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Metal ions play an important role in various biological processes, their abnormal homeostasis in cells is related to many diseases, such as neurodegenerative disease, cancer and diabetes. Fluorescent imaging offers a unique route to detect metal ions in cells via a contactless and damage-free way with high spatial and temporal fidelity. Consequently, it represents a promising method to advance the understanding of physiological and pathological functions of metal ions in cell biology. In this highlight article, we will discuss recent advances in fluorescent imaging of metal ions by small-molecule sensors for understanding the role of metals in related diseases. We will also discuss challenges and opportunities for the design of small-molecule sensors for fluorescent detection of cellular metal ions as a potential method for disease diagnosis. [ABSTRACT FROM AUTHOR]

Abstract: A new ratiometric fluorescent probe for fluoride ions was developed which complexed fluoride by a tridentate receptor of boronic acid and imidazolium. In the current study, a tridentate receptor 1 with one ortho boronic acid and two imidazolium groups was designed. The boron center can co-operate with imidazolium to bind F−. The formation of B–F complex stabilizes the interaction between fluoride and imidazolium which induces a ratiometric fluorescence response. With the addition of F−, a strongly increased fluorescent emission centered at 370nm appears at the expense of the fluorescent emission centered at 445nm. [Copyright &y& Elsevier]

In this work, a 1,8-naphthalimide-derived fluorescent probe for H2S based on the thiolysis of dinitrophenyl ether is reported. This probe exhibits turn-on fluorescence detection of H2S in bovine serum and lysosome-targetable fluorescent imaging of H2S with excellent selectivity. [ABSTRACT FROM AUTHOR]

Abstract: A fluorescent chemosensor N-n-butyl-3,4-diamino-1,8-naphthalimide (DAN) for detecting NO was developed on the basis of 1,8-naphthalimide with a similar structure of o-phenylenediamine as a NO reaction site. Due to the interaction between the photoinduced electron transfer (PET) and the intramolecular charge transfer (ICT), the chemosensor exhibits a remarkable enhancement in the emission intensity that is ca. 160-fold increase and a blue shift in the emission wavelength after the addition of NO. Meanwhile, it displays a colorimetric response accompanied with a color change from yellow to colorless. The chemosensor DAN shows a high selectivity for NO in the presence of various reactive nitrogen species (RNS) and reactive oxygen species (ROS). Furthermore, DAN can be used for bioimaging of NO in living cells. [Copyright &y& Elsevier]

Due to the biological importance of nucleotides and related species, such as XNP (where X = adenosine (A), uridine (U), cytidine (C), guanosine (G), and N = mono, di, tri), FAD and NADH, the development of optical probes for these molecules has recently been an active area of research. This tutorial reviewfocuses on the contributions between 2004–2010 concerning the fluorescent or colorimetric sensors for these biomolecules, and is organized according to their target molecule's structural classification. [ABSTRACT FROM AUTHOR]

An ideal fluorescent probe should show the strongest affinity with the relevant target (binding-selectivity) by means of a selective fluorescence change (signal-selectivity). [15]aneNO2S2(1,4-dioxa-7,13-dithia-10-azacyclopentadecane) based probes usually show high binding selectivity for Ag+but signal selectivity for Hg2+, because Ag+can quench or silence the fluorescence. To amplify the Ag+binding to the greatest extent, a carbonyl group was positioned between 1,8-naphthalimide and [15]aneNO2S2which played a key role of displaying selective fluorescence enhancements with Ag+through increasing the oxidation potential of the fluorophore, blocking Ag+from sterically interacting with the naphthalimide fluorophore, and by acting as a sacrificial donor. Probe 2can detect Ag+with a selective fluorescence enhancement (∼14 fold) and high affinity (Ka= 1.64 × 105M−1). [ABSTRACT FROM AUTHOR]

Abstract: Two 4,5-disubstituted-1,8-naphthalimide derivatives 1 and 2 were synthesized as ratiometric fluorescent and colorimetric sensors for Cu2+, respectively. In 100% aqueous solutions of 1, the presence of Cu2+ induces a strong and increasing fluorescent emission centered at 478nm at the expense of the fluorescent emission of 1 centered at 534nm. Compound 2 senses Cu2+ by means of a colorimetric (primrose yellow to pink) method with a thorough quench in emission attributed to the deprotonation of the secondary amine conjugated to the naphthalimide fluorophore. 1-Cu2+ and 2-Cu2+ sense cyanide in ratiometric way via colorimetric and fluorescent changes. [Copyright &y& Elsevier]

Abstract: A new 7-nitrobenz-2-oxa-1,3-diazole (NBD) based colorimetric and fluorescence chemosensor for Zn2+, an ion involved in many biological processes, was designed and synthesized. The NBD-probe 1 displays a red-to-yellow color change and an enhancement of fluorescent intensity in the presence of an aqueous solution of Zn2+ ions (pH 7.2). Internal charge transfer (ICT) and photoinduced electron transfer (PET) mechanisms are responsible for these changes. The practical use of this probe was demonstrated by its application to the biologically relevant detection of Zn2+ ions in pancreatic β-cells. [Copyright &y& Elsevier]

