Virus Particles Monitored by Fluorescence Spectroscopy: A Potential Detection Assay for Macromolecular Assembly¶

Native fluorescence spectroscopy was used for in situ investigations of two lipid‐containing bacteriophages from the cystovirus family as well as their Pseudomonad host cells. Both the viruses φ6 and φ12 and their bacterial host proteins contain the amino acid tryptophan (trp), which is the predominant fluorophore in UV. Within proteins, trp's structural environment differs, and the differences are reflected in their spectroscopic signatures. It was observed that the peak of the trp emission from both viruses was at 330 nm, a significantly shorter wavelength than trp in either the Pseudomonad host cells or the amino acid's chemical form. This allowed us to monitor the viral attachment process and subsequent lytic release of progeny virus particles by measurement of the trp emission spectra during the infection process. This work demonstrates that fluorescence may offer a novel tool to detect viruses and monitor viral infection of cells and may be part of a biodefense application.     

Tetra‐μ‐acetato‐κ2O:O′‐bis[(4‐phenylpyridine‐κN)copper(II)]

The title compound, [Cu₂(C₂H₃O₂)₄(C₁₁H₉N)₂] or [Cu₂(MeCO₂)₄(phpy)₂] (phpy is 4‐phenyl­pyridine), consists of centrosymmetric dimers in which the Cu^II atoms display a square‐pyramidal CuO₄N coordination, with four acetate O atoms in the basal plane [Cu—O 1.975 (3)–1.987 (3) Å] and the phpy N atom in the apical position [Cu—N 2.150 (3) Å]. The Cu atoms are 2.654 (1) Å apart and are bridged by four acetate groups. The discrete dimers are extended into a three‐dimensional supramolecular array through intermolecular π–π‐stacking interactions.     

Recognition of single nucleotide polymorphisms using scanning potential hairpin denaturation

Conventional single nucleotide polymorphism (SNP) assays, which based their detection on the stringency or temperature of the washing buffers, have encountered difficulties to distinguish a single base pair mismatch from a perfect match. In this study, scanning potential hairpin denaturation (SPHD) has been developed to detect SNP in a sensitive and reliable manner. Combined with hairpin oligonucleotide probes, scanning surface electric potential was used to induce a dissociation of double-stranded DNA around a unique "melting potential" (Vm), and it generated a high-contrast SNP recognition signal. A 21 base pair p53 gene segment was used to test this novel method. A single nucleotide mismatch to the hairpin probes caused an average of 400-800 mV difference in melting potential against the perfect match, while the error of this assay was lower than 20 mV. Experiments demonstrated that the hairpin stem was critical to the method. The concept of scanning potential hairpin denaturation could also be used extensively in different areas of nucleotide hybridization based assays.     

Copper-catalyzed cross-coupling of sulfonamides with aryl iodides and bromides facilitated by amino acid ligands

A highly general, convenient, and inexpensive catalyst system was developed for the N-arylation of sulfonamides with aryl iodides or bromides by using 5-20 mol % of CuI as catalyst, 20 mol % of N-methylglycine (for aryl iodides) or N,N-dimethylglycine (for aryl bromides) as ligand, and K₃PO₄ as base.     

Four New Podocarpane‐Type Trinorditerpenes from Aleurites moluccana

Four new podocarpane‐type trinorditerpenenes, (5β,10α)‐12,13‐dihydroxypodocarpa‐8,11,13‐trien‐3‐one ( 1 ), (5β,10α)‐12‐hydroxy‐13‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 2 ), (5β,10α)‐13‐hydroxy‐12‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 3 ), and (3α,5β,10α)‐13‐methoxypodocarpa‐8,11,13‐triene‐3,12‐diol ( 4 ), together with four known diterpenes, 12‐hydroxy‐13‐methylpodocarpa‐8,11,13‐trien‐3‐one ( 5 ), spruceanol ( 6 ), ent‐3α‐hydroxypimara‐8(14),15‐dien‐12‐one ( 7 ), and ent‐3β,14α‐hydroxypimara‐7,9(11),15‐triene‐12‐one ( 8 ), were isolated from the twigs and leaves of Aleurites moluccana. Their structures were elucidated by means of comprehensive spectroscopic analyses, including NMR and MS. Except 8 , all compounds were evaluated for their cytotoxicity; compound 4 exhibited moderate inhibitory activity against Raji cells with an IC₅₀ value of 4.24 μg/ml.     

