Complete NMR assignments of the antibacterial biflavonoid GB1 from Garcinia kola

From the antibacterial fraction of the roots of Garcinia kola, 3',4',4',5,5',7,7'-heptahydroxy-3,8'-biflavanone (GB1) was isolated as the major constituent, whose interesting conformations were studied on the basis of its 1D and 2D NMR spectra obtained at different temperatures and in different solvents. GB1 showed antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) with MIC of 32 and 128 microg/ml, respectively.     

Chemiluminescence detection coupled to high-performance frontal analysis for the determination of unbound concentrations of drugs in protein binding equilibrium

High-performance frontal analysis coupled with chemiluminescence detection (HPFA-CL) was developed for the determination of unbound oxacillin concentration in human serum albumin solution. The HPFA system consisted of an ISRP column and a mobile phase of 67 mM potassium phosphate buffer of pH 7.4 and ionic strength of 0.17. The luminol-H2O2-Co2+ system was used in the chemiluminescence detection. An enhancement of luminol chemiluminescence by oxacillin was investigated and employed for determining the concentration of oxacillin in the HPFA eluate. Sample solutions were directly injected onto the column; the drug was eluted as a zonal peak with a plateau region. The unbound drug concentrations were determined by using the height of the plateau. The results agreed with those obtained with conventional ultrafiltration-HPLC method. Good reproducibility was confirmed by the within run and between run RSD < or = 7.4%. HPFA-CL provided a selective method for determination of unbound drug concentration in protein binding equilibrium.     

A general approach to cyathin diterpenes. Total synthesis of allocyathin B(3)

[reaction: see text] The synthesis of allocyathin B(3) from an advanced intermediate possessing the ring system and relative stereochemistry but lacking the isopropyl and hydroxymethyl groups is reported. The isopropyl group was introduced by radical cyclization of a methyl propargyl acetal of an alpha-bromo ketone, and the hydroxymethyl group was generated by Pd-catalyzed carbonylation of a vinyl triflate. The route provides functionalized intermediates that could allow access to more complex members of the cyathin family of diterpenes.     

酞菁化合物LB单分子膜的SERRS

酞菁类化合物具有优良的光电特性,选择适当的取代侧链可得到稳定的LB成膜材料,可望在微电子器件等方面获得重要的应用.本工作观测了四-4-(2,4-二特戊基苯氧基)酞菁铜(CuPc(Dt-PP)_4)在银岛膜上的LB单分子层的表面增强共振拉曼散射(SERRS)光谱。比较其固体粉末的共振拉曼散射(RRS)光谱,讨论了酞菁铜分子大环在载片表面的取向及其可能的原因。1 实验CuPc(Dt-PP)_4样品由陈文启等合成,经元素分析、IR、NMR、色谱等研究确认其结构如图1所示.银岛膜用真空蒸镀法制备在玻璃载片上。用同时蒸镀在铜网上的银膜的透射电     

Diffusion exchange NMR spectroscopic study of dextran exchange through polyelectrolyte multilayer capsules

Diffusion exchange of dextran with molecular weights 4.4 and 77 kDa through polyelectrolyte multilayer (PEM) hollow capsules consisting of four bilayers of polystyrene sulfonate/polydiallyldimethylammonium chloride has been investigated using two-dimensional nuclear-magnetic-resonance methods: diffusion-diffusion exchange spectroscopy (DEXSY) and diffusion-relaxation correlation spectroscopy (DRCOSY). Results obtained in DRCOSY experiments show that the diffusion process of dextran 77 kDa exhibits an observation time dependence suggesting a diffusion behavior restricted by confinement. We find evidence for both single capsule and capsule aggregate states, with a partitioning of the 77-kDa dextran between the free and capsule states much larger than that suggested by volume fraction alone. Results from DEXSY experiments show that dextran 77 kDa is in diffusive exchange through the capsules with an exchange time of around 1 s. In contrast, the capsules have no detectable influence on the diffusion process of the dextran 4.4 kDa. This quantitative information may be used in designing PEM capsules as drug carriers.     

The growth of perylene on Ru(0001)

The structure of perylene adsorbed on Ru(0001) surface has been studied by ultraviolet photoemission spectroscopy (UPS) and low-energy electron diffraction. An ordered p(4x4) structure is observed from a monolayer (about 4 A thickness) of the perylene on Ru(0001) surface. UPS measurements show the molecular features, from the perylene multiplayer, between 2 and 10 eV below the Fermi level. Angle-resolved ultraviolet photoemission spectroscopy measurements suggest that the perylene molecular plane is parallel to the substrate. Temperature dependent UPS measurements show that the perylene multilayer is stable on Ru(0001) surface up to 125 degrees C. The desorption of the multilayer and the decomposition of the monolayer are observed above 125 degrees C.     

