4-巯乙基吡啶配基与IgG相互作用的分子模拟研究

4-巯乙基吡啶(MEP)是一种新型的疏水性电荷诱导层析(HCIC)配基,具有良好的抗体分离性能,采用分子模拟方法研究MEP配基与IgG间的分子相互作用,以探讨HCIC分离机制.先通过分子对接搜索IgG分子Fc片段A链的蛋白表面,确定12个可能与MEP结合的位点区域,然后用分子动力学模拟考察了其中6个位点的结合性能.结果表明,MEP在Fc-A链表面的结合具有疏水倾向性,pH中性条件下,MEP能稳定地结合在TYR319和LEU309附近的位点,并与两者形成氢键作用,该区域具有疏水性极强的口袋结构;其他位点的结合较不稳定,受MEP取向影响大.在pH4.0酸性条件下,原先稳定结合的MEP快速从Fc-A链表面脱离,主要原因是MEP和Fc间的静电排斥作用,以及疏水作用减弱和氢键结合的消失.通过分子模拟方法,从分子水平验证了HCIC独特的作用机理:疏水相互作用主导吸附,静电排斥作用协助解吸.     

可见光响应的镍硅共掺杂二氧化钛及其光催化性能

为了更好地利用太阳光和提高二氧化钛的光催化性能,以钛酸四正丁酯、正硅酸乙酯、六水合硝酸镍为原料,在高压釜中140℃非水溶剂热反应,所得材料经400℃焙烧制得镍硅共掺杂的二氧化钛光催化剂.所得材料用X射线衍射、氮吸附、透射电镜、X射线光电子能谱、傅里叶变换红外光谱、紫外漫反射等测试手段分析,结果显示所有样品均为锐钛矿型二氧化钛,Si和Ni均掺杂到TiO2体相中,样品具有较大的比表面积,其最大达303.3m2·g-1.在可见光照射下,以降解罗丹明-B为探针反应研究其可见光催化性能,与未掺杂和镍掺杂的二氧化钛相比较,共掺杂的二氧化钛具有更高的可见光催化性能,当Ni/Ti和Si/Ti的物质的量的比分别为0.01和0.20时,可见光催化性能最好.可见光催化性能的提高归因于镍和硅的协同作用.     

Platinum Nanoflowers on Scratched Silicon by Galvanic Displacement for an Effective SALDI Substrate

We report a new and facile method for synthesizing 3D platinum nanoflowers (Pt Nfs) on a scratched silicon substrate by electroless galvanic displacement and discuss the applications of the Pt Nfs in surface‐assisted laser desorption/ionization‐mass spectrometry (SALDI‐MS). Surface scratching of n‐type silicon is essential to induce Pt Nf growth on a silicon substrate (to obtain a Pt Nf silicon hybrid plate) by the galvanic displacement reaction. The Pt Nf silicon hybrid plate showed excellent SALDI activity in terms of the efficient generation of protonated molecular ions in the absence of a citrate buffer. We propose that the acidity of the Si? OH moieties on silicon increases because of the electron‐withdrawing nature of the Pt Nfs; hence, proton transfer from the Si? OH groups to the analyte molecules is enhanced, and finally, thermal desorption of the analyte ions from the surface occurs. Signal enhancement was observed for protonated molecular ions produced from a titania nanotube array (TNA) substrate on which Pt nanoparticles had been photochemically deposited. Moreover, surface modification of the Pt Nf silicon hybrid plate by perfluorodecyltrichlorosilane (FDTS) (to obtain an FDTS‐Pt Nf silicon hybrid plate) was found to facilitate soft SALDI of labile compounds. More interestingly, the FDTS‐Pt Nf silicon hybrid plate acts 1) as a high‐affinity substrate for phosphopeptides and 2) as a SALDI substrate. The feasibility of using the FDTS‐Pt Nf silicon hybrid plate for SALDI‐MS has been demonstrated by using a β‐casein digest and various analytes, including small molecules, peptides, phosphopeptides, phospholipids, carbohydrates, and synthetic polymers. The hybridization of Pt Nfs with a scratched silicon substrate has been found to be important for achieving excellent SALDI activity.     

Determination of cadmium with a sequential injection lab-on-valve by anodic stripping voltammetry using a nafion coated bismuth film electrode

This work exploited a sequential injection lab-on-valve (LOV) system for the determination of cadmium by anodic stripping voltammetry (ASV). A miniaturized electrochemical flow cell (EFC) was fabricated in LOV, in which a nafion coated bismuth film electrode was used as working electrode. The cadmium was electrodeposited on the electrode surface in bismuth solution, and measured with the subsequential stripping scan. Under optimal conditions, the proposed system responded linearly to cadmium concentrations in a range 2.0-100.0 μg L⁻¹. The detection limit of this method was found to be 0.88 μg L⁻¹. By loading a sample volume of 800 μL, a sampling frequency of 22 determinations h⁻¹ was achieved. The repeatability expressed as relative standard derivation (R.S.D.) was 3.65% for 20 μg L⁻¹ cadmium (n = 11). The established method was applied to analysis of trace cadmium in environmental water samples and the spiked recoveries were satisfactory.     

