Synthesis of difluoromethylated spiropyrazolones via [3 + 2] cycloaddition of difluoroacetohydrazonoyl bromides with alkylidene pyrazolones.

An effective [3 + 2] cycloaddition reaction of difluoromethyl or trifluoromethyl hydrazonoyl bromides with alkylidene pyrazolones was disclosed. This method provides an efficient approach for accessing a variety of highly functionalized fluoroalkyl spiropyrazolones in good yields. This protocol also features some advantages such as easily available and stable substrates, simple operation procedures, and atom and step economy. The formation of (cis)- and (trans)-products was discussed.

Tandem Addition/Cyclization/Halogenation Reaction of Difluoromethylated N-Acylhydrazones with Allyltrimethylsilanes.

As novel difluoromethyl building blocks, difluoromethylated N-acylhydrazones react with allyltrimethylsilanes and the halogen source via a tandem addition/cyclization/halogenation strategy, which produces various difluoromethylpyrazoline compounds in good yields. The method features mild reaction conditions, broad substrate scopes, and a transition metal-free process with easy operation. It also proves that difluoromethylated N-acylhydrazones are useful difluoromethyl building blocks for the construction of difluoromethylated nitrogen heterocycles.

The cyclization/rearrangement of α-hydroxy ketones with trifluoromethyl N-acylhydrazones to synthesize multi-substituted trifluoromethyloxazolines.

A highly efficient and metal-free [3+2] cyclization/rearrangement reaction toward the synthesis of multisubstituted trifluoromethyloxazolines from α-hydroxyketones and trifluoromethyl N-acylhydrazones has been developed. The unprecedented rearrangement of the amide fragment under acidic conditions after cleavage of the N-N bond of acylhydrazones has opened up new avenues for the development of reactions involving trifluoromethyl N-acylhydrazones. DFT calculations show that the mechanism involves multiple proton transfer processes.

Synthesis of 3(2H)-furanone derivatives: p-TsOH/halotrimethylsilane promoted cycloketonization of γ-hydroxyl ynones.

A p-TsOH/halotrimethylsilane facilitated cycloketonization of γ-hydroxyl ynones is detailed. This methodology enables the one-step synthesis of polysubstituted 3(2H)-furanone products. It is remarkable that the reaction exhibits excellent regio- and chemoselectivity by the addition of very small quantities of p-toluenesulfonic acid and water.

Selective binding of retrotransposons by ZFP352 facilitates the timely dissolution of totipotency network.

Acquisition of new stem cell fates relies on the dissolution of the prior regulatory network sustaining the existing cell fates. Currently, extensive insights have been revealed for the totipotency regulatory network around the zygotic genome activation (ZGA) period. However, how the dissolution of the totipotency network is triggered to ensure the timely embryonic development following ZGA is largely unknown. In this study, we identify the unexpected role of a highly expressed 2-cell (2C) embryo specific transcription factor, ZFP352, in facilitating the dissolution of the totipotency network. We find that ZFP352 has selective binding towards two different retrotransposon sub-families. ZFP352 coordinates with DUX to bind the 2C specific MT2_Mm sub-family. On the other hand, without DUX, ZFP352 switches affinity to bind extensively onto SINE_B1/Alu sub-family. This leads to the activation of later developmental programs like ubiquitination pathways, to facilitate the dissolution of the 2C state. Correspondingly, depleting ZFP352 in mouse embryos delays the 2C to morula transition process. Thus, through a shift of binding from MT2_Mm to SINE_B1/Alu, ZFP352 can trigger spontaneous dissolution of the totipotency network. Our study highlights the importance of different retrotransposons sub-families in facilitating the timely and programmed cell fates transition during early embryogenesis.

Visible-Light-Induced Four-Component Ritter-Type Reaction: Access to ß-Trifluoromethyl Imides.

A visible-light-induced four-component Ritter-type reaction was developed for the synthesis of ß-trifluoromethyl imides from CF3Br, alkenes, carboxylic acids, and nitriles. This protocol features mild reaction conditions, a broad substrate scope, and excellent functional group compatibility. Furthermore, this method has been proven to be suitable for the late-stage diversification of drug molecules. A mechanism involving a Ritter-type reaction and Mumm rearrangement was proposed on the basis of the control experiments.

Molecular mechanisms of glycogen particle assembly in Escherichia coli.