Abstract: A new naphthalimide–calix[4]arene was synthesized as a two-faced and highly selective fluorescent chemosensor for Cu2+ or F−. This chemosensor displayed a selective fluorescence quenching effect only with Cu2+ among the various metal ions. On the other hand, among the various anions, the title chemosensor displayed a selective fluorescence quenching effect only with F−. The binding mode with F− was further investigated using fluorescence changes and 1H NMR experiments. [Copyright &y& Elsevier]

Abstract: A new fluorescent chemosensor bearing two imidazolium groups as well as two anthracene groups has been synthesized. This chemosensor displayed a highly selective fluorescence quenching effect and a unique excimer peak only with . The association constant of 1 with was calculated as >106 M−1. [Copyright &y& Elsevier]

Abstract: The design, synthesis, and photophysical evaluation of a new naphthalimide-based fluorescent chemosensor, N-butyl-4-[di-(2-picolyl)amino]-5-(2-picolyl)amino-1,8-naphthalimide (1), were described for the detection of Zn2+ in aqueous acetonitrile solution at pH 7.0. Probe 1 showed absorption at 451nm and a strong fluorescence emission at 537nm (Φ F=0.33). The capture of Zn2+ by the receptor resulted in the deprotonation of the secondary amine conjugated to 1,8-naphthalimide so that the electron-donating ability of the N atom would be greatly enhanced; thus probe 1 showed a 56nm red-shift in absorption (507nm) and fluorescence spectra (593nm, Φ F=0.14), respectively, from which one could sense Zn2+ ratiometrically and colorimetrically. The deprotonated complex, [(1-H)/Zn]+, was calculated at m/z 619.1800 and measured at m/z 618.9890. In contrast to these results, the emission of 1 was thoroughly quenched by Cu2+, Co2+, and Ni2+. The addition of other metal ions such as Li+, Na+, K+, Mg2+, Ca2+, Fe3+, Mn2+, Al3+, Cd2+, Hg2+, Ag+, and Pb2+ produced a nominal change in the optical properties of 1 due to their low affinity to probe 1. This means that probe 1 has a very high fluorescent imaging selectivity to Zn2+ among metal ions. [Copyright &y& Elsevier]

A flow injection system for the determination of organophosphate and carbamate pesticides is described. A sensitive fluorescence probe was synthesized and used as the pH indicator to detect the inhibition of the enzyme acetylcholinesterase (AChE). The percentage inhibition of enzyme activity is correlated to the pesticide concentration. Several parameters influencing the performance of the system are discussed. The detection limits of 3.5, 50, 12 and 25 μg/l for carbofuran, carbaryl, paraoxon and dichlorvos, in pure water, respectively were achieved with an incubation time of 10 min. A complete cycle of analysis, including incubation time, took 14 min. The detection system has been applied to the determination of carbofuran in spiked vegetable juices (Chinese cabbage and cole), achieving recovery values between 93.2 and 107% for Chinese cabbage juice and 108 and 118% for cole juice at the different concentration levels assayed. [Copyright &y& Elsevier]

Abstract: Poly(3,4-ethylenedioxythiophene) (PEDOT) stands out for its optimized conductivity, stability, and high degree of transparency which has led to its successful commercialization. These excellent properties of PEDOT are mostly ascribed to the alkylenedioxy bridge across the 3- and 4-positions, and thus much effort has been dedicated to synthesizing 3,4-ethylenedioxythiophene (EDOT) analogs. However, only few homologous compounds were successfully synthesized, such as 3,4-propylenedioxythiophene (PrDOT) or 3,4-(1,4-butylenedioxy)thiophene (BuDOT). In this Letter, we use Mitsunobu reaction to synthesize a series of 3,4-alkylenedioxythiophenes (ADOTs) derivatives with 8- to 16-membered rings. The eight-membered compounds were obtained in high or excellent yield. We also found that the 9- to 16-membered EDOT analogs were obtained in relatively low yield because of the competitive reaction to make dimers. Our method provides an easy way to modify ethylenedioxythiophenes (EDOTs), and these obtained ADOTs compounds are promising building blocks for the synthesis of functional π-conjugated systems used in material chemistry. [Copyright &y& Elsevier]

In the realm of cell research, membraneless organelles have become a subject of increasing interest. However, their ever‐changing and amorphous morphological characteristics have long presented a formidable challenge when it comes to studying their structure and function. In this paper, a fluorescent probe Nu‐AN is reported, which exhibits the remarkable capability to selectively bind to and visualize the nucleolus morphology, the largest membraneless organelle within the nucleus. Nu‐AN demonstrates a significant enhancement in fluorescence upon its selective binding to nucleolar RNA, due to the inhibited twisted intramolecular charge–transfer (TICT) and reduced hydrogen bonding with water. What sets Nu‐AN apart is its neutral charge and weak interaction with nucleolus RNA, enabling it to label the nucleolus selectively and reversibly. This not only reduces interference but also permits the replacement of photobleached probes with fresh ones outside the nucleolus, thereby preserving imaging photostability. By closely monitoring morphology‐specific changes in the nucleolus with this buffering fluorogenic probe, screenings for agents are conducted that induce nucleolar stress within living cells. [ABSTRACT FROM AUTHOR]

