Carbazole-based mitochondria-targeted fluorescent probes for in vivo viscosity and cyanide detection in cells and zebrafish.

Cells of most eukaryotic species contain mitochondria, which play a role in physiological processes such as cellular senescence, metabolism, and autophagy. Viscosity is considered a key marker for many illnesses and is involved in several crucial physiological processes. Cyanide (CN-) can target cytochrome-c oxidase, disrupting the mitochondrial electron transport chain and causing cell death through asphyxiation. In this study, a fluorescent probe named HL-1, which targets mitochondria and measures viscosity and CN- levels, was designed and synthesized. HL-1 is viscosity-sensitive, with a linear correlation coefficient of up to 0.992. In addition, HL-1 was found to change color substantially during a nucleophilic addition reaction with CN-, which has a low detection limit of 47 nM. HL-1 not only detects viscosity and exogenous CN- in SKOV-3 cells and zebrafish but also monitors viscosity changes during mitochondrial autophagy in real time. Furthermore, HL-1 has been used successfully to monitor changes in mitochondrial membrane potential during apoptosis. Endogenous CN- in plant samples was quantified. HL-1 provides new ideas for studying viscosity and CN-.

Epigenetic modifications of 45S rDNA associates with the disruption of nucleolar organisation during Cd stress response in Pakchoi.

The role of the nucleolus in Pakchoi response to Cd stress remains largely unknown. In this work, we focus on exploring the underling mechanism between nucleolus disruption and epigenetic modification in Cd stressed-Pakchoi. Our results indicated that the proportion of nucleolus disruption, decondensation of 45 S rDNA chromatin, and a simultaneous increase in 5' external transcribed spacer region (ETS) transcription were observed with increasing Cd concentration, accompanied by genome-wide alterations in the levels of histone acetylation and methylation. Further results showed that Cd treatment exhibited a significant increase in H3K9ac, H4K5ac, and H3K9me2 levels occurred in promoter regions of the 45 S rDNA. Additionally, DNA methylation assays in the 45 S rDNA promoter region revealed that individual site-specific hypomethylation may be engaged in the activation of 45 S rDNA transcription. Our study provides some molecular mechanisms for the linkage between Cd stress, rDNA epigenetic modifications, and nucleolus disintegration in plants.

A Small-Molecule Fluorescent Probe for the Detection of Mitochondrial Peroxynitrite.

Reactive oxygen species (ROS) are pivotal signaling molecules that control a variety of physiological functions. As a member of the ROS family, peroxynitrite (ONOO-) possesses strong oxidation and nitrification abilities. Abnormally elevated levels of ONOO- can lead to cellular oxidative stress, which may cause several diseases. In this work, based on the rhodamine fluorophore, we designed and synthesized a novel small-molecule fluorescent probe (DH-1) for ONOO-. Upon reaction with ONOO-, DH-1 exhibited a significant fluorescence signal enhancement (approximately 34-fold). Moreover, DH-1 showed an excellent mitochondria-targeting capability. Confocal fluorescence imaging validated its ability to detect ONOO- changes in HeLa and RAW264.7 cells. Notably, we observed the ONOO- generation during the ferroptosis process by taking advantage of the probe. DH-1 displayed good biocompatibility, facile synthesis, and high selectivity, and may have potential applications in the study of ONOO--associated diseases in biosystems.

A highly sensitive NIR fluorescence probe for hypoxia imaging in cells and ulcerative colitis.

Ulcerative colitis, a kind of inflammatory bowel disease (IBD), is caused by dysregulated immune response of intestinal bacteria. This chronic disorder can lead to a deficiency of O2 (hypoxia) in the colon microenvironment. Nitroreductase (NTR) is a highly expressed endogenous enzyme under hypoxia, so the detection of NTR can provide diagnostic information about ulcerative colitis. Herein, an ultrasensitive NTR-triggered fluorescence probe (WS-1-NO2) is developed for hypoxia imaging in ulcerative colitis. The probe shows a significant fluorescence enhancement (45-fold) after reacting with NTR, with an extremely low detection limit of 0.096 ng/mL. Furthermore, we apply it for fluorescence imaging of hypoxia in living cells, tumors and dextran sulphate sodium (DSS)-induced ulcerative colitis mouse models. We believe that the probe may be investigated as an effective potential tool for gaining insight into the hypoxia-relevant diseases, such as cancer and ulcerative colitis.

