008, a concept of element substitution was proposed for designing long wavelength fluorescent dyes which is urgently desired in life science. By replacing the rhodamine dyes’ oxygen-bridge atom by silicon we gained a nearly 90 nm’s red shift. At the same time, the novel silicon-substituted dye kept a high brightness similar to conventional rhodamines. Since our report was published, the values of this pioneering work have been evidently displayed. This idea is so practical that a large number of Silicon-rhodamine derivatives have been developed as fluorescent sensors and probes by a lot of research teams. And this strategic innovation is also very illuminating to initiate the generations of quite a few wonderful element-substituted dyes, among which the elements are no longer limited in silicon, and the dye precursors are not limited in rhodamines either. In this minireview, we would like to present this original concept as a tutorial guidance, then to briefly comment the major practices of this strategy, and finally to prospect the future trend of the element substituted fluorescent dyes.

A hallmark of cancer cells is a reversed transmembrane pH gradient, which could be exploited for robust and convenient intraoperative histopathological analysis. However, pathologically relevant pH changes are not significant enough for sensitive detection by conventional Henderson–Hasselbalch-type pH probes, exhibiting an acid–base transition width of 2 pH units. This challenge could potentially be addressed by a pH probe with a reduced acid–base transition width (i.e., Hill-type probe), appropriate pKa, and membrane permeability. Yet, a guideline to allow rational design of such small-molecule Hill-type pH probes is still lacking. We have devised a novel molecular mechanism, enabled sequential protonation with high positive homotropic cooperativity, and synthesized small-molecule pH probes (PHX1–3) with acid–base transition ranges of ca. 1 pH unit. Notably, PHX2 has a pKa of 6.9, matching the extracellular pH of cancer cells. Also, PHX2 is readily permeable to cell membrane and allowed direct mapping of...

Nitric oxide (NO) is a versatile endogenous molecule, involved in various physiological processes and implicated in the progression of many pathological conditions. Therefore, NO donors are valuable tools in NO related basic and applied applications. The traditional spontaneous NO donors are limited in scenarios where flux, localization, and dose of NO could be monitored. This has promoted the development of novel NO donors, whose NO release is not only under control, but also self-calibrated. Herein, we reported a phototriggered and photocalibrated NO donor (NOD565) with an N-nitroso group on a rhodamine dye. NOD565 is nonfluorescent and could release NO efficiently upon irradiation by green light. A bright rhodamine dye is generated as a side-product and its fluorescence can be used to monitor the NO release. The potentials of NOD565 in practical applications are showcased in in vitro studies, e.g., platelet aggregation inhibition and fungi growth suppression.

Caged-fluorophores are potentially suitable for photo-activated localization microscopy (PALM) for super-resolution imaging. N-Nitroso is a simple and robust photo-cage with biocompatible nitric oxide as the only byproduct upon photolysis. We herein reported a novel PALM probe (NOR535) for super-resolution imaging of lysosomes with high localization precision.

Based on the principle of supramolecular recognition and fluorescent chemical sensors, a novel kind of material for the separation of toxic heavy metal ions was designed and synthesized. Mesoporous silica nanoparticles MCM-41 with high surface areas and large ordered pores were used as the supporting matrix. Poly-amide derivative, was grafted to the mesoporous silica nanoparticles for extracting and separating trace Hg(2+) from aqueous solution, with a short adsorption time (t=3min) and a wide range of pH application (pH 3-11). The separation material could also extract trace mercury from Traditional Chinese Medicine, and has no influence on their effective components.

Synthetic dual-function ligands targeting specific DNA sequences and histone-modifying enzymes were applied to achieve regulatory control over multi-gene networks in living cells. Unlike the broad array of targeting small molecules for histone deacetylases (HDACs), few modulators are known for histone acetyltransferases (HATs), which play a central role in transcriptional control. As a novel chemical approach to induce selective HAT-regulated genes, we conjugated a DNA-binding domain (DBD) "I" to N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-benzamide (CTB), an artificial HAT activator. In vitro enzyme activity assays and microarray studies were used to demonstrate that distinct functional small molecules could be transformed to have identical bioactivity when conjugated with a targeting DBD. This proof-of-concept synthetic strategy validates the switchable functions of HDACs and HATs in gene regulation and provides a molecular basis for developing versatile bioactive ligands.

