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A galactosaminoglycan (CO-N) obtained by ultrasonication from a protein-bound polysaccharide SN-C, which was isolated from Cordyceps ophioglossoides culture, has a direct cytotoxicity against tumor cells (Ohmori et al., Chem. Pharm. Bull., 37, 1019 (1989). High performance liquid chromatographic analysis revealed that CO-N shows a broad molecular weight distribution with an average molecular weight of 33000. A potent antitumor activity of CO-N was observed in the higher-molecular-weight fraction on gel filtration, and the low-molecular-weight fraction below 6600 showed a weak activity. However, the depolymerized CO-N (ca. 5500) obtained by further ultrasonication of the original CO-N still retained the antitumor activity of CO-N against Ehrlich ascitic carcinoma or MM46 solid mammary carcinoma.  相似文献   

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Using quantum molecular dynamics simulations based on density functional theory including dispersion corrections (DFT-D), we have studied the thermophysical properties of liquid carbon monoxide and nitrogen (CO-N(2)) mixture under extreme conditions. Density functional theory (DFT) method significantly overestimates the pressure as compared to DFT-D. It is demonstrated that the van der Waals (vdW) interaction has a negative contribution to the pressure and tends to reduce the overestimation of the equilibrium volume. We also demonstrate that a negative slope of Hugoniot curve could possibly be caused by both the absorption of dissociation energy and the uncertainties in composition. As density and temperature increase along the Hoguniot curve, the system appears to undergo a continuous transition and provides for a much richer set of dissociation products. The influence of dissociated carbon and oxygen atoms on nitrogen molecules is also discussed.  相似文献   

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An efficient method was developed for the preparation of a series of zinc Schiff base complexes. Introduction of a pyridyl group as a bridging unit as well as incorporation of ethynyl and electron-donating groups into the salicylidene moiety of these complexes moderately enhances the photoluminescence intensity and quantum yield. Electron-rich palladium groups possibly influence the photophysical character through the bridging C[triple bond]C bond. The crystal structure of the pyridine adduct of a salen Zn complex is determined by X-ray diffraction analysis.  相似文献   

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A crude polysaccharide possessing antitumour, radiation-resistant and anti-ageing attributes was extracted from Tricholoma matsutake by water extraction and alcohol precipitation. From this crude polysaccharide, a homogeneous polysaccharide, TMP-5II, was successfully purified by Sephacryl S-300 column chromatography. The average molecular weight (Mw) of TMP-5II was 15.76 kDa. Monosaccharide analysis indicated that the homogeneous polysaccharide contained four different residues: d-glucose, d-galactose, d-mannose and d-fucose. Attenuated total reflectance infrared spectroscopy revealed characteristics typical of carbohydrate polymers and a peak typical of a β-type glycosidic bond. TMP-5II was selected for structural characterisation by nuclear magnetic resonance (NMR) analysis. According to 1H NMR, 13C NMR and two-dimensional-NMR analysis, TMP-5II contains two kinds of linkages, β and α, at a ratio of 4:1. Preliminary results indicated that the polysaccharide had (1-4)-beta-pyran glucose as the main chain, and a branched chain in the O-6 location with fucose (1-2) mannose (1-3)-alpha-pyran galactose.  相似文献   

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The [CrIII(salen)]+ complex moiety is immobilized in MCM-41 matrix to obtain a new hybrid catalytic system; to test its activity, epoxidation of norbornene and hydroxylation reaction of 1-naphthol are carried out by using TBHP (tert-butylhydroperoxide) as oxidant.  相似文献   

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Despite intensified efforts to develop an effective antibiotic, S. aureus is still a major cause of mortality and morbidity worldwide. The multidrug resistance of bacteria has considerably increased the difficulties of scientific research and the concomitant emergence of resistance is to be expected. In this study we have investigated the in vitro activity of 15 ethanol extracts prepared from Moroccan medicinal plants traditionally used for treatment of skin infections. Among the tested species I. viscosa, C. oxyacantha, R. tinctorum, A. herba alba, and B. hispanica showed moderate anti-staphylococcal activity. However, R. alaternus showed promising growth-inhibitory effects against specific pathogenic bacteria especially methicillin-susceptible Staphylococcus aureus Panton-Valentine leucocidin positive (MSSA-PVL) and methicillin-resistant S. aureus (MRSA). The bioguided fractionation of this plant using successive chromatographic separations followed by nuclear magnetic resonance (NMR) and mass spectrometry (MS) including EIMS and HREIMS analysis yielded the emodin (1) and kaempferol (2). Emodin being the most active with MICs ranging between 15.62 and 1.95 µg/mL and showing higher activity against the tested strains in comparison with the crude extract, its mechanism of action and the structure-activity relationship were interestingly discussed. The active compound has not displayed toxicity toward murine macrophage cells. The results obtained in the current study support the traditional uses of R. alaternus and suggest that this species could be a good source for the development of new anti-staphylococcal agents.  相似文献   

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Photoprocesses in bis(diethylaminobenzylidene)cyclopentanone (D1) and its bis(aza-18-crown-6) derivative (D2) have been studied in acetonitrile. The absorption, fluorescence, and phosphorescence spectra of D1 are similar to those of D2. Laser excitation of oxygen-free solutions of D1 and D2 leads to generation of a triplet state with a lifetime of ~1 μs and two intermediate species with lifetimes of ~100 μs and longer than 1 s.  相似文献   

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The structure of a radiation-protective sulfated polysaccharide, SP-APS, isolated from Spirulina platensis, was investigated by methylation analysis, partial acetolysis and 1H-NMR spec-troscopy. The repeating-unit of SP-APS as branched structures was elucidated.  相似文献   

