880 resultados para Lipid Raft


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In this study, we used a rheological method to study the shape of DNA-cationic lipid complexes and model polyelectrolyte-lipid complexes. We introduced two kinds of anionic polyelectrolytes, sodium polygalacturonate (PGU) and sodium dextran sulfate (DSS), of varying size, as models for DNA. The prepared complexes were incubated under laminar flow conditions. The results show the same quantitative relation between the shape parameter of lipoplexes and the length of anionic polyelectrolytes, including DNA. The rheological behavior of PGU and DSS were similar to that of DNA. (C) 2004 Elsevier Inc. All rights reserved.

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A minicapillary viscometer utilizing <0.5 ml of sample at a volume fraction of <0.1% is described. The calculated a/b of DPPC/DPPG multilamellar liposome was 1.14 as prolate ellipsoids and a/b of dioleoylpropyltrimethyl ammonium methylsulfate-DNA complex at a charge ratio of 4: 1 (+/-) was 3.7 as prolate ellipsoids or 4.9 as oblate ellipsoids. The deviation of shape from perfect sphere is thus expressed quantitatively in more than two significant figures. In these measurement, the necessary amount of DNA is <0.5 mg.

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We have developed a novel strategy for the preparation of ion-bonded supramolecular star polymers by RAFT polymerization. An ion-bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert-butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by H-1 NMR and GPC. The results show that the polymerization possesses the character of living free-radical polymerization and the ion-bonded supramolecular star polymers PSt, PtBA, and PSt-b-PtBA, with six well-defined arms, were successfully synthesized.

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Amphiphilic supramolecular miktoarm star copolymers linked by ionic bonds with controlled molecular weight and low polydispersity have been successfully synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using an ion-bonded macromolecular RAFT agent (macro-RAFT agent). Firstly, a new tetrafunctional initiator, dimethyl 4,6-bis(bromomethyl)-isophthalate, was synthesized and used as an initiator for atom transfer radical polymerization (ATRP) of styrene to form polystyrene (PSt) containing two ester groups at the middle of polymer chain. Then, the ester groups were converted into tertiary amino groups and the ion-bonded supramolecular macro-RAFT agent was obtained through the interaction between the tertiary amino group and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP). Finally, ion-bonded amphiphilic miktoarm star copolymer, (PSt)(2)-poly(N-isopropyl-acrylamide)(2), was prepared by RAFT polymerization of N-isopropylacrylamide (NIPAM) in the presence of the supramolecular macro-RAFT agent. The polymerization kinetics was investigated and the molecular weight and the architecture of the resulting star polymers were characterized by means of H-1-NMR, FTIR, and GPC techniques. (c) 2008 Wiley Periodicals, Inc.

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In this paper, electrochemical surface plasmon resonance (SPR) method was first used to detect enzymatic reaction in bilayer lipid membrane (BLM) based on immobilizing horseradish peroxidase (HRP) in the BLMs supported by the redox polyaniline (PAn) film. By SPR kinetic curve in situ monitoring the redox transformation of PAn film resulted from the reaction between HRP and PAn, the enzymatic reaction of HRP with H2O2, was successfully analyzed by electrochemical SPR spectroscopy.

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Here, we demonstrated dimethyldioctadecylammonium bromide (DODAB), a cationic lipid, bilayer coated Au nanoparticles (AuNPs) could efficiently deliver two types of plasmid DNA into human embryonic kidney cells (HEK 293) in the presence of serum. The transfection efficiency of AuNPs was about five times higher than that of DODAB. The interaction of AuNPs with DNA was characterized with dye intercalation assay and agarose gel electrophoresis. The morphology of the complex of AuNPs with DNA was observed with scanning electron microscope (SEM). The intracellular trafficking of the complex was monitored with transmission electron microscope (TEM).

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In this study, varieties of lipid bilayer-protected gold nanoparticles (AuNPs) were synthesized through a simple wet chemical method, and then the effect of freeze-thawing on the as-prepared AuNPs was investigated. The freeze-thawing process induced fusion or fission of lipid bilayers tethered on the AuNPs. The UV-vis spectra and transmission electron microscopy experiments revealed that the disruption of lipid bilayer structures on the nanoparticles led to the fusion or aggregation of AuNPs.

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A facile phospholipid/room-temperature ionic liquid (RTIL) composite material based on dimyristoylphosphatidylcholine (DMPC) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) was exploited as a new matrix for immobilizing protein. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were adopted to characterize this composite film. Hemoglobin (Hb) was chosen as a model protein to investigate the composite system. UV-vis absorbance spectra showed that Hb still maintained its heme crevice integrity in this composite film.

