纳米钛酸钙粉体的制备及其对水中铅和镉的吸附行为

采用柠檬酸络合溶胶-凝胶法制备了纳米钛酸钙粉体. 以X射线衍射(XRD)、透射电子显微镜(TEM)和傅立叶变换红外光谱(FTIR)对其进行了表征. 考察了该纳米粉体对水中重金属铅和镉的吸附性能, 并以镉离子为例, 系统地研究了吸附热力学和动力学. 结果表明, 该法合成的钛酸钙为钙钛矿结构的纳米粉体, 粒径大小受灼烧温度的影响, 灼烧温度越高, 粉体平均粒径越大, 600 ℃灼烧2 h条件下, 粉体的平均粒径最小, 约为20 nm. 当介质的pH值为4～8时, 钛酸钙对水中的铅和镉具有很强的吸附能力. 其对镉离子的吸附行为符合Langmuir 吸附等温模型和HO准二级动力学方程式, 吸附过程焓变(ΔH)为39.312 kJ•mol－1, 各温度下的自由能变(ΔG)均小于零, 熵变(ΔS)均为正值, 吸附过程的活化能(Ea)为20.359 kJ•mol－1. 该吸附过程是自发的吸热物理过程. 被吸附的铅和镉均可用1 mol•L－1的硝酸完全洗脱回收. 对铅和镉的富集因子均超过200. 将其应用于水中痕量铅和镉的吸附富集和测定, 回收率分别为96.3%～107.2%和93.5%～104.0%, 与石墨炉原子吸收光谱法测定结果一致.     

α-SrMnO3电子结构的第一性原理研究

采用平面波赝势方法对钙钛矿型锰酸盐氧化合物α-SrMnO3的电子结构进行了第一性原理研究. 六方钙钛矿型结构α-SrMnO3化合物为磁性绝缘体, 磁基态对应于共面八面体及共顶点八面体间的磁性交换作用均为反铁磁性(AFM), 其禁带宽度为1.6 eV; 费米能级附近的Mn3d态与O2p态存在很强的杂化作用, 属于共价绝缘体, 这种强共价性使得Mn4+的自旋磁矩偏离理想值. 采用Noodleman的对称性破缺方法, 根据α-SrMnO3不同磁有序态的总能量拟合出α-SrMnO3中的自旋交换耦合常数. α-SrMnO3的局部微结构(Mn—O—Mn)决定了整个体系的特殊磁性交换作用. 共面及共顶点的八面体间均存在AFM交换作用, 并且共顶点八面体间的AFM作用比较强.     

Determination of senkirkine and senecionine in Tussilago farfara using microwave-assisted extraction and pressurized hot water extraction with liquid chromatography tandem mass spectrometry

Tussilago farfara (Kuan Donghua) is an important Chinese herbal medicine which has been shown to contain many bioactive compounds and widely used to relieve cough and resolve phlegm. However, besides therapeutic bioactive compounds, this herb has been found to contain toxic pyrrolizidine alkaloids (PAs), mainly senkirkine and traces of senecionine. In this report, conditions for microwave-assisted extraction (MAE) and pressurized hot water extraction (PHWE) were optimized for the extraction of the PAs. The results were compared against heating under reflux. It was found that the binary mixture of MeOH:H₂O (1:1) acidified using HCl to pH 2-3 was the optimal solvent for the extraction of the PAs in the plant materials. Liquid chromatography (LC) with ultra-violet (UV) detection and electrospray ionization mass spectrometry (ESI-MS) in the positive mode was used for the determination and quantitation of senkirkine and senecionine in the botanical extract. The proposed extraction methods with LC/MS allow for the rapid detection of the major and the minor alkaloids in T. farfara in the presence of co-eluting peaks. With LC/MS, the quantitative analysis of PAs in the extract was done using internal standard calibration and the precision was found to vary from 0.6% to 5.4% on different days. The limits of detection (LODs) and limits of quantitation (LOQs) for MAE and PHWE were found to vary from 0.26 μg/g to 1.04 μg/g and 1.32 μg/g to 5.29 μg/g, respectively. The method precision of MAE and PHWE were found to vary from 3.7% to 10.4% on different days. The results showed that major and minor alkaloids extracted using MAE and PHWE were comparable to that by heating under reflux. Our data also showed that significant ion suppression was not observed in the analysis of senkirkine and senecionine in the botanical extracts with co-eluting peaks.     