Dual-response near-infrared fluorescent probe for detecting cyanide and mitochondrial viscosity and its application in bioimaging.

Viscosity has a significant impact on aerobic respiration in mitochondria. Many foods contain cyanide (CN-) and can cause serious toxicity when consumed in excess. This study discusses the design and synthesis of a dual-response coumarin-based near-infrared fluorescent probe (CCB) for the simultaneous detection of mitochondrial viscosity and CN-. CCB and viscosity have a strong log-linear relationship with a correlation coefficient of 0.997. Additionally, CN- detection can be visualized using a colorimetric method with a detection limit as low as 0.22 µM. Test strips were prepared to facilitate CN- detection in plants. Additional studies have shown the remarkable biocompatibility of CCB, which may be used for real time detection of exogenous CN- and intracellular mitochondrial viscosity and in vivo bioimaging of viscosity in mice. The probe is crucial for understanding disorders connected with mitochondrial viscosity and identifying CN- in daily living.

Palladium-Catalyzed Asymmetric Cascade Intramolecular Cyclization/Intermolecular Michael Addition Reaction of Allenyl Benzoxazinones with 1-Azadienes.

We herein designed and synthesized allenyl benzoxazinones of a novel type, which were then involved in a Pd-catalyzed asymmetric cascade intramolecular cyclization/intermolecular Michael addition reaction with 1-azadienes. A broad range of chiral C2-functionalized quinoline derivatives were afforded in moderate to good yields (up to 93%) with high enantioselectivities (up to 93% ee) in this reaction.

A sensitive NIR mitochondria-targeting fluorescence probe for visualizing viscosity in living cells and mice.

Mitochondria are the powerhouses in cells, providing the energy needed for cellular activities. However, the abnormalities in the mitochondrial microenvironment (e.g., the increased viscosity) can lead to mitochondrial dysfunctions and diseases. Herein, we develop a series of near-infrared (NIR) fluorescence probes for the detection of viscosity. After screening, probe CQ-4 is selected since it shows a great fluorescence enhancement (89-fold) in the NIR window. Its specific response to viscosity is not influenced by pH, polarity and biological species. Under stimulation with monensin or nystatin, CQ-4 can measure the cellular viscosity changes with good biocompatibility. In addition, we can observe an increase of viscosity during starvation. CQ-4 is applied to distinguish cancer cells from normal cells based on the viscosity differences. Furthermore, the probe has been successfully applied to image viscosity in inflamed and tumor-bearing mice in vivo. Therefore, CQ-4 may contribute to the future study about viscosity in the physiological and pathological processes.

Activatable near-infrared fluorescent probe triggered by nitroreductase for in vivo ulcerative colitis hypoxia imaging.

Ulcerative colitis is a prevalent inflammatory disease caused by the intestinal bacterial infection. And it is related to the hypoxic degrees in the colon microenvironment. Hypoxia, a condition of imbalance in O2 supply and consumption, is accompanied by the overexpressed level of nitroreductase (NTR). Therefore, the NTR detection has been widely applied for the diagnosis of hypoxia-related diseases. In this study, we developed a novel near-infrared fluorescent probe (IW-1) for NTR. Upon reaction with NTR, IW-1 exhibited a significant fluorescence off-on response at 740 nm with a low detection limit of 0.043 µg/mL. Confocal fluorescence imaging verified its ability to detect the overexpression of NTR in cancer cells. More significantly, IW-1 was applied for in vivo hypoxia imaging in tumors and dextran sulphate sodium (DSS)-induced ulcerative colitis mouse model. We expect that the probe may present a new tool for better understanding the biological functions of NTR as well as revealing essential information about hypoxia-related pathological processes, including cancer and ulcerative colitis.

Technology for Position Correction of Satellite Precipitation and Contributions to Error Reduction-A Case of the '720' Rainstorm in Henan, China.

