Study of the reactions and reaction mechanisms of phosphine (Ph3P) and of phosphite ((PhO)3P) with sulphur (S8)

The reactions of sulphur with phosphine and phosphite were investigated by low-energy electron impact mass spectrometry and fast atom bombardment mass spectrometry. A previously reported mechanism of the Ph₃P–S₈ reaction was supported and a possible mechanism for the (PhO)₃P–S₈ reaction is proposed.     

Chemical Constituents from Cynoglossum gansuense

Two new alkaloids, i.e., (2,3‐dihydro‐1‐oxo‐1H‐pyrrolo[1,2‐a]pyrrol‐7‐yl)methyl (2S*,3S*)‐3‐[(β‐D ‐glucopyranosyl)oxy]‐2‐hydroxy‐2‐(1‐methylethyl)butanoate ( 1 ) and 1,2‐dihydro‐8‐methoxy‐2‐oxoquinoline‐4‐carboxylic acid ( 2 ), were isolated from the alcoholic extract of the whole plant of Cynoglossum gansuense, together with twelve known compounds Their structures were characterized by means of spectroscopic methods, especially by ¹H‐, ¹³C‐, and 2D‐NMR, as well as by HR‐MS experiments and comparison with literature data.     

Baker''''s yeast mediated reduction of substituted acenaphthenequinones: Regio-and enantioselective preparation of mono-hydroxyacenaphthenones

Baker's yeast mediated reduction of acenaphthenequinone within 4-10 h afforded mono-hydroxyacenaphthenone mainly with low enantioselectivity, the substrate and mono-hydroxyacenaphthenone product almost converted to dihydroxyacenaphthene after 48 h. By control of the reaction time and in the presence of DMF as co-solvent, the reduction of 6-substituted acenaphthenequinones under vigorous agitation afforded the corresponding 2-hydroxyacenaphthenones in 24-84% yields with 10-93% ee.     

Dexmedetomidine promotes the progression of hepatocellular carcinoma through hepatic stellate cell activation

Dexmedetomidine (DEX) is an anesthetic that is widely used in the clinic, and it has been reported to exhibit paradoxical effects in the progression of multiple solid tumors. In this study, we sought to explore the mechanism by which DEX regulates hepatocellular carcinoma (HCC) progression underlying liver fibrosis. We determined the effects of DEX on tumor progression in an orthotopic HCC mouse model of fibrotic liver. A coculture system and a subcutaneous xenograft model involving coimplantation of mouse hepatoma cells (H22) and primary activated hepatic stellate cells (aHSCs) were used to study the effects of DEX on HCC progression. We found that in the preclinical mouse model of liver fibrosis, DEX treatment significantly shortened median survival time and promoted tumor growth, intrahepatic metastasis and pulmonary metastasis. The DEX receptor (ADRA2A) was mainly expressed in aHSCs but was barely detected in HCC cells. DEX dramatically reinforced HCC malignant behaviors in the presence of aHSCs in both the coculture system and the coimplantation mouse model, but DEX alone exerted no significant effects on the malignancy of HCC. Mechanistically, DEX induced IL-6 secretion from aHSCs and promoted HCC progression via STAT3 activation. Our findings provide evidence that the clinical application of DEX may cause undesirable side effects in HCC patients with liver fibrosis.Subject terms: Cancer microenvironment, Cell growth     

Synthesis of new trans double-bond sphingolipid analogues: Delta(4,6) and Delta(6) ceramides

Unsaturation was introduced at Delta(4,6) and Delta(6) of the sphingoid chain of naturally occurring ceramide 1 via a beta-keto sulfoxide (12) and sulfone (18) derived from N-Boc-L-serine methyl ester acetonide (9), affording two novel ceramide analogues, (2S,3R)-2-octanoylamidooctadeca-(4E,6E)-diene-1,3-diol (2) and (2S,3R)-2-octanoylamidooctadec-(6E)-ene-1,3-diol (3). After C-alkylation of 12 with (E)-1-bromo-2-tetradecene (8), a trans double bond was installed by elimination of PhS(O)H, providing conjugated dienone oxazolidine 13. Reaction of 18 with 8, followed by desulfonation (Al(Hg)), afforded keto-oxazolidine 20, which bears a (E)-Delta(6) double bond. The syntheses of analogues 2 and 3 from ketones 13 and 20, respectively, were completed by the following sequence of reactions: diastereoselective reduction (NaBH(4)/CeCl(3) or DIBAL-H), hydrolysis of the oxazolidine ring, liberation of the amino group, and installation of the N-amide group.     

