New Dammarane‐Type Saponins from the Rhizomes of Panax japonicus

Phytochemical investigation of the rhizomes of Panax japonicus C. A. Meyer (Araliaceae) resulted in the isolation of two new dammarane‐type triterpenoid saponins, yesanchinoside R₁ ( 1 ) and yesanchinoside R₂ ( 2 ), together with one new natural product, 6′′′‐O‐acetylginsenoside Re ( 3 ). In addition, 25 known compounds, including 23 triterpenoid saponins, 4 – 26 , β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 27 ), and ecdysterone ( 28 ), were also identified. The known saponins 12, 15 , and 18 – 22 were reported for the first time from the title plant. Their structures were elucidated on the basis of detailed spectroscopic analyses, including 1D‐ and 2D‐NMR techniques, as well as acidic hydrolysis.     

N-(4-(di-tert-butyl[F]fluorosilyl)benzyl)-2-hydroxy-N,N-dimethylethylammonium bromide ([F]SiFANBr): A novel lead compound for the development of hydrophilic SiFA-based prosthetic groups for F-labeling

¹⁸F-labeled compounds play a major role in the development of new in vivo imaging agents for Positron Emission Tomography (PET), a non invasive imaging modality depicting the biodistribution of radioactive compounds in humans. Recently we reported a new method for the introduction of fluorine-18 into a range of organic molecules exploiting the very fast ¹⁸F-¹⁹F isotope exchange of fluorosilanes (termed SiFA compounds). Here, we wish to report the labeling of the first charged SiFA molecule N-(4-(di-tert-butylfluorosilyl)benzyl)-2-hydroxy-N,N-dimethylethylammonium bromide (SiFAN⁺Br⁻) serving as a lead compound in the development of SiFA-based prosthetic groups of reduced lipophilicity for biomolecule labeling. Mild conditions for synthesis of [¹⁸F]SiFAN⁺Br⁻ and an easy purification procedure using simple C-18 solid phase cartridge have been developed yielding the [¹⁸F]SiFAN⁺Br⁻ in radiochemical yields of 34% (non-decay corrected) within 40 min. A series of kinetic experiments were performed that show high isotopic exchange rate constants. Low activation energy (15.7 kcal/mol) and a large preexponential factor (7.9 × 10¹³ M⁻¹ s⁻¹) were calculated for the isotopic exchange reaction from a corresponding Arrhenius plot. For comparison, the ¹⁸F-fluorination of ethyleneglycol-di-p-tosylate via the formation of a carbon-¹⁸F bond showed a 1.3 kcal/mol higher activation energy and a much lower preexponential factor of 2.9 × 10⁹ M⁻¹ s⁻¹. Moderate hydrophilicity (log D = 0.44), stability in aqueous media at pH up to 7.4 and a high specific activity of [¹⁸F]SiFAN⁺Br⁻ (SA = 20.4 GBq/μmol, 0.55 Ci/μmol) make this charged SiFA compound useful for the development of novel SiFA-based ¹⁸F-labeling synthons.     

An efficient one-pot synthesis of flavones

Flavones were prepared using a one-pot procedure starting from the corresponding 2′-hydroxyacetophenones. The latter were treated with 3 equiv of aroyl chloride in wet K₂CO₃/acetone (1% w/w water) to afford a good yield of flavone and a smaller amount of 3-aroylflavone. Evidence was obtained that the reaction proceeds via a triketone intermediate. When the reactants were heated in 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and pyridine, the 3-aroylflavone was obtained exclusively. Use of a stoichiometric amount of aroyl chloride afforded only the corresponding flavone.     

Effect of mono-, di- and tri-ethanolammonium tetrafluoroborate protonic ionic liquids on the volatility of water, ethanol, and methanol

Vapor pressure data were measured for nine binary systems containing water, ethanol, or methanol with one of three protonic ionic liquids (PILs), viz. mono-, di- and tri-ethanolammonium tetrafluoroborate ([HMEA][BF₄], [HDEA][BF₄], and [HTEA][BF₄]), at varying temperatures and PIL-contents using a quasi-static ebulliometer. The vapor pressure data were correlated by NRTL model with an overall average absolute relative deviation (AARD) of 0.0175. It is showed that the effect of PILs on the vapor pressure lowering of solvents follows the order of [HMEA][BF₄] > [HDEA][BF₄] > [HTEA][BF₄], and the vapor pressure lowering degree follows the order of water > methanol > ethanol. Besides, the activity coefficients of solvent for binary system {solvent + PIL} at fixed PIL mole fraction of 0.10 were calculated using the regressed NRTL parameters. The results indicate that three PILs can give rise to a negative deviation from the Raoult's law for water and methanol and a positive deviation for ethanol to a varying degree, leading to the variation of relative volatility of a solvent.     

Dual Illumination Enhances Transformation of an Engineered Green-to-Red Photoconvertible Fluorescent Protein

The molecular mechanisms for the photoconversion of fluorescent proteins remain elusive owing to the challenges of monitoring chromophore structural dynamics during the light-induced processes. We implemented time-resolved electronic and stimulated Raman spectroscopies to reveal two hidden species of an engineered ancestral GFP-like protein LEA, involving semi-trapped protonated and trapped deprotonated chromophores en route to photoconversion in pH 7.9 buffer. A new dual-illumination approach was examined, using 400 and 505 nm light simultaneously to achieve faster conversion and higher color contrast. Substitution of UV irradiation with visible light benefits bioimaging, while the spectral benchmark of a trapped chromophore with characteristic ring twisting and bridge-H bending motions enables rational design of functional proteins. With the improved H-bonding network and structural motions, the photoexcited chromophore could increase the photoswitching-aided photoconversion while reducing trapped species.     

