Silver to Gold Metallic Luster Changes in Stimuli-Responsive Diacetylene Derivatives Uniquely Arranged within Crystals.

Eye-catching metallic luster materials, especially those whose colors can be controlled by external stimuli, have many potential applications. Here, we present a silver luster material that changes color to gold upon UV irradiation. Diacetylene (DA) derivatives with stilbenes introduced via linkers at both ends ( ( = 1-6)) exhibited significantly different metallic luster and color change behaviors depending on the linker carbon number ().

Multi-responsive organo- and hydrogelation based on the supramolecular assembly of fluorocarbon- and hydrocarbon-containing hybrid surfactants.

Hypothesis: Novel photoresponsive hybrid surfactants, in which a combination of perfluoroalkyl and alkyl chains and cationic head groups are connected via azobenzene moieties, are excellent candidates for assembling low-molecular-weight organogels (LMOGs) with reversibly switchable viscoelasticities triggered by external stimuli.

Experiments: The structure-composition-property relationships of gels assembled with the hybrid surfactants were investigated by UV-vis and NMR spectroscopy, SEM, XRD, and rheology.

Findings: Hybrid surfactants containing perfluorohexyl chains with more than six carbons gelled in a variety of organic solvents at concentrations of less than a few percent.

Synthesis and surface activity of photoresponsive hybrid surfactants containing both fluorocarbon and hydrocarbon chains.

Hypothesis: Hybrid surfactants containing both alkyl and fluoroalkyl chains within the same molecule where modification of the azobenzene group will enable us to switch the superhydrophobic nature with an external light source, and the optical behavior will vary depending on the structure of the hydrophobic chains.

Experiments: Surface activity and its optically-induced variation of the azobenzene-modified hybrid surfactants were characterized using the surface tensiometry, UV-vis and NMR spectroscopy and theoretical calculation.

Findings: The hybrid surfactants are superhydrophobic in nature reducing the surface tension of water to near 20 mN/m.

Screening and isolation of the liamocin-producing yeast Aureobasidium melanogenum using xylose as the sole carbon source.

Xylose, the main component of xylan, is the second most abundant sugar in nature after glucose. Consequently, xylose represents an attractive feedstock for the production of value-added compounds such as biosurfactants (BSs), which are produced by various bacteria and yeasts. In this study, we screened and isolated yeast strains that synthesize BSs using xylose as the sole carbon source.

Reversible Destabilization of UV-Responsive Polymer Particles (Latex) using a Photoresponsive Surfactant.

Production of aqueous dispersions of polymeric nanoparticles via heterogeneous radical polymerization in emulsion-type systems is of enormous commercial importance. The ability to reversibly destabilize such a latex is highly desirable, for example, to save transportation costs. Herein, a method for synthesis of photo-responsive polymer latexes that can be destabilized (leading to sedimentation) by only using UV irradiation (no addition of chemicals or change in the experimental conditions) and subsequently redispersed by stirring under visible light irradiation is described.

Synthesis and Characterization of a Novel Glycolipid with Glucosylglycerate as a Hydrophile Showing Protective Effects on Heat-induced Protein Denaturation.

A novel glycolipid featuring a glucosylglycerate moiety as a polar head group was synthesized in two steps from sucrose, glycerate, and N-dodecylamine. Glucosylglyceric acid was formed from sucrose and glyceric acid using sucrose synthase as a catalyst, followed by condensation with N-dodecylamine using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) as a condensing agent. A white solid compound was recovered with a yield of 21% after purification by hydrophobic column chromatography.

Boosting Effect of Amphiphilic Random Copolymers for Bicontinuous Phases.

Amphiphilic random copolymers, poly(oxyethylene)/poly(oxypropylene) butyl ethers (C4EmPn), have been used as raw materials for cosmetics. This paper reports on the influence of amphiphilic random copolymers on mixtures of n-decane, water, and a nonionic surfactant, hexa(oxyethylene) dodecyl ether (C12E6). Bicontinuous phases are formed from decane/water/C12E6 mixtures at high C12E6 weight fractions (> 70 wt%).

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 °C.

Demulsification of Redox-Active Emulsions by Chemical Oxidation.

This article reports the influence of redox reactions on emulsions of n-octane and an aqueous solution of a ferrocene-containing surfactant (FTMA; (11-ferrocenylundecyl)trimethylammonium bromide). Above a certain surfactant concentration, stable O/W emulsions were formed from an aqueous solution of reduced FTMA; in contrast, mixtures of n-octane and an aqueous solution of oxidized FTMA did not form emulsions at any surfactant concentration. Furthermore, adding an oxidant to the stable O/W emulsions of reduced FTMA led to coalescence of the oil (octane) droplets in the emulsions, and subsequently, the oil and water (aqueous FTMA solution) phases fully separated from the emulsions, i.

Photoinduced formation of threadlike micelles from mixtures of a cationic surfactant and a stilbene amphiphile.

