Efficient Separation of Hydrophobic Molecules by Molecularly Imprinted Cyclodextrin Polymers

Cyclodextrins were cross-linked with toluene 2,4-diisocyanate in dimethyl sufoxide in the presence of hydrophobic biomolecules as templates, and the imprinted polymers were applied to the stationary phases of high performance liquid chromatography. Molecular imprinting efficiently promoted the binding-affinity and substrate-selectivity towards the template molecule, compared with the control polymers prepared in their absence. When cholesterol (template molecule) was complexed with cyclodextrins prior to the polymerization, for example, the imprinted polymer retained cholesterol more strongly than other steroids. Upon the polymerization without a template molecule, the binding towards steroids was much weaker. Besides steroids, imprinting was effective for various hydrophobic and rigid template molecules. Since binding of the guest molecule was based on inclusion complex formation with cyclodextrins, separation could be achieved in the solvents containing water. These polymeric receptors are also applicable to selective recognition of biologically important molecules or removal of toxic molecules from aqueous media. Thus, imprinting of cyclodextrins is useful for the preparation of synthetic tailor-made receptors for various kinds of hydrophobic guest molecules.     

Preparation and characterization of nanoaggregates of poly(ethylene oxide)-b-polymethacrylate and poly-L-lysine

Poly(ethylene oxide)-b-polymethacrylate (PEO-b-PMA), one of the double-hydrophilic block copolymers, has proved to the form nanoaggregates with poly-L-lysine (PLS). This was confirmed by turbidimetry, zeta-potential measurements, and dynamic light scattering. The nanoaggregate formation is induced by electrostatic charge neutralization of the PMA block with PLS. The properties of the aggregates are affected by PLS concentration as well PEO-b-PMA concentration. The aggregates have potential applications in biomedical science.     

Electrophoretic mobility of a cylindrical colloidal particle in a salt-free medium

Approximate expressions are derived for the electrophoretic mobility of dilute cylindrical colloidal particles in a salt-free medium containing only counterions. The cylinder is assumed to be infinitely long. It is shown that as in the case of a spherical particle, there is a certain critical value of the particle surface charge separating two cases. When the particle surface charge is lower than the critical value (case 1), the electrophoretic mobility increases with increasing particle surface charge per unit length. When the particle surface charge is higher than the critical value (case 2), the mobility becomes constant (for a cylinder in a transverse field) or the increase in the electrophoretic mobility with the particle surface charge becomes suppressed (for a cylinder in a tangential field). These phenomena are caused by the effect of counterion condensation in the vicinity of the particle surface. The critical value of the particle charge is essentially independent of the particle volume fraction phi for the dilute case, unlike the case of a sphere, in which case the critical charge value is proportional to ln(1/phi).     

Molecular structure of glucopyranosylamide lipid and nanotube morphology

A series of glucopyranosylamide lipids, N-(X-octadecenoyl)-beta-D-glucopyranosylamine [X = 13-cis (1), 11-cis (2), 9-cis (3), 6-cis (4), and 9-cis,12-cis (5)] and their saturated homologue N-octadecanoyl-beta-d-glucopyranosylamine (6), which differ in the position of a cis double bond in the C18 hydrocarbon chains, have been synthesized. The effect of the cis double bond position on the chiral self-assembly of each glycolipid has been examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV, and circular dichroism (CD). The 11-cis derivative 2 was observed to self-assemble in water to form a uniform hollow cylinder structure with about 200-nm outer diameters in >98% yields. The obtained nanotubes from 2 showed the narrowest distribution of outer diameters and also gave a negative CD band around 234-236 nm, showing the largest CD intensity among the glycolipids investigated. Thus, we found that the position of a cis double bond significantly influences the homogeneity of the outer diameters as well as growth behavior of the self-assembled nanotube structures. Chiral molecular packing driven by a possible bending structure of the unsaturated glycolipids is playing a critical role in determining tubular morphology through molecular self-assembly.     

Regioselective oxygenative tetraamination of [60]fullerene. Fullerene-mediated reduction of molecular oxygen by amine via ground state single electron transfer in dimethyl sulfoxide

The reaction of [60]fullerene with a variety of a secondary aliphatic amines in 20% v/v dimethyl sulfoxide in chlorobenzene under an atmospheric pressure of molecular oxygen allows regioselective introduction of four amino groups and one epoxide group around one pentagon of the fullerene molecule in good to high yield. This new synthesis of tetraaminofullerene expoxide can be carried out with a simple procedure on a multigram scale at room temperature and affords a variety of functionalized fullerene derivatives. Near-infrared analysis of a mixture of [60]fullerene and piperidine in a deaerated dimethyl sulfoxide/chlorobenzene mixture indicated equilibrium formation of [60]fullerene radical anion (C60*-) that persists at least for 2 weeks at room temperature but reacts immediately with molecular oxygen to give the tetraaminofullerene expoxide. The Benesi-Hildebrand analysis of the concentration dependency of the near-infrared absorption indicated that a [C60*- piperidine*+] radical ion pair is formed with an equivalent constant of K = 0.62 +/- 0.02 M(-1) at 25 degrees C. This and other lines of evidence suggest that the oxygenative amination reaction involves C60-mediated reduction of molecular oxygen by the amine.     

Electrophoretic mobility of a highly charged colloidal particle in a solution of general electrolytes.

