Temperature-responsive stationary phase utilizing a polymer of proline derivative for hydrophobic interaction chromatography using an aqueous mobile phase

A new method of chromatography is proposed, utilizing a thermo-responsive polymer carrying an amino acid ester residue for the stationary phase of high-performance liquid chromatography (HPLC). We have been investigating the new concept of chromatography, a temperature-responsive chromatography, using temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm)-modified surface for HPLC with a constant aqueous media as the mobile phase. In this study, we designed and synthesized thermo-responsive poly(acryloyl-L-proline methyl ester) and its copolymer with N-isopropylacrylamide (NIPAAm). Homopolymers of acryloyl-L-proline methyl ester and copolymer were prepared by the reaction of radical telomerization. These polymers underwent a reversible phase transition from water-soluble forms into aggregates by changing the temperature, similar to PNIPAAm. The surface properties and functions of stationary phases modified with poly(acryloyl-L-proline methyl ester) were controlled by the external temperature. In the chromatographic system, we separated steroids and amino acids with a variety of hydrophobicities using a sole aqueous mobile phase. In contrast to a PNIPAAm-modified surface, a poly(acryloyl-L-proline methyl ester)-modified surface showed a greater affinity for hydrophobic amino acids.     

Phosphorylation of D-glucose derivatives with inorganic monoimido-cyclo-triphosphate

Phosphorylation of several D-glucose derivatives has been achieved using inorganic monoimido-cyclo-triphosphate (MCTP, Na(3)P(3)O(8)NH) in aqueous solution. In the phosphorylation of D-glucose, D-glucuronic acid, 2-deoxy-D-glucose and D-galactose, 1-O-diphosphoramidophosphono-beta-D-glucose, 1-O-diphosphoramidophosphono-beta-D-glucuronic acid, 1-O-diphosphoramidophosphono-2-deoxy-beta-D-glucose, and 1-O-diphosphoramidophosphono-beta-D-galactose were stereoselectively synthesized with yields of 54, 32, 37 and 46%, respectively. In the case of methyl alpha-D-glucoside, the phosphorylated products were methyl 3-O-diphosphoramidophosphono-alpha-D-glucoside and methyl 4-O-diphosphoramidophosphono-alpha-D-glucoside, and in the case of methyl beta-D-glucoside the products were methyl 2-O-diphosphoramidophosphono-beta-D-glucoside, methyl 3-O-diphosphoramidophosphono-beta-D-glucoside, and methyl 4-O-diphosphoramidophosphono-beta-D-glucoside. For D-mannose and D-allose, several phosphorylated products were obtained and the main products were 1-O-diphosphoramidophosphono-beta-D-aldoses.     

Acerogenin M, a cyclic diarylheptanoid, and other phenolic compounds from Acer nikoense and their anti-inflammatory and anti-tumor-promoting effects

A new cyclic diarylheptanoid, acerogenin M (1), has been isolated along with nine known diarylheptanoids, 2-10, and two known phenolic compounds, 11 and 12, from a MeOH extract of the stem bark of Acer nikoense MAXIM. (Aceraceae). The structure of 1 was determined on the basis of a spectroscopic method. Upon evaluation of the inhibitory effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation (1 microg/ear) in mice of nine of the compounds (2-6, 8, 10-12), six (2, 4-6, 8, 10) showed a marked anti-inflammatory effect with a 50% inhibitory dose (ID(50)) of 0.26-0.81 mg per ear. In addition, upon an evaluation against the Epstein-Barr virus early antigen (EBV-EA) activation induced by TPA for all of the compounds, all exhibited moderate inhibitory effects against EBV-EA induction (IC(50) values of 356-534 mol ratio/32 pmol TPA).     