This study examined the influence of ultraviolet (UV) irradiation on aqueous surfactant solutions containing an anionic stilbene derivative (sodium [4-[(E)-2-(4-butylphenyl)ethenyl]phenoxy]acetate; C4StilNa) as a photoresponsive skeleton. Prior to UV irradiation, an aqueous solution of cetyltrimethylammonium bromide (CTAB) and C4StilNa was a low-viscosity fluid forming spheroidal micelles. Exposure of the low-viscosity fluid to UV light resulted in the formation of threadlike micelles and an increase in the viscosity of the aqueous CTAB/C4StilNa solution.

Synthesis and Characterization of Dioctanoyl Glycerate as Water-soluble Trypsin Inhibitor.

Glyceric acids (GAs) esterified with long acyl chains (> C16) exhibit antitrypsin activity (Folia Microbiol. 46, 21-23 (2001)). However, their hydrophobic nature, derived from the long acyl chains, has limited the number of studies on their physical and biological properties.

Active Demulsification of Photoresponsive Emulsions Using Cationic-Anionic Surfactant Mixtures.

The influence of ultraviolet (UV) light irradiation on the emulsification properties of mixtures of an anionic surfactant, sodium dodecyl sulfate (SDS), and a photoresponsive cationic surfactant, 2-(4-(4-butylphenyl)diazenylphenoxy)ethyltrimethylammonium bromide (C4AzoTAB), containing an azobenzene group has been investigated. When mixtures of n-octane and aqueous SDS/trans-C4AzoTAB solution are homogenized, stable emulsions are obtained in regions of specific surfactant concentrations and molar ratios of the mixed surfactants. The stable emulsions are stable for over a week and found to be of the oil-in-water (O/W) type.

Influence of the Phase State of Self-Assembling Redox Mediators on their Electrochemical Activity.

Self-assembling redox mediators have the potential to be broadly useful in a range of interfacial electrochemical contexts because the oxidation state and state of assembly of the mediator are closely coupled. In this paper, we report an investigation of the self-assembly of single- and double-tailed ferrocenyl amphiphiles (FTMA and BFDMA, respectively) at the surfaces of Pt electrodes and the impact of the dynamic assembled state of the amphiphiles on their rate of oxidation. We conclude that frozen aggregates of BFDMA adsorb to the surfaces of the Pt electrodes, and that slow dynamics of reorganization BFDMA within these aggregates limits the rate of electrooxidation of BFDMA.

Gold-colored organic crystals of an azobenzene derivative.

A new azobenzene derivative, bis[4-(3-methylbutoxy)phenyl]diazene (DC-azo), was synthesized as yellow powder through a three-step reaction. DC-azo was crystallized from a mixture of acetone/water in the form of highly insulating gold-colored crystals with a specular reflectance of 21% over the wavelength range of 520-800 nm. The CIELAB color space of the crystals indicated that the crystals were slightly more reddish and less yellowish than metallic Au.

Control of dual stimuli-responsive vesicle formation in aqueous solutions of single-tailed ferrocenyl surfactant by varying pH and redox conditions.

This paper reports a method to control the formation and disruption of vesicles from a novel single-tailed surfactant (11-ferrocenylundecylammonium bromide, 11-FAB), which contains two stimuli-responsive groups corresponding to pH variation and redox reaction conditions, by external stimuli. Although 11-FAB is a single-tailed surfactant, pure 11-FAB spontaneously forms vesicles in water. Microscopic observations of 2.

Photoinduced demulsification of emulsions using a photoresponsive gemini surfactant.

This Article reports on the influence of light irradiation on the stability of emulsions prepared using a photoresponsive gemini surfactant (C7-azo-C7) having an azobenzene skeleton as a spacer. When mixtures of trans C7-azo-C7 aqueous solution and n-octane are homogenized, stable emulsions are obtained in a specific region of weight fraction and surfactant concentration. Fluorescence microscopy observations using a small amount of fluorescent probes show that the stable emulsions are oil-in-water (O/W)-type.

Spatial control of cell transfection using soluble or solid-phase redox agents and a redox-active ferrocenyl lipid.

We report principles for active, user-defined control over the locations and timing with which DNA is expressed in cells. Our approach exploits unique properties of a ferrocenyl cationic lipid that is inactive when oxidized, but active when chemically reduced. We show that methods that exert spatial control over the administration of reducing agents can lead to local activation of lipoplexes and spatial control over gene expression.

Unusual viscoelasticity behaviour in aqueous solutions containing a photoresponsive amphiphile.

Here, we report unusual behaviour of the viscoelasticity of surfactant aqueous solutions consisting of cationic cetyltrimethylammonium bromide (CTAB) and an anionic photoresponsive amphiphile, sodium [4-(4-butylphenylazo)phenoxy]acetate (C4AzoNa). When C4AzoNa molecules are trans-isomers, spheroidal micelles are formed in the surfactant solution, the viscosity of which is low. Irradiation of this solution by ultraviolet (UV) light yields an aqueous solution of CTAB/cis-C4AzoNa (cis-isomers of C4AzoNa), which is a highly viscous gel consisting of wormlike micelles.

