LC-MS/MS定量测定大鼠和人肝微粒体孵育液中丁苯酞浓度方法的建立

正丁苯酞(n-butylphthalide,NBP),又名芹菜甲素,是我国心脑血管领域第一个拥有自主知识产权的药物,它具有很强的抗脑缺血损伤作用,而毒副作用较低[1-2].     

Embedded polymerization driven asymmetric PEM for direct methanol fuel cells

This work reports the fabrication of proton exchange membranes (PEM) with stronger resistance to methanol penetration than Nafion^®117. A three-component acrylic polymer blend (TCPB) consisting of a copolymer of 4-vinylphenol-methyl methacrylate, poly(butyl methacrylate) (PBMA) and a copolymer of methyl methacrylate-ethyl acrylate is used as the methanol barrier. In order to implant a proton source phase within the membrane as homogeneously as possible, the hydrophilic monomers, 2-acrylamido-2-methyl propanesulfonic acid (AMPS), 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) dimethylacrylate (PEGDMA), are polymerized only after they have been embedded in the TCPB matrix. The embedded polymerization has resulted in an asymmetric membrane structure, in which the hydrophilic network is sandwiched by two layers of matrixes with high percentages of TCPB. As expected, this asymmetric membrane structure exhibits lower methanol uptake than Nafion^®117; and a proton conductivity in the range of 10⁻³–10⁻⁴ S/cm, which is dependent on the concentration of the sulfonic acid content. It is suggested that the two external layers in this asymmetric membrane provide primarily methanol-blocking and supporting proton-conducting properties; while the middle layer supplies protons and conserves water. This unique sandwiched PEM structure from embedded polymerization is confirmed by microstructure characterizations and by physical property measurements.     

SYNTHESIS OF SEGMENTED COPOLYMERS WITH POLYSULFONES CONTAINING BISPHENOL A OR PHENOLPHTHALEIN UNITS AS HARD SEGMENT

Two series of segmented copolymers with polysulfones, containing bisphenol A and phenol-phthalein units as hard segments respectively, were synthesized. Isocyanate-terminated polyoxy-propylene was used as soft segments for both series.     

Improving the quality of 3D-QSAR by using flexible-ligand receptor models

To address the problems associated with molecular conformations and alignments in the 3D-QSAR studies, we have developed the Flexible Ligand - Atomic Receptor Model (FLARM) 2.0 method. The FLARM 2.0 method has three unique features as compared to other pseudoreceptor model methods: (1) the training ligands are flexibly optimized inside the receptors to achieve minimal docking energies; (2) the receptor atoms are spatially moveable in the process of genetic evolving in order to avoid improper initial receptor shapes; and (3) void receptor sites are specially favored in order to obtain open receptor models that allow large gaps. Advantages of an open model include less noise information, a smaller risk of overfitting, and ease of locating the key interaction sites. The latter two features, inherited from the previous FLARM 1.0 method, can improve the predictive ability of the 3D-QSAR models, while the first feature is newly implemented to relieve the uncertainty caused by improper conformation and alignment. Three FLARM 2.0 case studies were performed, and the results show that FLARM 2.0 models are highly predictive and robust. FLARM 2.0 pseudoreceptor models can correspond well with the pharmacophore models and/or the binding sites of the real protein receptors.     

Application of Headspace Liquid-Phase Microextraction to the Analysis of Volatile Halocarbons in Water

The determination of four volatile halocarbons (CHCl₃, CCl₄, C₂HCl₃ and C₂Cl₄) in water by headspace liquid-phase microextraction (HS-LPME) with gas chromatography using a micro electron capture detector (GC-μECD) is described. The effects of the type and volume of the extraction solvent, headspace volume, stirring rate, extraction temperature and time and ionic strength on the extraction performance are investigated and optimized. The developed protocol yields a linear calibration curve in the concentration range from 0.05 to 50 µg L^?1 for the target analytes; the detection limits ranged from 0.003 to 0.146 µg L^?1 and the relative standard deviation (R.S.D.) values below 8.45%. The results demonstrate that HS-LPME followed with GC-μECD is a simple and reliable technique for the determination of volatile halocarbons in water samples.     