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Well-defined polyacrylonitrile with a higher number-average molecular weight (R.) up to 200,000 and a lower polydispersity index (PDI, 1.7-2.0) was firstly obtained via reversible addition-fragmentation chain transfer (RAFT) process. This was achieved by selecting a stable, easy way to prepare disulfide compound intermediates including bis(thiobenzoyl) disulfide (BTBDS) and bis(thiophenylacetoyl) disulfide (BTPADS) to react with azobis(isobutyronitrile) to directly synthesize RAFT agents in situ.

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Nonviral vectors are safer than viral systems for gene therapy applications. However, the limited efficacy always prevents their being widely used in clinical practice. Aside from searching new gene nonviral vectors, many researchers focus on finding out new substances to improve the transfection efficiency of existent vectors. In this work, we found a transfection enhancer, nocodazole (NCZ), for dimethyldioctadecylammonium (DODAB, a cationic lipid) bilayer coated gold nanoparticles (AuNPs) mediated gene delivery. It was found that NCZ produces 3-fold transfection enhancement to HEK 293T cells assessed by flow cytometry (FCM). The result was further confirmed by luciferase assay, in which NCZ induced more than 5 times improvement in transfection efficiency after 48 h of transfection. The results from the inductively coupled plasma mass spectrometry (ICP-MS) and FCM showed that NCZ did not affect the internalization of DODAB-AuNPs/DNA complexes. The trafficking of the complexes by transmission electron microscopy (TEM) indicated that the interrupted transportation of the complexes to the lysosomes contributed greatly to the transfection enhancement.

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Hyperbranched polymers with numerous pendent norbornene functionalities have been synthesized via the radical polymerization of a novel asymmetrical divinyl monomer hearing a higher reactivity methacrylate group and it lower reactivity norbornene group. Mediated by a rapid reversible addition-fragmentation chain transfer (RAFT) equilibrium, the concentration of polymeric chain radicals is decreased, and thus the gelation did not occur until higher monomer conversions (ca. 90%). An increase in reaction temperature call also significantly promote the formation of the hyperbranched structure owing to the decreased stability of the intermediate radicals derived from the norbornene group, which was confirmed by a model copolymerization system of two single vinyl monomers with similar structures to the vinyl groups in the asymmetrical divinyl monomer. Furthermore, Tri-SEC and conventional Sin-SEC as well as H-1 NMR.

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Hyperbranched vinyl polymers were prepared by reversible addition-fragmentation chain transfer ( RAFT) polymerization of a styrenic asymmetric divinyl monomer. This was achieved by using cumyl dithiobenzoate or S-dodecyl-S'-(alpha,alpha'-dimethyl-alpha ''-acetic acid) trithiocarbonate as the chain transfer agent, 1,1'-azobis(cyclohexanecarbonitrile) or thermal initiation as a source of radicals. Cross-linking was inhibited by a rapid RAFT-based equilibrium between active propagation chains and dormant species, and thus a hyperbranched polymer with a monomer conversion as high as 80% was obtained. The hyperbranched structure and properties of the resultant polymers were characterized by a combination of H-1-NMR spectroscopy and a triple detection size exclusion chromatography (TRI-SEC). The hyperbranched vinyl polymer has a broad molecular weight distributions and a low Mark-Houwink exponent alpha value compared with the linear counterpart.

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Branched polyacrylonitriles were prepared via the one-pot radical copolymerization of acrylonitirle and an asymmetric divinyl monomer (allyl methacrylate) that possesses both a higher reactive methacrylate and a lower reactive allyl. RAFT technique was used to keep a low-propagation chain concentration via a fast reversible chain transfer euilibration and thus the cross-linking was prevented until a high level of monomer conversions. This novel strategy was demonstrated to engenerate a branched architecture with abundant pendant functional vinyl and nitrile groups, and controlled molecular weight as a behavior of controlled/living radical polymerization characteristics. The effect of the various experimental parameters, including temperature, brancher to monomer molar ratio, and chain transfer agent to initiator molar ratio, on the control Of moleculer dimension (molecular weight and polydispersity indices) and the degree of branching were investigated in detail. Moreover, H-1 NMR and gel permeation chromatography confirm the branched architecture of the resultant polymer. The intrinsic viscosity of the copolymer is also lower than the linear counterpart.