查找使用阿拉丁产品的科研文献

Molecular identification and quantification of defect sites in metal-organic frameworks with NMR probe molecules

Yin Jinglin,Kang Zhengzhong,Fu Yao,Cao Weicheng,Wang Yiran,Guan Hanxi,Yin Yu,Chen Binbin,Yi Xianfeng,Chen Wei,Shao Wei,Zhu Yihan,Zheng Anmin,Wang Qi,Kong Xueqian

The defects in metal-organic frameworks (MOFs) can dramatically alter their pore structure and chemical properties. However, it has been a great challenge to characterize the molecular structure of defects, especially when the defects are distributed irregularly in the lattice. In this work, we applied a characterization strategy based on solid-state nuclear magnetic resonance (NMR) to assess the chemistry of defects. This strategy takes advantage of the coordination-sensitive phosphorus probe molecules, e.g., trimethylphosphine (TMP) and trimethylphosphine oxide (TMPO), that can distinguish the subtle differences in the acidity of defects. A variety of local chemical environments have been identified in defective and ideal MOF lattices. The geometric dimension of defects can also be evaluated by using the homologs of probe molecules with different sizes. In addition, our method provides a reliable way to quantify the density of defect sites, which comes together with the molecular details of local pore environments. The comprehensive solid-state NMR strategy can be of great value for a better understanding of MOF structures and for guiding the design of MOFs with desired catalytic or adsorption properties.

Simultaneous quantification of cellulose and pectin in tobacco using a robust solid-state NMR method

Mingyu Yang,Zechun Liu,Jianping Zhang,Xiaolan Zhu,Wei Xie,Hongqiao Lan,Yanjun Huang,Xin Ye,Jun Yang

Cellulose and pectin are the important components of tobacco ( Nicotiana tabacum L.) cell wall, which affect the formation of undesirable compounds. Their contents are closely related to the harmfulness of tobacco. But the simultaneous quantitative analysis of cellulose and pectin is hard to be achieved for traditional analytical methods. A solid-state 13 C cross-polarization by multiple contact periods (multiCP) NMR method was developed for the simultaneous quantification of cellulose and pectin in tobacco. The multiCP spectrum at optimal parameters agreed well with the direct polarization (DP) spectrum within one-thirtieth of the measurement time and provided satisfactory signal to noise ratio (SNR). After three simple procedures of sample preparation and spectra deconvolution, simultaneous quantification of cellulose and pectin extracted from tobacco was effectively achieved. Compared with the chemical method, this interesting method was rapid, practicable, and very promising, which provided the technical support for the simultaneous quantification of cell wall substances in biological sample.

A Novel Serum Glucose Quantitative Method Based on a Miniature NMR Analyzer With High Accuracy

Yi Chen,Qing Yang,Xiaowen Jiang,Zhengxiu Wu,Zhonghua Ni,Hong Yi,Rongsheng Lu

Structural characteristic of pectin-glucuronoxylan complex from Dolichos lablab L. hull

Dan Liu,Wei Tang,Xiao-Jun Huang,Jie-Lun Hu,Jun-Qiao Wang,Jun-Yi Yin,Shao-Ping Nie,Ming-Yong Xie

Polysaccharides are important constituents in Dolichos lablab hull. Herein, pectin-glucuronoxylan complex from D. lablab hull designated as DLHP-3 ( D. lablab hull polysaccharide,) was prepared by ion exchange and gel permeation chromatography , and further characterized by acid degradation and enzymatic hydrolysis , methylation combined with GC–MS, NMR and MALDI-TOF-MS analysis. Both of pectin and glucuronoxylan regions were found in DLHP-3. The glucuronoxylan region consisted of a →4)-β-Xyl p -(1→ backbone with branches of α-Glc p A-(1→ substituted at O -2 site, and the ratio of xylose to glucuronic acid was about 5:1. Acetyl groups were mainly attached to O -3 site of →2,4)-β-Xyl p -(1→ residues. The main chain of pectin region could be represented by →4)-α-Gal p A-(1→4)-α-Gal p A-(1→ and →2)-α-Rha p -(1→4)-α-Gal p A-(1→ with partial methyl-esterification. The side chains were deduced to embrace arabinan and arabinogalactan linked to rhamnogalacturonan-I region. Pectin was probably covalently bound to glucuronoxylan. Our findings uncovered the molecular structure of pectin-glucuronoxylan complex from D. lablab hull.

Microsphere-structured hydrogel crosslinked by polymerizable protein-based nanospheres

Chunhua Wang,Lan Yang,Yujing He,Huining Xiao,Wei Lin

In this work, the vinyl groups were introduced onto gelatin to create methacrylated gelatin nanoparticles (MA-GNP) as crosslinking centers for fabricating macromolecular microsphere composite (MMC) hydrogels. The MA-GNPs with an average size of ~100 nm, measured with dynamic light scattering , were also visualized using AFM . The presence of C C bonds in the nanoparticles was further confirmed with the proton NMR . Then, the MA-GNP was incorporated as a cross-linker to synthesize MMC hydrogels using acrylamide as the monomer . The resulting hydrogels are porous with tunable pore sizes; and exhibit the improved compressive resistance and elasticity. Increasing the dosage of MA-GNP appropriately led to the reduction of the equilibrium swelling ratio but improved thermal stability of the gels. Moreover, the MA-GNP can endow the gels with enhanced biocompatibility. Overall, the novel protein-based nanospheres are of great potential as both nano-crosslinker and reinforcer to create polymer hydrogels with tailored properties.

