Effect of double quaternary ammonium groups on micelle formation of partially fluorinated surfactant

Water-in-oil microemulsions (w/o μEs) stabilized by the cationic surfactant cetyltrimethylammonium chloride (CTACl) have been used as reaction media to generate Au nanoparticles (Au-NPs). In addition the pure μEs have been used as media to disperse Au and Pd-NPs, which have been pre-synthesised in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, and also commercially available SiO(2)-NPs. A general method for recovery and separation of the nanoparticles from these mixed NP-μE systems has been demonstrated by tuning phase behavior of the background microemulsions. Addition of appropriate aliquots of water drives a clean liquid-liquid phase transition, resulting in two macroscopic layers, the NPs preferentially partition into an upper oil-rich phase and are separated from excess surfactant which resides in a lower aqueous portion. UV-vis and (1)H NMR spectroscopy have been used to follow these separation processes and quantify the recovery and recycle efficiencies for the different NPs. For example, ～90% of the microemulsion-prepared Au-NPs can be recovered; with even greater separation efficiencies attainable for pre-synthesised MES-stabilized Au-MES-NPs (～98%) and Pd-MES-NPs (92%). For the silica NP-μE dispersions gravimetry indicates ～84% recovery of the NPs. TEM images of all systems showed that NP shapes and size distributions were generally preserved after these phase transfer processes. This low-energy and cost-effective purification route appears to be a quite general approach for processing different inorganic NPs, having advantages of being isothermal, using only commercially available inexpensive components and requiring no additional organic solvents.     

Novel Copolymers of Vinyl Acetate and Some Ring‐Substituted 2‐Phenyl‐1,1‐dicyanoethylenes

Electrophilic trisubstituted ethylene monomers, some ring‐substituted 2‐phenyl‐1,1‐dicyanoethylenes, RC₆H₄CH?C(CN)₂ (where R is 3‐Br, 4‐CH₃O; 5‐Br, 2‐CH₃O; 4‐Cl, 3‐NO₂; 5‐Cl, 2‐NO₂; 2‐CN, 3‐CN, 4‐CN, and 4‐(CH₃)₂N), were synthesized by piperidine catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and malononitrile, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and vinyl acetate were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C‐NMR, GPC, DSC, and TGA. High T _g of the copolymers, in comparison with that of polyvinyl acetate, indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 190–800°C range.     

Phytochemical Analysis and Molecular Identification of Green Macroalgae Caulerpa spp. from Bali,Indonesia

The studies of the Bulung Boni and Bulung Anggur (Caulerpa spp.) species and secondary metabolites are still very limited. Proper identification will support various aspects, such as cultivation, utilization, and economic interests. Moreover, understanding the secondary metabolites will assist in developing algae-based products. This study aimed to identify these indigenous Caulerpa algae and analyze their bioactive components. The tufA sequence was employed as a molecular marker in DNA barcoding, and its bioactive components were identified using the GC-MS method. The phylogenetic tree was generated in MEGA 11 using the maximum likelihood method, and the robustness of the tree was evaluated using bootstrapping with 1000 replicates. This study revealed that Bulung Boni is strongly connected to Caulerpa cylindracea. However, Bulung Anggur shows no close relationship to other Caulerpa species. GC-MS analysis of ethanolic extracts of Bulung Boni and Bulung Anggur showed the presence of 11 and 13 compounds, respectively. The majority of the compounds found in these algae have been shown to possess biological properties, such as antioxidant, antibacterial, anticancer, anti-inflammation, and antidiabetic. Further study is necessary to compare the data obtained using different molecular markers in DNA barcoding, and to elucidate other undisclosed compounds in these Caulerpa algae.     

Bitterness suppression of BCAA solutions by L-ornithine

The purpose of the present study was to evaluate the bitterness-suppressing effect of L-ornithine (L-Orn) on single or mixed solutions of branched-chain amino acids (BCAAs) using human gustatory sensation tests and an artificial taste sensor. The BCAAs tested (L-isoleucine (L-Ile), L-leucine (L-Leu), and L-valine (L-Val)) are the main components of various enteral nutrients or supplements. The bitterness-suppression effect of L-Orn was also compared with the effect of L-Arg. L-Orn was effective in suppressing the bitterness of single or mixed solutions of BCAAs in human gustatory sensation tests, the effect being similar to or greater than that of L-Arg. The artificial taste sensor was able to predict the bitterness-suppressing effects of L-Orn and L-Arg. The response electric potential patterns of L-Val, L-Leu and L-Ile solutions to which 100 mM L-Arg had been added were quite similar to the sensor response patterns of the 100 mM L-Arg solutions alone. The relative response electric potential patterns of L-Val, L-Leu or L-Ile solutions containing 100 mM L-Orn in channels 5-8 (positively charged) are similar to that of single solution of 100 mM L-Orn.     

Novel calixarene hemisphere synthesized via pinacol rearrangement of [2.1.2.1]metacyclophane

[reaction: see text] Tetramethoxy[2.1.2.1]metacyclophane ([2.1.2.1]MCP) was prepared by the pinacol coupling reaction of diphenylmethane dialdehyde. The treatment of [2.1.2.1]MCP with trimethylsilyl chloride and sodium iodide yielded two unexpected calixarene derivatives, cone (hemisphere) and 1,2-alternate types, instead of octahydroxy[2.1.2.1]MCP. The X-ray structure of the cone-type derivative and its inclusion property with acetonitrile were also discussed.     