α-Fe2O3纳米微粒/硬脂酸交替L-B膜的结构表征

We reported in this paper FTIR linear diehroic spectroscopy and anisotropic properties of the nanoparticulate α-Fe_2O_3-stearate alternating Langmuir-Blodgett films (Fe_2O_3-St LB films) a new inorganic-organic quantum superlattice system. A new method fitted to inorganic-organic alternating films is used to study the molecular orientation and discuss the order arrangement of the nanopartieles in the films. The the results show that a configuration of stearate ions bound to the surface of the nano-particles: COO~- group are spherically bound to the surface of the nanoparticles; the hydrocarbon chains are almost perpendicular (31°±5°) to the substrate (7 nm-Fe_2O_3-St LB films). The orientation of hydrocarbon chains and CH_2 scissors vibration show the existence of trans-zigzag planar structure for C—C broken bone of the hy7drocarbon chains, which is related to high-order structure of the alternate films.     

Two New Xanthone Glycosides from Polygala tenuifolia

Two new xanthone glycosides,polygalaxanthone IV and V were isolated from the roots of Polygala tenuifolia Willd. Their structures were established as 6-O-[α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranosyl]-1-hydroxy-3,7-dimethoxyxanthone(polygalaxanthone IV), and 6-O-[α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranosyl]-1,3-dihydroxyl-7-methoxyxanthone (polyga-laxanthone V),respectively, on the basis of chemical and spectral evidence.     

Determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples using hollow fiber-protected liquid-phase microextraction and high performance liquid chromatography

A new method based on hollow fiber-protected liquid-phase microextraction (LPME) was developed for the simultaneous determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples. In LPME, analytes were extracted into 1-octanol immobilized in the micropores of a poly(vinylidene fluoride) porous hollow fiber membrane, and back extracted into the acceptor (4 M HCl) filled in the lumen of the hollow fiber. After LPME, the analytes trapped in the acceptor were analyzed with high-performance liquid chromatography after neutralization. The effect of extraction factors such as sample pH, acceptor pH, salinity, extraction time, stirring rate, and humic acid were studied. Under the optimized conditions, the limits of detection and relative standard deviations were respectively in the range of 0.5–1.0 μg L⁻¹ and 3.9–4.7% (n = 5). The proposed method was applied to determine atrazine, desethyl atrazine and desisopropyl atrazine in wastewater and groundwater samples. The three analytes were below the limits of detection, but good relative spiked recoveries over 90.1 ± 5.9% at 5 μg L⁻¹ spiked level were obtained.     

Adsorption, desorption and activities of acid phosphatase on various colloidal particles from an Ultisol

Adsorption, desorption and activity of acid phosphatase on various soil colloidal particles and pure clay minerals were studied. Higher adsorption amounts and low percentage of desorption of acid phosphatase were found on fine soil clays (<0.2 μm). Electrostatic force and ligand exchange are the major driving forces that are involved in the adsorption of enzymes on soil clays. More enzyme molecules were adsorbed on soil clays in the presence of organic components. However, enzymes on organic clays were more easily released. One-third of the enzyme on goethite was adsorbed via ligand exchange process. Some other interactions, such as van der Waals force, hydrophobic force and hydrogen bonding may be more important in the adsorption of enzyme on kaolinite and the enzyme in this system cannot be easily removed. Coarse clays (0.2–2 μm) and inorganic soil clays had higher affinities for enzyme molecules than fine clays and organic clays, respectively. The activity of enzyme bound on soil clays was inhibited and the thermal stability was increased in the presence of organic matter. Data obtained in this study are helpful for a better understanding of the interactions of enzymes with inorganic and organic constituents in soil and associated environments.     

Controlling the agglomeration of anisotropic Ru nanoparticles by the microwave-polyol process

A rapid polyol process for the synthesis of ruthenium nanoparticles was developed using microwave irradiation. A colloidal solution of monodispersed anisotropic Ru metal nanoparticles (mean particle size 2-6 nm) with different aspect ratios was obtained first. Particles with different degrees of agglomeration have also been synthesized using monodisperse particles as seeds and PVP (poly-N-vinyl-2-pyrrolidone) as the stabilization reagent. The stabilization mechanisms of different protective reagents were studied by UV-vis spectra. The HRTEM images indicated that dendritic particles formed by controlling agglomeration consisted of single-crystal domains with a random crystalline orientation.