It has been reported that glycogen in Escherichia coli has two structural states, that is, fragility and stability, which alters dynamically. However, molecular mechanisms behind the structural alterations are not fully understood. In this study, we focused on the potential roles of two important glycogen degradation enzymes, glycogen phosphorylase (glgP) and glycogen debranching enzyme (glgX), in glycogen structural alterations. The fine molecular structure of glycogen particles in Escherichia coli and three mutants (ΔglgP, ΔglgX and ΔglgP/ΔglgX) were examined, which showed that glycogen in E. coli ΔglgP and E. coli ΔglgP/ΔglgX were consistently fragile while being consistently stable in E. coli ΔglgX, indicating the dominant role of GP in glycogen structural stability control. In sum, our study concludes that glycogen phosphorylase is essential in glycogen structural stability, leading to molecular insights into structural assembly of glycogen particles in E. coli.

Visible Light Promotes Cascade Trifluoromethylation/Cyclization, Leading to Trifluoromethylated Polycyclic Quinazolinones, Benzimidazoles and Indoles.

Efficient visible-light-induced radical cascade trifluoromethylation/cyclization of inactivated alkenes with CF3Br, which is a nonhygroscopic, noncorrosive, cheap and industrially abundant chemical, was developed in this work, producing trifluoromethyl polycyclic quinazolinones, benzimidazoles and indoles under mild reaction conditions. The method features wide functional group compatibility and a broad substrate scope, offering a facile strategy to pharmaceutically produce valuable CF3-containing polycyclic aza-heterocycles.

Metaomics in Clinical Laboratory: Potential Driving Force for Innovative Disease Diagnosis.

Currently, more and more studies suggested that reductionism was lack of holistic and integrative view of biological processes, leading to limited understanding of complex systems like microbiota and the associated diseases. In fact, microbes are rarely present in individuals but normally live in complex multispecies communities. With the recent development of a variety of metaomics techniques, microbes could be dissected dynamically in both temporal and spatial scales. Therefore, in-depth understanding of human microbiome from different aspects such as genomes, transcriptomes, proteomes, and metabolomes could provide novel insights into their functional roles, which also holds the potential in making them diagnostic biomarkers in many human diseases, though there is still a huge gap to fill for the purpose. In this mini-review, we went through the frontlines of the metaomics techniques and explored their potential applications in clinical diagnoses of human diseases, e.g., infectious diseases, through which we concluded that novel diagnostic methods based on human microbiomes shall be achieved in the near future, while the limitations of these techniques such as standard procedures and computational challenges for rapid and accurate analysis of metaomics data in clinical settings were also examined.

Photoinduced Trifluoromethylation with CF3Br as a Trifluoromethyl Source: Synthesis of α-CF3-Substituted Ketones.

An efficient and novel photoinduced trifluoromethylation employing CF3Br as a trifluoromethyl source is described. With commercially accessible fac-Ir(III)(ppy)3 as the catalyst, radical trifluoromethylation between O-silyl enol ether and CF3Br occurs successfully. This method provides various α-CF3-substituted ketones with a broad substrate scope in good yields under mild reaction conditions.

Synthesis of 3-Trifluoromethyl-1,2,4-triazolines and 1,2,4-Triazoles via Tandem Addition/Cyclization of Trifluoromethyl N-Acylhydrazones with Cyanamide.

A tandem addition/cyclization reaction between trifluoromethyl N-acylhydrazones and cyanamide is described, which provides a novel and efficient process for the synthesis of polysubstituted 3-trifluoromethyl-1,2,4-triazolines and their derivatives. The method has the advantages of mild reaction conditions, a broad substrate scope, good product yields, and atom economy.

A Non-Degradative Extraction Method for Molecular Structure Characterization of Bacterial Glycogen Particles.

Currently, there exist a variety of glycogen extraction methods, which either damage glycogen spatial structure or only partially extract glycogen, leading to the biased characterization of glycogen fine molecular structure. To understand the dynamic changes of glycogen structures and the versatile functions of glycogen particles in bacteria, it is essential to isolate glycogen with minimal degradation. In this study, a mild glycogen isolation method is demonstrated by using cold-water (CW) precipitation via sugar density gradient ultra-centrifugation (SDGU-CW). The traditional trichloroacetic acid (TCA) method and potassium hydroxide (KOH) method were also performed for comparison. A commonly used lab strain, Escherichia coli BL21(DE3), was used as a model organism in this study for demonstration purposes. After extracting glycogen particles using different methods, their structures were analyzed and compared through size exclusion chromatography (SEC) for particle size distribution and fluorophore-assisted capillary electrophoresis (FACE) for linear chain length distributions. The analysis confirmed that glycogen extracted via SDGU-CW had minimal degradation.