Solid-state fluorescence study of naphthalene adsorption on porous material

Naphthalene adsorption profile on porous materials was studied using solid-state fluorescence spectroscopy. When naphthalene crystals were simply mixed with porous crystalline cellulose (PCC), excimer emission of naphthalene was observed after 1 min of mixing, suggesting a drastic change in the naphthalene molecular environment during the mixing procedure. For the naphthalene-octadesyl silane (ODS)-80A or naphthalene-ODS-2 systems, the changes in adsorption profiles and fluorescence spectral pattern of naphthalene were similar to those of the naphthalene-PCC system. The final amounts of naphthalene adsorbed to ODS-80A and ODS-2 were 0.05 and 0.024 g/g adsorbent, respectively, even though the two materials had comparable values of specific surface area. The relative emission intensity (I(excimer)/I(monomer)) in the ODS-80A system was higher than that in the ODS-2 system when compared at the same amount of naphthalene adsorbed. It was concluded that the pore size of porous materials affected the naphthalene excimer formation on the surface.     

Wrightiamines A and B,two new cytotoxic pregnane alkaloids from Wrightia javanica

Two new pregnane alkaloids, wrightiamines A (1) and B (2), were isolated from the extract of the tropical Apocynaceous plant Wrightia javanica collected in Thailand, and their structures were elucidated by spectral data. Wrightiamine B (2) was preparaed from 3beta-hydroxy-5alpha-pregnan-20-one to establish the configuration of the C-20 position as S. Wrightiamine A (1) exhibited cytotoxic activity against vincristine-resistant murine leukemia P388 cells.     

Intermediate-range order in glassy GexSe1−x around the stiffness transition composition

X-ray scattering measurements on glassy Ge_xSe_1−x were performed in a concentration range x=0.07-0.333 in fine steps of 0.005-0.05, in order to explore the relation between the intermediate-range order (IRO) and the stiffness transition in this glassy system. The oscillations beyond the first peak around 20.5 nm⁻¹ in the structure factor, S(Q), remain almost unchanged or damp very slowly with decreasing the Ge concentration x, suggesting the preserve of the short-range order. On the other hand, the pre-peak around 10-12 nm⁻¹, indicating the existence of IRO, systematically changes with decreasing x; its Q position shifts towards the higher Q values and its area decreases. Especially near the onset of the stiffness transition, x=0.20, the peak position starts to deviate from the linear relation. The origin of the pre-peak is discussed in connection with results of a recent anomalous X-ray scattering measurement indicating two contributions of Ge-Ge and Se-Se correlations. Around the onset composition of the stiffness transition, the area of the pre-peak associated with the Ge-Ge correlation has a plateau-like gradual decrease with x followed by a rapid decrease at x<0.18, which is in good agreement with Raman data.     

Bioaccumulation of Antimony by Chlorella vulgaris and the Association Mode of Antimony in the Cell

The bioaccumulation and excretion of antimony by the freshwater alga Chlorella vulgaris , which had been isolated from an arsenic-polluted environment, are described. When this alga was cultured in a medium containing 50 μg cm⁻³ of antimony(III) for 14 days, it was found that Chlorella vulgaris bioaccumulated antimony at concentrations up to 12 000 μg Sb g⁻¹ dry wt after six days' incubation. The antimony concentration in Chlorella vulgaris decreased from 2570 to 1610 μg Sb g⁻¹ dry wt after the cells were transferred to an antimony-free medium. We found that the excreted antimony consists of 40% antimony(V) and 60% antimony(III). This means that the highly toxic antimony(III) was converted to the less toxic antimony (V) by the living organism. Antimony accumulated in living Chlorella vulgaris cells was solvent-fractionated with chloroform/methanol (2:1), and the extract residue was fractionated with 1% sodium dodecyl sulfate (SDS). Gel-filtration chromatography of the solubilized part showed that antimony was combined with proteins whose molecular weight was around 4×10⁴ in the antimony-accumulated living cells. © 1997 by John Wiley & Sons, Ltd.     

Behavior of nitroxyl radical in the polymerization process forming copolymers bearing diarylnitrone pendants and photocontrol of refractive indices for these copolymers

To establish the reaction condition under which the radical copolymerization of methyl methacrylate (MMA) with α‐(2‐hydroxy‐4‐methacryloyloxyphenyl)‐N‐(2,6‐dimethylphenyl)nitrone (HMDN) proceeds smoothly to give photoreactive copolymers, the effects of the nitrone chromophore on the extent to which the radical polymerization of MMA is inhibited were investigated. It was found that the reversible addition of initiating radical to the CH?N⁺(? O^?) moiety in the nitrone chromophore readily occurs to give the nitroxyl radical. It was also found that the latter radical undergoes an efficient coupling reaction with propagating radical to inhibit the radical copolymerization of MMA with HMDN. However, on raising the reaction temperature and the radical concentration, the copolymerization was successfully carried out. This polymerization condition allowed us to prepare the HMDN/MMA, HMDN/styrene, and HMDN/cyclohexyl acrylate copolymers in good yields. The photoirradiation of the copolymer film prepared on a silicon wafer lowered its refractive index by 0.003–0.023, depending on the relative composition of the diarylnitrone chromophore in these copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 88–97, 2006