Diterpenoids of Isodon macrophylla

Two new ent‐abietane diterpenoids, macrophynin E ( 1 ) and macrophynin F ( 2 ), and a known related ent‐abietanoid (?)‐lambertic acid ( 3 ), together with four known ent‐kauranoids, were isolated from the roots and aerial parts of Isodon macrophylla, respectively. The structures of the new compounds were elucidated on the basis of spectroscopic‐data analysis and chemical correlations.     

Scanning tunneling microscopy of prochiral anthracene derivatives on graphite: chain length effects on monolayer morphology

The morphology of monolayers formed upon adsorption of prochiral 1,5-substituted anthracene derivatives on highly oriented pyrolytic graphite is investigated using scanning tunneling microscopy at the liquid-solid interface. The adsorption orientation of these prochiral anthracene derivatives positions one of their enantiotopic faces in contact with the graphite. The molecules adsorb in rows with contact between adjacent anthracenes. The anthracene side chains extend perpendicular to the direction of the row repeat. All molecules within a single row adsorb via the same enantiotopic face. Anthracenes with side chains containing an even number of non-hydrogenic atoms (C, S) form monolayers in which molecules in adjacent rows adsorb via opposite enantiotopic faces. Anthracenes with side chains that contain an odd number of non-hydrogenic atoms form two-dimensional chiral domains in which all rows contain molecules adsorbed via the same enantiotopic face. This chain length effect on monolayer morphology represents a generalized example of structural effects previously observed in alkanoic acid monolayers formed on HOPG. The variation of the STM current with position in the vicinity of the anthracenes indicates that the highest occupied molecular orbital is the predominant mediator of tunneling for the aromatic group.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

AB2星型杂臂共聚物的合成及其结晶行为

通过分子设计, 用过量丁二酸酐将单硬酯酸甘油酯的两个羟基转变为羧基, 再以辛酸亚锡为催化剂, 二苯醚为共沸脱水剂, 使其进一步与不同分子量的端羟基聚乙二醇在负压下共沸脱水偶联, 成功地制备了一系列AB2星型杂臂共聚物, 并采用1H NMR、XRD、DSC、FTIR和偏光显微镜等手段对产物及其结晶行为进行了研究. 1H NMR测试结果表明, 所得聚合物是以二丁二酸甘油酯为核, 一条硬酯酸烷基(GMS)臂和两条聚乙二醇(PEG)臂构成的AB2星型杂臂共聚物[GMS-(SA-PEG)2]. DSC和XRD测试结果表明, 在GMS-(SA-PEG)2中, GMS臂和PEG臂都能结晶; GMS臂的存在不仅影响PEG臂的结晶速度, 同时也影响其结晶的完善程度, 导致结晶温度和结晶熔融温度发生变化; GMS臂相对含量越大, 对PEG结晶行为的影响也越大. 利用偏光显微镜对结晶过程的在线观察结果表明, GMS-(SA-PEG)2的结晶形貌不同于线型聚乙二醇的大球晶, 其先形成细碎的束状晶核, 然后逐步出现生长中的球晶结构, 最后所形成的晶体尺寸有大幅度的减小, 而且其形貌和PEG臂的分子量密切相关. 可见AB2星型杂臂共聚物的结晶是先由GMS臂结晶形成小晶核, 然后再诱导PEG臂球晶的生长. 杂臂的引入对于控制星型多臂共聚物的晶形、晶貌具有重要意义.     

Electrophilic monofluoromethylation of O-, S-, and N-nucleophiles with chlorofluoromethane

CH₂ClF has been found to be a useful electrophilic monofluoromethylating agent for a variety of O-, S-, and N-nucleophiles. The reaction is not sensitive to the radical scavenger such as nitrobenzene, which strongly supports an S_N2 mechanism rather than an SET mechanism. Although most of these products (fluoromethyl ethers, sulfides, and amines) can be isolated with good purity, some of these compounds do intend to decompose (via defluorination) during storage. The electrophilic monofluoromethylation of carbon-nucleophiles was attempted with CH₂ClF, CH₂FI, or FCH₂OTs as monofluoromethylating agents, but with no success.