In this study, we have uncovered that trifluoroethylamine-substituted solvatochromic fluorophores maintain consistently high and stable fluorescence intensity in diverse polar environments, including highly polar and protic solvents. The 1,8-naphthalimide derivatives serve as a buffering fluorogenic indicator for lipid droplet morphology during the fusion process and ratiometric probe for microenvironment polarity based on Halo-tag technology. [ABSTRACT FROM AUTHOR]

Single‐molecule localization microscopy (SMLM) has found extensive applications in various fields of biology and chemistry. As a vital component of SMLM, fluorophores play an essential role in obtaining super‐resolution fluorescence images. Recent research on spontaneously blinking fluorophores has greatly simplified the experimental setups and extended the imaging duration of SMLM. To support this crucial development, this review provides a comprehensive overview of the development of spontaneously blinking rhodamines from 2014 to 2023, as well as the key mechanistic aspects of intramolecular spirocyclization reactions. We hope that by offering insightful design guidelines, this review will contribute to accelerating the advancement of super‐resolution imaging technologies. [ABSTRACT FROM AUTHOR]

Single‐molecule localization microscopy (SMLM) has found extensive applications in various fields of biology and chemistry. As a vital component of SMLM, fluorophores play an essential role in obtaining super‐resolution fluorescence images. Recent research on spontaneously blinking fluorophores has greatly simplified the experimental setups and extended the imaging duration of SMLM. To support this crucial development, this review provides a comprehensive overview of the development of spontaneously blinking rhodamines from 2014 to 2023, as well as the key mechanistic aspects of intramolecular spirocyclization reactions. We hope that by offering insightful design guidelines, this review will contribute to accelerating the advancement of super‐resolution imaging technologies. [ABSTRACT FROM AUTHOR]

Establishing a comprehensive understanding of the dynamical multiscale diffusion and reaction process is crucial for zeolite shape-selective catalysis and is urgently demanded in academia and industry. So far, diffusion and reaction for methanol and dimethyl ether (DME) conversions have usually been studied separately and focused on a single scale. Herein, we decipher the dynamical molecular diffusion and reaction process for methanol and DME conversions within the zeolite material evolving with time, at multiple scales, from the scale of molecules to single catalyst crystal and catalyst ensemble. Microscopic intracrystalline diffusivity is successfully decoupled from the macroscopic experiments and verified by molecular dynamics simulation. Spatiotemporal analyses of the confined carbonaceous species allow us to track the migratory reaction fronts in a single catalyst crystal and the catalyst ensemble. The constrained diffusion of DME relative to methanol alleviates the high local chemical potential of the reactant by attenuating its local enrichment, enhancing the utilization efficiency of the inner active sites of the catalyst crystal. In this context, the dynamical cross-talk behaviors of material, diffusion and reaction occurring at multiple scales is uncovered. Zeolite catalysis not only reflects the reaction characteristics of heterogeneous catalysis, but also provides enhanced, moderate or suppressed local reaction kinetics through the special catalytic micro-environment, which leads to the heterogeneity of diffusion and reaction at multiple scales, thereby realizing efficient and shape-selective catalysis. [ABSTRACT FROM AUTHOR]

The OXZEO (oxide−zeolite) bifunctional catalyst concept has enabled selective syngas conversion to a series of value-added chemicals and fuels such as light olefins, aromatics and gasoline. Herein we report for the first time a dynamic confinement of SAPO-17 cages on the selectivity control of syngas conversion observed during an induction period. Structured illumination microscopy, intelligent gravimetric analysis, UV-Raman, X-ray diffraction, thermogravimetry and gas chromatography-mass spectrometer analysis indicate that this is attributed to the evolution of carbonaceous species as the reaction proceeds, which gradually reduces the effective space inside the cage. Consequently, the diffusion of molecules is hindered and the hindering is much more prominent for larger molecules such as C4+. As a result, the selectivity of ethylene is enhanced whereas that of C4+ is suppressed. Beyond the induction period, the product selectivity levels off. For instance, ethylene selectivity levels off at 44% and propylene selectivity at 31%, as well as CO conversion at 27%. The findings here bring a new fundamental understanding that will guide further development of selective catalysts for olefin synthesis based on the OXZEO concept. [ABSTRACT FROM AUTHOR]

The visualization of self‐assembled structure and dynamics at the molecular level has become a powerful method to understand structure–function relationships of self‐assembly. Herein, we in situ real‐time imaged the dynamic process of benzyl‐naphthalimide dyes at the nanoscale and inspected their internal structure with minimum 2.8 nm localization accuracy through single‐molecule localization microscopy (SMLM) imaging. We monitored the growth process of three different assemblies in situ, which possessed highly heterogeneous dynamics with different shapes and growth rates. Furthermore, diverse growth rates were also found at different sites in the same assembly. These results highlight the application of super‐resolution microscopy techniques for real‐time visualization of internal assembled structure and dynamics in situ. [ABSTRACT FROM AUTHOR]

