Study of interactions between actinomycin D and oligonucleotides by microchip electrophoresis and ESI-MS

In the present study, the interactions between actinomycin D (ActD) and single stranded DNA (ssDNA) 5′-CGTAACCAACTGCAACGT-3′ and a duplex stranded DNA (dsDNA) with this sequence were investigated by microchip-based non-gel sieving electrophoresis and electrospray ionization mass spectrometry (ESI-MS). The ssDNA was designed according to the conserved regions of open reading frame 1b (replicase 1B) following the Tor 2 SARS genome sequence of 15611-15593. The binding constants of the interactions between ActD and ssDNA/dsDNA were (8.3 ± 0.32) × 10⁶ M⁻¹ (ssDNA) and (2.8 ± 0.02) × 10⁵ M⁻¹ (dsDNA), respectively, calculated from microchip electrophoresis via Scatchard plot. The binding stoichiometries were 1:1 (single/1ActD molecule) and 1:2 (duplex/2ActD molecules) calculated from microchip electrophoresis, and the results were further verified by ESI-MS. The results obtained by these two methods indicated that ActD bound much more tightly to ssDNA used in this work than dsDNA. Furthermore, this is shown that the microchip-based non-gel sieving electrophoresis method is a rapid, highly sensitive and convenient method for the studies of interactions between DNA and small molecule drugs.     

Equation of state for square-well chain molecules with variable range II. Extension to mixtures

An equation of state (EOS) developed in our previous work for square-well chain molecules with variable range is further extended to the mixtures of non-associating fluids. The volumetric properties of binary mixtures for small molecules as well as polymer blends can well be predicted without using adjustable parameter. With one temperature-independent binary interaction parameter, satisfactory correlations for experimental vapor–liquid equilibria (VLE) data of binary normal fluid mixtures at low and elevated pressures are obtained. In addition, VLE of n-alkane mixtures and nitrogen + n-alkane mixtures at high pressures are well predicted using this EOS. The phase behavior calculations on polymer mixture solutions are also investigated using one-fluid mixing rule. The equilibrium pressure and solubility of gas in polymer are evaluated with a single adjustable parameter and good results are obtained. The calculated results for gas + polymer systems are compared with those from other equations of state.     

甲基丙烯酸甲酯在聚偏氟乙烯膜上的辐照接枝

采用电子加速器(EB)预辐照接枝的方法,在聚偏氟乙烯(PVDF)膜上接枝甲基丙烯酸甲酯(MMA),制备了PVDF-g-PMMA膜。研究了辐照剂量、单体浓度、反应温度、反应时间以及溶剂等因素对接枝率的影响规律。结果表明,接枝率随辐照剂量的增大而增加;反应初期接枝率随着单体质量分数的增大迅速增加,当单体质量分数达40%时,增加缓慢;单体质量分数达70%时,接枝率最高;从40℃开始接枝率缓慢上升,至60℃时陡增,之后接枝率基本不变;醇类是接枝反应很好的溶剂。用FT-IR、DSC分析了接枝物的组成及热性能。接枝膜成分为PVDF-g-PMMA共聚物,接枝膜在117℃处出现Tg峰,随着接枝率的增加该峰越来越明显,说明发生了接枝反应。随着接枝率的增加,熔融峰左移并最终消失,说明PMMA的接枝破坏了原PVDF膜的结晶性。吸液率随着浸泡时间的增加而增大,PVDF接枝膜达到的最大吸液率为290%,所需要的时间比原PVDF膜长。接枝率为50%的PVDF膜的离子电导率为6.0×10-3S/cm,吸液率达290%,MMA的接枝改善了PVDF电解质膜的电学性能。     

Sample introduction techniques for microchip electrophoresis: A review

The number of applications of microfluidic analysis systems continues to increase, along with the variety of substrate materials and complexity of the devices themselves. One of the most common features of these devices that has remained relatively unchanged, however, is the introduction of a sample mixture into a separation channel so that individual components can be separated by electrophoresis. Whether a relatively simple mixture of amino acids or a more complex sample of DNA fragments extracted and amplified on-chip, the ability to reliably and reproducibly inject a representative sample is arguably the most significant requirement for an electrophoretic micro total analysis system (μTAS). This review will focus on the different methods reported for sample introduction in microchip electrophoresis, highlighting both pressure-driven and electrokinetic techniques, with an emphasis on the methods employed in μTAS applications.     