High-performance affinity monolith chromatography for chiral separation and determination of enzyme kinetic constants

A new kind of immobilized human serum albumin (HSA) column was developed by using the sub-micron skeletal polymer monolith based on poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [poly(GMA-EDMA)] as the support of high-performance affinity chromatography. Using the epoxide functional groups presented in GMA, the HSA immobilization procedure was performed by two different means. The affinity columns were successfully adopted for the chiral separation of d,l-amino acids (AAs). Then this method was shown to be applicable to the quantitative analysis of d-tryptophan, with a linear range between 12.0 μM and 979.0 μM, and a correlation coefficient above 0.99. Furthermore, it was used for the analysis of urine sample. This assay is demonstrated to be facile and relatively rapid. So it allows us to measure the enzyme catalytic activity in the incubation of d,l-AAs with d-AA oxidase and to study the kinetics of the enzyme reaction. It implied that the affinity monolithic columns can be a useful tool for studying DAAO enzyme reaction and investigating the potential enzyme mechanism requirement among chiral conversion.     

Monoterpenoids from the Fruit of Gardenia jasminoides

Eight new monoterpenoids, jasminoside J ( 1 ), jasminoside K ( 2 ), 6′‐O‐trans‐sinapoyljasminoside B ( 3 ), 6′‐O‐trans‐sinapoyljasminoside L ( 4 ), jasminosides M–P ( 5 – 8 ), together with three known analogues, jasminoside C ( 9 ), jasminol E ( 10 ), and sacranoside B ( 11 ), were isolated from the fruit of Gardenia jasminoides Ellis (Rubiaceae). Their structures were elucidated by spectral and chemical methods.     

Four New Terpenoids from Xylaria sp. 101

One new diterpenoid, xylarenolide ( 1 ), and three new sesquiterpenoids, xylaranol A ( 2 ), xylaranol B ( 3 ), and xylaranic acid ( 4 ), were obtained from the fungal strain Xylaria sp. 101, which was isolated from the fruiting body of Xylaria sp. collected in Gaoligong Mountain, Yunnan Province. Their structures were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR experiments, and by HR‐Q‐TOF mass spectrometry. Their antimicrobial activities were evaluated.     

Phytoquinoids and Secoprezizaane‐Type Sesquiterpenes from Illicium arborescens

A phytochemical investigation of the MeOH extract of Illicium arborescens yielded the two new phytoquinoid epimers, 2,3‐didehydro‐5‐O‐methyl‐11‐epiillifunone E ( 1 ) and 2,3‐didehydro‐5‐O‐methylillifunone E ( 2 ), as well as five new sesquiterpene lactones (8,9‐secoprezizaane‐type sesquiterpenes). Two of them, i.e., 3 and 4 , were minwanensin‐type sesquiterpenes, the other two, i.e., 5 and 6 , had the anisatin‐type (or floridanolide type) skeleton, and the fifth, i.e., 7 , was a dunnianin‐type sesquiterpene. Their structures were established by analyses of 1D‐ and 2D‐NMR, HR‐MS, and chemical evidence. The in vitro cytotoxic activity of compounds 1 – 7 was tested against four human tumor cell lines, including HeLa (cervical epitheloid), WiDr (colon), Daoy (medulloblastoma), and Hep2 (liver carcinoma) human‐tumor cells.     

Isopiestic Determination of Water Activity on the System LiNO<Subscript>3</Subscript>+KNO<Subscript>3</Subscript>+H<Subscript>2</Subscript>O at 273.1 and 298.1 K

Water activities in the ternary LiNO₃+KNO₃+H₂O system and its sub-binary systems have been measured by the isopiestic method at 273.1 and 298.1 K. The measured results were treated by a Pitzer-Simonson-Clegg thermodynamic model, from which the predicted solubility isotherms were compared with the experimental results. Based on this comparison, the reliability of the measured results was discussed. The measured results help in predicting the phase diagram of the ternary system, as well as other multi-component systems based on the ternary system.     

Bi3In4S10 and Bi14.7In11.3S38: Two new bismuth sulfides with interesting Bi-Bi bonding

Two new ternary bismuth chalcogenides, Bi₃In₄S₁₀ and Bi_14.7In_11.3S₃₈, were synthesized from the reactions of binary sulfides via a two-step flux technique. Single-crystal X-ray diffraction analyses indicate that Bi₃In₄S₁₀ crystallizes in the non-centrosymmetric space group Pm and Bi_14.7In_11.3S₃₈ crystallizes in the centrosymmetric space group P2₁/m. Both compounds adopt three-dimensional frameworks. A distinct structural feature in the two structures is the presence of chains of Bi atoms with alternating short Bi-Bi bonds of around 3.1 Å and longer distances of around 4.6 Å. The optical band gaps of 1.42(2) eV for Bi₃In₄S₁₀ and 1.45(2) eV for Bi_14.7In_11.3S₃₈ were deduced from the diffuse reflectance spectra.