Solubility of methane in octane + ethanol at temperatures from 303.15 K to 333.15 K and pressures up to 12.01 MPa

Solubility of methane in octane + ethanol was measured at temperatures ranging from 303.15 K to 333.15 K and pressures ranging from 2.60 MPa to 12.01 MPa. Experimental data were analyzed using the Soave-Redlich-Kwong equation of state with three types of mixing rules, and the estimated average deviation from the experimental solubility data was less than 3.5 %.     

Screening of glycoside isomers in P. scrophulariiflora using ionic liquid‐based ultrasonic‐assisted extraction and ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

A powerful ionic liquid‐based ultrasonic‐assisted extraction (ILUAE) method combined with ultra‐performance liquid chromatography coupled to electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (UPLC/ESI‐QTOFMSⁿ) was employed in the rapid simultaneous screening of iridoid glycosides, phenylethanoid glycosides, and cucurbitacin glycosides from P. scrophulariiflora. The ILUAE procedure was optimized over several ultrasonic parameters, including the ultrasonic power, concentration of the ionic liquid, and solid–liquid ratio. A comparison with conventional heat‐reflux extraction and regular UAE demonstrated that the optimized approach yielded a high extraction efficiency (Picroside I, 2.84%; Picroside II, 3.57%; 6‐O‐E‐feruloyl catalpol, 2.20%) within a short extraction time of 30 min. Negative ion mode ESI‐QTOFMS² analysis of the fragmentation reactions of the [M–H]^– ions was conducted to characterize the diagnostic ions related to the glycosyl moieties, aglycone units, and the type and substituted position of the ester groups. Interestingly, the positional isomers of the iridoid glycosides could be easily discriminated based on the characteristic ions. A total of 15 glycosides, including three groups of iridoid glycoside isomers and two groups of phenylethanoid glycoside isomers, were conveniently identified within 13.5 min. Moreover, 6'‐O‐vanilloyl catalpol was identified in P. scrophulariiflora for the first time. The method developed here was further validated by measuring the recovery, correlation coefficient (R²), and reproducibility (RSD, n = 5) of three iridoid glycosides: 89.60%–109.02%, 0.9991–0.9998, and 0.93%–1.44%, respectively. This study demonstrated the capabilities of ILUAE combined with UPLC/ESI‐QTOFMSⁿ for the rapid screening of glycosides in P. scrophulariiflora. This method offers an approach to similar studies on other natural plants. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and characterization of fluorine-containing cholesteric liquid crystalline polysiloxanes bearing trifluoromethyl-substituted mesogens

A series of side-chain liquid crystal (LC) polysiloxanes were synthesised with Poly(methylhydrogeno)siloxane, 4?-(undec-10-enoyloxy) biphenyl – 4 – yl 4- (trifluoromethyl) benzoate (M_th) and a chiral nematic (N*) LC monomer 1-allyl 10-(cholesteryl)-decanedioate (M_ch). The chemical structures and LC properties of the monomers and polymers were characterised by FTIR, ¹H-NMR, differential scanning calorimetry, thermogravimetric analysis, POM and X-ray diffractometer. M_ch is monotropic N* LC. The homopolymer derived from monomer M_ch is enantiotropic N* LC. Monomer M_th is a smectic A liquid crystal. The copolymers derived from M_ch and M_th are N* LCs. The temperatures at which 5% weight loss occurred are greater than 300°C for all the fluoro-containing polymers, and the residue weights of the samples at 600°C increased slightly as the content of trifluoromethyl mesogens increased in the polymers. The glass transition temperatures of the polymers increased as trifluoromethyl mesogens increased, too. The N*–I phase transition temperatures show a negative deviate from ideal or linear behaviour. The values of the enthalpy changes for the cholesteryl containing polymers are rather low and this is attributed to the biaxiality of cholesteryl moiety which tends to reduce the change in the orientational order at the N*–I transition. Compared to the monomers, the polymers show wider mesophase region.     

Solvothermal synthesis of nanoscaled LiFePO4 with thinner thickness along [010] direction

Single-phased nanosized LiFePO₄ with thinner thickness along [010] crystallographic direction were successfully fabricated under solvothermal condition by using glycerol as co-solvent. The as-obtained product with thinner thickness is beneficial for fast migration of Li ions in the olivine-structured LiFePO₄, hence exhibiting excellent electrochemical performance.