Classic fluorescent dyes, such as coumarin, naphthalimide, fluorescein, BODIPY, rhodamine, and cyanines, are cornerstones of various spectroscopic and microscopic methods, which hold a prominent position in biological studies. We recently found that 9-amino-benzo[c]cinnoliniums make up a novel group of fluorophores that can be used in biological studies. They are featured with a succinct conjugative push-pull backbone, a broad absorption band, and a large Stokes shift. They are potentially useful as a small-molecule alternative to R-phycoerythrin to pair with fluorescein in multiplexing applications.

Summary The altered metabolism of tumor cells confers a selective advantage for survival and proliferation, and studies have shown that targeting such metabolic shifts may be a useful therapeutic strategy. We developed an intensely fluorescent, rapidly responsive, pH-resistant, genetically encoded sensor of wide dynamic range, denoted SoNar, for tracking cytosolic NAD + and NADH redox states in living cells and in vivo. SoNar responds to subtle perturbations of various pathways of energy metabolism in real time, and allowed high-throughput screening for new agents targeting tumor metabolism. Among > 5,500 unique compounds, we identified KP372-1 as a potent NQO1-mediated redox cycling agent that produced extreme oxidative stress, selectively induced cancer cell apoptosis, and effectively decreased tumor growth in vivo. This study demonstrates that genetically encoded sensor-based metabolic screening could serve as a valuable approach for drug discovery.

We report herein an efficient, general and green method for decarboxylative fluorination of aliphatic carboxylic acids. By using a transition-metal-free, organocatalytic photoredox system, the reaction of various aliphatic carboxylic acids with the Selectfluor reagent afforded the corresponding alkyl fluorides in satisfactory yields under visible light irradiation at room temperature.

A reusable fluorescent material FCM, which was obtained through the dip-dyeing process of immobilizing the fluorescent sensor CM onto natural cotton fibers, exhibited high selectivity for detecting and separating Cd2+ in water.

A novel polycyclic aromatic molecule, i.e. 1-oxo-1H-phenalene-2,3-dicarbonitrile (compound 1, initially misidentified as 8-oxo-8H-acenaphtho[1,2-b]pyrrolecarbonitrile) was discovered by our group in 2005. This parent compound is highlighted for its unique oxidative S(N)Ar(H) (nucleophilic substitution of aromatic hydrogen) reactivity that provides easy approaches to diverse derivatives with different long-wavelength fluorescence and important biological activities. To date, a large number of derivatives have been synthesized and evaluated by several international research groups, indicating the formation of a new and valuable family of functional chemicals. Some members have been functionalized for molecular or nanoparticle-based probes applicable in chemical and environmental sensing, biomolecule imaging and tumor diagnosis. Others have qualified as high potency anticancer agents specifically targeting different functional proteins in tumor cells. With regard to the increasing attention paid to this new chemical family, it is a good time to review major achievements in order to promote further and deeper investigation.

A selective heterogeneous fluorescent sensor (FSM) for palladium was synthesized by grafting a small molecular fluorescent sensor onto mesoporous silica microspheres. FSM can selectively detect Pd2+ with a significant fluorescent quenching response, and the limit of detection was calculated to be 0.18 ppm. On the other hand, with silica microspheres as the matrix material, FSM is found to be able to remove trace palladium from water.

Using the self-assembly of aromatic boronic acids with Alizarin Red S (ARS), we developed a new chemosensor for the selective detection of peroxynitrite., Using the self-assembly of aromatic boronic acids with Alizarin Red S (ARS), we developed a new chemosensor for the selective detection of peroxynitrite. Phenylboronic acid (PBA), benzoboroxole (BBA) and 2-(N,N-dimethylaminomethyl)phenylboronic acid (NBA) were employed to bind with ARS to form the complex probes. In particular, the ARS–NBA system with a high binding affinity can preferably react with peroxynitrite over hydrogen peroxide and other ROS/RNS due to the protection of the boron via the solvent-insertion B–N interaction. Our simple system produces a visible colorimetric change and on–off fluorescence response towards peroxynitrite. By coupling a chemical reaction that leads to an indicator displacement, we have developed a new sensing strategy, referred to herein as RIA (Reaction-based Indicator displacement Assay).

