Versatile Fluorescent Probes for Imaging the Superoxide Anion in Living Cells and In Vivo

The superoxide anion (O₂^.−) is widely engaged in the regulation of cell functions and is thereby intimately associated with the onset and progression of many diseases. To ascertain the pathological roles of O₂^.− in related diseases, developing effective methods for monitoring O₂^.− in biological systems is essential. Fluorescence imaging is a powerful tool for monitoring bioactive molecules in cells and in vivo owing to its high sensitivity and high temporal-spatial resolution. Therefore, increasing numbers of fluorescent imaging probes have been constructed to monitor O₂^.− inside live cells and small animals. In this minireview, we summarize the methods for design and application of O₂^.−-responsive fluorescent probes. Moreover, we present the challenges for detecting O₂^.− and suggestions for constructing new fluorescent probes that can indicate the production sites and concentration changes in O₂^.− as well as O₂^.−-associated active molecules in living cells and in vivo.     

Polymer Lamellae as Reaction Intermediates in the Formation of Copper Nanospheres as Evidenced by In Situ X-ray Studies

The classical nucleation theory (CNT) is the most common theoretical framework used to explain particle formation. However, nucleation is a complex process with reaction pathways which are often not covered by the CNT. Herein, we study the formation mechanism of copper nanospheres using in situ X-ray absorption and scattering measurements. We reveal that their nucleation involves coordination polymer lamellae as pre-nucleation structures occupying a local minimum in the reaction energy landscape. Having learned this, we achieved a superior monodispersity for Cu nanospheres of different sizes. This report exemplifies the importance of developing a more realistic picture of the mechanism involved in the formation of inorganic nanoparticles to develop a rational approach to their synthesis.     

In Situ Synthesis of an Aptamer-Based Polyvalent Antibody Mimic on the Cell Surface for Enhanced Interactions between Immune and Cancer Cells

An ability to promote therapeutic immune cells to recognize cancer cells is important for the success of cell-based cancer immunotherapy. We present a synthetic method for functionalizing the surface of natural killer (NK) cells with a supramolecular aptamer-based polyvalent antibody mimic (PAM). The PAM is synthesized on the cell surface through nucleic acid assembly and hybridization. The data show that PAM has superiority over its monovalent counterpart in powering NKs to bind to cancer cells, and that PAM-engineered NK cells exhibit the capability of killing cancer cells more effectively. Notably, aptamers can, in principle, be discovered against any cell receptors; moreover, the aptamers can be replaced by any other ligands when developing a PAM. Thus, this work has successfully demonstrated a technology platform for promoting interactions between immune and cancer cells.     

Mechanochemical Reaction of Aromatic Ketones and Aldehydes in the Presence of Zn-ZnCl2

The solvent-free reactions of aromatic ketones and aldehydes in the presence of Zn-ZnCl2 were performed with the aid of high-speed vibration mill, Retsch MM200 mixer mill and Retsch RM100 mortar grinder to give pinacol coupling and reduction products in varying yields.     

Photoredox Catalysis of Aromatic β-Ketoesters for in Situ Production of Transient and Persistent Radicals for Organic Transformation

Radical formation is the initial step for conventional radical chemistry. Reported herein is a unified strategy to generate radicals in situ from aromatic β-ketoesters by using a photocatalyst. Under visible-light irradiation, a small amount of photocatalyst fac-Ir(ppy)₃ generates a transient α-carbonyl radical and persistent ketyl radical in situ. In contrast to the well-established approaches, neither stoichiometric external oxidant nor reductant is required for this reaction. The synthetic utility is demonstrated by pinacol coupling of ketyl radicals and benzannulation of α-carbonyl radicals with alkynes to give a series of highly substituted 1-naphthols in good to excellent yields. The readily available photocatalyst, mild reaction conditions, broad substrate scope, and high functional-group tolerance make this reaction a useful synthetic tool.     

Thin Layer Chromatographic and “In Situ” Spectrophotometric Determination of Products in Solid-Solid Thermal Reaction

Abstract

A method coupling thin layer chromatography and direct spectrophotometry is outlined. The visible spectra of the separated species were obtained by scanning, at constant intervals of wavelenght, the chromatographic plates in the reflectance mode. The method is applied to the determination of unknown products obtained in thermal solid-solid reactions between [Co(bipy)₂(en)]Cl₃ and NH₄Cl.     

Balancing the Crystallinity and Film Formation of Metal–Organic Framework Membranes through In Situ Modulation for Efficient Gas Separation

Polycrystalline metal–organic framework (MOF) layers hold great promise as molecular sieve membranes for efficient gas separation. Nevertheless, the high crystallinity tends to cause inter-crystalline defects/cracks in the nearby crystals, which makes crystalline porous materials face a great challenge in the fabrication of defect-free membranes. Herein, for the first time, we demonstrate the balance between crystallinity and film formation of MOF membrane through a facile in situ modulation strategy. Monocarboxylic acid was introduced as a modulator to regulate the crystallinity via competitive complexation and thus concomitantly control the film-forming state during membrane growth. Through adjusting the ratio of modulator acid/linker acid, an appropriate balance between this structural “trade-off” was achieved. The resulting MOF membrane with moderate crystallinity and coherent morphology exhibits molecular sieving for H₂/CO₂ separation with selectivity up to 82.5.     

