Correlated atomic force microscopy and fluorescence lifetime imaging of live bacterial cells

We report on imaging living bacterial cells by using a correlated tapping-mode atomic force microscopy (AFM) and confocal fluorescence lifetime imaging microscopy (FLIM). For optimal imaging of Gram-negative Shewanella oneidensis MR-1 cells, we explored different methods of bacterial sample preparation, such as spreading the cells on poly-L-lysine coated surfaces or agarose gel coated surfaces. We have found that the agarose gel containing 99% ammonium acetate buffer can provide sufficient local aqueous environment for single bacterial cells. Furthermore, the cell surface topography can be characterized by tapping-mode in-air AFM imaging for the single bacterial cells that are partially embedded. Using in-air rather than under-water AFM imaging of the living cells significantly enhanced the contrast and signal-to-noise ratio of the AFM images. Near-field AFM-tip-enhanced fluorescence lifetime imaging (AFM-FLIM) holds high promise on obtaining fluorescence images beyond optical diffraction limited spatial resolution. We have previously demonstrated near-field AFM-FLIM imaging of polymer beads beyond diffraction limited spatial resolution. Here, as the first step of applying AFM-FLIM on imaging bacterial living cells, we demonstrated a correlated and consecutive AFM topographic imaging, fluorescence intensity imaging, and FLIM imaging of living bacterial cells to characterize cell polarity.     

Star-shaped and linear nanosized molecules functionalized with hexa-peri-hexabenzocoronene: synthesis and optical properties

[structure: see text] A synthetic strategy promising the establishment of a new star-shaped and linear polycyclic aromatic hydrocarbons (PAHs) family with distinct molecular topologies has been developed. The Sonogashira reaction between the iodide derivatives 2a-e and phenylacetylene catalyzed with Pd(0) affords 3a-e in high yields. The Diels-Alder and decarbonylation reactions between 3a-e and tetraphenylcyclophentadiene following the oxidation by FeCl(3) produce the star-shaped and linear PAHs 5a-e containing a five-membered ring. The structural analysis and the optical properties of all new compounds are performed by a combination of MALDI-TOF mass spectrometry, UV-vis, and fluorescence spectrometry. The electronic and photophysical properties are studied by orthogonal comparisons of the absorption and fluorescence spectra in THF solutions, which not only give insight into the interactions among aromatic submoieties in each molecule and the effects of meta-conjugation and para-conjugation on electronic delocalization, but also indicate effective conjugation length variations from oligophenylacetylenes 3a-e to oligophenylene dendrimers 4a-e and PAHs 5a-e. The star-shaped 5c exhibits the highest aggregation in excited states compared with the other four hexa-peri-hexabenzocoronene (HBC) derivatives.     

Structure and electrical properties of Pb(Zr<Subscript>0.25</Subscript>Ti<Subscript>0.75</Subscript>)O<Subscript>3</Subscript> thin films on LaNiO<Subscript>3</Subscript>—Coated thermally oxidized Si substrates

Pb(Zr_0.25Ti_0.75)O₃ (PZT25) thin films were prepared on LaNiO₃-coated thermally oxidized silicon substrates by chemical solution deposition method, where LaNiO₃ electrodes were also prepared by a chemical solution deposition technique. The dielectric constant and dielectric loss of the PZT25 thin films were 570 and 0.057, respectively. The remanent polarization and coercive field were 20.11 μC/cm² and 60.7 kV/cm, respectively. The PZT25 thin films on LaNiO₃-coated thermally oxidized silicon substrates showed improved fatigue characteristics compared with their counterparts on plantium-coated silicon substrates.     

可变色形状记忆材料

以聚乙烯醇和单宁酸为原料制备出了形状记忆水凝胶,以乙二胺四乙酸、二水合氯化铜、六水合氯化镁、氧化铝为原料制备出了无机热致变色材料,以结晶紫内酯、硼酸、十六醇为原料制备出了有机热致变色材料,并将形状记忆材料与热致变色材料结合,成功制备出了两种既能记忆形状又能变色的新型复合高分子材料。本实验原料简单易得,方法简便,并与本科阶段有机化学、无机化学、仪器分析、精细化学品化学等课程中所学习的自由基聚合反应、化学交联、络合反应等知识结合,可作为本科教学的一个综合实验,提高学生的动手能力,激发学生学习化学的兴趣和热情。     

Synthesis,characterization and antifungal activity of glycylglycine Schiff base complexes of 3d transition metal ions

