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A simple on-line preconcentration method of protein for capillary electrophoresis (CE) using a cellulose acetate (CA)-coated porous membrane was proposed. CA membrane is fabricated at one of the ends of the column that allows the passage of buffer ions but excludes larger protein molecules. Protein sample is continuously electrokinetically loaded and trapped by the membrane. When injection is completed, the direction of the electric field is switched and the trapped proteins are then separated by conventional CE procedure. The results achieved showed that the preconcentration mechanism of this method was based on size-exclusion effect. Bovine serum albumin (BSA) was used for model protein sample, and signal enhancement of 550-fold with 15 min injection time was achieved. 相似文献
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Juan He Hongzhe Tang Liqin You Haijun Zhan Jing Zhu Kui Lu 《Mikrochimica acta》2013,180(9-10):903-910
Fragment-imprinted microspheres (FIMs) were synthesized by suspension polymerization of 4-sulfa-6-chloropyrimidine (the template), methacrylic acid and styrene (the mixed functional monomers), divinylbenzene (the crosslinker), and azobisisobutyronitrile (the initiator). The optimum conditions were obtained by an orthogonal experiment. After removal of the templates, the microspheres serve as a material to fairly specifically bind sulfonamides, the absorption capacity being 6.32 mg g–1, whereas the absorption by non-imprinted microspheres is 1.68 mg g?1. A method was worked out for the simultaneous determination of five sulfonamides by solid phase extraction (using the FIMs) coupled to HPLC, and applied to analyze milk samples. The recoveries are within 87.6 and 96.5 %, with relative standard deviations between 1.25 and 2.89 %. Figure
Graphical abstract showed that fragment imprinted-solid phase extraction had the best selective adsorption performance of the five sulfonamide antibiotics compare with C18, Silica and Florisil column. It was satisfactory by using fragment imprinted microspheres as sorbents of solid phase extraction for enriching and separating target compounds from complex matrices. 相似文献
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Two supramolecular complexes, [Cu(L)(H2O)2(beta-CD)](ClO4)2.10.5H2O.CH3OH (1) and [Cu(L)(H2O)2(beta-GCD)](HClO4)(ClO4)2.10H2O (2) (L = 4-(4'-tert-butyl-benzyl)diethylenetriamine, beta-CD = beta-cyclodextrin, and beta-GCD = mono-6-deoxy-6-guanidinocycloheptaamylose cation), have been synthesized. The structure of 1 has been characterized by X-ray crystallography. The 4-tert-butyl-benzyl of [Cu(L)(H2O)2]2+ moiety in 1 as a guest inserts into the hydrophobic cavity of the beta-CD as a host along the primary hydroxyl side. On the basis of the structure data of 1, complex 2 was modeled, which showed that the distance between the Cu and C atom of the guanidinium is 5.2 A, comparable to the corresponding distance in bovine erythrocyte Cu, Zn-SOD (5.9 A) (SOD = superoxide dismutase). Apparent inclusion stability constants of the host and the guest were measured to be 0.66 (+/-0.01) x 104 and 1.15 (+/-0.03) x 104 M-1 for 1 and 2 respectively. The electronic absorption bands and electronic reflection bands of each complex are almost the same, indicating an identical structure of the complex in aqueous solution and in solid state. The two complexes showed quasi-reversible one-electron Cu(II)/Cu(I) redox waves with redox potentials of -0.345 and -0.338 V for 1 and 2, respectively. Their SOD-like activities (IC50) were measured to be 0.30 +/- 0.01 and 0.17 +/- 0.01 microM by xanthine/xanthine oxidase-NBT assay. The enhanced SOD activity of 2 by approximately 40% compared with 1 suggests that the guanidyl cation in the host of the supramolecular system of 2 can effectively mimic the side chain of Arg141 in the enzyme, which is known to be essential for high SOD activity possibly through steering of the superoxide substrate to and from the active copper ion. 相似文献
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This article gives a normal criterion for families of holomorphic mappings of several complex variables into P N(C)for moving hypersurfaces in pointwise general position,related to an Eremenko’s theorem. 相似文献
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Haibo Wang Xinming Yang Minji Wang Menglong Hu Xiaohan Xu Aixin Yan Quan Hao Hongyan Li Hongzhe Sun 《Chemical science》2020,11(43):11714
Understanding how metallodrugs interact with their protein targets is of vital importance for uncovering their molecular mode of actions as well as overall pharmacological/toxicological profiles, which in turn facilitates the development of novel metallodrugs. Silver has been used as an antimicrobial agent since antiquity, yet there is limited knowledge about silver-binding proteins. Given the multiple dispersed cysteine residues and histidine–methionine pairs, Escherichia coli malate dehydrogenase (EcMDH) represents an excellent model to investigate silver coordination chemistry as well as its targeting sites in enzymes. We show by systematic biochemical characterizations that silver ions (Ag+) bind EcMDH at multiple sites including three cysteine-containing sites. By X-ray crystallography, we unravel the binding preference of Ag+ to multiple binding sites in EcMDH, i.e., Cys113 > Cys251 > Cys109 > Met227. Silver exhibits preferences to the donor atoms and residues in the order of S > N > O and Cys > Met > His > Lys > Val, respectively, in EcMDH. For the first time, we report the coordination of silver to a lysine in proteins. Besides, we also observed argentophilic interactions (Ag⋯Ag, 2.7 to 3.3 Å) between two silver ions coordinating to one thiolate. Combined with site-directed mutagenesis and an enzymatic activity test, we unveil that the binding of Ag+ to the site IV (His177-Ag-Met227 site) plays a vital role in Ag+-mediated MDH inactivation. This work stands as the first unusual and explicit study of silver binding preference to multiple binding sites in its authentic protein target at the atomic resolution. These findings enrich our knowledge on the biocoordination chemistry of silver(i), which in turn facilitates the prediction of the unknown silver-binding proteins and extends the pharmaceutical potentials of metal-based drugs.Silver-binding preference in its authentic protein targets with MDH as a paradigm was uncovered. 相似文献
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Shuangfeng Cai Yaran Wu Yanan Li Shuying Yang Zhi Liu Yuwen Ma Jianqiang Lv Yujia Shao Hongzhe Jia Yan Zhao Lei Cai 《Molecules (Basel, Switzerland)》2021,26(23)
The chlorophyll ethanol-extracted silkworm excrement was hardly biologically reused or fermented by most microorganisms. However, partial extremely environmental halophiles were reported to be able to utilize a variety of inexpensive carbon sources to accumulate polyhydroxyalkanoates. In this study, by using the nile red staining and gas chromatography assays, two endogenous haloarchaea strains: Haloarcula hispanica A85 and Natrinema altunense A112 of silkworm excrement were shown to accumulate poly(3-hydroxybutyrate) up to 0.23 g/L and 0.08 g/L, respectively, when using the silkworm excrement as the sole carbon source. The PHA production of two haloarchaea showed no significant decreases in the silkworm excrement medium without being sterilized compared to that of the sterilized medium. Meanwhile, the CFU experiments revealed that there were more than 60% target PHAs producing haloarchaea cells at the time of the highest PHAs production, and the addition of 0.5% glucose into the open fermentation medium can largely increase both the ratio of target haloarchaea cells (to nearly 100%) and the production of PHAs. In conclusion, our study demonstrated the feasibility of using endogenous haloarchaea to utilize waste silkworm excrement, effectively. The introduce of halophiles could provide a potential way for open fermentation to further lower the cost of the production of PHAs. 相似文献
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