In July 2021, an extreme precipitation event occurred in Henan, China, causing tremendous damage and deaths; so, it is very important to study the observation technology of extreme precipitation. Surface rain gauge precipitation observations have high accuracy but low resolution and coverage. Satellite remote sensing has high spatial resolution and wide coverage, but has large precipitation accuracy and distribution errors. Therefore, how to merge the above two kinds of precipitation observations effectively to obtain heavy precipitation products with more accurate geographic distributions has become an important but difficult scientific problem. In this paper, a new information fusion method for improving the position accuracy of satellite precipitation estimations is used based on the idea of registration and warping in image processing. The key point is constructing a loss function that includes a term for measuring two information field differences and a term for a warping field constraint. By minimizing the loss function, the purpose of position error correction of quantitative precipitation estimation from FY-4A and Integrated Multisatellite Retrievals of GPM are achieved, respectively, using observations from surface rain gauge stations. The errors of different satellite precipitation products relative to ground stations are compared and analyzed before and after position correction, using the '720' extreme precipitation in Henan, China, as an example. The experimental results show that the final run has the best performance and FY-4A has the worse performance. After position corrections, the precipitation products of the three satellites are improved, among which FY-4A has the largest improvement, IMERG final run has the smallest improvement, and IMERG late run has the best performance and the smallest error. Their mean absolute errors are reduced by 23%, 14%, and 16%, respectively, and their correlation coefficients with rain gauge stations are improved by 63%, 9%, and 16%, respectively. The error decomposition model is used to examine the contributions of each error component to the total error. The results show that the new method improves the precipitation products of GPM primarily in terms of hit bias. However, it does not significantly reduce the hit bias of precipitation products of FY-4A while it reduces the total error by reducing the number of false alarms.

Visual monitoring of the mitochondrial pH changes during mitophagy with a NIR fluorescent probe and its application in tumor imaging.

Mitophagy, a mitochondria-selective autophagy process, plays critical roles in maintaining intracellular homeostasis by removing the damaged mitochondria and recycling the nutrients in a lysosome-dependent manner. Mitophagy process could result in the changes of mitochondrial pH. So fluorescent probes for detecting mitochondrial pH during mitophagy are highly needed for exploring the functions of mitochondria. Herein, a series of near-infrared pH probes were designed based on the rhodamine framework. The probes showed high sensitivity for pH with the tunable pKa from 4.74 to 6.54. Particularly, for probe 5 (with the pKa of 6.54), a linear relationship between fluorescence intensity and pH in the range of 5.6-7.2 was observed, which was suitable for mitochondrial pH detection. The probe displayed excellent mitochondria-targeting ability. It was applied to monitor pH changes during mitophagy caused by starvation. Besides, in vivo non-invasive visualization of tumor pH variations was achieved via the fluorescence imaging in the near-infrared region. We anticipate that the probe may be a useful tool for revealing essential information about mitophagy-related research and clinical tumor diagnosis.

Benzoindoxazine derivatives containing carbazole for detection of CN- and its application in plant seed extracts and cell imaging.

Cyanide (CN-) is a highly toxic compound that exists in many substances and is harmful to the environment and human health. Therefore, it is of great significance to develop excellent CN- ion probes, especially solvent-induced on-off fluorescent probes. Based on the condensation reaction of indolo[2,1-b][1,3]oxazine molecules with aldehydes, probes (E)-13a-(2-(9-ethyl-9H-carbazol-3-yl)vinyl)-14,14-dimethyl-10-nitro-13a,14-dihydro-8H-benzo[e]benzo[5,6][1,3]oxazino[3,2-a]indole (NCO) and (E)-13a-(2-(9-benzyl-9H-carbazol-3-yl)vinyl)-14,14-dimethyl-10-nitro-13a,14-dihydro-8H-benzo[e]benzo[5,6][1,3]oxazino[3,2-a]indole (NBO) were synthesized to detect CN-. Compared with other cyanogen ion probes, NCO and NBO have special carbazole ring structures and large conjugate systems. When CN- is added to the probe-detection solution, color changes that are visible to the naked eye can occur. The UV-vis spectrum test using differential spectroscopy shows that the probe (i) has excellent solvent-induced switching characteristics and stability (CH3OH-H2O) and (ii) high selectivity, anti-interference ability, and sensitivity for the detection of CN-. The fluorescence limit of detections (LODs) are 1.05 µM for NCO and 1.34 µM for NBO. The UV LODs are 0.83 µM for NCO and 0.87 µM for NBO. Fluorescence spectroscopy shows that the probe has remarkable fluorescence properties. Fluorescence titration experiments, liver cancer cell (Hep G2) imaging, and cytotoxicity experiments all show that the probes have high biocompatibility, low toxicity, high cell permeability, and high sensitivity for the detection of CN- in cells. In addition, NCO and NBO have been successfully used for the detection of cyanogenic glycosides in the seeds of ginkgo, crabapple, apple, and cherry. Test strips were fabricated to detect CN-. After adding CN-, the color of the test strip changed significantly-from brown to light yellow; thus, the test strips have a high application value in the fields of drug quality control, drug safety testing, and pharmacological research.

