Fingerprinting and simultaneous determination of alkaloids in Picrasma quassioides from different locations by high performance liquid chromatography with photodiode array detection

A simple and sensitive method was developed and validated for profiling and simultaneous quantitation of seven alkaloids (6-hydroxy-β-carboline-1-carboxylic acid, β-carboline-1-carboxylic acid, β-carboline-1-propanoic acid, 3-methylcanthin-5,6-dione, 5-hydroxy-4-methoxycanthin-6-one, 1-methoxycarbony-β-carboline, and 4,5-dimethoxycanthin-6-one) in Picrasma quassioide grown in different locations by high-performance liquid chromatography with photodiode array detection. The analysis was conducted on a Phenomenex Gemini C(18) column at 35°C with mobile phase of 25 mM aqueous ammonium acetate (pH 4.0, adjusted by glacial acetate acid) and acetonitrile. A common fingerprint chromatograph under 254 nm consisting of 27 peaks was constructed for the evaluation of the similarities among 31 P. quassioide samples. Samples from Guangdong and Guangxi Provinces were found to be within group linkage and showed significant difference from that of Jiangxi Province origin by using principal component analysis and hierarchical clustering analysis. In addition, the seven alkaloids were identified by electrospray ionization mass spectrometry and comparing with reference standards and literature data. All of them were determined simultaneously using the established HPLC method. This rapid and effective analytical method could be employed for quality assessment of P. quassioide, as well as pharmaceutical products containing this herbal material.     

丝组二肽对牛血清白蛋白的切割作用研究

肽与蛋白质的切割作为生物化学中的热点之一 ,具有非常广泛的应用 .长期以来 ,天然存在的多种蛋白酶如胰蛋白酶 (Trypsin)、糜蛋白酶 (Chymotrypsin)由于其高活性及区域选择性 ,一直是蛋白切割的主要工具 .但是这些酶只能在某些特定的条件 (如 p H值和温度等 )下使用 ,而且由于蛋白酶对底物的特异性要求高 ,因而切割蛋白的断裂位点相对较少 ,有一定的局限性 .而现代生物化学及分子生物学的发展在蛋白切割方面提出了越来越多的要求 [1,2 ] ,如蛋白部分合成 ,大蛋白的序列测定 ,蛋白区域结构与功能的分析 ,蛋白与其它蛋白、核酸、膜形成复合…     

A Stable Vector for High-Level Expression and Secretion of Human Interferon αA in Yeast

Yeast high stable plasmid vector pHC11 was constructed by introducing pEMBL Yi27 cleaved with SmaI into the SnaBI site of intact 2 μm plasmid. The result of plasmid stability assay revealed that 82% of the host cells still harbored the vector after 50-generations growth in non-selective medium, which confirmed the existence of a non-functional region in 2 μm plasmid. The human interferon αA (IFN αA) gene expression-secretion cassette was inserted into pHC11, and the yeast transformant was cultured in complex medium. Tbe data showed that the expressed product was 36.8% of the total protein amount in the culture supernatant and the IFN αA biological activity was 2.6×10~(10) units per liter, demonstrating that high-level expression and secretion of IFN αA were achieved in yeast by using the stable vector pHC11.     

Characterization of electrospray ionization mass spectrometry for N-diisopropyloxyphosphoryl dipeptide methyl esters

A systematic study of the fragmentation pattern of N-diisopropyloxyphosphoryl (DIPP) dipeptide methyl esters in an electrospray ionization (ESI) tandem mass spectrometry (MS/MS) was presented. A combination of accurate mass measurement and tandem mass spectrometry had been used to characterize the major fragment ions observed in the ESI mass spectrum. It was found that the alkali metal ions acted as a fixed charge site and expelled the DIPP group after transferring a proton to the amide nitrogen. For all the N-phosphoryl dipeptide methyl esters, under the activation of a metal ion, the rearrangement product ion at m/z 163 was observed and confirmed to be the sodium adduct of phosphoric acid mono-isopropyl esters (PAIE), via a specific five-membered penta-co-ordinated phosphorus intermediate. However, no rearrangement ion was observed when a beta-amino acid was at the N-terminal. This could be used to develop a novel method for differentiating isomeric compounds when either alpha- or beta-amino acid are at the N-terminus of peptides. From the [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters (DIPP Xaa1 Xaa2 OMe), the peaks corresponding to the [M+Na Xaa1 C3H6]+ were observed and explained. The [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters with Phe located in the C-terminal, such as DIPPValPheOMe, DIPPLeuPheOMe, DIPPIlePheOMe, DIPPAlaPheOMe and DIPPPhePheOMe, had characteristic fragmentation. Two unusual gas-phase intramolecular rearrangement mechanisms were first proposed for this fragmentation. These rearrangements were not observed in dipeptide methyl ester analogs which did not contain the DIPP at the N-terminal, suggesting that this moiety was critical for the rearrangement.     

