Interfacial properties of Pluronics and the interactions between Pluronics and cholesterol/DPPC mixed monolayers

Pluronics are triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) with wide range of hydrophilic-lipophilic balance. In order to investigate the relationship between the chemical structures of Pluronics and the interfacial properties at the air-water interface by monolayer techniques, Pluronics L61, P65, F68, P84, P123, L35, and P105 were selected. Since cholesterol influenced substantially the molecular packing stage and the characteristics of cell membranes, the interactions between Pluronics and model cell membranes in the absence and presence of cholesterol were compared. The results of pi-A isotherms and surface elasticities of Pluronic monolayers indicated that the first and second transition like stage were mainly affected by the numbers of EO and PO monomers, respectively. Pluronics with higher hydrophobicities demonstrated larger surface activities and penetration abilities to dipalmitoylphosphatidylcholine (DPPC) monolayers, which might be due to hydrophobic interactions and van der Waals forces. In the presence of cholesterol, hydrogen bonding effects was supposed to exist between the 3beta-hydroxy group of cholesterol and ether oxygen of PEO chains, which led Pluronic F68, with the longest PEO chain herein, to exhibit significantly higher penetration ability. Our findings proposed a theoretical basis for selection of optimized drug carriers and the starting point for further investigations.     

Simple and efficient nickel-catalyzed cross-coupling reaction of alkynylalanes with benzylic and aryl bromides

Highly efficient and simple coupling reactions of benzylic and aryl bromides with aluminium acetylide catalyzed by NiCl(2)(PPh(3))(2) are reported. The coupling reactions proceed at room temperature employing 4 mol% catalyst, affording coupling products in excellent yields of up to 95% in short reaction times. The system worked efficiently with aryl and heterocyclic bromides as well.     

Hybrid electrokinetic manipulation in high-conductivity media

This study reports a hybrid electrokinetic technique for label-free manipulation of pathogenic bacteria in biological samples toward medical diagnostic applications. While most electrokinetic techniques only function in low-conductivity buffers, hybrid electrokinetics enables effective operation in high-conductivity samples, such as physiological fluids (～1 S m(-1)). The hybrid electrokinetic technique combines short-range electrophoresis and dielectrophoresis, and long-range AC electrothermal flow to improve its effectiveness. The major technical hurdle of electrode instability for manipulating high conductivity samples is tackled by using a Ti-Au-Ti sandwich electrode and a 3-parallel-electrode configuration is designed for continuous isolation of bacteria. The device operates directly with biological samples including urine and buffy coats. We show that pathogenic bacteria and biowarfare agents can be concentrated for over 3 orders of magnitude using hybrid electrokinetics.     

An efficient nickel-catalyzed alkenylation of functionalized benzylic halides with alkenylaluminum reagents

Highly efficient and simple coupling reactions of benzylic bromides or chlorides with alkenylaluminum reagents catalyzed by NiCl(2)(PPh(3))(2) are reported. The coupling reactions proceed effectively at room temperature employing low loading of catalyst, 0.5 mol% for benzylic bromides having either electron-donating or -withdrawing substituents on the aromatic ring, affording coupling products in excellent yields of up to 94% in short reaction times. The coupling reactions of benzylic chloride require 5 mol% of the catalyst and a longer reaction time of 2 h.     

The enthalpy of formation of 2II CH

The standard enthalpy of formation, δ_fH^o, of² II CH has been determined at converged levels of ab initio electronic structure theory, including high order coupled cluster and full configuration interaction benchmarks. The atomic Gaussian basis sets employed include the (aug)-cc-p(C)VXZ family with X = 3, 4, 5 and 6. Extrapolations to the complete one-particle basis set and the full configuration interaction limits, where appropriate, have been performed to reduce remaining computational errors. Additional improvements in the enthalpy of formation of ²II CH were achieved by appending the valence-only treatment with core-valence correlation, relativistic effects including spin-orbit correlation, and the diagonal Born-Oppenheimer correction. The recommended values for δfH^o ₀ and δA_f H _o ²⁹⁸ of ²II CH are 592.48^+0.47 _?0.56 kJ mol_?1 and 595.93 ^+0.47 _?0.56 kJ mol_?1, respectively.     

Method development for the determination of teicoplanin in patient serum by solid phase extraction and micellar electrokinetic chromatography

In-hospital deaths caused by the infection of methicillin-resistant Staphylococcus aureus (MRSA) are on the increase worldwide. Teicoplanin is a potent glycopeptide antibiotic against MRSA. A rapid and cost-saving micellar electrokinetic chromatography (MEKC) method combined with solid phase extraction (SPE) was developed and then validated to quantify teicoplanin in patient serum in this work. The method includes the following steps: (1) pretreatment of the serum samples with 10 M urea to denature proteins, (2) application of SPE by using an OASIS HLB cartridge to clean up and concentrate the serum samples, and (3) use of MEKC for sample analysis. Under the optimized conditions, the SPE recovery of teicoplanin is higher than 90%. The six major components of teicoplanin could be baseline-separated from one another and endogenous materials in 12 min with a background electrolyte composed of 20 mM sodium tetraborate buffer pH 8.8, 40 mM sodium dodecyl sulfate, and 11% (v/v) ACN. The relative standard deviation (R.S.D.) of the peak area ratios for method repeatability (n = 6) and intermediate precision (inter-day, n = 3) were found to be lower than 4.18% and 5.30%, respectively. The calibration curves were linear between the chromatographic response and total teicoplanin concentration over the range of 5 μg/mL to 55 μg/mL. Limit of detection (LOD) for each of the six components was found to be lower than 0.06 μg/mL. Pearson’s correlation revealed that a good correlation (r = 0.98) was obtained between the SPE-MEKC method and the fluorescence polarization immunoassay (FPIA) method. The developed method can be used to quantitatively determine serum teicoplanin concentration in patients for dose monitoring and clinical research.     

Thermal property changes of poly(N-isopropylacrylamide) microgel particles and block copolymers

Investigation of the thermo-reversible properties of different poly(N-isopropyl acrylamide) samples, including microgels and block copolymers, with a combination of methods such as electron microscopy, dynamic light scattering, analytical ultracentrifugation, electrophoresis and ultrasound resonator technology allows comprehensive characterisation of the phase transition. By the combination of methods, it was possible to show that the precipitated polymer phase contains at 40 °C between 40 and 50 vol.% of water. Besides free bulk water, there is also bound water that strongly adheres to the N-isopropyl acrylamide units (about 25 vol.%). Ultrasound resonator technology, which is a non-sizing characterisation method, revealed for the microgel particles two more temperatures (at about 35 and between 40 °C and 50 °C depending on the chemical nature) where characteristic changes in the ultrasound attenuation take place. Moreover, the experimental data suggest that the phase transition temperature is related to surface charge density of the precipitated particles.     

SOI波长信号分离器的研制

根据大截面单模脊形波导理论和双模干涉机制，在硅片直接键合、背面抛光减薄的ＳＯＩ材料上，通过氢氧化钾各向异性腐蚀的方法，成功地研制出ＳＯＩ波长信号分离器，在波长为１．３μｍ，其插入损耗为４．８１ｄＢ，串音小于－１８．６ｄＢ。