Reaction between ortho‐Hydroxy Aromatic Aldehydes and Dialkyl Acetylenedicarboxylates in the Presence of Silica Gel in Solvent‐Free Conditions

A two‐component condensation reaction between an ortho‐hydroxy aromatic aldehyde and an electron‐poor acetylenic ester efficiently provides fully substituted electron‐poor aryl vinyl ethers and chromenes in a one‐pot reaction in the presence of silica‐gel in solvent‐free conditions.     

Study of Binary Rare－Earth Oxyfluoride for ODE Reaction and Their XRD ＆In－Situ Raman Characterization

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Biuret—A Crucial Reaction Intermediate for Understanding Urea Pyrolysis To Form Carbon Nitrides: Crystal-Structure Elucidation and In Situ Diffractometric,Vibrational and Thermal Characterisation

The crystal structure of biuret was elucidated by means of XRD analysis of single crystals grown through slow evaporation from a solution in ethanol. It crystallises in its own structure type in space group C2/c (a=15.4135(8) Å, b=6.6042(3) Å, c=9.3055(4) Å, Z=8). Biuret decomposition was studied in situ by means of temperature-programmed powder XRD and FTIR spectroscopy, to identify a co-crystalline biuret–cyanuric acid phase as a previously unrecognised reaction intermediate. Extensive thermogravimetric studies of varying crucible geometry, heating rate and initial sample mass reveal that the concentration of reactive gases at the interface to the condensed sample residues is a crucial parameter for the prevailing decomposition pathway. Taking these findings into consideration, a study on the optimisation of carbon nitride synthesis from urea on the gram scale, with standard solid-state laboratory techniques, is presented. Finally, a serendipitously encountered self-coating of the crucible inner walls by graphite during repeated synthetic cycles, which prove to be highly beneficial for the obtained yields, is reported.     

Sensitive Near-Infrared Fluorescent Probes for Thiols Based on Se?N Bond Cleavage: Imaging in Living Cells and Tissues

Cy-NiSe and Cy-TfSe were designed and synthesized as sensitive near-infrared (NIR) fluorescent probes for detecting thiols on the basis of Se N bond cleavage both in cells and in tissues. Since a donor-excited photoinduced electron transfer (d-PET) process occurs between the modulator and the fluorophore, Cy-NiSe and Cy-TfSe have weak fluorescence. On titration with glutathione, the free dye exhibits significant fluorescence enhancement. The two probes are sensitive and selective for thiols over other relevant biological species. They can function rapidly at pH 7.4, and their emission lies in the NIR region. Confocal imaging confirms that Cy-NiSe and Cy-TfSe can be used for detecting thiols in living cells and tissues.     

AuPt Bipyramid Nanoframes as Multifunctional Platforms for In Situ Monitoring of the Reduction of Nitrobenzene and Enhanced Electrocatalytic Methanol Oxidation

Multifunctional metal nanostructures with a hollow feature, especially for nanoframes, are highly attractive owing to their high surface-to-volume ratios. However, pre-grown metal nanocrystals are always involved during the preparation procedure, and a synthetic strategy without the use of a pre-grown template is still a challenge. In this article, a template-free strategy is reported for the preparation of novel AuPt alloy nanoframes through simply mixing HAuCl₄ and H₂PtCl₆ under mild conditions. The alloy nanostructures show a bipyramid-frame hollow architecture with the existence of only the ten ridges and absence of their side faces. This is the first report of bipyramid-like nanoframes and a template-free method under mild conditions. This configuration merges the plasmonic features of Au and highly active catalytic sites of Pt in a single nanostructure, making it an ideal multifunctional platform for catalyzing and monitoring the catalytic reaction in real time. The superior catalytic activity is demonstrated by using the reduction of nitrobenzene to the corresponding aminobenzene as a model reaction. More importantly, the AuPt nanoframes can track the reduction process on the basis of the SERS signals of the reactants, intermediates, and products, which helps to reveal the reaction mechanism. In addition, the AuPt nanoframes show much higher electrocatalytic properties toward the methanol oxidation reaction than commercial Pt/C electrocatalysts.     

Study on the Singlet and Triplet StateElectron Transfer between Hypocrellin A and Aromatic Amines in Solvents of Various Polarity

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Water-Mediated Strecker Reaction: An Efficient and Environmentally Friendly Approach for the Synthesis of α-Aminonitriles via a Three-Component Condensation

The synthesis of α-aminonitriles by a direct three component Strecker reaction has been achieved in water, which is found to be an inexpensive, non-toxic and eco-friendly reaction medium for the nucleophilic addition. This protocol is effective to a wide variety of substrates with different functional groups and does not require the use any other catalyst.     

