Instantaneous normal mode analysis of orientational motions in liquid water: local structural effects

We have investigated the effects of local structures on the orientational motions in liquid water in terms of the instantaneous normal mode (INM) analysis. The local structures of a molecule in liquid water are characterized by two different kinds of index: the asphericity parameter of its Voronoi polyhedron and the numbers of the H bonds donated and accepted by the molecule. According to the two kinds of index, the molecules in the simulated water are classified into subensembles, for which the rotational contributions to the INM spectrum are calculated. Our results indicate that by increasing the asphericity, the rotational contribution has a shift toward the high-frequency end in the real spectrum and a decrease in the fraction of the imaginary modes. Furthermore, we find that this shift essentially relies on the number of the donated H bonds of a molecule, but has almost nothing to do with that of the accepted H bonds. The local structural effects resulting from the geometry of water molecule are also discussed.     

表面附聚薄壳型单分散高效阳离子柱填料的研制及其性能

 报道了一种新的表面附聚薄壳型阳离子柱填料的简易制备方法。首次合成了单分散高效阳离子柱填料。以10μm的单分散聚苯乙烯 二乙烯基苯(PSTDVB)微球为基球,对其表面季铵化,然后均匀附聚一层磺化的阳离子乳胶(0 2μm),即得到阳离子固定相。分别用碱金属及碱土金属离子对用该填料制成的柱的性能进行了测试,结果表明该柱填料对常见阳离子具有很好的分离效果、良好的重现性和低的检测限。     

Simple and cheap microfluidic devices for the preparation of monodisperse emulsions

Droplet microfluidics, which can generate monodisperse droplets or bubbles in unlimited numbers, at high speed and with complex structures, have been extensively investigated in chemical and biological fields. However, most current methods for fabricating microfluidic devices, such as glass etching, soft lithography in polydimethylsiloxane (PDMS) or assembly of glass capillaries, are usually either expensive or complicated. Here we report the fabrication of simple and cheap microfluidic devices based on patterned coverslips and microscope glass slides. The advantages of our approach for fabricating microfluidic devices lie in a simple process, inexpensive processing equipment and economical laboratory supplies. The fabricated microfluidic devices feature a flexible design of microchannels, easy spatial patterning of surface wettability, and good chemical compatibility and optical properties. We demonstrate their utilities for generation of monodisperse single and double emulsions with highly controllable flexibility.     

Mixed hemimicelles solid-phase extraction based on cetyltrimethylammonium bromide-coated nano-magnets Fe3O4 for the determination of chlorophenols in environmental water samples coupled with liquid chromatography/spectrophotometry detection

Mixed hemimicelles solid-phase extraction (SPE) based on cetyltrimethylammonium bromide (CTAB)-coated nano-magnets Fe3O4 was investigated for the preconcentration of four chlorophenols (CPs) in environmental water samples prior to HPLC-spectrophotometry determination in this paper. By the rapid isolating (about 5 min) of Fe3O4 nanoparticles (NPs) through placing a Nd-Fe-B strong magnet on the bottom of beaker, the time-consuming preconcentration process of loading large volume sample in conversional SPE method with a column can be avoided. The unique properties of Fe3O4 NPs such as high surface area and strong magnetism were utilized adequately in the SPE process. This novel separation method produced a high preconcentration rate and factor. A comprehensive study of the adsorption conditions such as the Fe3O4 NPs zeta-potential, CTAB added amounts, pH value, standing time and maximal extraction volume was also presented. Under optimized conditions, four analytes of 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) were quantitatively extracted. The method was then used to determine four CPs in five real environmental water samples. High concentration factors (700) were achieved for each of the analytes, with observed detection limits ranging between 0.11 and 0.15 microg L(-1). The accuracy of method was evaluated by recovery measurements on spiked samples. Good recovery results (83-98%) with satisfactory relative standard deviation (RSD) were achieved. It is important to note that satisfactory preconcentration factors and extraction recoveries for the four CPs were obtained with only a little amount of Fe3O4 NPs (0.1g) and CTAB (60 mg). To the best of our knowledge, this was the first time a mixed hemimicelles SPE method based on Fe3O4 NPs magnetic separation had been used for the pretreatment of environmental water samples.     

Hemoglobin-imprinted polymer gel prepared using modified glucosamine as functional monomer

A new functional glycomonomer was obtained from modified glucosamine. Hemoglobin-imprinted polymer gel was prepared with allyl-bromide modified glucosamine as functional monomer, poly（ethylene-glycol）diacrylate （PEGDA） as cross-linker and ammonium persulfate [（NHn）2S2O8]/sodium hydrogen sulfite （NaHSO3） as initiators in a phosphate buffer. The adsorption capacity and selective adsorption of the molecular imprinting polymer （MIP） were also discussed.     

