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31.
Saeed Aminzadeh Hossein Naderi-Manesh Khosro Khajeh Bijan Ranjbar Naser Farrokhi 《Applied biochemistry and biotechnology》2010,160(7):1921-1932
Acid-induced unfolding of a Tetracoccosporium sp. polygalacturonase enzyme (PG) was studied by a comprehensive series of biophysical and biochemical techniques. At pH 1.0,
PG acquires partially folded state, which reveals characteristics of molten globule (MG) state, i.e., reduction of defined
tertiary structure with minimal changes in the secondary structure. In this study PG unfolds exposing its hydrophobic surface
to a greater extent than the native form at acidic pH with more tryptophan residues exposed to the solvent. Collectively,
our data imply the presence of MG state of PG at low pH, suggesting the phenomenon of hydrophobic collapse model for folding
and integration into cell membrane. 相似文献
32.
A series of palladium complexes bearing monodentate and bidentate ligands were applied in the Suzuki reaction of aryl halides and the Heck reaction of styrene with phenylboronic acid. The complexes were found to be effective catalysts for these reactions affording the cross-coupled products in moderate to excellent yields. 相似文献
33.
34.
Rozita Zoghi Majid M. Heravi Naser Montazeri Masoud Mohammadi Zeydi Tayebeh Hosseinnejad 《应用有机金属化学》2020,34(4):e5435
A novel polymer supported [poly (styrene-co-maleic imide) (SMI)]Cu(I) nano-particles was prepared via in situ reaction of 4-amino-5-methyl-4H-1,2,4-triazole-3-thione with [poly (styrene-co-maleic anhydride)] (SMA) along with immobilization of CuI. These nano-particles were fully characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy analysis, Xray (EDAX), inductively coupled plasma (ICP) analysis, 1H NMR and FT-IR techniques. Moreover, the structural and electronic features of metal–ligand interactions in the complex model of polymer-supported copper nanocatalyst were assessed using density functional theory calculations. The catalytic activity of these supported Cu(I) nonoparticles was examined in one of the classiest name reaction so–called “click reaction” which is coined K. B Sharpless for the regioselective synthesis of 1,2,3-triazole derivatives using a multicomponent reaction (MCR) involving benzyl halides, sodium azide and terminal alkynes in water as a green solvent. This heterogeneous catalyst showed excellent catalytic activity and was separated by simple filtration and was used at least in five consecutive runs without a significant decrease in its activity. 相似文献
35.
Copolymers of -methyl styrene and 2-ethylhexyl acrylate were prepared in a benzene solution. The presence of the copolymers were confirmed by solubility, IR and NMR tests. The molecular weight and the polydispersity of the polymers were estimated by GPC. The copolymers obtained were blended with paraffinic and naphthenic base oils. The viscosity, the viscosity index (VI) the Q value as well as the stability to shear and oxidation were obtained for these blends. The results are compared with the results obtained with an oil blend containing a commonly used high temperature additive. Two of the copolymers obtained have shown to be good alternatives for specific applications.Presented at the Symposium, 76th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65th birthday. 相似文献
36.
In this report, TiO(2) -SiO(2) composite nanoparticles were prepared by the thermal hydrolysis method using titanium tetrachloride and tetraethylorthosilicate as TiO(2) and SiO(2) precursors, respectively. The prepared nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption/desorption and UV-Vis diffuse reflectance spectroscopy (DRS). The results indicated that, in comparison with pure TiO(2), TiO(2)-SiO(2) composite nanoparticles had a higher thermal stability, which prevents phase transformation from anatase to rutile. In addition, the TiO(2)-SiO(2) nanoparticles had a higher specific surface area, larger pore volume, greater band gap energy and smaller crystallite size. Thus, the surface area of TiO(2)-40% SiO(2) composite nanoparticles was about 17 times higher than that of pure TiO(2) nanoparticles. The photocatalytic activity of TiO(2)-SiO(2) composite nanoparticles in the photodegradation of C.I. Basic Violet 2 was investigated. The photodegradation rate of Basic Violet 2 using TiO(2)-40% SiO(2) nanoparticles calcined at 600°C was much faster than that using pure TiO(2) and Degussa P25 TiO(2) by 10.9 and 4.3 times, respectively. The higher photoactivity of the TiO(2)-SiO(2) composite nanoparticles was attributed to their higher surface area, larger pore volume, greater band-gap energy and smaller crystallite size compared with pure TiO(2). 相似文献
37.
