Reexamination of 2-Naphthol Adsolubilization on Alumina with Sodium Dodecyl Sulfate Adsorption

Adsolubilization behavior of 2-naphthol on alumina with adsorption of sodium dodecyl sulfate (SDS) at pH 3.5 in the presence of 10 mmol dm(-3) NaCl was reexamined. The adsolubilized amount of 2-naphthol increased sharply and reached a maximum, then decreased with SDS concentration. The decrement of the adsolubilized amount began below the critical micelle concentration of SDS. From the dispersion state of the alumina suspension and the SDS adsorption isotherm, it is demonstrated that the decrement of adsolubilization of 2-naphthol is not due to the partition of 2-naphthol between the SDS adsorbed layer and SDS micelles, but is due to the difference of SDS adsorption states such as monolayers and admicelles. Copyright 2000 Academic Press.     

Synthesis and surface properties of anionic gemini surfactants with amide groups

Novel anionic gemini surfactants, 1,2-bis(N-beta-carboxypropanoyl-N-alkylamino)ethane (2CnenAm; n is hydrocarbon chain length of 6, 8, 10, 12, or 14), with two hydrocarbon chains, two carboxylate groups, and two amide groups, were synthesized by three-step reactions. Their solution properties were characterized by equilibrium and dynamic surface tension, steady-state fluorescence spectroscopy of pyrene, and dynamic light-scattering techniques. The surface tension measurements of 2CnenAm give low critical micelle concentrations (cmc), great efficiency in lowering the surface tension, and strong adsorption at air/water interface. Gemini surfactants behave normally with the logarithm of cmc decrease linearly with the chain length. In addition, adsorption and micellization behavior of 2CnenAm was estimated by parameter of pC20, cmc/C20, and standard free energy (DeltaG(0)mic and DeltaG(0)ads); they are significantly influenced by hydrocarbon chain length, and the adsorption is promoted more than the micellization as chain length becomes longer. The results of dynamic light-scattering and fluorescence quenching indicate that small micelles of 2CnenAm are observed at the concentrations above the cmc, and further large particles are also seen. Further, from the dynamic surface tension measurements, it is found that the shorter hydrocarbon chain length of 2CnenAm, the faster the rate of decrease of surface tension.     

Fiber-like Gold Particles Prepared in Cationic Micelles by UV Irradiation: Effect of Alkyl Chain Length of Cationic Surfactant on Particle Size

Fiber-like gold particles were prepared by irradiation of HAuCl(4) solutions at 253.7 nm in the presence of alkyltrimethylammonium chlorides (C(n)TAC: n=10, 12, 14, and 16). Fiber-like gold particles were obtained above a threshold concentration of C(n)TAC. The length of fiber-like gold particles increases with increasing alkyl chain length of C(n)TAC. Copyright 2001 Academic Press.     

Characteristics of mixed bilayers of surfactants formed on alumina

The interaction between hydrocarbon and fluorocarbon surfactants on-alumina has been studied through the dispersion behavior of-alumina. When a low concentration of anionic hydrocarbon or fluorocarbon surfactant as a first additive is added to positively charged alumina, the alumina flocculates. The flocculated alumina redisperses upon addition of different surfactant from the first one by the manner that the hydrophobic parts of hydrocarbon and fluorocarbon surfactants are in contact with hydrophobic parts of the first surfactants and the hydrophilic polar groups direct out to liquid phase, resulting in the formation of mixed bilayers on the alumina. From the measurements of mean particle size, zeta potential of the alumina, and adsorbed amount of surfactants, the mixed bilayers consisting of anionic fluorocarbon-noniomc hydrocarbon surfactants and of anionic fluorocarbon-noioic hydrocarbon ones are found to be formed more preferentially than anionic hydrocarbon-anioic fluorocarbon surfactants. The property of the mixed bilayer on the alumina is also discussed using the fluorescence spectra of pyrene.     

Characterization of aliphatic and aromatic polyester hyperbranched dendrimers by AFM imaging

The aggregates of aliphatic (AL-PE) and aromatic polyester (AR-PE) hyperbranched dendrimers were imaged by tapping mode atomic force microscopy (AFM). The second and third generations of AL-PE dendrimers were adsorbed on mica in large aggregates of 150- and 166-nm diameters with little heights (ca. 1–2 nm). The origin of such flattened aggregates is attributed to their favorable adsorption on mica in view of the presence of –OH surface groups. AR-PE did not show such flattened aggregates instead small aggregates of 63 nm were observed in an organized manner beaving a cavity in the center of each aggregate. The organized aggregates of AR-PE with smaller dimension than AL-PE are ascribed to less favorable adsorption of the latter on mica in view of its stronger hydrophobicity.     

