Synthesis and controlled polymerization of p-(1-methylcyclohexyloxy)styrene and quick-response deblocking ability of the obtained polymer

p-(1-Methylcyclohexyloxy)styrene (PC6ST) was synthesized by acid catalyzed addition reaction of p-bromophenol with 1-methylcyclohexene, followed by Grignard coupling with vinyl bromide catalyzed by NiCl₂(dppp). Radical polymerization of PC6ST in the presence or absence of TEMPO afforded poly(PC6ST) with narrow molecular weight distribution without the elimination of the protective group. The obtained poly(PC6ST) showed a higher deprotection ability in response to external stimulation such as an acid compared with poly(p-tert-butoxystyrene).     

Efficient Method for the Elongation of the N‐Acetylglucosamine Unit by Combined Use of Chitinase and β‐Galactosidase

A novel strategy for the regio‐ and stereoselective synthesis by two enzymatic steps of oligosaccharides having an N‐acetylglucosamine unit at the nonreducing end was developed. The first step involves a chitinase‐catalyzed highly selective β‐N‐acetyllactosamination of an oligosaccharide acceptor with a 4,5‐dihydrooxazole derivative of N‐acetyllactosamine as the glycosyl donor. The usage of a transition‐state‐analogue substrate for the chitinase under basic conditions allows the reaction to proceed only in the synthetic direction while suppressing hydrolysis of the product in aqueous media. Several chitinase mutants also catalyzed the glycosylation efficiently under neutral conditions. The second step is a regioselective cleavage of the glycosidic bond between the terminal galactose unit and the adjacent N‐acetylglucosamine unit by the action of a β‐galactosidase. This constitutes a very useful method to add an N‐acetylglucosamine unit to the nonreducing end of chito‐ and cello‐oligosaccharide derivatives in a regio‐ and stereoselective manner.     

Covalent conjugation of tetrameric bovine liver catalase to liposome membranes for stabilization of the enzyme tertiary and quaternary structures

Tetrameric bovine liver catalase (BLC) is unstable because of its dissociation into subunits at low enzyme concentrations and the conformational change of the subunits at high temperatures. In this work, for stabilization of BLC, the enzyme was covalently conjugated with liposome membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), cholesterol and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-glutaryl (NGPE). The NGPE, which was responsible for the BLC/membrane coupling, was altered from 0.05 to 0.2 in its liposomal mole fraction f_G. The catalase-conjugated liposome (CCL) with f_G of 0.15 showed the maximum number of the conjugated BLC molecules of 28 per liposome. The reactivity of CCLs to H₂O₂ was as high as that of free BLC at 25 °C in Tris–HCl buffer of pH 7.4. Among the CCLs, the catalyst with f_G of 0.15 was the most stable at 55 °C in its enzyme activity in the buffer because the appropriate number of BLC/liposome covalent bonding prevented the dissociation-induced enzyme deactivation. Furthermore, the CCL showed much higher stability at 55 °C than the free BLC/enzyme-free liposome mixture and free BLC at the low BLC concentration of 340 ng/mL. This was because BLC in the CCL was located in the vicinity of the host membrane regardless of the catalyst concentration, which could induce the effective stabilization effect of the membrane on the enzyme tertiary structure as indicated by the intrinsic tryptophan fluorescence analysis. The results obtained demonstrate the high structural stability of BLC in the CCL system, which was derived from the covalent bonding and interaction between BLC and liposomes.     

A solid phase extraction using a chelate resin immobilizing carboxymethylated pentaethylenehexamine for separation and preconcentration of trace elements in water samples

A chelate resin immobilizing carboxymethylated pentaethylenehexamine (CM-PEHA resin) was prepared, and the potential for the separation and preconcentration of trace elements in water samples was evaluated through the adsorption/elution test for 62 elements. The CM-PEHA resin could quantitatively recover various elements, including Ag, Cd, Co, Cu, Fe, Ni, Pb, Ti, U, and Zn, and rare earth elements over a wide pH range, and also Mn at pH above 5 and V and Mo at pH below 7. This resin could also effectively remove major elements, such as alkali and alkaline earth elements, under acidic and neutral conditions. Solid phase extraction using the CM-PEHA resin was applicable to the determination of 10 trace elements, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn, in certified reference materials (EnviroMAT EU-L-1 wastewater and ES-L-1 ground water) and treated wastewater and all elements except for Mn in surface seawater using inductively coupled plasma atomic emission spectrometry. The detection limits, defined as 3 times the standard deviation for the procedural blank using 500 mL of purified water (50-fold preconcentration, n = 8), ranged from 0.003 μg L⁻¹ (Mn) to 0.28 μg L⁻¹ (Zn) as the concentration in 500 mL of solution.     