The visualization of self‐assembled structure and dynamics at the molecular level has become a powerful method to understand structure–function relationships of self‐assembly. Herein, we in situ real‐time imaged the dynamic process of benzyl‐naphthalimide dyes at the nanoscale and inspected their internal structure with minimum 2.8 nm localization accuracy through single‐molecule localization microscopy (SMLM) imaging. We monitored the growth process of three different assemblies in situ, which possessed highly heterogeneous dynamics with different shapes and growth rates. Furthermore, diverse growth rates were also found at different sites in the same assembly. These results highlight the application of super‐resolution microscopy techniques for real‐time visualization of internal assembled structure and dynamics in situ. [ABSTRACT FROM AUTHOR]

Simple Summary: A liquid biopsy has the characteristics of low trauma and easy acquisition in the diagnosis of cholangiocarcinoma. Many researchers try to find diagnostic or prognostic biomarkers of CCA through blood, urine, bile and other body fluids. Due to the close proximity of bile to the lesion and the stable nature, bile gradually comes into people's view. The evaluation of human bile diagnostic biomarkers is not only to the benefit of screening more suitable clinical markers but also of exploring the pathological changes of the disease. Cholangiocarcinoma (CCA) is a multifactorial malignant tumor of the biliary tract, and the incidence of CCA is increasing in recent years. At present, the diagnosis of CCA mainly depends on imaging and invasive examination, with limited specificity and sensitivity and late detection. The early diagnosis of CCA always faces the dilemma of lacking specific diagnostic biomarkers. Non-invasive methods to assess the degree of CAA have been developed throughout the last decades. Among the many specimens looking for CCA biomarkers, bile has gotten a lot of attention lately. This paper mainly summarizes the recent developments in the current research on the diagnostic biomarkers for CCA in human bile at the levels of the gene, protein, metabolite, extracellular vesicles and volatile organic compounds. [ABSTRACT FROM AUTHOR]

The escalating health threats posed by bacteria and the pressing issue of antibiotic resistance underscore the urgent need for selective detection technologies and antimicrobial reagents. Fluorescein's biocompatibility renders it the preferred fluorescent dye for in vivo imaging. This study reveals that compounds from the aliphatic chain-derived fluorescein series (BMP-alkyl) not only selectively stain and fluorescently image Gram-positive bacteria but also demonstrate the ability to rapidly eliminate them. The discovery of fluorescein's antibacterial properties is poised to have applications in antibiotic research due to its excellent biocompatibility. These amphiphilic BMP-alkyl compounds were easily synthesized through a one-step amidation process involving dicarboxyfluorescein and long-chain fatty amines. In aqueous solutions, the formed aggregates exhibited complete fluorescence quenching. Upon encountering the Gram-positive bacterial membrane, BMP-alkyl compounds underwent depolymerization, resulting in a single fluorescent molecule and the activation of fluorescence. Subsequently, as these amphiphilic fluoresceins continuously combined and entered the bacterial interior, the potential for bacterial membrane depolarization, membrane structure damage, and ultimately bacterial death ensued. [Display omitted] • Fluorescein was found to be fluorescent antibiotics against Gram-positive bacteria. • Aliphatic chain-derived fluorescein has dual functions of bacterial imaging and antibiotics. • Fluorescein aggregation and depolymerization modulates wash-free imaging of bacteria. • Antibacterial activity results from fluorescein's negative charge altering bacterial membrane potential. [ABSTRACT FROM AUTHOR]

The applications of nanoporous crystalline materials are closely related to the mass transfer of guest molecules. However, the fundamental knowledge of mass transfer, and in particular the surface barriers controlled by the permeation of guest molecules through the external surfaces of materials, is still incomplete. The diversity of surface permeability at the single‐crystal level, caused by the varying origins of surface transport resistance, hinders the rational materials design and needs better understanding. Herein, we probe the molecular transport in single zeolite crystals with fluorescent 4‐(4‐diethylaminostyryl‐1‐methylpyridinium iodide) (DAMPI) using super‐resolution structured illumination microscopy (SIM). It showed that both the inter‐ and intra‐crystal diversity of surface barriers could be monitored by detecting the diffusion behaviors on the center and surface planes in single crystals. This adds a new perspective for studying the origins of the surface barriers as well as the molecular transport mechanisms in nanoporous materials. [ABSTRACT FROM AUTHOR]

The applications of nanoporous crystalline materials are closely related to the mass transfer of guest molecules. However, the fundamental knowledge of mass transfer, and in particular the surface barriers controlled by the permeation of guest molecules through the external surfaces of materials, is still incomplete. The diversity of surface permeability at the single‐crystal level, caused by the varying origins of surface transport resistance, hinders the rational materials design and needs better understanding. Herein, we probe the molecular transport in single zeolite crystals with fluorescent 4‐(4‐diethylaminostyryl‐1‐methylpyridinium iodide) (DAMPI) using super‐resolution structured illumination microscopy (SIM). It showed that both the inter‐ and intra‐crystal diversity of surface barriers could be monitored by detecting the diffusion behaviors on the center and surface planes in single crystals. This adds a new perspective for studying the origins of the surface barriers as well as the molecular transport mechanisms in nanoporous materials. [ABSTRACT FROM AUTHOR]

