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151.
Xiangtang Li Ruichuan Yin Hang Hu Yingju Li Prof. Xiaofei Sun Prof. Sudhansu K. Dey Prof. Julia Laskin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22574-22577
Ambient ionization based on liquid extraction is widely used in mass spectrometry imaging (MSI) of molecules in biological samples. The development of nanospray desorption electrospray ionization (nano-DESI) has enabled the robust imaging of tissue sections with high spatial resolution. However, the fabrication of the nano-DESI probe is challenging, which limits its dissemination to the broader scientific community. Herein, we describe the design and performance of an integrated microfluidic probe (iMFP) for nano-DESI MSI. The glass iMFP, fabricated using photolithography, wet etching, and polishing, shows comparable performance to the capillary-based nano-DESI MSI in terms of stability and sensitivity; a spatial resolution of better than 25 μm was obtained in these first proof-of-principle experiments. The iMFP is easy to operate and align in front of a mass spectrometer, which will facilitate broader use of liquid-extraction-based MSI in biological research, drug discovery, and clinical studies. 相似文献
152.
He C Qian X Xu Y Yang C Yin L Zhu W 《Dalton transactions (Cambridge, England : 2003)》2011,40(5):1034-1037
A novel ratiometric fluorescent probe for oxalic acid was designed and synthesized, based on the zinc-containing [DAQZ@2Zn(2+)] complex. It shows highly selective "on-off" fluorescence changes with a more than 20 nm blue shift in wavelength for oxalic acids in aqueous solution. Moreover, it can fluorescently respond to oxalic acid in living cells. 相似文献
153.
Density functional calculations have been performed to comparatively investigate two possible pathways of Au(I)‐catalyzed Conia‐ene reaction of β‐ketoesters with alkynes. Our studies find that, under the assistance of trifluoromethanesulfonate (TfO), the β‐ketoester is the most likely to undergo Model II to isomerize into its enol form, in which TfO plays a proton transfer role through a 6‐membered ring transition state. The coordination of the Au(I) catalyst to the alkynes triple bond can enhance the eletrophilic capability and reaction activity of the alkynes moiety, which triggers the nucleophilic addition of the enol moiety on the alkynes moiety to give a vinyl‐Au intermediate. This cycloisomerizaion step is exothermal by 21.3 kJ/mol with an energy barrier of 56.0 kJ/mol. In the whole catalytic process, the protonation of vinyl‐Au is almost spontaneous, and the formation of enol is a rate‐limiting step. The generation of enol and the activation of Au(I) catalyst on the alkynes are the key reasons why the Conia‐ene reaction can occur in mild condition. These calculations support that Au(I)‐catalyzed Conia‐ene reactions of β‐ketoesters with alkynes go through the pathway 2 proposed by Toste. 相似文献
154.
Qiang Ma Qi Deng Hang Sheng Wei Ling Hong-Rui Wang Hai-Wen Jiao Xiong-Wei Wu Wen-Xin Zhou Xian-Xiang Zeng Ya-Xia Yin Yu-Guo Guo 《中国科学:化学(英文版)》2018,61(6):732-738
A mild and simple synthesis process for large-scale vanadium redox flow batteries (VRFBs) energy storage systems is desirable. A graphite felt/MnO2 (GF-MNO) composite electrode with excellent electrocatalytic activity towards VO2+/VO2+ redox couples in a VRFB was synthesized by a one-step hydrothermal process. The resulting GF-MNO electrodes possess improved electrochemical kinetic reversibility of the vanadium redox reactions compared to pristine GF electrodes, and the corresponding energy efficiency and discharge capacity at 150 mA cm?2 are increased by 12.5% and 40%, respectively. The discharge capacity is maintained at 4.8 A h L?1 at the ultrahigh current density of 250 mA cm?2. Above all, 80% of the energy efficiency of the GFMNO composite electrodes is retained after 120 charge-discharge cycles at 150 mA cm?2. Furthermore, these electrodes demonstrated that more evenly distributed catalytic active sites were obtained from the MnO2 particles under acidic conditions. The proposed synthetic route is facile, and the raw materials are low cost and environmentally friendly. Therefore, these novel GFMNO electrodes hold great promise in large-scale vanadium redox flow battery energy storage systems. 相似文献
155.
20(R)-panaxadiol (PD) was metabolised by the fungus Aspergillus niger AS 3.3926 to its C-3 carbonylated metabolite and five other hydroxylated metabolites (1–6). Their structures were elucidated as 3-oxo-20(R)-panaxadiol (1), 3-oxo-7β-hydroxyl- 20(R)-panaxadiol (2), 3-oxo-7β,23α-dihydroxyl-20(R)-panaxadiol (3), 3,12-dioxo- 7β,23β-dihydroxyl-20(R)-panaxadiol (4), 3-oxo-1α,7β-dihydroxyl-20(R)-panaxadiol (5) and 3-oxo-7β,15β-dihydroxyl-20(R)-panaxadiol (6) by spectroscopic analysis. Among them, compounds 2–6 were new compounds. Pharmacological studies revealed that compound 6 exhibited significant anti-hepatic fibrosis activity. 相似文献
156.