二维层状磷酸亚磷酸钒(Ⅳ)化合物[V_2O_2(OH)(HPO_3)(HPO_3)_(0·7)(PO_3OH)_(0·3)]·(C_6N_2H_(16))_(0·5)的水热合成与结构表征

迄今,在中温水热条件下已合成了大量具有空旷骨架结构的过渡金属磷酸盐微孔材料[1],这类材料在非线性光学材料、磁性材料、超导材料及催化等诸多方面具有潜在的应用前景[2~5].自从第一个以有机胺为模板的磷钒氧化合物[(CH3)2NH2]K4[V10O10(H2O)2(OH)4(PO4)7]·4H2O[6]的合成以来,又有几十种结构的磷钒氧化合物被报道.但以亚磷酸为结构基元构筑的磷钒氧化合物的报道较少.1995年,Zubieta等[7]报道了以哌嗪为模板剂的两个亚磷酸钒化合物[HN(Me)(CH2CH2)2N·(Me)H][(VO)4(OH)2(HPO3)4]和[H2N(CH2CH2)2NH2][(VO)3(HPO3)4(H2O…     

可见光高催化活性GO/Ag3PO4/Ni复合薄膜的制备和性能

以磷酸铵和氧化石墨烯悬浊液的混合液为电解液,采用电化学共沉积法制备了Ag3PO4基GO/Ag3PO4/Ni复合薄膜。运用扫描电子显微镜(SEM)、能量色散谱(EDS)、X射线衍射(XRD)、拉曼光谱(Raman)和紫外可见漫反射光谱(UV-Vis DRS)等对其形貌、物相和光谱特性进行分析。最佳工艺制备的GO/Ag3PO4/Ni复合薄膜呈现出GO包覆在直径为100 nm左右的Ag3PO4纳米球外的表面形貌。GO片与Ag3PO4纳米球之间存在强电荷相互作用。与单独的Ag3PO4纳米球相比,GO片的附着导致带隙缩小,可见光区的吸收率增强。可见光下考察了复合薄膜降解罗丹明B的光催化活性和稳定性,并利用荧光光谱和捕获剂法对薄膜的光催化机理进行了探索。结果表明,GO片的加入不仅显著提高了Ag3PO4的光催化活性,而且提高了Ag3PO4的结构稳定性。光催化降解罗丹明B 60 min时,GO/Ag3PO4/Ni复合薄膜的降解率是Ag3PO4/Ni薄膜的1.32倍。在保持薄膜光催化活性基本不变的前提下可循环使用7次。GO优异的电荷传导性能,以及Ag3PO4纳米球与GO片之间的正协同效应是提高复合薄膜光催化性能的主要原因。     

窄带随机激励双稳压电悬臂梁响应机制与能量采集研究

具有中心频率的窄带随机振动是一种典型的环境振动,其振动特征与环境的变化密切相关.本文以双稳压电悬臂梁能量采集系统为研究对象,分析系统在不同磁铁间距下的等效线性固有频率特性,以带通滤波器输出一定带宽的窄带随机激励模拟环境振动,研究系统的响应和能量采集特征.研究表明,对于一定带宽的窄带随机激励,一方面系统始终存在一个固定的磁铁间距使其输出达到峰值,另一方面当激励中心频率在一定范围内变化时,系统还分别存在另外两个或一个不同磁铁间距也能使系统输出达到峰值,而且该峰值特性是系统在其等效线性固有频率处诱导双稳或单稳“共振”形成的.研究结果可为具有窄带随机激励特征的振动能量采集提供一定的理论和技术支持.     

Electronic structures and vibrational properties of coronene on Ru(0001): first-principles study

We calculate the configurations, electronic structures, vibrational properties at the coronene/Ru(0001) interface, and adsorption of a single Pt atom on coronene/Ru(0001) based on density functional theory calculations. The geometric structures and electronic structures of the coronene on Ru(0001) are compared with those of the graphene/Ru(0001). The results show that the coronene/Ru(0001) can be a simplified model system used to describe the interaction between graphene and ruthenium. Further calculations of the vibrational properties of coronene molecule adsorbed on Ru(0001) suggest that the phonon properties of differently corrugated regions of graphene on Ru(0001) are different. This model system is also used to investigate the selective adsorption of Pt atoms on graphene/Ru(0001). The configurations of Pt on coronene/Ru(0001) with the lowest binding energy give clues to explain the experimental observation that a Pt cluster selectively adsorbs on the second highest regions of graphene/Ru(0001). This work provides a simple model for understanding the adsorption properties and vibrational properties of graphene on Ru(0001) substrate.     

NiTi形状记忆合金相变过程的正电子湮没研究

采用正电子湮没技术研究了NiTi合金在降温和升温过程中缺陷和电子密度随温度的变化.在降温过程中,当温度从295K降至225K时,合金的电子密度nb随温度的降低而下降,在225K时降至最小;随后,nb随温度的降低而升高.当温度从295K降至221K时,合金缺陷的开空间随温度的下降而升高,在221K时达到最大值;随后,缺陷的开空间随温度的下降而下降.在升温过程中,当温度从25K升至253K时,合金的电子密度nb随温度的升高而降低,并在253K时达到最小;当温度从253K升至295K时,合金电子密度nb随温度的升高而升高.在相变临界温度点Ms=222K,Mf=197.2K,As=237.5K,Af=255.5K附近,合金的电子密度nb及合金缺陷的开空间均有异常的变化.