Surface passivation of III-V semiconductors for future CMOS devices—Past research, present status and key issues for future

Currently, III-V metal-insulator-semiconductor field effect transistors (MISFETs) are considered to be promising device candidates for the so-called “More Moore Approach” to continue scaling CMOS transistors on the silicon platform. Strong interest also exists in III-V nanowire MISFETs as a possible candidate for a “Beyond CMOS”-type device. III-V sensors using insulator-semiconductor interfaces are good candidates for “More Moore”-type of devices on the Si platform. The success of these new approaches for future electronics depends on the availability of a surface passivation technology which can realize pinning-free, high-quality interfaces between insulator and III-V semiconductors.This paper reviews the past history, present status and key issues of the research on the surface passivation technology for III-V semiconductors. First, a brief survey of previous research on surface passivation and MISFETs is made, and Fermi level pinning at insulator-semiconductor interface is discussed. Then, a brief review is made on recent approaches of interface control for high-k III-V MIS structures. Subsequently, as an actual example of interface control, latest results on the authors’ surface passivation approach using a silicon interface control layer (Si ICL) are discussed. Finally, a photoluminescence (PL) method to characterize the interface quality is presented as an efficient contactless and non-destructive method which can be applied at each step of interface formation process without fabrication of MIS capacitors and MISFETs.     

Facile One‐Pot Synthesis of [1, 2, 3]Triazolo[1, 5‐a]Pyridines from 2‐Acylpyridines by Copper(II)‐Catalyzed Oxidative NN Bond Formation

An efficient and simple method for the synthesis of various [1, 2, 3]triazolo[1, 5‐a]pyridines has been established. The method involves a copper(II)‐catalyzed oxidative N?N bond formation that uses atmospheric oxygen as the terminal oxidant following hydrazonation in one pot. The use of ethyl acetate as the solvent dramatically promotes the oxidative N?N bond‐formation reaction and enables the application of oxidative cyclization in the efficient one‐pot reaction. A mechanism for the reaction was proposed on the basis of the results of a spectroscopic study.     

Temperature-responsive chromatography using poly(N-isopropylacrylamide) hydrogel-modified silica.

Poly(N-isopropylacrylamide) (PNIPAAm) has the sharpest phase transition of the class of thermo-sensitive N-alkyl acrylamide polymers. We developed a new method of HPLC using packing materials modified with cross-linked poly(N-isopropylacrylamide) (PNIPAAm) hydrogel. A temperature-responsive surface was prepared by polymerization of NIPAAm in the presence of a cross-linker on the silica support. The surface properties and functions of the stationary phases change in response to the external temperature. Therefore it easily changes the interaction of a solute with the surface with a constant aqueous mobile phase. A temperature-responsive elution behavior was observed on the separation of steroids and PTH-amino acids. The method is expected to be applicable to separation in the pharmaceutical and biomedical fields.     

Protein modification by arginylation

The modification of protein by arginine catalyzed by arginyltransferases (ATE1) described by the Kashina group in this issue shows that arginylation of protein occurs widely in biology and is being recognized as a key regulatory reaction such as phosphorylation of proteins (Wang et?al., 2011).     

Temperature-responsive chromatography for the separation of biomolecules

Temperature-responsive chromatography for the separation of biomolecules utilizing poly(N-isopropylacrylamide) (PNIPAAm) and its copolymer-modified stationary phase is performed with an aqueous mobile phase without using organic solvent. The surface properties and function of the stationary phase are controlled by external temperature changes without changing the mobile-phase composition. This analytical system is based on nonspecific adsorption by the reversible transition of a hydrophilic-hydrophobic PNIPAAm-grafted surface. The driving force for retention is hydrophobic interaction between the solute molecules and the hydrophobized polymer chains on the stationary phase surface. The separation of the biomolecules, such as nucleotides and proteins was achieved by a dual temperature- and pH-responsive chromatography system. The electrostatic and hydrophobic interactions could be modulated simultaneously with the temperature in an aqueous mobile phase, thus the separation system would have potential applications in the separation of biomolecules. Additionally, chromatographic matrices prepared by a surface-initiated atom transfer radical polymerization (ATRP) exhibit a strong interaction with analytes, because the polymerization procedure forms a densely packed polymer, called a polymer brush, on the surfaces. The copolymer brush grafted surfaces prepared by ATRP was an effective tool for separating basic biomolecules by modulating the electrostatic and hydrophobic interactions. Applications of thermally responsive columns for the separations of biomolecules are reviewed here.