Separation and pre‐concentration of glucocorticoids in water samples by ionic liquid supported vortex‐assisted synergic microextraction and HPLC determination

We have developed a synergic microextraction procedure based on ionic liquid for the pre‐concentration and determination of glucocorticoids in water samples. Using nonionic surfactant Triton X‐100 (TX‐100) as synergic reagent, 1‐butyl‐3‐methylimidazolium hexa‐fluorophosphate accomplished extraction rapidly without heating in water bath. One key property of ionic liquids that highlights their potential is their wide liquid temperature range. The improved extraction was named as ionic liquid supported vortex‐assisted synergic microextraction. Compared with the traditional liquid–liquid extraction and cloud point extraction, ionic liquid supported vortex‐assisted synergic microextraction was accomplished in 8 min with considerably high recovery. The proposed method greatly improved the sensitivity of HPLC for the determination of glucocorticoids. The results obtained indicated a good linearity with the correlation coefficient of 0.997 over the range of 0.6–300 ng/mL and high sensitivity with LODs of 4.11, 9.19, and 7.50 ng/mL for hydrocortisone butyrate, beclomethasone dipropionate, and nandrolone phenylpropionate, respectively. The RSD of the method was 1.57–1.81% (n = 6) with enrichment factor of 99.85, and good recovery (≥97.24%). The method was successfully applied to the determination of glucocorticoids in mineral water, water of Dianchi lake, and tap water samples.     

Synthesis,characterization, and bioactivities of copper complexes with N-substituted Di(picolyl)amines

Three new Cu(II) complexes with ethyl bis(2-pyridylmethyl)amino-2-propionate (Etdpa), or bis(2-pyridylmethyl)amino-2-propionate (Adpa), were synthesized and characterized by physico-chemical and spectroscopic methods. The X-ray crystal structure of [(Adpa)CuCl] shows that the copper(II) atom is coordinated by three N atoms, one oxygen atom from the ligand (Adpa) and one chloride anion, forming a trigonal bipyramidal geometry. The spectrophotometric and fluorescence titration data indicate that the interaction of square pyramidal [(Etdpa)CuCl₂] with ct-DNA is weak, but the trigonal bipyramidal complexes [(Adpa)Cu(H₂O)](ClO₄) and [(Adpa)CuCl] interact with ct-DNA with the mode of intercalation. The inhibition activities of the three new copper(II) complexes on the four cancer cells (Mcf-7, Eca-109, A549, and Hela) are in the order: [(Adpa)Cu(H₂O)](ClO₄) > [(Adpa)CuCl] > [(Etdpa)CuCl₂], which correlates with their DNA-binding properties. The results show that the substituents introduced on the secondary amino nitrogen atom of dpa have great contribution to the antitumor activities of these copper(II) complexes. It is also found that the coordination of copper(II) ions with AdpaH can decrease the toxicity of AdpaH. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Surface chemistry of gold nanoparticles for health-related applications

Functionalization of gold nanoparticles is crucial for the effective utilization of these materials in health-related applications. Health-related applications of gold nanoparticles rely on the physical and chemical reactions between molecules and gold nanoparticles. Surface chemistry can precisely control and tailor the surface properties of gold nanoparticles to meet the needs of applications. Gold nanoparticles have unique physical and chemical properties, and have been used in a broad range of applications from prophylaxis to diagnosis and treatment. The surface chemistry of gold nanoparticles plays a crucial role in all of these applications. This minireview summarizes these applications from the perspective of surface chemistry and explores how surface chemistry improves and imparts new properties to gold nanoparticles for these applications.

Functionalization of gold nanoparticles is crucial for the effective utilization of these materials in health-related applications.     

Chemoenzymatic Synthesis of Cylindrocyclophanes A and F and Merocyclophanes A and D

Incorporating enzymatic reactions into natural product synthesis can significantly improve synthetic efficiency and selectivity. In contrast to the increasing applications of biocatalytic functional-group interconversions, the use of enzymatic C−C bond formation reactions in natural product synthesis is underexplored. Herein, we report a concise and efficient approach for the synthesis of [7.7]paracyclophane natural products, a family of polyketides with diverse biological activities. By using enzymatic Friedel–Crafts alkylation, cylindrocyclophanes A and F and merocyclophanes A and D were synthesized in six to eight steps in the longest linear sequence. This study demonstrates the power of combining enzymatic reactions with contemporary synthetic methodologies and provides opportunities for the structure–activity relationship studies of [7.7]paracyclophane natural products.