Xuejiao Tang Haitao Liao Tao Zheng Pan Yin Prof. Jing Cao Assoc. Prof. Xiaoying Zeng Dr. Chao Weng Prof. Ping Shen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(58):14508-14519
Two dithienocyclopentafluorene-based small-molecule acceptors (SMAs) were developed that feature methylene-functionalized conjugated side chains, to study the effect of arylmethylene substitution and its number on structure, optoelectronic properties and device performance. Results showed that two SMAs have better absorption properties and planarity, lower bandgaps and higher LUMOs compared with the control SMA without conjugated side chains. The synthesized SMAs were tested in polymer solar cells for examples of their applicability. This work argues that the introduction of methylene-functionalized conjugated side chains has great potential in tuning molecular structure, optoelectronic properties, device physics and photovoltaic performance of SMAs. 相似文献
157.
Jinhua Ji Hao Liu Zewei Chen Yajun Fu Prof. Weijun Yang Prof. Shuang-Feng Yin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(43):11102-11109
Metal-organic framework (MOF) is an ideal precursor/template for porous carbon, and its active components are uniformly doped, which can be used in energy storage and catalytic conversion fields. Metal-organic framework PCN-224 with carboxylporphyrin as the ligand was synthesized, and then Zn2+ and Co2+ ions were coordinated in the center of the porphyrin ring by post-modification. Here, PCN-224−ZnCo with different ratios of bimetallic Zn2+/Co2+ ions were used as the precursor, and the metal-nitrogen-carbon(M−N−C) material of PCN-224−ZnCo-950 was obtained by pyrolyzing the precursor at 950 °C in Ar. Because Zn is easy to volatilize at 950 °C, the formed M−N−C materials can reflect different Co contents and different basic site concentrations. The formed material still maintains the original basic framework. With the increase of Zn2+/Co2+ ratio in precursor, the concentration of N-containing alkaline sites in pyrolysis products gradually increase. Compared with the precursor, PCN-224−ZnCo1-950 with Zn2+/Co2+=1 : 1 has greatly improved basicity and suitable acidic/ alkaline site concentration. It can be efficiently used to carbon dioxide absorption and catalyze the cycloaddition of CO2 with epoxide. More importantly, the current method of adjusting the acidic/basic sites in M−N−C materials through volatilization of volatile metals can provide an effective strategy for adjusting the catalysis of MOF derivatives with porphyrin structure. 相似文献
158.
Yin H Chacon A Porter NA Masterson DS 《Journal of the American Society for Mass Spectrometry》2007,18(5):807-816
Protein identification is routinely accomplished by peptide sequencing using mass spectrometry (MS) after enzymatic digestion.
Site-specific chemical modification may improve peptide ionization efficiency or sequence coverage in mass spectrometry. We
report herein that amino group of lysine residue in peptides can be selectively modified by reaction with a peroxycarbonate
and the resulting lysine peroxycarbamates undergo homolytic fragmentation under conditions of low-energy collision-induced
dissociation (CID) in electrospray ionization (ESI) and matrix-assisted laser desorption and ionization (MALDI) MS. Selective
modification of lysine residue in peptides by our strategy can induce specific peptide cleavage at or near the lysine site.
Studies using deuterated analogues of modified lysine indicate that fragmentation of the modified peptides involves apparent
free-radical processes that lead to peptide chain fragmentation and side-chain loss. The formation of a-, c-, or z-types of
ions in MS is reminiscent of the proposed free-radical mechanisms in low-energy electron capture dissociation (ECD) processes
that may have better sequence coverage than that of the conventional CID method. This site-specific cleavage of peptides by
free radical- promoted processes is feasible and such strategies may aid the protein sequencing analysis and have potential
applications in top-down proteomics. 相似文献
159.
Qiaoxia Liu Binbin Zhou Xinliang Wang Yanxiong Ke Yu Jin Lihui Yin Xinmiao Liang 《Journal of separation science》2012,35(23):3317-3325
A search library about benzylisoquinoline alkaloids was established based on preparation of alkaloid fractions from Rhizoma coptidis, Cortex phellodendri, and Rhizoma corydalis. In this work, two alkaloid fractions from each herbal medicine were first prepared based on selective separation on the “click” binaphthyl column. And then these alkaloid fractions were analyzed on C18 column by liquid chromatography coupled with tandem mass spectrometry. Many structure‐related compounds were included in these alkaloids fractions, which led to easy separation and good MS response in further work. Therefore, a search library of 52 benzylisoquinoline alkaloids was established, which included eight aporphine, 19 tetrahydroprotoberberine, two protopine, two benzyltetrahydroisoquinoline, and 21 protoberberine alkaloids. The information of the search library contained compound names, structures, retention times, accurate masses, fragmentation pathways of benzylisoquionline alkaloids, and their sources from three herbal medicines. Using such a library, the alkaloids, especially those trace and unknown components in some herbal medicine could be accurately and quickly identified. In addition, the distribution of benzylisoquinoline alkaloids in the herbal medicines could be also summarized by searching the source samples in the library. 相似文献
160.
Zhengcui Wu Lidan Jiang Yanan Zhu Chengrong Xu Yin Ye Xiuhua Wang 《Journal of Solid State Electrochemistry》2012,16(10):3171-3177
NiO nanosheets with uniformly distributed mesoporosity were successfully synthesized on a large scale by calcination of β-Ni(OH)2 nanosheet precursor, which was simply prepared using 1,6-hexanediamine-assisted solution approach. The as-prepared mesoporous NiO nanosheets have been introduced for the first time for the sensing of mercury ions, which were found to be useful for selective electrochemical detection of Hg2+ with a linear range of 0.8 to 500?μM in pH?6.0 phosphate-buffered solutions, providing us another opportunity for exploring new electrochemical application of NiO nanomaterials. 相似文献