Polarization time effect on PMMA space-charge relaxation by TSDC

The effect of the polarization time in the formation of the PMMA space charge relaxation has been studied. The study has been carried out by thermally stimulated depolarization currents of electrets formed by windowing polarization. The results obtained have been fitted to the general kinetic order model, and they are consistent with the existence of a space-charge polarization mechanism with the kinetic order of 1.14. The intensity of the peak maxima results in being a good indicator of the trapped carrier number evolution. For high temperatures and high electrical fields the saturation of this mechanism is achieved faster, which is attributed to a carrier mobility increase with these parameters. Finally, a compensation law has been found for space-charge-relaxation in PMMA. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1971–1980, 1998     

Rheological,mechanical and morphological properties of thermoplastic vulcanizates based on NR‐g‐PMMA/PMMA blends

Graft copolymer of natural rubber and poly(methyl methacrylate) (NR‐g‐PMMA) was prepared using semi‐batch emulsion polymerization technique via bipolar redox initiation system. It was found that the grafted PMMA increased with the increase of methyl methacrylate (MMA) concentration used in the graft copolymerization. The NR‐g‐PMMA was later used to prepare thermoplastic vulcanizates (TPVs) by blending with PMMA through dynamic vulcanization technique. Conventional vulcanization (CV) and efficient sulphur vulcanization (EV) systems were studied. It was found that the CV system provided polymer melt with lower shear stress and viscosity at a given shear rate. This causes ease of processability of the TPVs via extrusion and injection molding processes. Furthermore, the TPVs with the CV system showed higher ultimate tensile strength and elongation. The results correspond to the morphological properties of the TPVs. That is, finer dispersion of the small vulcanized rubber particles were observed in the PMMA matrix. Various blend ratios of the NR‐g‐PMMA/PMMA blends using various types of NR‐g‐PMMA (i.e. prepared using various percentage molar ratios of NR and MMA) were later studied via dynamic vulcanization by a conventional sulphur vulcanization system. It was found that increasing the level of PMMA caused increasing trend of the tensile strength and hardness properties but decreasing level of elongation properties. Increasing level of the grafted PMMA in NR molecules showed the same trend of mechanical properties as in the case of increasing concentration of PMMA used as a blend component. From morphological studies, two phase morphologies were observed with a continuous PMMA phase and dispersed elastomeric phase. It was also found that more finely dispersed elastomeric phase was obtained with increasing the grafted PMMA in the NR molecules. Copyright © 2005 John Wiley & Sons, Ltd.     

Stress–strain behavior of low‐density polyethylene/poly(methyl methacrylate) blends with modulated interfaces with a hydrogenated polybutadiene‐block‐poly(methyl methacrylate) diblock copolymer

The stress–strain diagrams and ultimate tensile properties of uncompatibilized and compatibilized hydrogenated polybutadiene‐block‐poly(methyl methacrylate) (HPB‐b‐PMMA) blends with 20 wt % poly(methyl methacrylate) (PMMA) droplets dispersed in a low‐density polyethylene (LDPE) matrix were studied. The HPB‐b‐PMMA pure diblock copolymer was prepared via controlled living anionic polymerization. Four copolymers, in terms of the molecular weights of the hydrogenated polybutadiene (HPB) and PMMA sequences (22,000–12,000, 63,300–31,700, 49,500–53,500, and 27,700–67,800), were used. We demonstrated with the stress–strain diagrams, in combination with scanning electron microscopy observations of deformed specimens, that the interfacial adhesion had a predominant role in determining the mechanism and extent of blend deformation. The debonding of PMMA particles from the LDPE matrix was clearly observed in the compatibilized blends in which the copolymer was not efficiently located at the interface. The best HPB‐b‐PMMA copolymer, resulting in the maximum improvement of the tensile properties of the compatibilized blend, had a PMMA sequence that was approximately half that of the HPB block. Because of the much higher interactions encountered in the PMMA phase in comparison with those in HPB (LDPE), a shorter sequence of PMMA (with respect to HPB but longer than the critical molecular weight for entanglement) was sufficient to favor a quantitative location of the copolymer at the LDPE/PMMA interface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 22–34, 2005     

Effects of clay‐modifying agents on the morphology and properties of poly(methyl methacrylate)/clay nanocomposites synthesized via γ‐ray irradiation polymerization

Via γ‐ray irradiation polymerization, poly(methyl methacrylate) (PMMA)/clay nanocomposites were successfully prepared with reactive modified clay and nonreactive clay. With reactive modified clay, exfoliated PMMA/clay nanocomposites were obtained, and with nonreactive clay, intercalated PMMA/clay nanocomposites were obtained. Both results were confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. PMMA extracted from PMMA/clay nanocomposites synthesized by γ‐ray irradiation had higher molecular weights and narrow molecular weight distributions. The enhanced thermal properties of the PMMA/clay nanocomposites were characterized by thermogravimetric analysis and differential scanning calorimetry. The improved mechanical properties of PMMA/clay were characterized by dynamic mechanical analysis. In particular, the enhancement of the thermal properties of the PMMA/clay nanocomposites with reactive modified clay was much more obvious than that of the PMMA/clay nanocomposites with nonreactive clay. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3218–3226, 2003     

