Antibiotics-based fluorescent probes for selective labeling of Gram-negative and Gram-positive bacteria in living microbiotas

Gram-staining distinguishes bacteria into two major groups,Gram-positive and Gram-negative bacteria,and has become an essential technique in microbiology.However,Gram-staining is not compatible with living cells and thus limits its applications.Here,we report the development of a polymyxin B-based fluorescent probe that enables selective labeling of Gram-negative in the living microbiota samples.We first synthesized the polymyxin B-Cy3 conjugate and confirmed its specificity for labeling Gram-negative bacteria.In combination with a previously developed Gram-positive-specific fluorescent probe,we demonstrate two-color imaging of Gram-positive and Gram-negative bacteria in various kinds living microbiotas,including mouse gut,human oral,soil,and crude oil microbiotas,with high selectivity and coverage.Finally,a pilot use of the probes in staining bacteria on heat-fixed sputum smear was also demonstrated,showing its potentials in clinical microbiology.Our method provides a versatile tool for distinguishing Gram-positive and Gram-negative bacteria in both basic research and clinical settings.     

Palladium-catalyzed cycloaromatization polymerization of enediynes

Bergman cyclization has shown great promise in constructing conjugated polymers.However,the application of this reaction in polymer science is still limited due to the harsh reaction condition and ill-defined structure of the achieved polymers.To this end,the cycloaromatization polymerization of enediynes catalyzed by a series of transition metal catalysts is investigated in this work,by taking advantage of the coordination chemistry of the enediyne with the transition metal complexes.According to the nuclear magnetic resonance (NMR),Fourier transform infrared (FTIR),ultraviolet-visble (UV-Vis) spectroscopies and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis,the cycloaromatization polymerization of enediynes proceeds under milder conditions and in a more controlled manner in the presence of palladium(Ⅱ) complexes,giving structurally regulated conjugated polymers in high yields.     

Silane‐bridged diphosphine ligand for palladium‐catalyzed ethylene oligomerization

In this study, bis(diphenylphosphinemethyl)dimethyl silane ( L1 ) and its palladium(II) halide complex, L1 /PdCl₂ ( C1 ), were synthesized and characterized. Single‐crystal X‐ray analysis of the complex revealed bidentate coordination at the Pd center. In combination with methylaluminoxane (MAO) as co‐catalyst, C1 exhibited excellent catalytic activity and selectivity for ethylene dimerization toward butene. The maximum catalytic activity obtained from the C1 /MAO system for ethylene dimerization to yield butenes was 7.33 × 10⁵ g/(mol_Pd · h). The selectivity toward butene remained stable and high (> 96%) over the various conditions.     

The time-dependent cellular response mechanism upon exposure to zinc oxide nanoparticles

Zinc oxide nanoparticle is one of the nanomaterials people engaged most in their life and its health effect has been taken into concern. In this work, A549 cell line was used as cell model, and the cytotoxicity of zinc oxide nanoparticles was revealed to be concentration-dependent. Through the measurement of cellular proteome, much more differentially expressed proteins were observed after the cells being treated for 9 h than 24 h. Also, most of these proteins expressed in the pattern which showed a significant decrease after exposure to zinc oxide nanoparticles and then an increase at 24 h. Intracellular reactive oxygen species and glutathione determination indicated that high level of oxidative stress was presented in cell after treatment with zinc oxide nanoparticles for 9 h. It can be observed from western blot analysis that the expression of NF-κB p65, PNPase, and HSP90 rose significantly after 9 h of exposure. Thus, a deduction was reached that toxicity of nanoparticles consists both of particle toxicity and ion toxicity, and a long-time treatment may conceal the toxicity induced by particles. The conclusion we made highlighted the importance of exposure time in the study of nanoparticle toxicity and would provide a new perspective for studying toxicity mechanism of nanoparticles.     

Vertically aligned γ-AlOOH nanosheets on Al foils as flexible and reusable substrates for NH<Subscript>3</Subscript> adsorption

Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperature (25, 80, and 120 ?C) and time (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45 min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the assynthesized γ-AlOOH NSs exhibit an outstanding NH₃ adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH₃ adsorption on the in-plane of the γ-AlOOH NSs is explained by the Lewis acid/base theory. The H-bond interactions among the NH₃ molecules and the edge groups (-OH) further improve the capture ability of the nanosheets.     

Unraveling the Mechanisms of the Excited-State Intermolecular Proton Transfer (ESPT) for a D-π-A Molecular Architecture

Precise revealing the mechanisms of excited-state intermolecular proton transfer (ESPT) and the corresponding geometrical relaxation upon photoexcitation and photoionization remains a formidable challenge. In this work, the compound (E)-4-(((4H-1,2,4-triazol-4-yl)imino)methyl)-2,6-dimethoxyphenol (TIMDP) adopting a D-π-A molecular architecture featuring a significant intramolecular charge transfer (ICT) effect has been designed. With the presence of perchloric acid (35 %), TIMDP can be dissolved through the formation of a HClO₄–H₂O–OH(TIMDP)–N(TIMDP) hydrogen-bonding bridge. At the ground state, the ICT effect is dominant, giving birth to crystals of TIMDP. Upon external stimuli (e.g., UV light irradiation, electro field), the excited state is achieved, which weakens the ICT effect, and significantly promotes the ESPT effect along the hydrogen-bonding bridge, resulting in crystals of [HTIMDP]⁺ ⋅ [H₂O] ⋅ [ClO₄]⁻. As a consequence, the mechanisms of the ESPT can be investigated, which distorted the D-π-A molecular architecture, tuned the emission color with the largest Stokes shift of 242 nm, and finally, high photoluminescence quantum yields (12 %) and long fluorescence lifetimes (8.6 μs) have achieved. These results not only provide new insight into ESPT mechanisms, but also open a new avenue for the design of efficient ESPT emitters.     

Liquid-Repellent Metal Oxide Photocatalysts

Metal oxide photocatalysts (MOPCs) decompose organic molecules under illumination. However, the application of MOPCs in industry and research is currently limited by their intrinsic hydrophilicity because MOPCs can be wetted by most liquids. To achieve liquid repellency, the surface needs to possess a low surface energy, but most organic molecules with low surface energy are degraded by photocatalytic activity. Herein, current methods to achieve liquid repellency on MOPCs, while preventing degradation of hydrophobic coatings, are reviewed. Classically, composite materials containing MOPCs and hydrophobic organic compounds possess good liquid repellency. However, composites normally form irregular coatings and are hard to prepare on surfaces such as those that are mesoporous or nanostructured. In addition, the adhesion of composites to substrates is often weak, resulting in delamination. Recent studies have shown that the direct grafting reaction of polydimethylsiloxane (PDMS) from silicone oil (methyl-terminated PDMS) under illumination results in a stable polymer brush. This easy and simple grafting method allows us to create stable liquid-repellent surfaces on MOPCs of various types, structures, and sizes. In particular, super-liquid-repellent drops with an underlying air layer can be created on PDMS-grafted nano-/microstructured MOPCs. Potential applications of surfaces combining liquid repellency and photocatalytic activity are also discussed; thus offering new ways of using MOPCs in a wider range of applications.