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Ag-coated AgBr nanoparticles (Ag@AgBr) were fabricated via an aqueous, one-pot route. In this system, poly(vinyl alcohol) (PVA) acted as a stabilizer for the formation of nanoscale AgBr composites through interaction with Ag ions and their hydroxyl (–OH) groups. The mild reducing agent L-arginine was used for partial reduction of AgBr to form metallic Ag nanoparticles on the AgBr surface. The metallic Ag nanoparticles enhanced light absorption in the visible region due to surface plasmon resonance (SPR). The size of the synthesized nanoparticles was controlled by varying the reaction temperature, and was found to influence the light absorption of Ag@AgBr nanocomposites. The prepared nano-photocatalysts exhibited excellent photocatalytic activities under both visible light and direct sunlight.

Syndecan-4 (heparan sulfate proteoglycan), biologically important in cell-to-cell interactions and tumor suppression, was studied through mutation of the GXXXG motif of its transmembrane domain (Syd4-TM), a motif which governs dimerization. The expression and purification of the mutant (mSyd4-TM) were optimized here to assess the function of the GXXXG motif in the dimerization of Syd4-TM. mSyd4-TM was obtained in M9 minimal media and its oligomerization was identified by SDS PAGE, Circular Dichroism (CD) spectroscopy, mass spectrometry and NMR spectroscopy. The mutant, unlike Syd4-TM, did not form dimers and was observed as monomers. The GXXXG motif of Syd-4TM was shown to be an important structural determinant of its dimerization.

E-mail: yakim@hufs.ac.krReceived December 27, 2012, Accepted January 21, 2013The syndecan family consists of four transmembrane heparan sulfate proteoglycans present in most cell typesand each syndecan shares a common structure containing a heparan sulfate modified extracellular domain, asingle transmembrane domain and a C-terminal cytoplasmic domain. To get a better understanding of themechanism and function of syndecan-4 which is one of the syndecan family, it is crucial to investigate its three-dimensional structure. Unfortunately, it is difficult to prepare the peptide because it is membrane-bound proteinthat transverses the lipid bilayer of the cell membrane. Here, we optimize the expression, purification, andcharacterization of transmembrane, cytoplasmic and short extracellular domains of syndecan4 (syndecan-4eTC). Syndecan-4 eTC was successfully obtained with high purity and yield from the M9 medium. Thestructural information of syndecan-4 eTC was investigated by MALDI-TOF mass (MS) spectrometry, circulardichroism (CD) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. It was confirmed thatsyndecan-4 eTC had an α-helical multimeric structure like transmembrane domain of syndecan-4 (syndecan-4 TM) in membrane environments. Key Words : Syndecan, Syndecan-4, Transmembrane, NMR spectroscopy, Membrane proteinIntroductionThe syndecan family consists of heparan sulfate proteo-glycans, which are present on the surface of all cell types inhumans. This family regulates cell-to-cell interaction, celladhesion, cell proliferation and angiogenesis, as well ashelps in healing wounds by activation of growth factors.

Silver-nanoparticle-decorated polypyrrole (PPy) nanotubes (NTs) were fabricated by vapor deposition polymerization (VDP)-mediated hard-template method. Fe/Ag cations were attached on the wall of an AAO template by electrostatic interactions, and pyrrole monomers were polymerized by the reduction of Fe/Ag cations due to chemical oxidation polymerization. The Ag NPs/PPy NTs are applied as antimicrobial agents against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. The antimicrobial results show that the antimicrobial performance of Ag NPs/PPy NTs increases with the increasing of the population of Ag NPs loaded on PPy NT. At 30% (wt/wt) Ag NPs/PPy NTs, the minimum inhibitory concentrations (MICs) were 10 and 200 μg/mL against Escherichia coli and Staphylococcus aureus, respectively. Open image in new window

Novel fluorescent polyacrylonitrile nanoparticles were synthesized by microemulsion polymerization and Schiff base modification. By further modification with europium, the polyacrylonitrile nanoparticles could be used as a highly sensitive and rapid sensor for Bacillus anthracis spore detection in aqueous solution. The europium-modified polyacrylonitrile nanoparticles were readily combined with dipicolinic acid as a unique biomarker of B. anthracis , leading to high fluorescence emission. These nanoparticles enabled ratiometric detection without instrument-specific calibration due to the internal fluorescence reference. Additionally, the europium-modified polyacrylonitrile nanoparticle sensors exhibited a remarkable limit of detection (10 pM) for dipicolinic acid and outstanding selectivity (160×) over aromatic ligands in aqueous solution. The ultrafine nanoparticle sensor showed a high capability for detecting anthrax due to the increased surface area-to-volume ratio and enhanced dispersibility.

Quaternary ammonium compounds have been considered as excellent antibacterial agents due to their effective biocidal activity, long term durability and environmentally friendly performance. In this work, 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride as a quaternary ammonium silane was applied for the surface modification of silica nanoparticles. The quaternary ammonium silane provided silica surface with hydrophobicity and antibacterial properties. In addition, the glass surface which was coated with the surface modified silica nanoparticles presented bacterial growth inhibition activity. For comparison of bacterial growth resistance, hydrophobic silane (alkyl functionalized silane) modified silica nanoparticles and pristine silica nanoparticles were prepared. As a result of bacterial adhesion test, the quaternary ammonium functionalized silica nanoparticles exhibited the enhanced inhibition performance against growth of Gram-negative Escherichia coli (96.6%), Gram-positive Staphylococcus aureus (98.5%) and Deinococcus geothermalis (99.6%) compared to pristine silica nanoparticles. These bacteria resistances also were stronger than that of hydrophobically modified silica nanoparticles. It could be explained that the improved bacteria inhibition performance originated from the synergistic effect of hydrophobicity and antibacterial property of quaternary ammonium silane. Additionally, the antimicrobial efficacy of the fabricated nanoparticles increased with decreasing size of the nanoparticles.