Long‐term super‐resolution imaging appears to be increasingly important for unraveling organelle dynamics at the nanoscale, but is challenging due to the need for highly photostable and environment‐sensitive fluorescent probes. Here, we report a self‐blinking fluorophore that achieved 12 nm spatial resolution and 20 ms time resolution under acidic lysosomal conditions. This fluorophore was successfully applied in super‐resolution imaging of lysosomal dynamics over 40 min. The pH dependence of the dye during blinking made the fluorophore sensitive to lysosomal pH. This probe enables simultaneous dynamic and pH recognition of all lysosomes in the entire cell at the single‐lysosome‐resolved level, which allowed us to resolve whole‐cell lysosome subpopulations based on lysosomal distribution, size, and luminal pH. We also observed a variety of lysosome movement trajectories and different types of interactions modes between lysosomes. [ABSTRACT FROM AUTHOR]

Long‐term super‐resolution imaging appears to be increasingly important for unraveling organelle dynamics at the nanoscale, but is challenging due to the need for highly photostable and environment‐sensitive fluorescent probes. Here, we report a self‐blinking fluorophore that achieved 12 nm spatial resolution and 20 ms time resolution under acidic lysosomal conditions. This fluorophore was successfully applied in super‐resolution imaging of lysosomal dynamics over 40 min. The pH dependence of the dye during blinking made the fluorophore sensitive to lysosomal pH. This probe enables simultaneous dynamic and pH recognition of all lysosomes in the entire cell at the single‐lysosome‐resolved level, which allowed us to resolve whole‐cell lysosome subpopulations based on lysosomal distribution, size, and luminal pH. We also observed a variety of lysosome movement trajectories and different types of interactions modes between lysosomes. [ABSTRACT FROM AUTHOR]

Although doping can induce room‐temperature phosphorescence (RTP) in heavy‐atom free organic systems, it is often challenging to match the host and guest components to achieve efficient intersystem crossing for activating RTP. In this work, we developed a simple descriptor ΔE to predict host molecules for matching the guest RTP emitters, based on the intersystem crossing via higher excited states (ISCHES) mechanism. This descriptor successfully predicted five commercially available host components to pair with naphthalimide (NA) and naphtho[2,3‐c]furan‐1,3‐dione (2,3‐NA) emitters with a high accuracy of 83 %. The yielded pairs exhibited bright yellow and green RTP with the quantum efficiency up to 0.4 and lifetime up to 1.67 s, respectively. Using these RTP pairs, we successfully achieved multi‐layer message encryption. The ΔE descriptor could provide an efficient way for developing doping‐induced RTP materials. [ABSTRACT FROM AUTHOR]

Although doping can induce room‐temperature phosphorescence (RTP) in heavy‐atom free organic systems, it is often challenging to match the host and guest components to achieve efficient intersystem crossing for activating RTP. In this work, we developed a simple descriptor ΔE to predict host molecules for matching the guest RTP emitters, based on the intersystem crossing via higher excited states (ISCHES) mechanism. This descriptor successfully predicted five commercially available host components to pair with naphthalimide (NA) and naphtho[2,3‐c]furan‐1,3‐dione (2,3‐NA) emitters with a high accuracy of 83 %. The yielded pairs exhibited bright yellow and green RTP with the quantum efficiency up to 0.4 and lifetime up to 1.67 s, respectively. Using these RTP pairs, we successfully achieved multi‐layer message encryption. The ΔE descriptor could provide an efficient way for developing doping‐induced RTP materials. [ABSTRACT FROM AUTHOR]

The twisted intramolecular charge transfer (TICT) mechanism has guided the development of numerous bright and sensitive fluorophores. This review briefly overviews the history of establishing the TICT mechanism, and systematically summarizes the molecular design strategies in modulating the TICT tendency of various organic fluorophores towards different applications, along with key milestone studies and representative examples. Additionally, we also succinctly review the twisted intramolecular charge shuttle (TICS) and twists during photoinduced electron transfer (PET), and compare their similarities and differences with TICT, with emphasis on understanding the structure–property relationships between the twisted geometries and how they can directly affect the fluorescence of the molecules. Such structure–property relationships presented herein will greatly aid the rational development of fluorophores that involve molecular twisting in the excited state. [ABSTRACT FROM AUTHOR]

Although super‐resolution imaging offers an opportunity to visualize cellular structures and organelles at the nanoscale level, cellular heterogeneity and unpredictability still pose a significant challenge in the dynamic imaging of live cells. It is thus vital to develop better‐performing and more photostable probes for long‐term super‐resolution imaging. Herein, we report a probe, LD‐FG, for imaging lipid droplet (LD) dynamics using structured illumination microscopy (SIM). LD‐FG allows wash‐free imaging of LDs, owing to a hydrogen‐bond sensitive fluorogenic response. The replacement of photobleached LD‐FG by intact probe molecules outside the LDs ensures the long‐time stability of the fluorescence imaging. With this buffering fluorogenic probe, fast and unpredictable dynamic processes of LDs can be visualized. Using this probe, two LD coalescence modes were discovered. The dynamic imaging also allowed us to propose a new model of LD maturation during adipocyte differentiation, i.e. a fast LD coalescence followed by a slow ripening step. The excellent performance of LD‐FG makes the buffer strategy an effective method for designing fluorescent probes for cell dynamic imaging. [ABSTRACT FROM AUTHOR]

