Specific interaction between polyethylenimine and azo dyes carrying hydroxyl groups

The binding of acid azo dyes having phenolic hydroxyl groups such as orange I ( I ), orange II ( II ), chrome violet ( III ), 4-hydroxyazobenzene-4′-sulfonate ( IV ), and 2,4-dihydroxyazobenzene-4′-sulfonate ( V ) by polyethylenimine was studied by equilibrium dialysis and spectroscopic methods. The results obtained indicate that dyes ( III ) and ( V ) with two OH groups are bound much more strongly than dyes ( I ), ( II ), and ( IV ) with one OH group. Also polyethylenimine is far superior to any other polymers which have been examined, including bovine serum albumin, polyvinylpyrrolidone, and poly-L -lysine, in its ability to form complexes with these dyes ( III ) and ( V ). The OH groups involved participate preferentially in complex formation with polyethylenimine. The unusual affinity of polyethylenimine for the dyes carrying OH groups is discussed.     

Binding of methyl orange and the hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate,by 2-dialkylaminoethyl methacrylate-N-vinyl-2-pyrrolidone and related copolymers

The copolymers of N-vinyl-2-pyrrolidone and 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, 2-dimethylaminoethyl acrylate, or 2-dimethylaminopropyl acrylamide have been prepared. Studies were made of the binding of a “binding probe,” methyl orange, by the copolymers in aqueous solution. The first binding constants accompanying the binding were evaluated. Furthermore, the intensity of fluorescence of a hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate, in the presence of these polymers was investigated. The nature and phenomena of dye binding and hydrophobic fluorescent probe binding with the polymers are discussed.     

Asymmetric cyclization of 2-alkenylphenols. A comparative study on the use of palladium(II) and titanium(IV) complexes

The oxidative cyclization of 2-(3-pentenyl)phenol catalyzed by [(η³-pinene)PdOAc]₂ gives optically active (+)-2-vinylchroman (25% e.e.), while (−)-2-(1-hydroxyethyl)chroman (56% e.e.) is formed as a single diastereomer upon treatment with t-BuOOH in the presence of Ti(OⁱPr)₄ and -(+)-diethyl tartrate. 2-(2-Butenyl)phenol also undergoes the Ti-promoted asymmetric cyclization to give (2S,1′R)-(−)-2-(1-hydroxyethyl)-2,3-dihydrobenzofuran (29% e.e.).     

Total synthesis of ingenol

A total synthesis of the biologically important diterpene ingenol has been completed. Ring-closing olefin metathesis was used to construct the strained "inside-outside" tetracyclic skeleton, and a series of diastereoselective reactions were employed to complete the synthesis. Another naturally occurring ingenane, 20-deoxyingenol, has also been prepared.     

Hemin-adsorbed carbon felt for sensitive and rapid flow-amperometric detection of dissolved oxygen

Hemin was physically adsorbed onto porous carbon felt (CF), a microelectrode ensemble of micro-carbon fiber (ca. 7 μm in diameter) and possessing a three-dimensional random structure. The hemin-CF exhibited a well-defined redox wave that is due to Fe(III)/Fe(II) redox process in hemin, with a formal potential of ?0.32 V (vs. Ag/AgCl) in deoxygenated buffer solution of pH 7.0. The surface coverage of the electroactive hemin molecules on the surface of the CF was calculated to be 5.0?×?10^?11 mol cm^?2, and the apparent heterogeneous electron transfer rate constant is 3.35 s^?1. The hemin-CF electrode displays excellent electrocatalytic activity for the reduction of dissolved oxygen (DO), and the magnitude of the cathodic current increases with increasing concentrations of DO in the sample solution. The electrode was used as a flow-through detector for sensitive and rapid consecutive determination of DO. Deoxygenated pH 7.0 solutions were analyzed at a flow rate of 8.0 mL min^?1 at an applied potential of ?0.2 V, and highly reproducible cathodic peak current responses to DO were observed in the 0.72 to 13.3 mg L^?1 concentration range. The maximum throughput is 170 samples h^?1. The hemin-CF-based amperometric flow-sensor was applied to determine the concentration of DO in environmental water samples.