Formation of (±)-1,2-O-Ethylidene-myo-Inositol During the Reaction Between Triethyl Orthoformate and myo-Inositol in DMSO

Besides myo-inositol monoorthoformate (1), (±)-1,2-O-ethylidene-myo-inositol (2) was obtained as another product in the reaction between triethyl orthoformate and myo-inositol in DMSO catalyzed by acid under N₂     

One‐Pot,Three‐Component Condensation Reaction in Water: An Efficient and Improved Procedure for the Synthesis of Pyran Annulated Heterocyclic Systems

Environmentally friendly three‐component condensation reactions of an activated C‐H acid, an aldehyde, and alkyl nitriles to afford the corresponding pyran annulated heterocyclic systems in water in good yields, avoiding the addition of any catalyst, are reported.     

The Role of Catalyst Formation–Deactivation Processes and Evidence for a Nonlinear Mechanism in the Mizoroki–Heck Reaction with Aryl Chlorides

Kinetics and Catalysis - An operando kinetic study was made of the Mizoroki–Heck reaction with low-reactive aryl chlorides using the most practically attractive “ligand-free”...     

Samarium Diiodide-Induced Reductive Cleavage of Se-St Bond in Arylselenotrimethylsilane Leading to the Formation of Samarium Arylselenolate: Synthesis of β-Arylseleno Estsrs and β-Arylseleno Nitriles

Theapplicationofsamariumdiiodideinorganicsynthesishasreceivedmoreandmoreattenhoninthelastdecadel4.ItisapoWerfuloneelectrontransferreductant.OurpreviousworkonthereduchvecleavageofC-S,S-S,Se-Se,Te-TeandS-StbondwithSInly-'hasledustoinvershgatethereduchvecleavageofSe-StbondbySInI2.Organoseleniumcompoundshaveattractedconsiderableinterestasreagentsandintermedieatesinorganicsynthesisrecently'-".Somemethodsforthepreparationof0selenoesterand6-selenonitrilehavebeenreported.AusefulapproachistheMi…     

Formation Constants for the Ternary Complexes of Vanadium(III), 2,2′-Bipyridine, and the Amino Acids Histidine, Cysteine, Aspartic and Glutamic Acids

In this study we report the stability constants and the speciation of the ternary vanadium(III) complexes with 2,2??-bipyridine (Bipy) and the amino acids histidine (HHis), cysteine (H₂Cys), aspartic acid (H₂Asp) and glutamic acid (H₂Glu) by means of potentiometric titrations employing 3.0 mol?dm^?3 KCl as the ionic medium at 25?°C. The potentiometric data were analyzed taking into account the hydrolysis of the vanadium(III) cation and the respective stability constants of the binary complexes and the acid?Cbase reactions of the ligands, which were kept fixed during the analysis. The complexes detected in the different systems are: in the vanadium(III)?CBipy?CHHis system, [V(HBipy)(HHis)]⁴⁺ and [V(HBipy)(H₂His)]⁵⁺; in the vanadium(III)?CBipy?CH₂Cys system, [V₂O(Bipy)(Cys)]²⁺; in the vanadium(III)?CBipy?CH₂Asp system, [V(Bipy) (Asp)]⁺, [V₂O(Bipy)(Asp)]²⁺, and V₂O(Bipy)₂(Asp)₂; and finally in the vanadium(III)?CBipy?CH₂Glu system, [V(Bipy)(H₂Glu)]³⁺ and [V(Bipy)(Glu)]⁺. The respective stability constants were determined and the specie distribution diagrams as a function of pH are briefly discussed.     

To Be or Not To Be? that is the Entropic,Enthalpic, and Molecular Interaction Dilemma in the Formation of (Water)20 Clusters and Methane Clathrate

A detailed analysis under a comprehensive set of theoretical and computational tools of the thermodynamical factors and of the intermolecular interactions behind the stabilization of a well known set of (water)₂₀ cavities and of the methane clathrate is offered in this work. Beyond the available reports of experimental characterization at extreme conditions of most of the systems studied here, all clusters should be amenable to experimental detection at 1 atm and moderate temperatures since 280 K marks the boundary at which, ignoring reaction paths, formation of all clusters is no longer spontaneous from the 20H₂O→(H₂O)₂₀ and CH₄+20H₂O→CH₄@5¹² processes. As a function of temperature, a complex interplay leading to the free energy of formation occurs between the destabilizing entropic contributions, mostly due to cluster vibrations, and the stabilizing enthalpic contributions, due to intermolecular interactions and the PV term, is best illustrated by the highly symmetric 5¹² cage consistently showing signs of stronger intermolecular bonding despite having smaller binding energy than the other clusters. A fluxional wall of attractive non-covalent interactions, arising because of the cumulative effect of a large number of tiny individual charge transfers to the interstitial region, plays a pivotal role stabilizing the CH₄@5¹² clathrate.