优化金属辅助法腐蚀液组分制备多孔硅

金属辅助化学腐蚀法可以在无外加电路的条件下,在40%HF/30%H2O2/乙醇的混合溶液中完成多孔硅的制备,该方法简单快速。本文研究了金属辅助法腐蚀液体系各组分(HF、H2O2、乙醇)含量对多孔硅表面的SiHx成分和多孔层结构的影响,根据Si-H和Si-O的红外吸收峰强度的变化曲线优化了腐蚀液体系中各组分含量。在腐蚀液各组分体积比为V40%HF∶V30%H2O2∶V乙醇=2∶2∶1和腐蚀时间为4 min的条件下制备了形貌均匀、化学活性(SiHx成分)和多孔结构稳定性较好的多孔硅,并对金属辅助法与阳极蚀刻法制得的两种多孔硅进行比较,结果显示金属辅助法制备的多孔硅的化学活性和稳定性在后续的生物技术应用中具有明显的优越性。     

An E1-Catalyzed Chemoenzymatic Strategy to Isopeptide-N-Ethylated Deubiquitylase-Resistant Ubiquitin Probes

Triazole-based deubiquitylase (DUB)-resistant ubiquitin (Ub) probes have recently emerged as effective tools for the discovery of Ub chain-specific interactors in proteomic studies, but their structural diversity is limited. A new family of DUB-resistant Ub probes is reported based on isopeptide-N-ethylated dimeric or polymeric Ub chains, which can be efficiently prepared by a one-pot, ubiquitin-activating enzyme (E1)-catalyzed condensation reaction of recombinant Ub precursors to give various homotypic and even branched Ub probes at multi-milligram scale. Proteomic studies using label-free quantitative (LFQ) MS indicated that the isopeptide-N-ethylated Ub probes may complement the triazole-based probes in the study of Ub interactome. Our study highlights the utility of modern protein synthetic chemistry to develop structurally and new families of tool molecules needed for proteomic studies.     

Natural Soft/Rigid Superlattices as Anodes for High-Performance Lithium-Ion Batteries

Volume expansion and poor conductivity are two major obstacles that hinder the pursuit of the lithium-ion batteries with long cycling life and high power density. Herein, we highlight a misfit compound PbNbS₃ with a soft/rigid superlattice structure, confirmed by scanning tunneling microscopy and electrochemical characterization, as a promising anode material for high performance lithium-ion batteries with optimized capacity, stability, and conductivity. The soft PbS sublayers primarily react with lithium, endowing capacity and preventing decomposition of the superlattice structure, while the rigid NbS₂ sublayers support the skeleton and enhance the migration of electrons and lithium ions, as a result leading to a specific capacity of 710 mAh g⁻¹ at 100 mA g⁻¹, which is 1.6 times of NbS₂ and 3.9 times of PbS. Our finding reveals the competitive strategy of soft/rigid structure in lithium-ion batteries and broadens the horizons of single-phase anode material design.     

Impact of titanate coupling agent on properties of high density polyethylene composite filled with coal gangue

In this study, surface modification of coal gangue (CG) was performed with titanate coupling agent 201 (isopropyl tri(dioctylpyrophosphate) titanate), and the effects of surface modifier on mechanical properties and thermal stability of high-density polyethylene filled with CG (HDPE/CG) and high-density polyethylene filled with modified CG (HDPE/mCG) composites were investigated. The coupling agent was successfully grafted on CG surface through chemical reaction according to the analyses of Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the coupling agent can effectively enhance the hydrophobicity of surface that was verified by water contact angle beyond 90° of modified CG sample. With the introduction of coupling agent, some enhancements of tensile strength, flexural strength, and impact strength were observed in HDPE/mCG compared with HDPE/CG, due to the improved compatibility between mCG fillers and matrix. The increased storage modulus and decreased loss factor of HDPE/mCG composite further confirm the stronger interface adhesion after modification. Moreover, it is found that titanate coupling agent 201 can improve the thermal stability of HDPE/mCG composite to some extent.     

A small NGS–SNP panel of ancestry inference designed to distinguish African,European, East,and South Asian populations

In this study, a small set of ancestry informative SNPs was selected to differentiate African, European, East and South Asian samples, which was detected by the next-generation sequencing technology. A total of 127 Chinese Shaanxi Han individuals were collected as test samples. No statistically significant linkage disequilibrium of any pair of loci or departure from Hardy–Weinberg equilibrium of each locus was observed in the test population. To evaluate the performance of ancestry assignment using this panel, admixture analysis, principal component analysis, and likelihood ratio calculations were conducted based on the 1000 genome data and test samples. All populations were clustered into four groups, African, European, South and East Asian populations, which were consistent with their geographical origins. The pairwise fixation index (F_ST) between populations from different continental groups ranged from 0.140 to 0.621 with average 0.415, and the pairwise F_ST between populations from the same continent ranged from 0.000 to 0.056 with average 0.012. The likelihood ratio results of 125 test individuals indicated that their ancestry components were highly possible from East Asia. In conclusion, this small set of ancestry informative SNPs can be used as a reliable tool to identify and quantify ancestry components of unknown samples.