Controllable synthesis of nanosilica surface-grafted PMMA macromonomers via catalytic chain transfer polymerization

Catalytic chain transfer polymerization (CCTP) has emerged as an efficacious method to produce low-molecular weight polymers. In this paper, we reported the first controllable synthesis of nanosilica surface-grafted poly(methyl methacrylate) (PMMA) (SI-PMMA) macromonomers by using bis(aqua)bis((difluoroboryl)-dimethylglyoximato)cobalt(II) (CoBF) as a chain transfer catalyst via CCTP. In a typical run, we firstly prepared functionalized nanosilica by using 3-(trimethoxysilyl)propylmethacrylate (MPS) as the coupling agent, allowing naosilica containing unsaturated double bonds in end groups. Subsequently, SI-PMMA macromonomers were prepared by PMMA surface-grafted onto the functionalized nanosilica via CCTP. The as-prepared products were characterized by Fourier transforms infrared (FT-IR) spectrum, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transforms Raman (FT-Raman) spectrum and gel permeation chromatography (GPC). We also investigated the dependence of macromonomers on CoBF concentrations.     

Effect of magnesium dihydroxide nanoparticles on thermal degradation and flame resistance of PMMA nanocomposites

The influence of magnesium dihydroxide (MDH) nanoparticles on thermal degradation and fire behavior of poly(methyl methacrylate) (PMMA) has been investigated by thermogravimetric analysis (TGA), cone calorimeter, and pyrolysis‐combustion flow calorimeter (PCFC) tests, respectively. MDH nanoparticles with either lamellar or fibrous shape have been synthesized via a sol‐gel technique and characterized by transmission electron microscopy (TEM) and X‐ray diffraction analysis. PMMA–MDH nanocomposites have been prepared by melt blending the recovered MDH nanoparticles within PMMA at different loadings (5, 10, and 20 wt% MDH). According to TGA results, the incorporation of lamellar or fibrous MDH nanoparticles into PMMA leads to a significant improvement in PMMA thermal stability, both under air and inert atmosphere. The results obtained by PCFC and cone calorimeter tests show an important decrease in the peak of heat release rate (pHRR) concomitant with charring during the combustion. Lamellar MDH nanoparticles were found to be more efficient than fibrous MDH nanoparticles. Copyright © 2010 John Wiley & Sons, Ltd.     

PP/PMMA Block Copolymers by Combination of ATRP and Metallocene Catalysis

PP-b-PMMA has been synthesized by a combination of metallocene catalysis and the controlled radical polymerization technique ATRP. Cp₂ZrCl₂/MAO and (Me₄Cp)SiMe₂(N-tert-Bu)TiCl₂/MAO were used for the synthesis of atactic polypropylene. By a series of chemical modifications pp macroinitiators for the ATRP polymerization of MMA were synthesized. The PP-b-PMMA with polydispersities from 1.8–2.8 and an M_n ranging from 8 to 26 kg/mol was characterized by ¹H-NMR,SEC and DSC.     

微模塑法制备PMMA球面微透镜阵列

Micro-lens (ML) and Micro-lens array (MLA) are important optical components widely used in many fields;Soft-lithography, a vital little process technology, has its unique performance to produce ML and MLA;The cylinder and spherical MLA of polymethyl methacrylate (PMMA) were successfully obtained by micromolding inSoft-lithography. Some suitable experimental parameters in the process were discussed, and the imaging property of the MLA was also studied simply.     

Ricinus communis agglutinin I functionalisation of poly(methyl methacrylate) (PMMA) as a substrate for microfluidic device

We report a functionalisation strategy which is able to generate Ricinus communis agglutinin I (RCA 120) modified PMMA microfluidic device for binding and culturing living cells. The functionalisation is achieved by standard amine-aldehyde (Schiff base) reaction through the cross-linker, glutaraldehyde. To prove the ability of the RCA 120 modified PMMA surface, the PC 12 cell line (rat pheochromocytoma cells) has been captured and cultured by the microfluidic device. In the presence of tunicamycin, the dose/time-dependence on decreasing of binding affinity of RCA 120 modified device with PC 12 cell is also observed. The experimental results demonstrate that the lectin-functionalized microfluidic device can be employed as efficient cell culturing platform, and has a great promise of being used as a powerful tool for monitoring the interaction of drug with living cell.     