Discrimination between Carbapenem-Resistant and Carbapenem-Sensitive Klebsiella pneumoniae Strains through Computational Analysis of Surface-Enhanced Raman Spectra: a Pilot Study.

In clinical settings, rapid and accurate diagnosis of antibiotic resistance is essential for the efficient treatment of bacterial infections. Conventional methods for antibiotic resistance testing are time consuming, while molecular methods such as PCR-based testing might not accurately reflect phenotypic resistance. Thus, fast and accurate methods for the analysis of bacterial antibiotic resistance are in high demand for clinical applications. In this pilot study, we isolated 7 carbapenem-sensitive Klebsiella pneumoniae (CSKP) strains and 8 carbapenem-resistant Klebsiella pneumoniae (CRKP) strains from clinical samples. Surface-enhanced Raman spectroscopy (SERS) as a label-free and noninvasive method was employed for discriminating CSKP strains from CRKP strains through computational analysis. Eight supervised machine learning algorithms were applied for sample analysis. According to the results, all supervised machine learning methods could successfully predict carbapenem sensitivity and resistance in K. pneumoniae, with a convolutional neural network (CNN) algorithm on top of all other methods. Taken together, this pilot study confirmed the application potentials of surface-enhanced Raman spectroscopy in fast and accurate discrimination of Klebsiella pneumoniae strains with different antibiotic resistance profiles. IMPORTANCE With the low-cost, label-free, and nondestructive features, Raman spectroscopy is becoming an attractive technique with great potential to discriminate bacterial infections. In this pilot study, we analyzed surfaced-enhanced Raman spectroscopy (SERS) spectra via supervised machine learning algorithms, through which we confirmed the application potentials of the SERS technique in rapid and accurate discrimination of Klebsiella pneumoniae strains with different antibiotic resistance profiles.

Synthesis of Difluoromethylated Pyrazoles by the [3 + 2] Cycloaddition Reaction of Difluoroacetohydrazonoyl Bromides.

As novel and efficient difluoromethyl building blocks, difluoroacetohydrazonoyl bromides have been synthesized for the first time. The synthetic utility of this reagent for the construction of difluoromethyl organic compounds is demonstrated by their effective regioselective [3 + 2] cycloaddition reactions with ynones, alkynoates, and ynamides. The reactions provide a novel and efficient protocol to access difluoromethyl-substituted pyrazoles in good to excellent yields.

Effects of NaCl Concentrations on Growth Patterns, Phenotypes Associated With Virulence, and Energy Metabolism in Escherichia coli BW25113.

According to the sit-and-wait hypothesis, long-term environmental survival is positively correlated with increased bacterial pathogenicity because high durability reduces the dependence of transmission on host mobility. Many indirectly transmitted bacterial pathogens, such as Mycobacterium tuberculosis and Burkhoderia pseudomallei, have high durability in the external environment and are highly virulent. It is possible that abiotic stresses may activate certain pathways or the expressions of certain genes, which might contribute to bacterial durability and virulence, synergistically. Therefore, exploring how bacterial phenotypes change in response to environmental stresses is important for understanding their potentials in host infections. In this study, we investigated the effects of different concentrations of salt (sodium chloride, NaCl), on survival ability, phenotypes associated with virulence, and energy metabolism of the lab strain Escherichia coli BW25113. In particular, we investigated how NaCl concentrations influenced growth patterns, biofilm formation, oxidative stress resistance, and motile ability. In terms of energy metabolism that is central to bacterial survival, glucose consumption, glycogen accumulation, and trehalose content were measured in order to understand their roles in dealing with the fluctuation of osmolarity. According to the results, trehalose is preferred than glycogen at high NaCl concentration. In order to dissect the molecular mechanisms of NaCl effects on trehalose metabolism, we further checked how the impairment of trehalose synthesis pathway (otsBA operon) via single-gene mutants influenced E. coli durability and virulence under salt stress. After that, we compared the transcriptomes of E. coli cultured at different NaCl concentrations, through which differentially expressed genes (DEGs) and differential pathways with statistical significance were identified, which provided molecular insights into E. coli responses to NaCl concentrations. In sum, this study explored the in vitro effects of NaCl concentrations on E. coli from a variety of aspects and aimed to facilitate our understanding of bacterial physiological changes under salt stress, which might help clarify the linkages between bacterial durability and virulence outside hosts under environmental stresses.