Although super‐resolution imaging offers an opportunity to visualize cellular structures and organelles at the nanoscale level, cellular heterogeneity and unpredictability still pose a significant challenge in the dynamic imaging of live cells. It is thus vital to develop better‐performing and more photostable probes for long‐term super‐resolution imaging. Herein, we report a probe, LD‐FG, for imaging lipid droplet (LD) dynamics using structured illumination microscopy (SIM). LD‐FG allows wash‐free imaging of LDs, owing to a hydrogen‐bond sensitive fluorogenic response. The replacement of photobleached LD‐FG by intact probe molecules outside the LDs ensures the long‐time stability of the fluorescence imaging. With this buffering fluorogenic probe, fast and unpredictable dynamic processes of LDs can be visualized. Using this probe, two LD coalescence modes were discovered. The dynamic imaging also allowed us to propose a new model of LD maturation during adipocyte differentiation, i.e. a fast LD coalescence followed by a slow ripening step. The excellent performance of LD‐FG makes the buffer strategy an effective method for designing fluorescent probes for cell dynamic imaging. [ABSTRACT FROM AUTHOR]

Abstract: G-quadruplexes, formed of four stranded guanine bases stabilized by monovalent cations, serve important role in cancer cell growth and control gene expression in telomere. Since there are various types of quadruplex structures, rapid and simple screening methods with high selectivity, sensitivity and nontoxicity are required for understanding about the biological roles of quadruplex DNA as well as in designing therapeutics. Herein, we report a pyrene-imidazolium derivative, JY-1, which can with high selectivity recognize G-quadruplex using fluorescence and NMR spectroscopy. This is the first example based on the imidazolium derivative, which can detect the G-quadruplex directly to utilize the excimer/monomer emission change in pyrene fluorophore. The selectivity of strong binding to a specific sequence can allow for quadruplex sensing and the detection method presented here is very simple, using fluorescence and NMR study. Also, the groove binding characteristic of JY-1 to the G-quadruplex has a relatively low nonspecific toxicity and the structure-specific differences in fluorescent character between DNA duplex and G-quadruplex may offer more discovery and application in biological study. [Copyright &y& Elsevier]

Fluorescent thermometers based on organic dyes play an important role in the visualization of dynamic temperature topography with high resolution. Many molecular thermometers contain two fluorophores with different temperature responses to achieve ratiometric temperature detection. However, the stability and reliability of such ratiometric thermometers are highly dependent on the susceptibility of the fluorophores towards photobleaching. Despite the use of single-fluorophore ratiometric thermometers in previous reports, the difficulty and complexity in their molecular design and synthesis severely hinder their widespread applicability. In this work, we have investigated the use of commercially available dyes (i.e., BD140 and LD688) with conformational isomers as ratiometric thermometers. Each of these dyes consists of a mixture of conformers with distinct UV-vis absorption and emission spectra. The thermal equilibrium of these conformers successfully enabled the development of ratiometric thermometers with good stability and reliability. [ABSTRACT FROM AUTHOR]

The rare examples of B–H bond activation in a frustrated radical pair regime have been observed by treatment of TEMPO radicals with Piers' borane HB(C6F5)2 or bis-borane, respectively. The resulting concomitant formation of zwitterionic products and geminal N/B frustrated Lewis pairs implied a one electron process. In addition, the reaction of a TEMPO/B(C6F5)3 pair with H2O·B(C6F5)3 was assumed to involve one-electron reduction of water. Our results provide insights into chemical bond (e.g. B–H and O–H) activation via a single electron transfer. [ABSTRACT FROM AUTHOR]

• Fluorescent probes for biothiols have been reviewed. • The recognition mechanisms of probes for biothiols have been discussed. • Metal complexes work as receptor, reporter, or both. • Probes were collected in tables for comparision. Biothiols are small molecules with important physiological functions. Their detection is mainly achieved by changing the fluorescence emission of fluorophores by the nucleophilic reaction ability of sulfhydryl groups. In recent years, based on the coordination ability of sulfhydryl groups and metals, many more fluorescent probes that recognize biothiols have also been reported. We think this is an appropriate time to review progress in this field. In this paper, we systematically reviewed biothiol fluorescent probes based on metal complexes, including metal complexes as acceptors and fluorescent dyes as reporters; or nucleophilic or reduction reactions as recognition mechanisms, and metal complexes as reporters; or a metal complex acts as both an acceptor and a reporter. [ABSTRACT FROM AUTHOR]

