Evaluation of an anion-exchange hollow-fiber membrane adsorber containing γ-ray grafted glycidyl methacrylate chains

It is widely recognized that membrane adsorbers are powerful tools for the purification of biopharmaceutical protein products and for this reason a novel hollow-fiber AEX type membrane adsorber has been developed. The membrane is characterized by grafted chains including DEA ligands affixed to the pore surfaces of the membrane. In order to estimate the membrane performance, (1) dynamic binding capacities for pure BSA and DNA over a range of solution conductivity and pH, (2) virus reduction by flow-through process, and (3) HCP and DNA removal from cell culture, are evaluated and compared with several other anion-exchange membranes. The novel hollow-fiber membrane is tolerant of high salt concentration when adsorbing BSA and DNA. When challenged with a solution containing IgG the membrane has high impurity removal further indicating this hollow-fiber based membrane adsorber is an effective tool for purification of biopharmaceutical protein products including IgG.     

Photochemical control of dielectric properties based on intermolecular proton transfer in a hydrogen-bonded diarylethene crystal

The photochromic reaction of a diarylethene derivative having imidazoline rings reversibly modulates the dielectric properties of the crystal, which is based on the intermolecular proton transfer in one-dimensional (1D) hydrogen-bonded chains.     

Enzymatic Synthesis of α‐d‐Xylosylated Malto‐oligosaccharides by Phosphorylase‐catalyzed Xylosylation

This paper describes the enzymatic synthesis of α‐d‐xylosylated malto‐oligosaccharides by phosphorylase‐catalyzed xylosylation of maltotetraose. When the xylosylation was carried out using α‐d‐xylose‐1‐phosphate as a glycosyl donor in the presence of phosphorylase, xylosylated oligosaccharides were produced with high conversion. α‐d‐Xylosyl‐(1→4)‐maltotetraose was isolated as the main product. Glucoamylase‐catalyzed reaction of the isolated material revealed that one α‐xyloside unit is positioned at the nonreducing end.     

Photoviscosity Effect of Polymer Solutions

Poly(methyl methacrylate) and poly(methacrylic acid) having spirobenzopyran in the side groups and polyamide having azobenzene in the main chain were synthesized in attempting to construct photoresponsive polymer systems, the conformation of which can be photoregulated. The solution viscosity in benzene of poly(methyl methacrylate) containing spirobenzopyran groups (9 mole% in base unit) during irradiation was found to be 12% lower than the viscosity in the dark. The viscosity is restored to the initial value in less than 3 min in the dark after cutting off the light. A study of the solvent effect and a spectroscopic study have verified that the photoviscosity effect is due to the self-solvation of the ester side groups to the photo-produced merocyanines. Photoregulation of the polymer conformation was also achieved in methanol for poly(methacrylic acid) having spirobenzopyran and in dimethylacetamide for a polyamide having azobenzene in the main chain.     

Polymer-Supported Tetrabromooxomolybdate(V): A New Type of Catalyst for Oxidation by t-Butyl Hydroperoxide

Tetrabromooxomolybdate(V) was immobilized in alkylammonium cation-type polymers obtained by the reaction of poly(p-chloromethyl-styrene-co-divinylbenzene-co-styrene) (abbreviated CMS) with amines and derived from poly(p-vinylpyridine) and poly(p-vinylpyridine-co-divinylbenzene). These immobilized polymers were active catalysts for the oxidation of alcohols and epoxidation of olefins with t-butyl hydroperoxide (abbreviated t-BuOOH). Among these polymers, we could find a polymer catalyst showing specificity, which was obtained by immobilization of tetrabromooxomolybdate(V) in the polymer derived from the reaction of CMS with trimethylamine. This immobilized polymer does not catalyze epoxidation of olefins but catalyzes oxidation of alcohols with t-BuOOH. Ammonium tetrabromooxomolybdate(V) complex was stabilized by the immobilization in the polymers, and it was found that the reactivity of the active group is due to the microenvironment supplied by the polymer chain.     

Improved Negishi Cross‐Coupling Reactions of an Organozinc Reagent Derived from l‐Aspartic Acid with Monohalopyridines

The Negishi cross‐coupling reaction of an organozinc derivative prepared from protected l ‐aspartic acid with monohalopyridines was improved by employing a combination catalyst of Pd₂(dba)₃ and P(2‐furyl)₃ and removing an extra Zn from the organozinc reagent via centrifugation. The reactivity of halogenated pyridines (Cl, Br, I) with substituents at the C2, C3, and C4 positions of the pyridine ring was investigated, and it was found that the use of 4‐iodopyridine as a substrate gave the best yield (90%) for the cross‐coupling reaction.     

A $${C^\infty}$$ closing lemma for Hamiltonian diffeomorphisms of closed surfaces

We prove a \({C^\infty}\) closing lemma for Hamiltonian diffeomorphisms of closed surfaces. This is a consequence of a \({C^\infty}\) closing lemma for Reeb flows on closed contact three-manifolds, which was recently proved as an application of spectral invariants in embedded contact homology. A key new ingredient of this paper is an analysis of an area-preserving map near its fixed point, which is based on some classical results in Hamiltonian dynamics: existence of KAM invariant circles for elliptic fixed points, and convergence of the Birkhoff normal form for hyperbolic fixed points.     

Absolute asymmetric photocyclization in chiral diarylethene co-crystals with octafluoronaphthalene

A photochromic diarylethene containing naphthyl groups formed a chiral crystal when co-crystallized with octafluoronaphthalene, although both molecules are achiral, and underwent highly enantioselective photocyclization owing to the conformational confinement in the crystal.     

Rotational dynamics of benzene and water in an ionic liquid explored via molecular dynamics simulations and NMR T1 measurements

The rotational dynamics of benzene and water in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride are studied using molecular dynamics (MD) simulation and NMR T(1) measurements. MD trajectories based on an effective potential are used to calculate the (2)H NMR relaxation time, T(1) via Fourier transform of the relevant rotational time correlation function, C(2R)(t). To compensate for the lack of polarization in the standard fixed-charge modeling of the IL, an effective ionic charge, which is smaller than the elementary charge is employed. The simulation results are in closest agreement with NMR experiments with respect to the temperature and Larmor frequency dependencies of T(1) when an effective charge of ±0.5e is used for the anion and the cation, respectively. The computed C(2R)(t) of both solutes shows a bi-modal nature, comprised of an initial non-diffusive ps relaxation plus a long-time ns tail extending to the diffusive regime. Due to the latter component, the solute dynamics is not under the motional narrowing condition with respect to the prevalent Larmor frequency. It is shown that the diffusive tail of the C(2R)(t) is most important to understand frequency and temperature dependencies of T(1) in ILs. On the other hand, the effect of the initial ps relaxation is an increase of T(1) by a constant factor. This is equivalent to an "effective" reduction of the quadrupolar coupling constant (QCC). Thus, in the NMR T(1) analysis, the rotational time correlation function can be modeled analytically in the form of aexp (-t/τ) (Lipari-Szabo model), where the constant a, the Lipari-Szabo factor, contains the integrated contribution of the short-time relaxation and τ represents the relaxation time of the exponential (diffusive) tail. The Debye model is a special case of the Lipari-Szabo model with a = 1, and turns out to be inappropriate to represent benzene and water dynamics in ILs since a is as small as 0.1. The use of the Debye model would result in an underestimation of the QCC by a factor of 2-3 as a compensation for the neglect of the Lipari-Szabo factor.