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Amphiphilic Molecules (amphiphilic + molecule)
Selected AbstractsBiophysical characterization of synthetic rhamnolipidsFEBS JOURNAL, Issue 22 2006Jörg Howe Synthetic rhamnolipids, derived from a natural diacylated glycolipid, RL-2,214, produced by Burkholderia (Pseudomonas) plantarii, were analyzed biophysically. Changes in the chemical structures comprised variations in the length, the stereochemistry and numbers of the lipid chains, numbers of rhamnoses, and the occurrence of charged or neutral groups. As relevant biophysical parameters, the gel (,) to liquid crystalline (,) phase behavior of the acyl chains of the rhamnoses, their three-dimensional supramolecular aggregate structure, and the ability of the compounds to intercalate into phospholipid liposomes in the absence and presence of lipopolysaccharide-binding protein were monitored. Their biological activities were examined as the ability to induce cytokines in human mononuclear cells and to induce chemiluminescence in monocytes. Depending on the particular chemical structures, the physicochemical parameters as well as the biological test systems show large variations. This relates to the acyl chain fluidity, aggregate structure, and intercalation ability, as well as the bioactivity. Most importantly, the data extend our conformational concept of endotoxicity, based on the intercalation of naturally originating amphiphilic virulence factors into membranes from immune cells. This ,endotoxin conformation', produced by amphiphilic molecules with a hydrophilic charged backbone and apolar hydrophobic moiety, and adopting inverted cubic aggregate structures, causes high mechanical stress in target immune cells on integral proteins, eventually leading to cell activation. Furthermore, biologically inactive rhamnolipids with lamellar aggregate structures antagonize the endotoxin-induced activity in a way similar to lipid A-derived antagonists. [source] Molecular Mimetic Self-Assembly of Colloidal ParticlesADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Zhengwei Mao Abstract This article presents an overview of the current progress in molecular mimetic self-assembly of colloidal particles. Firstly, the recent study of colloidal particles at interfaces is highlighted, underlining the mesoscopic mimicry of the surface activity of amphiphilic molecules using colloidal particles. Secondly, various strategies developed thus far to impart colloidal particles with anisotropy in terms of chemical composition, surface chemistry and particle morphology, which are regarded as mesoscopic atoms and molecules, are reviewed. Thirdly, an overview of the current theoretical and experimental results of using the rules of molecular synthesis and self-assembly to direct self-assembly of colloidal particles is presented. Finally, the experimental challenges associated with molecular mimetic self-assembly of colloidal particles are outlined, giving a rather conservative conclusion of the status quo of this new research field with a very optimistic outlook. [source] Formation of Chiral Mesopores in Conducting Polymers by Chiral-Lipid-Ribbon Templating and "Seeding" Route,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2008Chaxing Fan Abstract Conducting polymer nanofibers with controllable chiral mesopores in the size, the shape, and handedness have been synthesized by chiral lipid ribbon templating and "seeding" route. Chiral mesoporous conducting poly(pyrrole) (CMPP) synthesized with very small amount of chiral amphiphilic molecules (usually,<,3%) has helically twisted channels with well-defined controllable pore size of 5,20,nm in central axis of the twisted fibers. The structure and chirality of helical mesopores have been characterized by high-resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM) and electron tomography. The average pore diameters of chiral mesopores were approximately estimated from the N2 adsorption,desorption data and calculated by the conversion calculation from helical ribbons to a rectangular straight tape. The pore size of CMPP has been controlled by choosing different alkyl chain lengths of chiral lipid molecules or precisely adjusting the H2O/EtOH volume ratio. [source] Synthesis of Half-Channels by the Anionic Polymerization of Ethylene Oxide Initiated by Modified CyclodextrinADVANCED MATERIALS, Issue 40 2009Nezha Badi Amphiphilic star-shaped oligomers are produced by anionic polymerization of ethylene oxide (EO) using per-2,3-di- O -heptyl- , -(or ,)cyclodextrins as initiators , a versatile way of synthesizing artificial channels bearing one polyEO branch per glucose unit. The behavior of the amphiphilic molecules in lipid membranes is studied by electrical measurements, which confirms the formation of transient, well-defined dimeric ionic channels (see figure). [source] Absorption of polyethylene glycol (PEG) polymers: The effect of PEG size on permeabilityJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2009Hema Gursahani Abstract Polyethylene glycol (PEG) polymers are large amphiphilic molecules that are highly hydrated in solution. To explore the permeability properties of different sized PEG polymers across epithelial membranes in vivo, we examined the absorption of fluorescently labeled PEG conjugates sized 0.55,20 kDa from the lung, since this system provides a reservoir that limits rapid diffusion of molecules away from the site of delivery and enables permeability over longer times to be examined. Following intratracheal delivery in rats, the PEG polymers underwent absorption with first-order kinetics described by single exponential decay curves. PEG size produced a marked influence on the rate of uptake from the lung, with half-lives ranging from 2.4 to 13 h, although above a size of 5 kDa, no further change in rate was observed. PEG size likewise affected retention in alveolar macrophages and in lung tissue; whereas smaller PEG sizes (<2 kDa) were effectively cleared within 48 h, larger PEG sizes (>5 kDa) remained in lung cells and tissue for up to 7 days. These data demonstrate that PEG polymers can be absorbed across epithelial membranes and that PEG size plays a dominant role in controlling the rate and mechanism of absorption. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2847,2856, 2009 [source] Encapsulation and Controlled Release of a Hydrophobic Drug Using a Novel Nanoparticle-Forming Hyperbranched Polyester,MACROMOLECULAR BIOSCIENCE, Issue 7 2005Jianhua Zou Abstract Summary: An amphiphilic, hyperbranched polymer suitable for use in controlled drug delivery is reported. This polymer was obtained by modification of the hyperbranched aliphatic polyester BoltornÔ H20 (H20) with succinic anhydride and then glycidyl methacrylate, and formed nanoparticles in aqueous solution. The critical association concentration was 7.4,×,10,3 g,·,L,1, as determined by fluorescence spectroscopy using pyrene as a molecular probe. A static/dynamic laser light scattering (LLS) study revealed that the average particle size was 39.4 nm with a low particle size distribution (PDI = 0.04), and that each particle was composed of about 350 amphiphilic molecules. Daidzein, a hydrophobic traditional Chinese medicine, was encapsulated during particle formation and the release properties were determined. The optimal feeding concentration of daidzein to hyperbranched polyester was 4.9,×,10,5 g,·,mL,1 to 5.0,×,10,3 g,·,mL,1 with a loading efficiency of 76.1%. In the presence of the enzyme Lipase PS, the drug loaded nanoparticles degraded in a random one-by-one manner and released the drug over a few days. This system is therefore a novel controlled drug release system based on nanoparticles formed of hyperbranched polyester. Encapsulation of daidzein by hyperbranched polyester particles. [source] Formation and characterization of polymersomes made by a solvent injection methodPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2007M. E. Yildiz Abstract In this article a solvent injection method is described for vesicle formation using poly(butadiene)- b-poly(acrylic acid) diblock copolymers as the amphiphilic molecules. Vesicles composed of polymer bilayers are commonly referred to as polymersomes. Solvent injection is shown to be a rapid method for polymersome formation suitable to make large volumes of polymersome solution. The method can be manipulated to obtain a wide range of vesicle sizes depending on the polymer concentration and preparation conditions. Polymersome solutions in this study are characterized using dynamic light scattering (DLS), fluorescent microscopy, and electron microscopy. Polymersome sizes range from tens of nanometers to several microns. The membrane thickness of smaller polymersomes is found to lie between 14,20,nm. Larger polymersomes are found to have somewhat thicker membranes. The procedure involves the addition of polymers dissolved in an organic solvent to a stirred aqueous solution. The formation of polymersomes by this method is proposed to be governed by the limited mutual solubility of the two solvents and the simultaneous diffusion of solvent and water out of and in to initially formed organic solvent droplets. Copyright © 2007 John Wiley & Sons, Ltd. [source] Designed synthesis of nanostructured siloxane,organic hybrids from amphiphilic silicon-based precursorsTHE CHEMICAL RECORD, Issue 2 2006Atsushi Shimojima Abstract This paper reports on recent progress in the synthesis of nanostructured siloxane,organic hybrids based on the self-assembly of amphiphilic silicon-based precursors. A variety of ordered hybrid materials have been obtained by molecular design of the precursors. Alkoxysilanes and chlorosilanes with covalently attached hydrophobic organic tails are hydrolyzed to form amphiphilic molecules containing silanol groups, leading to the formation of layered (lamellar) structures. Transparent and oriented thin films of lamellar hybrids were prepared by the reaction in the presence of tetraalkoxysilane. In addition, the design of molecules having alkyl chains and large oligosiloxane heads led to the formation of mesophases consisting of cylindrical assemblies, providing a direct pathway to ordered porous silica. The synthesis, structural features, and formation processes of these hybrid mesostructures are discussed. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 53,63; 2006: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20073 [source] Antimony-Doped Tin Oxide Nanocrystals: Synthesis and Solubility Behavior in Organic SolventsCHEMPHYSCHEM, Issue 5 2009Rafael O. da Silva Abstract The right mix: SnO2:Sb nanocrystals (NCs) can be solubilized into organic solvents with a suitable solvent/surfactant combination to achieve a stable colloid (see picture). A single synthesis route and different solvent/amphiphilic molecule pairs are used to obtain soluble NC colloids, instead of requiring several syntheses to obtain soluble NCs in different solvents. This work focuses on the nonaqueous synthesis of antimony-doped tin oxide nanocrystals in the size range of 2,6 nm and the investigation of their solubility in organic solvents (CHCl3 and THF) in the presence of amphiphilic molecules (oleic acid and oleylamine). To unravel the underlying processes, a set of molecular dynamics simulations is performed involving the compatibility of oleic acid and oleylamine in mixtures with both CHCl3 and THF. The results show that the method is useful for obtaining the desired oxide, and that the interaction between amphiphilic molecules and solvents can be predicted by molecular dynamics simulations with very good qualitative agreement. [source] | |||||||||||||