载银缓释型抗菌敷料

近10年来,载银缓释型抗菌敷料因其优良特性,在医药、卫生等领域引起科学家们的广泛关注。本文综述了银的抗菌机理和载银缓释型抗菌敷料的缓释机制;重点介绍了目前在国际市场上销售的代表性载银缓释型抗菌敷料的性能,并从不同的载体材料角度(如生物高分子、合成高分子、生物和合成高分子共用、有机硅材料)总结了新型载银抗菌敷料的研究进展;最后,讨论了载银抗菌医用敷料在研究和应用中需要解决的问题。     

Evaluation of lipid peroxidation inhibition and free radical scavenging abilities of 5,6,7-trimethoxy dihydroflavonols

Four naturally rare 5,6,7-trimethoxy-2,3-cis-dihydroflavonols(3-6) and two 5,6,7-trimethoxy-2,3-trans-dihydroflavonols(7-8) were designed and synthesized.Their antioxidative properties were evaluated by way of examining their scavenging capacities towards DPPH and O_2~(·-) free radicals,as well as by measuring their inhibitory ability against LPO.Both the 2,3-trans and the 2,3- cis conformers exhibited certain quenching abilities to DPPH and O_2~(·-) radicals,while most of the synthetic dihydroflavonols ...     

Spectroscopic and electrochemical studies on the interaction of an inclusion complex of β-cyclodextrin/fullerene with bovine serum albumin in aqueous solution

The potential effect of human exposure to carbonaceous nanomaterials (e.g., fullerenes or their derivatives) in the environment has become a concern. In the current study, we report the interaction of one water-soluble fullerene with bovine serum albumin using spectroscopic and electrochemical methods under aqueous solutions. The novel supramolecular inclusion complex of the water-soluble fullerene (β-CD)₂/C₆₀ was synthesized and characterized. In the mechanism discussed, the spectroscopic methods such as fluorescence quenching and ultraviolet-visible absorption, proved that the fluorescence quenching of BSA by (β-CD)₂/C₆₀ was the result of the formation of (β-CD)₂/C₆₀-BSA complex and that the mechanism of quenching might be a static quenching procedure. The binding constants K_a, the number of binding sites n, and the corresponding thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures were calculated through fluorescence spectroscopy, then as an auxiliary method, the electrochemical impedance spectroscopy (EIS) experiments confirmed this conclusion. The results indicated that the electrostatic interactions play a major role in (β-CD)₂/C₆₀-BSA association. The circular dichroism spectra show the conformation change of the effect of (β-CD)₂/C₆₀ on the conformation of BSA, which was confirmed by the results of the three-dimensional fluorescence spectra. Site marker competitive experiments indicate that the binding of (β-CD)₂/C₆₀ to BSA primarily took place in site I. The distance r between donor (BSA) and acceptor ((β-CD)₂/C₆₀) was obtained according to fluorescence resonance energy transfer (FRET). This work aims to demonstrate the mechanisms of the formation of the complex between water-soluble fullerene and protein under physiological conditions, as well as the remediation for the possible unwarranted biological effects of water-soluble fullerene.     