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1‐Benzocyclobutenyl vinyl ether (1) was easily prepared by the elimination reaction of hydrogen bromide from 1‐benzocyclobutenyl 1‐bromoethyl ether obtained by 1‐bromobenzocyclobutene and ethylene glycol via two steps in a good yield. Cationic polymerizations of 1 was carried out at −78°C for 2 h in toluene in the presence of BF3OEt2 as an initiator to give quantitatively the corresponding polymers (2) as white solids. As a model reaction of the polymer reaction of 2 with dienophiles, the Diels–Alder reactions of 1‐methoxybenzocyclobutene with maleic anhydride (MA) in toluene at 100–140°C for 3 h were carried out to obtain the corresponding Diels–Alder adduct quantitatively at 140°C. The polymer reactions of 2 with MA and N‐phenylmaleimide (MI) in toluene were carried out to yield the corresponding Diels–Alder adduct polymers in good yields. The degree of introduction of the dienophile could be controlled by temperature, and the unreacted benzocyclobutene moiety could further react with another benzocyclobutene moiety or dienophile. The properties (solubilities, Tg, and temperature of 10% weight loss) of the polymers obtained from the polymer reaction were quite different from those of 2. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 59–67, 1999  相似文献   

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The structure of an anti-diabetic polysaccharide (TAP) obtained from the fruiting bodies of Tremella aurantia was investigated by methylation analysis, Smith degradation, partial acid hydrolysis, 13C-NMR spectrometry, and enzymatic digestion. The results suggested that TAP was composed of (1-->3)-linked alpha-D-mannopyranosyl residues as a backbone, some of which were substituted at position 2 with (1-->3)-linked beta-D-xylopyranose side chains and with beta-D-glucopyransyluronic acid at position 4 linked to terminal alpha-D-mannopyranose.  相似文献   

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Clear elucidation of the oxidative relationships of the active metal hydroperoxide moiety with its corresponding metal oxo and hydroxo intermediates would help the understanding of the different roles they may play in redox metalloenzymes and oxidation chemistry. Using an Mn(Me(2)EBC)Cl(2) complex, it was found that, in t-butanol-water (4 : 1) with excess H(2)O(2) at pH 1.5, the Mn(IV)-OOH moiety may exist in the catalytic solution with a mass signal of m/z = 358.1, which provides a particular chance to investigate its oxidative properties. In catalytic oxidations, the Mn(IV)-OOH moiety demonstrates a relatively poor activity in hydrogen abstraction from diphenyl methane and ethylbenzene with TOF of only 1.2 h(-1) and 1.1 h(-1) at 50 °C, whereas it can efficiently oxygenate diphenyl sulfide, methyl phenyl sulfide and benzyl phenyl sulfide with TOF of 13.8 h(-1), 15.4 h(-1) and 17.8 h(-1), respectively. In mechanistic studies using H(2)(18)O and H(2)(18)O(2), it was found that, in the Mn(IV)-OOH moiety mediated hydrogen abstraction and sulfide oxygenations, the reaction proceeds by two parallel pathways: one by direct oxygen insertion/transfer, and the other by plausible electron transfer. Together with a good understanding of the corresponding manganese(IV) oxo and hydroxo intermediates, this work provides the first chance to compare the reactivity differences and similarities of the active metal oxo, hydroxo and hydroperoxide intermediates. The available evidence reveals that the Mn(IV)-OOH moiety has a much more powerful oxidizing capability than the corresponding Mn(IV)=O and Mn(IV)-OH functional groups in both hydrogen abstraction and oxygenation.  相似文献   

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A cytotoxic principle was newly isolated from Chrysosplenium grayanum Maxim. (Saxifragaceae) and identified as beta-peltoboykinolic acid (1) on the basis of spectral data. Cytotoxicity of compound 1 was tested against various human cancer cell lines in vitro, and antitumor effect of this compound was demonstrated on Meth.A mouse fibrosarcoma. The experiment of combined treatment with compound 1, mitomycin C, and OK-432 resulted in enhancing the antitumor effect against B16-BL6 mouse melanoma in C57BL/6 mice.  相似文献   

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A novel low-molecular-weight pectic polysaccharide was isolated from sunflower heads that are a useless side product produced from sunflower oil processing. The low-molecular-weight pectic polysaccharide was purified by using an optimized four-step procedure and named as SHPPB-1. The molecular weight of SHPPB-1 is about 1.69× 104 Da. Structure characterizations of SHPPB-1 by monosaccharide composition, methylation analysis, and Fourier transform infrared (FT-IR) spectroscopy showed that SHPPB-1 is consisted of 1,4-linked α-D-GalpA and 1,4-linked 2-OAc-5-COOMe-α-D-GalpA with rare α/β-D-Rhap, α/β-D-Manp, and α/β-D-GalpA. This was combined with NMR spectroscopic analysis to propose a structure of SHPPB-1 as: →4)-[α/β-D-monosaccharide-(1→3)]-α-D-GalpA-(1→4)-2-OAc-5-COOMe-α-D-GalpA-(1→ .  相似文献   

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Shrimps are important and highly demanded seafood, but they have been reported as a cause of food hypersensitive reaction. The major allergen of shrimp is tropomyosin (TM). However, so far, there has been few report on such purification procedure. In this study, we developed a strategy for the purification of TM from shrimp (Penaeus vannamei Boone). Subsequently, we demonstrated that the apparent MW of this protein is about 66 kDa, and this protein naturally contains two subunits (38.5 and 36.6 kDa) with a ratio of 1 to 1. Interestingly, different from other known TMs from vertebrates, shrimp TM can self-assemble into nanofibres at high ionic strength induced by ATP. These findings help to understand the structure and polymerisation property of TM from shrimps.  相似文献   

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