A novel fluorescent probe, E3, was designed, synthesized and evaluated. It responded to Co2+ with high selectivity and sensitivity under physiological neutral conditions specifically. Furthermore, notably, probe E3 was demonstrated to detect Co2+ in living cells, indicative of its practical application potential.

Nitrite is a heavily assayed substrate in the fields of food safety, water quality control, disease diagnosis, and forensic investigation and more recently in basic biological studies on nitric oxide physiology and pathology. The colorimetric Griess assay and the fluorimetric 2,3-diaminonaphthalene (DAN) assay are the current gold standards for nitrite quantification. They are not without limitations, yet have amazingly survived 156 and 44 years, respectively, due to the lack of a practical alternative. Both assays exhibit slow detection kinetics due to inactivation of nucleophiles under strongly acidic media, require an extensive incubation time for reaction to go completion, and hence offer a limited detection throughput. By converting an intermolecular reaction of the Griess assay intramolecularly, we designed a novel probe (NT555) for nitrite detection, which displays superior detection kinetics and sensitivity. NT555 was constructed following our "covalent-assembly" probe design principle. Upon detection, it affords a gigantic bathochromic shift of the absorption spectrum and a sensitive turn-on fluorescence signal from a zero background, both of which are typical of an "assembly" type probe. Overall, NT555 has addressed various difficulties associated with the Griess and the DAN assays and represents an attractive alternative for practical applications.

Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is essential for for biosynthetic reactions and antioxidant functions; however, detection of NADPH metabolism in living cells remains technically challenging. We develop and characterize ratiometric, pH-resistant, genetically encoded fluorescent indicators for NADPH (iNap sensors) with various affinities and wide dynamic range. The iNap sensors permitted quantification of cytosolic and mitochondrial NADPH pools that were controlled by cytosolic NAD+ kinase levels, and revealed cellular NADPH dynamics under oxidative stress depending on glucose availability. We find that mammalian cells have a strong tendency to maintain physiological NADPH homeostasis, which is regulated by glucose-6-phosphate dehydrogenase (G6PD) and AMP kinase (AMPK). Moreover, using the iNap sensors we monitor NADPH fluctuations during the activation of macrophage cells or wound response in vivo. These data demonstrate that the iNap sensors will be valuable tools for monitoring NADPH dynamics in live-cells, and gaining new insights into cell metabolism.

Development of a molecular probe for selective detection of MeHg+ in the presence of Hg2+ is a mission impossible to accomplish. Speciation analysis of two substrates with a single kinetic trace exploiting their differential reactivity toward a single probe, i.e., multiplexing in the time domain, is a cost-effective and powerful alternative. We have developed such a probe (Hg410) for simultaneously quantification of Hg2+ and MeHg+ in aqueous media. Hg410 is designed via the “covalent-assembly” approach, displays a zero background, and bears a very concise molecular construct. It has harnessed proximity-based catalysis to achieve high reactivity toward Hg2+ and MeHg+. An unprecedentedly low detection limit of ca. 4.6 pM and 160 pM was measured for Hg2+ and MeHg+, respectively.

Protein vicinal dithiols play fundamental roles in intracellular redox homeostasis due to their involvement in protein synthesis and function through the reversible vicinal dithiol oxidation to disulfide. To provide quantitative information about the global distribution and dynamic changes of protein vicinal dithiols in living cells, we have designed and synthesized a ratiometric fluorescent probe (VTAF) for trapping of vicinal dithiol-containing proteins (VDPs) in living cells. VTAF exhibits a ratiometric fluorescence signal upon single excitation, which enables self-calibration of the fluorescence signal and quantification of endogenous vicinal dithiols of VDPs. Its potential for in situ dynamic tracing of changes of protein vicinal dithiols under different cellular redox conditions was exemplified. VTAF facilitated the direct observation of subcellular distribution of endogenous VDPs via ratiometric fluorescence imaging and colocalization assay. And the results suggested that there are abundant VDPs in mitochondria. Moreover, some redox-sensitive VDPs are also present on cell surface which can respond to redox stimulus. This ratiometric fluorescence technique presents an important extension to previous fluorescence intensity-based probes for trapping and quantifying protein vicinal dithiols in living cells, as well as its visible dynamic tracing of VDPs.