Applications of Raman Spectroscopy in Bacterial Infections: Principles, Advantages, and Shortcomings.

Infectious diseases caused by bacterial pathogens are important public issues. In addition, due to the overuse of antibiotics, many multidrug-resistant bacterial pathogens have been widely encountered in clinical settings. Thus, the fast identification of bacteria pathogens and profiling of antibiotic resistance could greatly facilitate the precise treatment strategy of infectious diseases. So far, many conventional and molecular methods, both manual or automatized, have been developed for in vitro diagnostics, which have been proven to be accurate, reliable, and time efficient. Although Raman spectroscopy (RS) is an established technique in various fields such as geochemistry and material science, it is still considered as an emerging tool in research and diagnosis of infectious diseases. Based on current studies, it is too early to claim that RS may provide practical guidelines for microbiologists and clinicians because there is still a gap between basic research and clinical implementation. However, due to the promising prospects of label-free detection and noninvasive identification of bacterial infections and antibiotic resistance in several single steps, it is necessary to have an overview of the technique in terms of its strong points and shortcomings. Thus, in this review, we went through recent studies of RS in the field of infectious diseases, highlighting the application potentials of the technique and also current challenges that prevent its real-world applications.

Spatiotemporal variations and reduction of air pollutants during the COVID-19 pandemic in a megacity of Yangtze River Delta in China.

In recent decades, air pollution has become an important environmental problem in the megacities of eastern China. How to control air pollution in megacities is still a challenging issue because of the complex pollutant sources, atmospheric chemistry, and meteorology. There is substantial uncertainty in accurately identifying the contributions of transport and local emissions to the air quality in megacities. The COVID-19 outbreak has prompted a nationwide public lockdown period and provides a valuable opportunity for understanding the sources and factors of air pollutants. The three-month period of continuous field observations for aerosol particles and gaseous pollutants, which extended from January 2020 to March 2020, covered urban, urban-industry, and suburban areas in the typical megacity of Hangzhou in the Yangtze River Delta in eastern China. In general, the concentrations of PM2.5-10, PM2.5, NOx, SO2, and CO reduced 58%, 47%, 83%, 11% and 30%, respectively, in the megacity during the COVID-Lock period. The reduction proportions of PM2.5 and CO were generally higher in urban and urban-industry areas than those in suburban areas. NOx exhibited the greatest reduction (>80%) among all the air pollutants, and the reduction was similar in the urban, urban-industry, and suburban areas. O3 increased 102%-125% during the COVID-Lock period. The daytime elevation of the planetary boundary layer height can reduce 30% of the PM10, PM2.5, NOx and CO concentrations on the ground in Hangzhou. During the long-range transport events, air pollutants on the regional scale likely contribute 40%-90% of the fine particles in the Hangzhou urban area. The findings highlight the future control and model forecasting of air pollutants in Hangzhou and similar megacities in eastern China.

N-Arylations of trifluoromethylated N-acylhydrazones with diaryliodonium salts as arylation reagents.

A novel and efficient N-arylation of trifluoromethylated N-acylhydrazones is described by using diaryliodonium salts as arylation reagents in the presence of copper salts. A wide variety of N-aryl acylhydrazones are obtained with good to excellent yields under mild reaction conditions.

Palladium-catalyzed sp2 and sp3 C-H bond activation and addition to isatin toward 3-hydroxy-2-oxindoles.

The first Pd(II)-catalyzed C-H addition to isatins by direct sp(2)/sp(3) C-H bond activation for the construction of 3-substituted-3-hydroxy-2-oxindoles is reported. The bidentate nitrogen ligands were found to promote this reaction. Specifically, the preliminary bioassay indicated that 3-(5-chlorobenzoxazole)-3-hydroxy-N-benzyl-2-oxindole (2w) is a new inhibitor of human kidney cancer and hepatocellular carcinoma cells. Moreover, this reaction system exhibits great functional group tolerance and requires no directing group, extra base, or additives.

A mild, selective copper-catalyzed oxidative phosphonation of α-amino ketones.

A novel and selective method of simple copper-salt catalyzed phosphonation of α-amino carbonyl compounds to afford imidoylphosphonates is reported. This reaction system has a broad reaction scope. The convenient and environmentally benign process makes this protocol very attractive.