Structure and anticoagulant activity of fucosylated glycosaminoglycan degraded by deaminative cleavage

Longyan Zhao,Sensen Lai,Rong Huang,Mingyi Wu,Na Gao,Li Xu,Hongbo Qin,Wenlie Peng,Jinhua Zhao

Fucosylated glycosaminoglycans (FGs) are complex glycosaminoglycans that exhibit potent anticoagulant activity. To study the relationship between molecular size and biological activity, oligosaccharides with (2,5)-anhydro- d -talose units at new reducing ends were prepared by hydrazine deacetylation and nitrous acid depolymerization. The product chemical structures were analyzed by one- and two-dimensional NMR methods. Additionally, anticoagulant activities were evaluated by clotting assay and chromogenic substrate cleavage. The results demonstrated that under mild deacetylation and deaminative cleavage conditions, both products were relatively homogeneous and sulfated fucose branch types and sulfate substituents remained stable. These depolymerized FGs with different molecular sizes had potent intrinsic anticoagulant activities, which were similar to those that were obtained by free-radical depolymerization with similar molecular weights. Decreasing molecular weight may weaken activity but not significantly affect factor Xase and heparin cofactor II (HCII)-mediated thrombin inhibition.

Reaction of “unreactive” silicone: synthesis of long-chain alkyl fluorosilicone via a simple siloxane equilibration process

Zhang Yongjie,Fan Mingshuai,Li Xiaopei

Abstract Long-chain alkyl silicone is a type of modified silicones that finds potential applications in various areas. Long-chain alkyl fluorosilicone (LCAFS) can be considered as a modified long-chain alkyl silicone as it synergistically combines the properties of long-chain alkyl silicone and novel fluorosilicone. As far as we know, reports on the synthesis of LCAFS are rare. In this report, a facile method to synthesize LCAFS was explored. It was found that silicone bearing novel C30-45 alkyls and trifluoropropyl pendent groups, namely (C30-45 alkyl) methylsiloxane/trifluoropropylmethylsiloxane copolymer (TF-AMS), could be synthesized via a simple siloxane equilibration process between silanol-terminated polytrifluoropropylmethylsiloxane and (C30-45 alkyl)methyl silicone, a commercially available silicone that is generally considered as unreactive. The chemical structure of TF-AMS was characterized unambiguously by FTIR, NMR, GPC and DSC. The thermal stabilities of TF-AMS were investigated by TGA. Based on our experimental results, a plausible mechanism for the synthesis of TF-AMS was proposed. Graphic abstract A novel long-chain alkyl fluorosilicone was synthesized via a simple yet efficient siloxane equilibration process.

An efficient approach for simultaneously obtaining oil and epigoitrin from Orychophragmus violaceus seeds by microwave-mediated immiscible binary solvent extraction

Ru Zhao,Xinyu Yang,Aoqi Zhang,Tieyang Zhou,Yunwei Zhou,Lei Yang

Microwave-mediated immiscible binary solvent extraction (MIBSE) was applied to simultaneously extract oil and epigoitrin from Orychophragmus violaceus seeds . The upper phase of n -hexane was used to obtain oil, and the lower phase of ethanol solution was used to obtain epigoitrin. Factors potentially affecting the yields of oil and epigoitrin were systematically investigated. The optimum conditions were an ethanol volume fraction of 65%, liquid–solid ratio of lower-phase of 20 mL/g, liquid–solid ratio of upper-phase of 12 mL/g, microwave irradiation power of 393 W, and microwave irradiation time of 29 min. The actual yields of oil and epigoitrin were 34.08% ± 1.38% and 11.86 ± 0.47 mg/g, respectively. GC–MS analysis illustrated that the seed oils obtained by MIBSE and Soxhlet extraction exhibited similar fatty acid compositions. The separated epigoitrin was determined by HPLC analyses, which obtained a purity of 91.25% ± 3.83%, follwed by NMR determinations.

Synthesis, curing and thermal properties of the low melting point phthalonitrile resins containing glycidyl groups

Zhang Huadong,Yan Zhongyi,Yang Zhizhou,Mu Qiuhong,Peng Dan,Zhao Hui

Two low melting point phthalonitrile monomers (EPN and EEPN) containing flexible glycidyl groups were synthesized using hydroxyl-containing phthalonitrile and epichlorohydrin as raw materials. The structures of the synthesized monomers were characterized by Fourier transform infrared (FT-IR), nuclear magnetic resonance ( 1 H-NMR and 13 C-NMR) spectra and elemental analysis. Then each of them was blended with 4-(4-aminophenoxy)-phthalonitrile (APPN) and cured to obtain two kinds of amine-catalytic phthalonitrile-based crosslinked polymers. DSC results showed that two blending systems underwent a two-stage polymerization process with the increase of curing temperature. Rheological measurements exhibited that the introduction of glycidyl groups to phthalonitrile resin could greatly improve its processability. Moreover, after thermal cured at 300 ℃, the resulting phthalonitrile resins exhibited excellent mechanical performance, thermal and thermo-oxidative stability.