A near-infrared fluorescent probe based on the hemicyanine skeleton for the detection of hydrogen peroxide in vivo.

As a member of the reactive oxygen species, hydrogen peroxide (H2O2) plays critical roles in oxidative stress and cell signaling. Intracellular abnormal levels of H2O2 production are closely related to many diseases. Therefore, the real-time monitoring of H2O2 in the cells is important. In this work, we designed a novel fluorescent probe (Mito-H2O2) for the specific detection of H2O2 based on the hemicyanine skeleton, with bright near-infrared fluorescence emission. Mito-H2O2 displayed fast response, excellent water-solubility and great fluorescence intensity enhancement after the addition of H2O2. Furthermore, Mito-H2O2 has been successfully applied to image both of the exogenous and endogenous H2O2 in cells and mice with negligible cytotoxity.

Polar Vortex Multi-Day Intensity Prediction Relying on New Deep Learning Model: A Combined Convolution Neural Network with Long Short-Term Memory Based on Gaussian Smoothing Method.

The variation of polar vortex intensity is a significant factor affecting the atmospheric conditions and weather in the Northern Hemisphere (NH) and even the world. However, previous studies on the prediction of polar vortex intensity are insufficient. This paper establishes a deep learning (DL) model for multi-day and long-time intensity prediction of the polar vortex. Focusing on the winter period with the strongest polar vortex intensity, geopotential height (GPH) data of NCEP from 1948 to 2020 at 50 hPa are used to construct the dataset of polar vortex anomaly distribution images and polar vortex intensity time series. Then, we propose a new convolution neural network with long short-term memory based on Gaussian smoothing (GSCNN-LSTM) model which can not only accurately predict the variation characteristics of polar vortex intensity from day to day, but also can produce a skillful forecast for lead times of up to 20 days. Moreover, the innovative GSCNN-LSTM model has better stability and skillful correlation prediction than the traditional and some advanced spatiotemporal sequence prediction models. The accuracy of the model suggests important implications that DL methods have good applicability in forecasting the nonlinear system and vortex spatial-temporal characteristics variation in the atmosphere.

Revealing the Dynamic Process of Ion Pair Recognition by Calix[4]pyrrole: A Case Study of Cesium Chloride.

Ion pair receptors based on meso-octamethylcalix[4]pyrrole (CP) have been extensively investigated over recent years. However, the nature of their ion pair recognition has barely been reported, even for CP itself. Herein, cesium chloride was used as a guest ion pair to investigate the dynamic process of ion pair recognition by CP, and the "capture-bind" mechanism for this process is proposed for the first time. The results reveal that Cs+ can be first captured by Cl- at long distances, and then it is bound to the cavity through almost equal contributions of Cl- and CP. Although the effective charge of Cl- is obviously reduced by charge-transfer, the electrostatic interactions between Cl- and Cs+ are still strong even at long distances in the presence of CP.

Construction of cyclopentane-fused coumarins via DBU-catalyzed [3+2] cycloaddition of 3-homoacyl coumarins with cyclic 1-azadienes.

The metal-free DBU catalyzed [3+2] cycloaddition of 3-homoacyl coumarins with cyclic 1-azadienes proceeded smoothly to furnish the corresponding highly functionalized cyclopentane-fused coumarins with excellent diastereoselectivity and complete chemoselectivity and in good yields under mild conditions.