International audience; Recently, Apolygus lucorum (Hemiptera: Miridae) has become an important insect pest of Bt cotton and fruit trees in China. At present, the application of chemical insecticides is the main control option for this pest. We investigated the lethal effect of seven neonicotinoid insecticides on A. lucorum adults, including six commercialized neonicotinoids and a novel one, cycloxaprid, which is developed in China. In addition, we assessed the sublethal physiological (longevity, fecundity) and behavioral (preoviposition and oviposition periods) effects of LD10 (low lethal dose) and LD40 (moderate lethal dose) of cycloxaprid on the mirid bug. Lethal effect of the insecticides was determined using a topical exposure method; contact toxicity against the adults was ranked as follows: cycloxaprid, nitenpyram > clothianidin > acetamiprid, imidacloprid > thiamethoxam > dinotefuran. Among these insecticides, the toxicity of cycloxaprid against the adults was the highest; its LD50 value was 2.54 ng a.i .(active ingredient)/adult. Both LD10 (0.74 ng a. i./adult) and LD40 (1.98 ng a. i./ adult) of cycloxaprid induced sublethal effects in the adults; we observed a reduced longevity in males and the LD40 also shortened the longevity of females. In addition, the LD40 prolonged the pre-oviposition period and shortened the oviposition period of females, and it decreased their fecundity. The hatching rate of eggs laid by the females exposed to LD10 and LD40 greatly decreased (two-fold lower when exposed to LD40). Our results demonstrate that cycloxaprid is among the best candidate insecticides for controlling A. lucorum, and it showed significant lethal and sublethal effects on this mirid bug.

We have revisited the synthesis of a series of ICT fluorophores, which were reported to have a core structure of 8-oxo-8H-acenaphtho[1,2-b]pyrrol-9-carbonitrile. However, based on the 2D NMR and X-ray diffraction analysis, their core structure was corrected as 1-oxo-1H-phenalene-2,3-dicarbonitrile (1). Compound 1 shows a highly electron-deficient nature and can easily undergo oxidative SNArH reaction on the naphthyl ring to produce a series of novel ICT fluorophores. The regioselectivity of this substitution reaction was studied by introduction of representative nucleophiles. Moreover, due to the strong rigidity and efficient ICT nature, the obtained fluorescent dyes display very good spectroscopic properties even in an aqueous environment.

Naphthalimide has now become a class of most popular fluorophores for probe design, along with coumarin, fluorescein, rhodamine, BODIPY and cyanine. This account aims at the first-year graduate students as the primary audience and showcases the versatile design principles applicable to the naphthalimide fluorophore when designing a probe or label, with focused examples from the Qian research laboratory. We also provide a general synthetic scheme to naphthalimides of various substitution patterns.

Based on a semi-cyanine fluorophore, a selective turn-on fluorescent probe semi-CyHP for the detection of nitroreductase (NTR) and hypoxia was designed and synthesized. It can be activated by NTR and to restore the pull–push electronic systems of semi-CyHF, which strongly fluoresces at 556 nm. Besides, the investigation of the hypoxic tumor cell imaging with semi-CyHP was significant with minimal endogenous interference.

A ratiometric fluorescent probe for the detection of peroxynitrite (ONOO−) was developed based on a boronate receptor and intramolecular cyclization. It features fast response, good selectivity and high sensitivity with a detection limit of 35 nM. The potential in bio-imaging was exemplified in Hela cells.

A new naphthalimide-based fluorescent turn-on probe (ANAg) was developed for quantitative detection of iodide in aqueous solution. It exhibited a low nanomolar detection limit and high selectivity over other potentially interfering anions and implied the potential for practical applications.

A novel probe containing the azide–coumarin–aldehyde triad (S1) for hydrogen sulfide (H2S) was developed. The fluorophore for signaling is assembled in situ through a H2S triggered intramolecular reduction–cyclization cascade, and has a concomitant 10-fold enhancement of the fluorescent intensity at 520 nm. Fluorescence imaging of H2S in living cells proved its potential for biological application.