Cytotoxic iridoid aldehydes from Taiwanese Viburnum luzonicum

Four new iridoid aldehydes bearing (E)- or (Z)-p-coumaroyl group, luzonial A (1), luzonial B (2), luzonidial A (3), and luzonidial B (4), were isolated from a methanol extract of the dried leaves of Viburnum luzonicum collected in Kaoshiung, Taiwan and their structures were elucidated by analysis of spectroscopic data. Compounds 1-3 exhibited moderate inhibitory activity against HeLa S3 cancer cells.     

Isolation and structure determination of complexed poly(3-hydroxyalkanoate) from beet (Beta vulgaris L.)

Complexed poly(3-hydroxyalkanoate)s (cPHAs), one of two types of natural PHAs, occur in both prokaryotes and eukaryotes as a complex with biomacromolecules and could be involved in various physiological functions. In this study, a cPHA-component derived from a complex with calcium polyphosphate was isolated from sugar beet (Beta vulgaris L.) and determined to be a homopolymer composed of 3-hydroxybutyrate. MALDI MS provided the number-average molecular weight (Mn = 9,124 Da) and polydispersity index (PDI = 1.01), showing that beet cPHA has a slightly lower molecular mass than the known Escherichia coli cPHA. In addition, the structural analysis of both end groups showed that (i) 100 mol-% of the carboxyl end is free, while about 30 mol-% of the hydroxyl end is free and about 70 mol-% masked and (ii) the end hydroxyl group is masked by at least six identified short-chain alkanoic and alkanedioic acids. Based on such end-group characteristics, the polymerization mechanism of beet cPHA is discussed.     

Physicochemical properties of α, ω-type bolaform surfactant in aqueous solution. Eicosane-1,20-bis(triethylammonium bromide)

The physicochemical properties of the, - type (bolaform) surfactant, eicosane-1, 20-bis(triethylammonium bromide) (C₂₀Et₆), in aqueous solution have been investigated by means of surface tension, electrical conductivity, dye solubilization, and time-resolved fluorescence quenching (determination of average micelle aggregation number). Using electrical conductivity, the critical micelle concentration of C₂₀Et₆ was found to be 6.0×10^–3 mol dm^–3 and the ionization degree of C²⁰Et₆ micelle was found to be 0.42. From surface tension measurments, the molecular area of C₂₀Et₆ at the air-water interface was about twice that of normal type surfactants such as dodecyltrimethylammonium bromide (DTAB). The solubilizing power of micellar solution of C₂₀Et₆ toward Orange OT was 1.0×10^–2 mole of dye per mole of surfactant, i. e., slightly smaller than that of DTAB. The micelle aggregation number,N, was found to be 17±2 by time-resolved fluorescence quenching. C₂₀Et₆ showed a very small temperature dependence ofN, much less than for normal surfactants.     

First enantioselective synthesis of (−)-talaumidin, a neurotrophic diaryltetrahydrofuran-type lignan

The first enantioselective total synthesis of a neurotrophic (−)-talaumidin (1) is described in 16 steps from 4-benzyloxy-3-methoxybenzaldehyde in ca. 10.7% overall yield, and thus has established the absolute configurations of the four stereogenic centers C-2 ∼ C-5 of 1. The synthesis features the construction of the two successive chiral centers C-2 and C-3 by Evans asymmetric anti-aldol protocol as well as of the two chiral centers C-4 and C-5 in a highly stereocontrolled fashion by hydroboration/oxidation and epimerization, followed by Friedel-Crafts arylation.     

Leptonic and charged kaon decay modes of the phi meson measured in heavy-ion collisions at the CERN super proton synchrotron

We report on results of a measurement of meson production in central Pb-Au collisions at E(lab) = 158A GeV. For the first time in the history of high energy heavy-ion collisions, phi mesons were reconstructed both in the K+K- and the dilepton decay channels in the same experiment. This measurement yields rapidity densities near midrapidity, from the two decay channels, of 2.05 +/- 0.14(stat) +/- 0.25(syst) and 2.04 +/- 0.49(stat) +/- 0.32(syst), respectively. The shape of the measured transverse momentum spectrum is also in close agreement in both decay channels. The data rule out a possible enhancement of the phi yield in the leptonic over the hadronic decay channel of a factor 1.6 or larger at the 95% C.L. This rules out the discrepancy reported in the literature between measurements of the hadronic and dimuon decay channels by two different experiments.