Subcellular pH plays a key role to modulate protein structures or specific active sites to impact diverse biological processes. The heterogeneity and high dynamics of intracellular pH require probes that can detect pH in the vicinity of the protein and have a wide pH response range. Here, we reported a protein proximity ligation fluorescent probe for super-resolution imaging of subcellular pH dynamics. Relying on SNAP-tag protein labeling technology, the pH-sensitive fluorophore BG-NDM based on photo-induced electron transfer mechanism was localized to the adjacent positions of the target protein in different subcellular organelles. The equilibrium between the non-fluorescent aggregate and the fluorogenic monomer enabled BG-NDM to have the ability of wash-free super-resolution imaging in live cells. And the wide pH response ranges from pH 6 to pH 12 made the probe have the ability of recognizing pH dynamics. The pH changes around functional proteins during mitophagy, cellular alkalosis and acidosis were revealed. Through long-term super-resolution imaging, we could further record the pH dynamics around mitochondrial proteins COX8A during mitochondrial contacts, fusion and fission at the resolution of a single mitochondria. [Display omitted] • Probe BG-NDM was used to super-resolution imaging of subcellular pH dynamics. • SNAP-tag labeling ensures that BG-NDM detects the pH near the protein of interest. • The aggregate/monomer equilibrium endowed BG-NDM wash-free imaging in living cells. • Mitochondrial pH dynamics was recorded with Long-term SIM imaging. [ABSTRACT FROM AUTHOR]

Imidazolium based receptors selectively recognize anions, and have received more and more attention. In 2006 and 2010, we reviewed the mechanism and progress of imidazolium salt recognition of anions, respectively. In the past ten years, new developments have emerged in this area, including some new imidazolium motifs and the identification of a wider variety of biological anions. In this review, we discuss the progress of imidazolium receptors for the recognition of anions in the period of 2010–2019 and highlight the trends in this area. We first classify receptors based on motifs, including some newly emerging receptors, as well as new advances in existing receptor types at this stage. Then we discuss separately according to the types of anions, including ATP, GTP, DNA and RNA. [ABSTRACT FROM AUTHOR]

Water is the most important substance in nature. Imitating the formation of natural materials, molecular sieves have been synthesized under hydrothermal conditions and applied in industry. Herein, we reveal an unforeseen observation on a very special water‐induced structural dynamic process of these materials. Dynamic and reversible breaking and forming of T‐O‐T bonds in silicoaluminophosphate (SAPO) occurs through interactions between gaseous water and the molecular‐sieve framework under mild hydrothermal conditions and is confirmed by detection of the incorporation of 17O from H217O into molecular‐sieve framework. Encapsulation of the bulky molecules trimethylphosphine and pyridine (kinetic diameters much larger than the pore size of SAPO‐34) into CHA cavities consolidated the water‐induced dynamic process. Consequently, new insights into the dynamic features of molecular sieves in water are provided. The ship‐in‐a‐bottle strategy based on these findings also open new fields for fine acidity identification and gives extra boost in shape‐selective catalysis. [ABSTRACT FROM AUTHOR]

Water is the most important substance in nature. Imitating the formation of natural materials, molecular sieves have been synthesized under hydrothermal conditions and applied in industry. Herein, we reveal an unforeseen observation on a very special water‐induced structural dynamic process of these materials. Dynamic and reversible breaking and forming of T‐O‐T bonds in silicoaluminophosphate (SAPO) occurs through interactions between gaseous water and the molecular‐sieve framework under mild hydrothermal conditions and is confirmed by detection of the incorporation of 17O from H217O into molecular‐sieve framework. Encapsulation of the bulky molecules trimethylphosphine and pyridine (kinetic diameters much larger than the pore size of SAPO‐34) into CHA cavities consolidated the water‐induced dynamic process. Consequently, new insights into the dynamic features of molecular sieves in water are provided. The ship‐in‐a‐bottle strategy based on these findings also open new fields for fine acidity identification and gives extra boost in shape‐selective catalysis. [ABSTRACT FROM AUTHOR]

Herein, we reported a simple, fast, and quantitative theoretical descriptor ΔGC‐O that allows accurate predictions of a wide range of spontaneously blinking rhodamines. ΔGC‐O denotes the Gibbs free energy differences between the closed and open forms of rhodamines and has a good linear relationship with experimental pKcycl values. This correlation affords an effective guide for the quantitative designs of spontaneously blinking rhodamines and eliminates trial‐and‐error. We have validated the predictive power of ΔGC‐O via the development of two spontaneously blinking rhodamines of different colors and enhanced brightness. We also demonstrated their super‐resolution imaging utilities in dynamic live‐cell imaging. We expect that ΔGC‐O will greatly facilitate the efficient creations of spontaneously blinking fluorophores and aid the advancements of super‐resolution bioimaging techniques. [ABSTRACT FROM AUTHOR]

Herein, we reported a simple, fast, and quantitative theoretical descriptor ΔGC‐O that allows accurate predictions of a wide range of spontaneously blinking rhodamines. ΔGC‐O denotes the Gibbs free energy differences between the closed and open forms of rhodamines and has a good linear relationship with experimental pKcycl values. This correlation affords an effective guide for the quantitative designs of spontaneously blinking rhodamines and eliminates trial‐and‐error. We have validated the predictive power of ΔGC‐O via the development of two spontaneously blinking rhodamines of different colors and enhanced brightness. We also demonstrated their super‐resolution imaging utilities in dynamic live‐cell imaging. We expect that ΔGC‐O will greatly facilitate the efficient creations of spontaneously blinking fluorophores and aid the advancements of super‐resolution bioimaging techniques. [ABSTRACT FROM AUTHOR]