Determination of minor conformational changes of a doxorubicin-peptide conjugate under chromatographic conditions

Thermodynamic analysis of the reversed-phase retention behavior of a doxorubicin-peptide conjugate demonstrated that the degree of non-linearity observed in Van't Hoff plots was impacted by mobile phase acetonitrile content over the 25-38% acetonitrile (v/v) range tested. Small decreases in the non-polar surface area of the doxorubicin-peptide conjugate as a function of temperature were estimated from these data using linear solvent strength relationships, suggesting that the retention behavior may be the result of minor analyte conformational changes during the chromatographic experiment. This hypothesis was supported via circular dichroism (CD), Raman and 1H NMR spectroscopic studies of the doxorubicin-peptide conjugate in selected chromatographic mobile phase compositions. The CD and Raman data indicated small changes to the apparent analyte microenvironment as a function of temperature and bulk solvent environment, while 1H NMR studies specifically demonstrated the environmental sensitivity of protons on three non-polar peptide residues and the proximal aromatic region of the analyte. Together, these data suggest that minor changes to the conformational order of the essentially random structure of the doxorubicin-peptide conjugate are sufficient to impact chromatographic performance.     

Study on the Thermodynamic Stabilities of Te-Substituted Di-n-butyltellurium Ylide

SincethediscoveryofphosphoniumylidebyWittig',carbanionsstabilizedbyadjacentfifthorsixthgrouponiumionshavebeendevelopedasavaluablereactiveintermediate.However,despitethegreateffortsinylidechemistryinthepastfewdecades',relativelylittleisknownaboutthethermodynamicstabilitiesofylidecarbanions.Itiswellknowthatthequantitativemeasuresofthecarbanionstabilityhavecontributedagreatdealtothedevelopmentoforganicchemistry,thereforeitshouldbeexpectedthattheknowledgeaboutylidestabilitywillalsoprovidavaluableg…     

Contractions with a unilateral shift summand are reflexive

If T is a contraction on the Hilbert space H and there is an invariant subspace K for T such that T/K is similar to a backward shift, then T is reflexive. If similarity is replaced by quasi-similarity, then the same conclusion holds under the additional condition that the defect index of T be finite.This research was partially supported by National Science Council (Republic of China).     

Filtered backprojection for the reconstruction of a high-resolution (4,2)D CH3-NH NOESY spectrum on a 29 kDa protein

Projection-reconstruction (PR) NMR enables rapid collection of multidimensional NMR data. NOESY represents a particularly difficult challenge for currently existing reconstruction algorithms, as it requires the quantitative reconstruction of an unknown number of peaks, at full sensitivity. We have demonstrated the successful application of PR-NMR to NOESY by determining the 4D methyl/amide NOESY spectrum of a 29 kDa protein, human carbonic anhydrase II, from 2D projections, using filtered backprojection for reconstruction. Compared with a 3D control spectrum, all expected peaks were faithfully reconstructed, with correct volumes and with no artifacts. Filtered backprojection thus provides a way to obtain high-resolution 4D NOESY data in the time required for conventional 3D data collection.     

两种胶原纤维固化单宁对La3+的吸附特性研究

以皮胶原纤维为基质,通过交联剂分别将黑荆树单宁和杨梅单宁固化在胶原纤维上制备吸附材料。实验表明,这两种吸附材料对稀土金属离子La^3＋有很好的吸附作用。在pH为4.5的条件下,当吸附剂用量为0.1 g,La^3＋初始浓度为9.952 mmol·L^-1,固化杨梅单宁的平衡吸附量为0.388 mmol·g^-1,比固化黑荆树单宁略大,其吸附平衡均符合Freundlich方程。进一步研究了固化杨梅单宁的吸附动力学、温度、pH值等对吸附平衡的影响。结果表明,温度对吸附平衡的影响不明显;pH值对吸附平衡有较大影响,在适当范围内提高pH值会增加平衡吸附量;吸附动力学可用拟二级速度方程来描述。当吸附温度为293 K时,由拟二级速率方程计算所得的平衡吸附量与实测的平衡吸附量误差在3%以内。同时固化杨梅单宁也具有良好的柱动力学特性。