A fluorous tag-bound fluorescence derivatization reagent, F-trap pyrene, for reagent peak-free HPLC analysis of aliphatic amines

We have developed a novel pre-column fluorescence derivatization reagent for amines, F-trap pyrene. This reagent comprises a fluorescent pyrene moiety, an amine-reactive Marshall linker, and a fluorophilic perfluoroalkyl group known as fluorous tag. When the reagent reacts with aliphatic amines and amino acids to give fluorescent derivatives, the fluorous tag in the reagent is eliminated simultaneously. Therefore, excess unreacted reagents in the derivatization reaction solution still have the fluorous tag and could be removed by fluorous solid-phase extraction selectively before high-performance liquid chromatography (HPLC) analysis. By using this reagent, 13 kinds of aliphatic amine (C₂–C₁₆) derivatives can be separated within 40 min by reversed-phase HPLC with gradient elution. In this chromatogram, unreacted reagents peak at around 28 min, greatly decrease after fluorous solid-phase extraction, and do not interfere with the quantification of each amine. The detection limits (S/N = 3) for examined aliphatic amines are 3.6–25 fmol per 20 μL injection. We have also applied this reagent successfully to the amino acid analysis.

Physical Gels of a Syndiotactic Polystyrene Derivative with a Large Side-Chain Group

Summary: Gelation of syndiotactic poly(p-tert-butylstyrene) (sPTBS), a syndiotactic polystyrene (sPS) derivative having a larger side-chain group, was first examined with several solvents. The temperature-concentration phase diagram of sPTBS/trans-decalin gel clearly exhibited that sPTBS formed a polymer-solvent molecular compound with a ratio of 2.7 trans-decalin per one monomer unit. Our polarized fluorescence technique demonstrated that there appeared to exist more spacious free volume among sPTBS chains than sPS in a gel state. A cause determining the morphology of sPTBS with organic solvents was discussed in the present paper.     

Development of Computational Algorithms for Evaluating Option Prices Associated with Square-Root Volatility Processes

The stochastic volatility model of Heston (Rev Financ Stud 6:327–343, 1993) has been accepted by many practitioners for pricing various financial derivatives, because of its capability to explain the smile curve of the implied volatility. While analytical results are available for pricing plain Vanilla European options based on the Heston model, there hardly exist any closed form solutions for exotic options. The purpose of this paper is to develop computational algorithms for evaluating the prices of such exotic options based on a bivariate birth-death approximation approach. Given the underlying price process S _t , the logarithmic process U _t  = logS _t is first approximated by a birth-death process B^U_tB^U_t via moment matching. A second birth-death process B^V_tB^V_t is then constructed for approximating the stochastic volatility process V _t through infinitesimal generator matching. Efficient numerical procedures are developed for capturing the dynamic behavior of { B^U_t , B^V_t }\{ B^U_t , B^V_t \} . Consequently, the prices of any exotic options based on the Heston model can be computed as long as such prices are expressed in terms of the joint distribution of { S _t ,V _t } and the associated first passage times. As an example, the prices of down-and-out call options are evaluated explicitly, demonstrating speed and fair accuracy of the proposed algorithms.     

Ruthenium-catalyzed [1,n]-metallotropic shift (n = 3, 5) of alkynyl carbene complex intermediates

The ruthenium-catalyzed isomerization of diynes and triynes involving propargyl carboxylate moieties affords dienynes and dienediynes, respectively. The [1,n]-metallotropic shift (n = 3, 5) (carbene walk) of in situ generated alkynyl carbene complexes has been proposed for the catalytic isomerization reaction.