Redox-based control of the transformation and activation of siRNA complexes in extracellular environments using ferrocenyl lipids.

We report physical characterization and biological evaluation of complexes of small interfering RNA (siRNA) formed using a cationic lipid [bis(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA)] containing redox-active ferrocenyl groups at the end of each hydrophobic tail. We demonstrate that control over the redox state of BFDMA can be used to influence key physical properties and control the activities of lipoplexes formed using siRNA-based constructs. Specifically, lipoplexes of siRNA and reduced BFDMA lead to high levels of sequence-specific gene silencing in cells, but lipoplexes formed using oxidized BFDMA do not.

Chemical oxidation of a redox-active, ferrocene-containing cationic lipid: influence on interactions with DNA and characterization in the context of cell transfection.

We report an approach to the chemical oxidation of a ferrocene-containing cationic lipid [bis(11-ferrocenylundecyl)dimethylammonium bromide, BFDMA] that provides redox-based control over the delivery of DNA to cells. We demonstrate that BFDMA can be oxidized rapidly and quantitatively by treatment with Fe(III)sulfate. This chemical approach, while offering practical advantages compared to electrochemical methods used in past studies, was found to yield BFDMA/DNA lipoplexes that behave differently in the context of cell transfection from lipoplexes formed using electrochemically oxidized BFDMA.

Incorporation of DOPE into Lipoplexes formed from a Ferrocenyl Lipid leads to Inverse Hexagonal Nanostructures that allow Redox-Based Control of Transfection in High Serum.

We report small angle X-ray and neutron scattering measurements that reveal that mixtures of the redox-active lipid bis(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA) and dioleoylphosphatidylethanolamine (DOPE) spontaneously form lipoplexes with DNA that exhibit inverse hexagonal nanostructure (H(II) (c)). In contrast to lipoplexes of DNA and BFDMA only, which exhibit a multilamellar nanostructure (L(α) (c)) and limited ability to transfect cells in the presence of serum proteins, we measured lipoplexes of BFDMA and DOPE with the H(II) (c) nanostructure to survive incubation in serum and to expand significantly the range of media compositions (e.g.

Addition of ascorbic acid to the extracellular environment activates lipoplexes of a ferrocenyl lipid and promotes cell transfection.

The level of cell transfection mediated by lipoplexes formed using the ferrocenyl lipid bis(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA) depends strongly on the oxidation state of the two ferrocenyl groups of the lipid (reduced BFDMA generally mediates high levels of transfection, but oxidized BFDMA mediates very low levels of transfection). Here, we report that it is possible to chemically transform inactive lipoplexes (formed using oxidized BFMDA) to "active" lipoplexes that mediate high levels of transfection by treatment with the small-molecule reducing agent ascorbic acid (vitamin C). Our results demonstrate that this transformation can be conducted in cell culture media and in the presence of cells by addition of ascorbic acid to lipoplex-containing media in which cells are growing.

Synthesis and antimicrobial activity of quaternary ammonium silane coupling agents.

Fourteen novel silane coupling agents with a quaternary ammonium group introduced into the molecule, [CH(2)=CHCH(2)N(+)(CH(3))(C(n)H(2n+1))(CH(2))(3)Si(OCH(3))(3)]X(-) (n-X, n=10-18, X=Cl, Br, or I), were synthesized with the aim of using these agents to make material surfaces antimicrobial for a long period of time. Measurements of the minimum inhibitory concentrations (MIC) against 12 kinds of fungi and bacteria revealed that the coupling agent with a C(10) alkyl chain and Cl- or Br- counter-ion (10-Cl or 10-Br) has the highest antimicrobial activity among the n-X agents synthesized, but 14-Cl and 14-Br showed the highest activity on a modified porcelain plate.

Isolation of Pseudozyma churashimaensis sp. nov., a novel ustilaginomycetous yeast species as a producer of glycolipid biosurfactants, mannosylerythritol lipids.

An ustilaginomycetous anamorphic yeast species isolated from the leaves of Saccharum officinarum (sugarcane) in Okinawa, Japan, was identified as a novel Pseudozyma species based on morphological and physiological aspects and molecular taxonomic analysis using the D1/D2 domains of the large subunit (26S) rRNA gene and the internal transcribed spacer 1 (ITS1)-5.8S-ITS2 regions. The name Pseudozyma churashimaensis sp.

Influence of biological media on the structure and behavior of ferrocene-containing cationic lipid/DNA complexes used for DNA delivery.

Biological media affect the physicochemical properties of cationic lipid-DNA complexes (lipoplexes) and can influence their ability to transfect cells. To develop new lipids for efficient DNA delivery, the influence of serum-containing media on the structures and properties of the resulting lipoplexes must be understood. To date, however, a clear and general picture of how serum-containing media influences the structures of lipoplexes has not been established.