Controlled production of monodisperse double emulsions by two-step droplet breakup in microfluidic devices

A microfluidic device having both hydrophobic and hydrophilic components is exploited for production of multiple-phase emulsions. For producing water-in-oil-in-water (W/O/W) dispersions, aqueous droplets ruptured at the upstream hydrophobic junction are enclosed within organic droplets formed at the downstream hydrophilic junction. Droplets produced at each junction could have narrow size distributions with coefficients of variation in diameter of less than 3%. Control of the flow conditions produces variations in internal/external droplet sizes and in the internal droplet number. Both W/O/W emulsions (with two types of internal droplets) and oil-in-water-in-oil emulsions were prepared by varying geometry and wettability in microchannels.     

Exploring the thermochromism of sulfite-embedded polyoxometalate capsules

The Dawson-type polyanion [α-Mo(18)O(54)(SO(3))(2)](4-), with two SO(3)(2-) templates embedded inside a polyoxomolybdate(vi) cage, exhibits thermochromism over an exceptionally wide temperature range (～500 K). The temperature dependence of the cluster structure, established from X-ray crystallography, IR and Raman spectroscopy and DFT calculations, is related to a decreasing HOMO-LUMO gap in the near UV with increasing temperature. We postulate this is due to geometrical changes that affect both the occupied and unoccupied frontier molecular orbitals of this cluster anion.     

Slipping of a histidine improved the peroxidase activity of a de novo designed polypeptide packing an iron porphyrin

Polypeptides with two histidines and an iron porphyrin (1H⁴⁰-7H⁴⁶) were synthesized with a variety of positions of a histidine. In 4H⁴³, histidine (H⁴³) was in the hydrophobic region of an α-helix. The other polypeptides were of slightly or substantially distorted conformation. In the pH 7.2 buffer solution, two histidines of the polypeptide coordinated the iron porphyrin regardless of their positions. Some polypeptides (1H⁴⁰, 3H⁴², and 5H⁴⁴) showed an enhanced catalytic activity in the peroxidase reaction using cumene hydroperoxide compared to that of 4H⁴³, whereas some polypeptides (2H⁴¹ and 6H⁴⁵) were ineffective catalysts. The distortion of the peptide conformation by the addition of MeOH was also effective for the peroxidase reaction.     

Three novel diepoxy tetrahydrochromones from agarwood artificially produced by intentional wounding

Three novel diepoxy tetrahydrochromones, oxidoagarochromones A (1), B (2), and C (3), were isolated from agarwood artificially produced by intentional wounding of Aquilaria crassna. Inductive production of these compounds was also confirmed at the early stage of wounding in A. sinensis and A. crassna. These diepoxy tetrahydrochromones would play an important role in understanding the biosynthesis of chromone derivatives in agarwood.     

New asymmetric reactions of 2-formyl- and 2-acyl-1-[(2,4, 6-triisopropylphenyl)sulfinyl]naphthalenes via diastereomeric rotamers

Nucleophilic reactions with Grignard reagents and the Mukaiyama aldol reactions of the naphthaldehydes having the (2,4, 6-triisopropylphenyl)sulfinyl group produced products with high stereoselectivity. In these reactions, the stereochemistry of the major products changes depending on the Lewis acids used. Reduction of the 2-acyl-1-[(2,4,6-triisopropylphenyl)sulfinyl]naphthalenes also proceeds with high stereoselectivity but with a different stereochemistry depending on the reducing agents. We have demonstrated, by the mechanistic consideration based on the X-ray crystal structures as well as the (1)H and (13)C NMR spectral data, that the extremely high and specific stereoselectivities of these reactions are due to the predominant rotamer around the C(naph)-S axis. Synthesis of enantiomerically pure 2-naphthylmethanol is provided as an example.