Oxovanadium(IV) based hypocrellin B complexes with enhanced photodynamic activity

Hypocrellin B (HB), a naturally occurring photosensitizer, has been extensively and intensively studied as a promising photodynamic therapy (PDT) agent. In this work, three new oxovanadium(IV) complexes were designed and synthesized with HB as a bridging ligand and phen (1,10-phenanthroline, complex 1), tmp (3,4,7,8-tetramethyl-1,10-phenanthroline, complex 2) and dpq (dipyrido[3,2-f:2'3'-h]quinoxaline, complex 3) as terminal ligands. The use of a diimine terminal ligand avoids the formation of polymeric complexes and ensures the three VO(2+)-HB complexes possess a definite molecular formula and molecular weight to meet the single component requirement for an ideal PDT agent. Compared to HB, the VO(2+)-HB complexes exhibit improved water solubility, enhanced absorptivity in the phototherapeutic window, increased binding affinity toward dsDNA, and similar singlet oxygen quantum yield, therefore advanced DNA photocleavage activity. Both the DNA binding constants and photo nuclease activities of the complexes follow the order 2 (tmp) > 3 (dpq) > 1 (phen), demonstrating the importance of the binding affinity to biomolecules, which improves the bioavailability of reactive oxygen species. Our work opens a new avenue for the development of HB-based PDT agents.     

A smart gelator as a chemosensor: application to integrated logic gates in solution, gel, and film

A gelator that consisted of one benzimidazole moiety and four amide units was used as a chemosensor. We found that its absorption and emission spectra in solution were sensitive to two complementary chemical stimuli: protons and anions. Thus, YES and INH logic gates were obtained when absorbance was defined as an output. A combination gate of XNOR and AND with an emission output was also obtained. Moreover, wet gels in two solvents were used to construct two more-complicated three-input-three-output gates, owing to the existence of the gel phase as an additional output. Finally, in xerogel films that were formed from two kinds of wet gels, reversible changes in their emission spectra were observed when they were sequentially exposed to volatile acid and NH(3). Another combination two-output logic gate was obtained for xerogel films. Finally, three states of the gelator were used to construct not only basic logic gate, but also some combination gates because of their response to multiple chemical stimuli and their multiple output signals, in which one chemical input could erase the effect of another chemical input.     

Improving MCM‐41 as a Nitrosamines Trap through a One‐Pot Synthesis

Copper oxide was incorporated into MCM‐41 by a one‐pot synthesis under acidic conditions to prepare a new mesoporous nitrosamines trap for protection of the environment. The resulting composites were characterized by XRD, N₂ adsorption–desorption, and H₂ temperature‐programmed reduction techniques, and their adsorption capabilities were assessed in the gaseous adsorption of N‐nitrosopyrrolidine (NPYR). The adsorption isotherms were consistent with the Freundlich equation. The copper salt was deposited onto MCM‐41 during the evaporation stage and was fixed on the host in the calcination process that followed. MCM‐41 was able to capture NPYR in air below 373 K but not at 453 K. Loading of copper oxide on MCM‐41 greatly improved its adsorption capability at elevated temperatures. The influence of the incorporation of copper into MCM‐41 samples and the adsorption behavior of these samples are discussed in detail.     

Ab initio study of the reaction of propionyl (C2H5CO) radical with oxygen (O2)

The reaction of propionyl radical with oxygen has been studied using the full coupled cluster theory with the complete basis set. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for this important reaction in detail. The reaction takes place via a chemical activation mechanism. The barrierless association of propionyl with oxygen produces the propionylperoxy radical, which decomposes to form the hydroxyl radical and the three-center alpha-lactone predominantly or the four-center beta-propiolactone. The oxidation of propionyl radical to carbon monoxide or carbon dioxide is not straightforward rather via the secondary decomposition of alpha-lactone and beta-propiolactone. Kinetically, the overall rate constant is almost pressure independent and it approaches the high-pressure limit around tens of torr of helium. At temperatures below 600 K, the rate constant shows negative temperature dependence. The experimental yields of the hydroxyl radical can be well reproduced, with the average energy transferred per collision -DeltaE=20-25 cm(-1) at 213 and 295 K (helium bath gas). At low pressures, together with the hydroxy radical, alpha-lactone is the major product, while beta-propiolactone only accounts for about one-fifth of alpha-lactone. At the high-pressure limit, the production of the propionylperoxy radical is dominant together with a fraction of the isomers. The infrared spectroscopy or the mass spectroscopy techniques are suggested to be employed in the future experimental study of the C2H5CO+O2 reaction.