Herein, we reported a simple, fast, and quantitative theoretical descriptor ΔGC‐O that allows accurate predictions of a wide range of spontaneously blinking rhodamines. ΔGC‐O denotes the Gibbs free energy differences between the closed and open forms of rhodamines and has a good linear relationship with experimental pKcycl values. This correlation affords an effective guide for the quantitative designs of spontaneously blinking rhodamines and eliminates trial‐and‐error. We have validated the predictive power of ΔGC‐O via the development of two spontaneously blinking rhodamines of different colors and enhanced brightness. We also demonstrated their super‐resolution imaging utilities in dynamic live‐cell imaging. We expect that ΔGC‐O will greatly facilitate the efficient creations of spontaneously blinking fluorophores and aid the advancements of super‐resolution bioimaging techniques. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen sulfide has emerged as an important biological messenger and much attention has been paid to the design of fluorescent probes for H2S to meet the requirement of accurate measurement of H2S. In this work, a new red emission fluorescent probe for H2S was developed based on the reduction reaction of azide with H2S to amine with the fluorophore of dicyanomethylenedihydrofuran because of its long excitation and emission wavelength. The probe has a high selectivity for H2S over competitive anions and sulfide-containing analytes. Finally, the probe was applied to sense H2S in living cells. [Copyright &y& Elsevier]

Inhibition of TICT can significantly increase the brightness of fluorescent materials. Accurate prediction of TICT is thus critical for the quantitative design of high‐performance fluorophores and AIEgens. TICT of 14 types of popular organic fluorophores were modeled with time‐dependent density functional theory (TD‐DFT). A reliable and generalizable computational approach for modeling TICT formations was established. To demonstrate the prediction power of our approach, we quantitatively designed a boron dipyrromethene (BODIPY)‐based AIEgen which exhibits (almost) barrierless TICT rotations in monomers. Subsequent experiments validated our molecular design and showed that the aggregation of this compound turns on bright emissions with ca. 27‐fold fluorescence enhancement, as TICT formation is inhibited in molecular aggregates. [ABSTRACT FROM AUTHOR]

Inhibition of TICT can significantly increase the brightness of fluorescent materials. Accurate prediction of TICT is thus critical for the quantitative design of high‐performance fluorophores and AIEgens. TICT of 14 types of popular organic fluorophores were modeled with time‐dependent density functional theory (TD‐DFT). A reliable and generalizable computational approach for modeling TICT formations was established. To demonstrate the prediction power of our approach, we quantitatively designed a boron dipyrromethene (BODIPY)‐based AIEgen which exhibits (almost) barrierless TICT rotations in monomers. Subsequent experiments validated our molecular design and showed that the aggregation of this compound turns on bright emissions with ca. 27‐fold fluorescence enhancement, as TICT formation is inhibited in molecular aggregates. [ABSTRACT FROM AUTHOR]

We reported fluorescent probes to image Zn2+ with plasma membrane-specific and Zn2+-specific fluorogenicities. The probes contained hydrophobic alkyl chains as membrane-anchored domains and hydrophilic zinc sensor ZTRS, and aggregated to display quenched fluorescence. Cells dissolved the aggregates and the liberated probes were dispersed on the outside of the cell plasma membrane. Aggregates that did not bind to the cell membrane still exhibited aggregation-induced fluorescence quenching after complexing with zinc ions, while probes anchored on the membrane surface exhibited a fluorescence-enhanced response upon recognition of zinc ions. [ABSTRACT FROM AUTHOR]

Charge transfer and separation are important processes governing numerous chemical reactions. Fundamental understanding of these processes and the underlying mechanisms is critical for photochemistry. Herein, we report the discovery of a new charge‐transfer and separation process, namely the twisted intramolecular charge shuttle (TICS). In TICS systems, the donor and acceptor moieties dynamically switch roles in the excited state because of an approximately 90° intramolecular rotation. TICS systems thus exhibit charge shuttling. TICSs exist in several chemical families of fluorophores (such as coumarin, BODIPY, and oxygen/carbon/silicon–rhodamine), and could be utilized to construct functional fluorescent probes (i.e. viscosity‐ or biomolecule‐sensing probes). The discovery of the TICS process expands the current perspectives of charge‐transfer processes and will inspire future applications. [ABSTRACT FROM AUTHOR]

Charge transfer and separation are important processes governing numerous chemical reactions. Fundamental understanding of these processes and the underlying mechanisms is critical for photochemistry. Herein, we report the discovery of a new charge‐transfer and separation process, namely the twisted intramolecular charge shuttle (TICS). In TICS systems, the donor and acceptor moieties dynamically switch roles in the excited state because of an approximately 90° intramolecular rotation. TICS systems thus exhibit charge shuttling. TICSs exist in several chemical families of fluorophores (such as coumarin, BODIPY, and oxygen/carbon/silicon–rhodamine), and could be utilized to construct functional fluorescent probes (i.e. viscosity‐ or biomolecule‐sensing probes). The discovery of the TICS process expands the current perspectives of charge‐transfer processes and will inspire future applications. [ABSTRACT FROM AUTHOR]