Summary Two new Schiff bases, N-4-hydroxysalicylidene-glycylglycine (K·GGRS·H₂O), N-O-vanillal-glycylglycine (K· GGVS·3H₂O) and their manganese(II), cobalt(II), nickel(II) and copper(II) complexes have been synthesized and characterized by elemental analysis, t.g.a., molar conductance, i.r. and u.v. spectral studies. The ¹³Cn.m.r. spectrum of one of the Schiff base ligands has been recorded. The results show that the ligand is coordinated to the central metal ion via amide nitrogen, imino nitrogen, phenolic oxygen and carboxyl oxygen to form a quadridentate complexes. Some of the complexes exhibit strong inhibitory action towards Candida albicans and Cryptococcus neoformans.     

阳离子改性HZSM-5沸石上低碳醇反应历程的TPSR-MS研究

用ＴＰＳＲ－ＭＳ技术研究了Ｃｕ，Ｚｎ和Ｇａ改性Ｈ－ＺＳＭ－５沸石的活性中心性质及Ｃ１～Ｃ４醇的反应历程。结果表明，Ｚｎ－和Ｇａ－ＺＳＭ－５有两种芳构化活性中心，即Ｂ酸和Ｚｎ，Ｇａ活性物种；甲醇在Ｃｕ－ＺＳＭ－５上只生成二甲醚、ＣＯ和ＣＯ２，而在Ｚｎ－ＺＳＭ－５上芳构化反应历程为：（１）醇经由醚脱水生成烯烃，Ｃ２～Ｃ４醇学可单分子脱水生成烯烃；（２）烯烃中间物齐聚，齐聚物通过氢转移和脱氢途径环化、芳     

Determination of protein by its enhancement effect on the Rayleigh light scattering of carboxyarsenazo

This is the first report on the determination of proteins based on the interaction with carboxyarsenazo (CAA) by Rayleigh light scattering (RLS). At pH 4, the weak RLS of CAA can be enhanced greatly by the addition of proteins, resulting in three characteristic peaks. Based on this, the interactions of CAA with nine kinds of proteins were studied and a new quantitative determination method for proteins has been developed. This method is very sensitive (0.10-15.3 mug ml(-1) for bovine serum albumin (BSA)), rapid (<2 min), simple (one step), tolerant of most interfering substances, and gives a close value to that of the Coomassie brilliant blue (CBB) method in the determination of proteins in human serum. Thus, the CAA assay can be useful for routine analytical purposes and may overcome some of the limitations of other currently employed methods. Mechanism studies show that the three RLS peaks correspond to the absorption valleys of the CAA-protein complex.     

Structure and Thermal Stability of a Novel 2‐D Layered Copper(II) Coordination Polymer with the Bidentate Ligand 1, 2, 4‐Triazol‐5‐one

Single crystals of {[Cu(TO)₂(H₂O)₂](NO₃)₂}_n (TO: 1, 2, 4‐triazol‐5‐one) were grown by slow evaporation from aqueous solution. It crystallizes in the orthorhombic space group Pbca, with a = 7.082(1), b = 10.285(1), c = 17.911(3)Å, V = 1304.6(3)ų, Z = 4. The Cu^II distorted octahedra are bridged by bidentate TO ligands into infinite 2‐D interlaced rhombic grid‐like network planes, {[Cu(TO)₂(H₂O)₂]²⁺}_n. Hydrogen bonds, electrostatic interactions, and weak van der Waals' forces assemble these planes and the NO₃^— anions to a layered structure. The title compound decomposes at 153.4 °C to the final products, Cu(CN)₂ and CuO.     

脱氧核糖核酸电化学传感器的原理及其应用

对电化学DNA传感器的组成及其在DNA损伤研究、环境污染监控、病原基因检测、基因疾病诊断和药物机理分析等方面的进行了总结，并对其发展趋势进行了评述。     

Organic functionalization of the sidewalls of carbon nanotubes by diels-alder reactions: a theoretical prediction

[structure: see text] The viability of the Diels-Alder (DA) cycloaddition of conjugated dienes onto the sidewalls of single-wall carbon nanotubes is assessed by means of a two-layered ONIOM(B3LYP/6-31G:AM1) approach. Whereas the DA reaction of 1,3-butadiene on the sidewall of an armchair (5,5) nanotube is found to be unfavorable, the cycloaddition of quinodimethane is predicted to be viable due to the aromaticity stabilization at the corresponding transition states and products.