The Total Solubility of the Co-Solubilized PAHs with Similar Structures Indicated by NMR Chemical Shift

Tao Chen,Xin Hu,Zhong Chen,Xiaohong Cui

The synergism/inhibition level, solubilization sites and the total solubility (St) of co-solubilization systems of phenanthrene, anthracene and pyrene in Tween 80 and sodium dodecyl sulfate (SDS) are studied by1H-NMR, 2D nuclear overhauser effect spectroscopy (NOESY) and rotating frame overhauser effect spectroscopy (ROESY). In Tween 80, inhibition for phenanthrene, anthracene and pyrene is observed in most binary and ternary systems. However, in SDS, synergism is predominant. After analysis, we find that the different synergism or inhibition situation between Tween 80 and SDS is related to the different types of surfactants used and the resulting different co-solubilization mechanisms. In addition, we also find that three polycyclic aromatic hydrocarbons (PAHs) have similar solubilization sites in both Tween 80 and SDS, which are almost unchanged in co-solubilization systems. Due to the similar solubilization sites, the chemical shift changes of surfactant and PAH protons follow the same pattern in all solubilization systems, and the order of chemical shift changes is consistent with the order of changes in the St of PAHs. In this case, it is feasible to evaluate Stof PAHs by chemical shift. In both Tween 80 and SDS solutions, the ternary solubilization system has relatively high Strankings. Therefore, in practical applications, a good overall solubilization effect can be expected.Keywords:polycyclic aromatic hydrocarbon;co-solubilization;surfactant;NMR;total solubility

NMR characterization and anticoagulant activity of the oligosaccharides from the fucosylated glycosaminoglycan isolated from Holothuria coluber

Wenjiao Yang,Dingyuan Chen,Zhicheng He,Lutan Zhou,Ying Cai,Hui Mao,Na Gao,Zhili Zuo,Ronghua Yin,Jinhua Zhao

A glycosaminoglycan was isolated from the sea cucumber Holothuria coluber (HcFG). A series of oligosaccharide fragments (dp range 3–11) were prepared from its β -eliminative depolymerized product (dHcFG). Extensive NMR characterization of the oligosaccharides indicated the d -GlcA- β 1,3- d -GalNAc 4S6S repeating disaccharide backbone was substituted by monosaccharide branches comprising of Fuc 2S4S , Fuc 3S4S and Fuc 4S , linked to O-3 of d -GlcA. For the prevailing Fuc 3S4S at nonreducing end of dHcFG, the β- eliminative depolymerization process of HcFG was compared with those of the FGs from Actinopyga miliaris (AmFG, branched with Fuc 3S4S ) and Stichopus variegatus (SvFG, branched with Fuc 2S4S ). The result suggested that d -GlcA substituted with Fuc 3S4S was more susceptible to depolymerization than that with Fuc 2S4S . It might be due to the larger steric hindrance effects from Fuc 2S4S on the esterification of GlcA . Biological assays confirmed that the minimum chain length (dp8), regardless of the Fuc branch types, was required for the potent anti-iXase and anticoagulant activities in FG fragments.

Molybdenum/ZSM-5 Catalyzes Methane Co-Aromatization with Furan: Unveiling the Mechanism with Solid-State NMR

Wei Gao,Guodong Qi,Chao Wang,Qiang Wang,Jiawei Liang,Jun Xu,Feng Deng

The co-aromatization of methane and organic compounds using metal-modified zeolite catalysts represents a promising approach for the direct conversion of natural gas into valuable aromatics. In this work, we employ solid-state nuclear magnetic resonance (NMR) spectroscopy to systematically examine the reaction mechanism and evaluate the impact of co-feeding furan on methane aromatization over Mo/ZSM-5 zeolite. The results reveal a dual role of furan in promoting methane to aromatics and stabilizing the Mo/ZSM-5 zeolite catalyst in the co-aromatization. It is found that co-feeding a moderate amount of furan enhances methane conversion and boosts the selectivity to benzene, toluene, and xylene (BTX). The 12C/13C isotope switching experiments coupled with 1H and 13C MAS NMR spectroscopy reveal that furan actively participates in the methane aromatization reaction by forming an olefin pool, which promotes methane activation and contributes to the following aromatics formation. Two-dimensional 1H–95Mo heteronuclear correlation NMR spectroscopy indicates that furan facilitates the activation of Mo oxides into MoOxCy species, which serve as the active sites for methane aromatization. The co-feeding furan also helps to enhance catalyst stability by limiting the agglomeration of Mo and the deposition of coking species.