For a highly charged particle in an electrolyte solution, counterions are condensed very near the particle surface. The electrochemical potential of counterions accumulated near the particle surface is thus not affected by the applied electric field, so that the condensed counterions do not contribute to the particle electrophoretic mobility. In the present paper we derive an expression for the electrophoretic mobility mu(infinity) of a highly charged spherical particle of radius a and zeta potential zeta in the limit of very high zeta in a solution of general electrolytes with large ka (where k is the Debye-Hückel parameter) on the basis of our previous theory for the case of symmetrical electrolytes (H. Ohshima, J. Colloid Interface Sci. 263 (2003) 337). It is shown that zeta can formally be expressed as the sum of two components: the co-ion component, zetaco-ion, and the counterion component, zetacounterion (where zeta = zetaco-ion + zetacounterion) and that the limiting electrophoretic mobility mu(infinity) is given by mu(infinity) = epsilonr epsilon0 zetaco-ion(infinity)/eta + 0(1/ka), where zetaco-ion(infinity) is the high zeta-limiting form of zetaco-ion, epsilonr and eta are, respectively, the relative permittivity and viscosity of the solution, and epsilon0 is the permittivity of a vacuum. That is, the particle behaves as if its zeta potential were zetaco-ion(infinity), independent of zeta. For the case of a positively charged particle in an aqueous electrolyte solution at 25 degrees C, the value of zetaco-ion(infinity) is 35.6 mV for 1-1 electrolytes, 46.0 mV for 2-1 electrolytes, and 12.2 mV for 1-2 electrolytes. It is also found that the magnitude of mu(infinity) increases as the valence of co-ions increases, whereas the magnitude of mu(infinity) decreases as the valence of counterions increases.     

Novel synthesis of 1,3-dienes from 1-alkenes via /ldene/rd reaction with pummerer rearrangement product: a short synthesis of the sex pheromone of the red bollworm moth

A Pummerer rearrangement product, 4-chlorophenylthiomethyl trifluoroacetate (6), obtained from 4-chlorophenyl methyl sulfoxide (5) and trifluoroacetic anhydride, reacted with 1-alkenes in trifluoroacetic acid to give the ene products 8, which were readily converted into the terminal 1,3-dienes 10 by oxidation and subsequent pyrolysis. Using this method, 9,11-dodecadien-1-yl acetate (12), a sex pheromone of the red bollworm moth, was synthesized.     

Depolymerization of poly(2,6-dimethyl-1,4-phenylene oxide) under oxidative conditions

Depolymerization of an engineering plastic, poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), was accomplished by using 2,6-dimethylphenol (DMP) under oxidative conditions. The addition of an excess amount of DMP to a solution of PPO in the presence of a CuCl/pyridine catalyst yielded oligomeric products. When PPO (M(n)=1.0x10(4), M(w)/M(n)=1.2) was allowed to react with a sufficient amount of DMP, the molecular weight of the product decreased to M(n)=4.9x10(2) (M(w)/M(n)=1.5). By a prolonged reaction with the oxidant, the oligomeric product was repolymerized to produce PPO essentially identical to the starting material, making the oligomer useful as a reusable resource. During the depolymerization reaction, an intermediate phenoxyl radical was observed by ESR spectroscopy. Kinetic analysis showed that the rate of the oxidation of PPO was about 10 times higher than that of DMP. These results show that a monomeric phenoxyl radical attacks the polymeric phenoxyl to induce the redistribution via a quinone ketal intermediate, leading to the substantial decrease in the molecular weight of PPO, which is much faster than the chain growth.     

Rapid analysis of intact phospholipids from whole bacterial cells by matrix-assisted laser desorption/ionization mass spectrometry combined with on-probe sample pretreatment

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), utilizing an on-probe sample pretreatment, was applied to the rapid and direct detection of intact phospholipids from whole bacterial cells. The sample preparation procedure involved depositing growing bacterial colonies from culture dishes directly onto the MALDI probe followed by treatment of the sample spot with a 3 micro L aliquot of an aqueous 0.05 M solution of sodium iodide prior to the addition of a 2,5-dihydroxybenzoic acid (DHB) matrix solution (ca. 8 mg dissolved in 70% acetonitrile/30% H(2)O containing 0.1% of trifluoroacetic acid). The MALDI spectra obtained from whole bacteria cells showed a series of ions generated from bacterial phospholipids, such as phosphatidylethanol-amines (PEs) and phosphatidylglycerols (PGs), which were clearly observed as well-resolved peaks. The ranges of the observed total carbon numbers in two acyl groups for PEs and PGs (30-36 and 33-36, respectively) were in good agreement with those reported previously. Furthermore, the distinct discrimination of four species of the Enterobacteriaceae family cultured identically was achieved by using principal components analysis (PCA) conducted on the relative peak intensities of phospholipids observed from the MALDI spectra.     

Indium-mediated beta-allylation,beta-propargylation,and beta-allenylation onto alpha,beta-unsaturated ketones: reactions of in-situ-generated 3-tert-butyldimethylsilyloxyalk-2-enylsulfonium salts with in-situ-generated organoindium reagents

3-tert-Butyldimethylsilyloxyalk-2-enylsulfonium salts, generated in situ from the reaction of alpha,beta-enones with dimethyl sulfide in the presence of TBSOTf, underwent a novel nucleophilic substitution with allylindiums to give silyl enol ethers of delta,epsilon-alkenyl ketones in good yields, which correspond to formal Michael addition products. In a similar manner, 1,4-propargylation of propargylindiums onto the sulfonium salts produced the corresponding silyl enol ethers of delta,epsilon-alkynyl ketones in good yields. Organoindium reagents derived from gamma-substituted propargyl bromide and indium afforded the corresponding silyl enol ethers of beta-allenyl ketones in good yields. The reaction proceeds via an addition-substitution mechanism involving the formation of allylic sulfonium salts. The presence of the intermediate sulfonium salt was confirmed by observation of the low-temperature (1)H NMR spectra.