Rapid and selective visualization of mitochondrial hypochlorite by a red region water-soluble fluorescence probe.

Hypochlorite (-OCl) has long been recognized as an effective microbicidal agent in immune system. Herein, we report the design, preparation and spectral characteristics of a -OCl fluorescent probe (FI-Mito). The probe exhibited remarkable fluorescence turn-on signal in the red region upon -OCl titration with the detection limit as low as 0.9 nM. FI-Mito displayed specific response for -OCl in completely aqueous solution. Meanwhile, the introduction of quaternized pyridine realized mitochondria-targeting ability. FI-Mito was further applied to monitor the generation of endogenous -OCl in the mitochondria of macrophage cells and mice. Therefore, it was established that FI-Mito may serve as a useful molecular tool for -OCl detection in vivo.

Synthesis of 1,4-diazepinone derivatives via a domino aza-Michael/SN2 cyclization of 1-azadienes with α-halogenoacetamides.

A novel cyclization of α-halogenoacetamides with 1-azadienes has been developed for the efficient preparation of monocyclic 1,4-diazepinones in one step under transition metal-free conditions. Various α-halogenoacetamides and 1-azadienes are well tolerated and give the desired products in good to excellent yields. This cyclization also demonstrates potential synthetic utility on a gram-scale and further transformation.

A near-infrared rhodamine-based lysosomal pH probe and its application in lysosomal pH rise during heat shock.

Heat shock is a potentially fatal condition characterized by high body temperature (>40 °C), which may lead to physical discomfort and dysfunctions of organ systems. Acidic pH environment in lysosomes can activate enzymes, thus facilitating the degradation of proteins in cellular metabolism. Owing to the lack of a practical research tool, it remains difficult to exploit relationship between heat shock and lysosome. Herein, a NIR lysosomal pH chemosensor (NRLH) was developed. One typical lysosome-locating group, morpholine, was incorporated into NRLH. The fluorescence intensity showed pH-dependent characteristics and responded sensitively to pH fluctuations in the pH range of 3.0-5.5. NRLH with a pKa of 4.24 displayed rapid response and high selectivity for H+ among common species. We also demonstrated NRLH was capable of targeting lysosomes. Importantly, NRLH was applied in cellular imaging and the data revealed that lysosomal pH increased but never decreased during the heat shock. Therefore, NRLH may act as an effective molecular tool for exploring the mechanisms of heat-related pathology in bio-systems.

A new ratiometric fluorescent probe for sensing lysosomal HOCl based on fluorescence resonance energy transfer strategy.

In this paper, ratiometric imaging of lysosomal HOCl was realized with a molecular probe (CR-Ly) based on fluorescence resonance energy transfer by using coumarin as the donor and rhodamine as acceptor. CR-Ly showed high sensitivity and fast response to HOCl. Moreover, CR-Ly exhibited excellent selectivity and sensitivity for HOCl over other biologically relevant species. Furthermore, it was successfully utilized to image the endogenous HOCl with low cytotoxity. And CR-Ly was capable of targeting lysosomes and monitoring lysosomal hypochlorous acid changes owing to the presence of the morpholine moiety. We believe that probe CR-Ly would be helpful to further research on the HOCl-associated diseases in lysosomes.

A ratiometric fluorescent probe for lysosomal hypochlorous acid based on through-bond energy transfer strategy.

In this paper, we synthesized a ratiometric fluorescence probe (IRh-Ly) for lysosomal hypochlorous acid (HOCl) by adopting a through-bond energy transfer (TBET) strategy on rhodamine-imidazo[1,5-a]pyridine platform. IRh-Ly showed brilliant selectivity, rapid response for HOCl. The probe also exhibited high sensitivity with the detection limit calculated to be 10.2 nM. Moreover, we demonstrated its successful application of detecting lysosomal HOCl in living RAW264.7 cells. Notably, the morpholine was integrated into the fluorescent probe IRh-Ly and the results revealed that IRh-Ly could target lysosome and detect the lysosomal HOCl. All the unique features made IRh-Ly particularly suitable for ratiometric HOCl detection and bio-imaging applications.