A simple synthetic method has been developed for the fabrication of antimicrobial polyrhodanine nanotubes with silver nanoparticles. Rhodanine monomer first forms one-dimensional complexes with silver ions due to coordinative interactions and consecutively reduces the silver ions during chemical-oxidation polymerization. The polymerization procedure is analyzed by transmission electron microscopy and scanning electron microscopy in situ. The synthesized silver nanoparticles/polyrhodanine nanotubes are applied as an antimicrobial agent against Gram-negative bacteria, E. coli and Gram-positive bacteria, S. aureus. The antimicrobial tests demonstrate that the silver/polyrhodanine nanotubes have superior antimicrobial properties to silver nanoparticles and rhodanine monomer.

A one pot and environmentally benign synthetic route for plasmonic photocatalytic Ag@AgCl nanoparticles in a PVA-dissolved aqueous solution system is presented. The synthesized AgCl has a cubic-shape and its edge length can be controlled from ~57 to ~170 nm by varying the reaction temperature. In this system, PVA was used as a stabilizer for the formation of Ag@AgCl nanoparticles through interaction with Ag(+) ions. After partial reduction with l-arginine, the metallic Ag is formed on the surface of the AgCl substrates and the contents of the metallic Ag mainly affect both the visible-light absorption properties and the plasmonic photocatalytic efficiency of the Ag@AgCl nanocomposites. A plausible growth mechanism of metallic silver during the reduction process is proposed. More importantly, it is verified that the size of the AgCl substrate affected the light absorption region of the Ag@AgCl nanocomposite.

This paper describes the one-pot, aqueous synthesis of cationic polymer nanofibers with embedded silver nanoparticles. Poly[2-(tert-butylaminoethyl) methacrylate] (PTBAM) was used as a cationic polymer substrate to reinforce the antimicrobial activity of the embedded silver nanoparticles. Electron microscope analyses revealed that the as-synthesized nanofibers had diameters of approximately 40 nm and lengths up to about 10 μm. Additionally, silver nanoparticles of approximately 8 nm in diameter were finely embedded into the prepared nanofibers. The embedded silver nanoparticles had a lower tendency to agglomerate than colloidal silver nanoparticles of comparable size. In addition, the nanofibers with embedded silver nanoparticles exhibited excellent antibacterial performance against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Interestingly, the prepared nanofibers exhibited enhanced bactericidal performance compared with the silver-embedded poly(methyl methacrylate) (PMMA) nanofibers, presumably because of the antibacterial properties of the PTBAM substrate.

Novel polymer based photoluminescent nanoparticles were fabricated by ultra-sound induced emulsion polymerization and applied to bioimaging of human breast cancer SK-BR-3 cells after ethylenediamine treatment and conjugation with anti-ErbB2 antibody.

Novel biocidal polymer-functionalized TiO(2) nanoparticles were prepared by surface-initiated photopolymerization using titania as an initiator. Vinyl monomer mixtures of nontoxic secondary amine-containing biocidal 2-(tert-butylamino)ethyl methacrylate and antifouling ethylene glycol dimethacrylate were used for the antimicrobial polymer shell. It was shown that the synthesized TiO(2)/poly[2-(tert-butylamino)ethyl methacrylate-co-ethylene glycol dimethacrylate] core/shell nanoparticles had enhanced photocatalytic antibacterial properties compared to the pristine TiO(2) nanoparticles due to the combined antibacterial activities of light-driven anti-infective TiO(2) core and biocidal polymer shell. In the dark condition, the TiO(2)/biocidal polymer nanoparticles exhibited high antimicrobial efficiency (95.7%) against gram-positive S. aureus. Furthermore, during UV irradiation, the TiO(2)/biocidal polymer showed improved inhibition of bacterial growth against gram-negative E. coli and gram-positive S. aureus in comparison to the pristine TiO(2) nanoparticles.

In this study, a complex-mediated synthetic growth method was used to embed silver (Ag) nanoparticles in poly(vinyl alcohol) (PVAI) nanofibers in an aqueous solution. Azobisisobutyronitrile (AIBN) played a pivotal role in the preparation of the Ag–PVAI nanofibers, via its cyano groups. AIBN was used to assemble the Ag ions to form Ag complexes in the early stages of the reaction. As the reaction temperature approached 60 °C, AIBN decomposed via breakage of its C–N bonds, and thus the Ag compounds became disassembled. During this stage, Ag nanoparticles were aligned with a PVAI assistant, which acted as a gelator and stabilizer for the formation of fibrous nanostructures under magnetic stirring conditions. As a result, PVAI nanofibers (diameter: ca. 35 nm) were synthesized, with Ag nanoparticles (diameter: ca. 8 nm) embedded compactly in the inner part of the fiber. The formation of Ag–PVAI composite nanofibers was systematically investigated with field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Additionally, we performed several control experiments and proposed a plausible mechanism for the synthesis of Ag–PVAI composite nanofibers.