一种连接石英毛细管的聚甲基丙烯酸甲酯电泳芯片的制作及其应用

利用模拟仿真软件模拟了死体积对于电泳分离的影响,并提出了一种实现聚甲基丙烯酸甲酯(Poly-methylmethacrylate,PMMA)电泳芯片与毛细管的最小死体积连接方法.将紫外吸收检测的检测窗口设计在石英毛细管上,使该PMMA芯片上的电泳分析可以直接采用紫外吸收检测器进行检测.利用该芯片对维生素B2进行了电泳分析,理论塔板数为73000/m;联磺甲氧苄啶片中的3种组分的分离度为4.5和1.9,3个峰迁移时间的RSD依次为1.0%,1.4%和1.0%,峰高的RSD依次为4.1%,3.0%和4.1%(n=5).     

Thermal stability of porous it‐PMMA thin film obtained by the extraction of st‐PMAA from it‐PMMA/st‐PMAA stereocomplex with layer‐by‐layer assembly on a substrate

The functionality of porous isotactic (it) poly(methyl methacrylate) (PMMA) thin films, which were previously developed by the selective extraction of syndiotactic (st) poly(methacrylic acid) (PMAA) from the it‐PMMA/st‐PMAA stereocomplex thin film on a substrate using the layer‐by‐layer assembly method was investigated after thermal treatment (70, 80, and 90 °C) in water for 4 h. Quartz crystal microbalance analysis and infrared spectra measurements revealed that the st‐PMAA incorporation ability of the porous it‐PMMA thin film decreased in order at 80 and 90 °C, while there was no decrease observed at 70 °C. X‐ray diffraction analysis also supported the thermal stability of the porosity at 70 °C, whereas two it‐PMMA crystalline peaks (2θ = 9° and 14°) were generated during heating at 90 °C. The loss of the functionality of the it‐PMMA thin film was thus shown to be due to crystallization, which was caused by the increase in polymer‐chain mobility during the heating process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3265–3270, 2010     

Evaluation of Spectroscopic and Morphological Properties of PMMA Modified with ILs

Summary: In recent years, an important class of new compounds, ionic liquids (ILs), has been investigated as additives for polymers. In this work, we carried out the synthesis of 4 different ILs: 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM.BF₄), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM.PF₆), and the chiral ILs acetyl-(−)menthol-1-buthylimidazole tetrafluoroborate ([amebim]BF₄) and acetyl-(−)menthol-1-buthylimidazole hexafluorophosphate ([amebim]PF₆). These ILs were added to poly(methyl methacrylate) (PMMA) in 10, 20 and 30% ratios by weight and the ILs, PMMA and the obtained materials (PMMA:ILs) were characterized by infrared, visible spectroscopy and atomic force microscope. The ILs added to PMMA did not provide significant changes in the infrared spectra, compared to pure PMMA. However, the absorption spectra in the visible region of the PMMA:ILs materials showed differences, compared to the spectrum of pure PMMA.     

Atomistic Molecular Dynamics Simulation of Surface Grafted PMMA

Properties characteristic of the size, shape, and orientation as well as the rigidity of PMMA end‐grafted to an amorphous silica surface are calculated by use of fully atomistic molecular dynamics simulations with MMA as explicit solvent. Both the number of grafted chains and their tacticity is varied. Firstly, properties of one atactic end‐grafted chain are compared to those of the same chain without any surface being present. Secondly one, two, and four atactic grafted chains are evaluated to study the influence of grafting density (at low surface occupancy) and thirdly, results of single grafted iso‐, syndio‐, and atactic chains, respectively, are compared to elucidate the influence of tacticity. Additionally, the used force field is validated by calculation of the diffusion coefficient of solvent molecules.

     

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with poly(butadiene-block-methyl methacrylate)

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 85–93, 1998     

PMMA/PC Blends: Effect of Mixing Conditions on Compatibility

In this work the effect of melt mixing condition and of a trans-esterification catalyst on miscibility of poly(methyl methacrylate) (PMMA)/polycarbonate of bisphenol A (PC) blends is studied. In particular, at high temperature chemical reactions between PMMA and PC phases can take place; these strongly change the compatibility in the blend and materials having single T_g can be obtained. FT-IR analyses, coupled with solvent extraction, suggest that a grafting reaction of PC on PMMA is involved. SEC and DSC data are consistent with spectroscopic results, and some decrement of the molar weight distribution (MWD) of PC phase is observed. On the other hand, the presence of a fraction of modified material having higher MWD of starting PMMA is also noticed. The single T_g characteristic of some materials has been confirmed by experimental data of structural relaxation performed by differential scanning calorimetry (DSC). These materials showed optical clarity and the morphological analysis performed by scanning electron microscopy (SEM) confirm the homogeneity of these materials.