Strom T Shokati T Klawitter J Klawitter J Hoffman K Schiebel HM Christians U 《Journal of mass spectrometry : JMS》2011,46(7):615-624
SAR-943 (32-deoxo rapamycin) is a proliferation signal inhibitor via interaction with the mammalian target of rapamycin (mTOR). Most importantly, SAR-943 has improved chemical stability compared to rapamycin (sirolimus) and is currently under investigation as a drug coated on coronary stents. It was the goal of this study to identify the SAR-943 metabolites generated after incubation with human liver microsomes using high-resolution mass spectrometry (MS) and MS/iontrap (MS(n)) and comparison of fragmentation patterns of the metabolites with those of SAR-943 and other known rapamycin derivatives. Our study showed that SAR-943 is mainly hydroxylated and/or demethylated by human liver microsomes. The structures of the following metabolites were identified: O-demethylated metabolites: 39-O-desmethyl, 16-O-desmethyl and 27-O-desmethyl SAR-943; hydroxylated metabolites: hydroxy piperidine SAR-943, 11-hydroxy, 12-hydroxy, 14-hydroxy, 23-hydroxy, 24-hydroxy, 25-hydroxy, 46-hydroxy and 49-hydroxy SAR-943; didemethylated metabolites: 16,39-O-didesmethyl and 27,39-O-didesmethyl SAR-943; demethylated-hydroxylated metabolites: 39-O-desmethyl, 23- or 24-hydroxy and 39-O-desmethyl, hydroxy piperidine SAR-943 and dihydroxylated metabolites: 12-,23- or 24-dihydroxy SAR-943. In addition, several other demethylated-hydroxylated and dihydroxylated metabolites were detected. However, their exact structures could not be identified. 相似文献
38.
Purification and Characterization of Pepsin-Solubilized Collagen from Skin of Sea Cucumber Holothuria parva 总被引:1,自引:0,他引:1
Nasim Adibzadeh Saeed Aminzadeh Shahla Jamili Ali Asghar Karkhane Naser Farrokhi 《Applied biochemistry and biotechnology》2014,173(1):143-154
Pepsin-solubilized collagen (PSC) was extracted from the skin of sea cucumber Holothuria parva and was fractionally characterized. The PSC from H. parva skin consisted of three α1 chains (α1)3, in contrast to calf skin collagen type I with two α1 and one α2 chains (α1)2α2 with approximately 130 kDa each. The maximum transition (Tm) and denaturation temperature (Td) of PSC were determined to be 46.94 and 32.5 °C, respectively. The amino acid composition analysis revealed that glycine, proline, alanine, and hydroxyproline were the abundant amino acids available in extracted PSC. The results showed that the isolated collagen from H. parva has some similar characteristics to previously reported collagens used in food and pharmaceutical industries. 相似文献
39.
Jost Klawitter Stephan Bek Marjorie Zakaria Chenhui Zeng Andrea Hornberger Richard Gilbert Touraj Shokati Jelena Klawitter Uwe Christians K. Olaf Boernsen 《Analytical and bioanalytical chemistry》2014,406(25):6399-6408
Stearoyl-CoA desaturase 1 (SCD1) plays a role in the development of obesity and related conditions, such as insulin resistance, and potentially also in neurological and heart diseases. The activity of SCD1 can be monitored using the desaturation index (DI), the ratio of product (16:1n-7 and 18:1n-9) to precursor (16:0 and 18:0) fatty acids. Here, different analytical strategies were applied to identify the method which best supports SCD1 biology. A novel effective approach was the use of the SCD1-independent fatty acid (16:1n-10) as a negative control. The first approach was based on a simple extraction followed by neutral loss triglyceride fatty acid analysis. The second approach was based on the saponification of triglycerides followed by fatty acid analysis (specific for the position of the double bond within monounsaturated fatty acids (MUFAs)). In addition to the analytical LC-MS assays, different matrices (plasma total triglyceride fraction and the very low-density lipoprotein (VLDL) fraction) were investigated to identify the best for studying changes in SCD1 activity. Samples from volunteers on a high-carbohydrate diet were analyzed. Both ultra HPLC (UHPLC)-MS-based assays showed acceptable accuracies (75–125 % of nominal) and precisions (<20 %) for the analysis of DI-specific fatty acids in VLDL and plasma. The most specific assay for the analysis of the liver SCD activity was then validated for specificity and selectivity, intra- and interday accuracy and precision, matrix effects, dilution effects, and analyte stability. After 3 days of high-carbohydrate diet, only the specific fatty acids in human plasma VLDL showed a significant increase in DI and associated SCD1 activity. 相似文献
40.
Mahboubeh Rahmati-Rostami Cyrus Ghotbi Masih Hosseini-Jenab Amir Naser Ahmadi Amir Hossein Jalili 《The Journal of chemical thermodynamics》2009,41(9):1052-1055
The solubility of hydrogen sulphide in three ionic liquids, viz. 1-hexyl-3-methylilmidazolium hexafluorophosphate ([hmim][PF6]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF4]), and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf2N]), at temperatures ranging from 303.15 K to 343.15 K and pressures up to 1.1 MPa were determined. The solubility values were correlated using the Krichevsky–Kasarnovsky equation and Henry’s constants were obtained at different temperatures. Partial molar thermodynamic functions of solvation such as standard Gibbs free energy, enthalpy, and entropy were calculated from the solubility results. Comparison of the values obtained show that the solubility of H2S in these three ionic liquids was in the sequence: [hmim][BF4] > [hmim][PF6] ≈ [hmim][Tf2N]. 相似文献