5-Hydroxymethylcytosine-selective oxidation with peroxotungstate

Tungsten oxidation worked as a simple chemical reaction for the effective detection of 5-hydroxymethylcytosine in DNA, distinguishing it from its epigenetic precursors, 5-methylcytosine and unmethylated cytosine. The tungsten-oxidation product obtained from 5-hydroxymethylcytosine was trihydroxylated thymine and was detected as a cleavage band in gel electrophoresis after treatment with hot piperidine.     

Biography of Nobel laureate Shuji Nakamura

Shuji Nakamura discovered p‐type doping in Gallium Nitride (GaN) and developed blue, green, and white “InGaN‐based” light emitting diodes (LEDs) and blue laser diodes (LDs). His inventions made possible energy efficient, solid‐state lighting systems and enabled the next generation of optical storage. In this biography, Shuji Nakamura tells the story of his personal life and his scientific career.

     

Synthesis of Aromatic Polythioethers Containing 1,3,5-Triazine Ring by Aromatic Nucleophilic Substitution Polymerization

Abstract

Reaction of 2,4-dichloro-6-phenyl-1,3,5-triazines with bis(4-mercaptophenyl) sulfide in the presence of a base in THF afforded the corresponding condensation polymer as a whole aromatic polythioether in moderate yield. The polymerization of several 2,4-dichloro-1,3,5-triazine derivatives with this dithiols also proceeded in the o-dichlorobenzene-water two-phase system by using phase transfer catalysts. The resulting polymers consisted of THF-soluble and -insoluble fractions. The x-ray diffraction pattern indicated that these THF-insoluble polymers have a highly crystalline nature. Further, the polymers obtained here showed high thermal stability.     

Preparation and Free-Radical Polymerizations of Methyl-4-vinylphenylsulfoxide and Methyl-4-vinylbenzylsulfoxide

Methyl-4-vinylphenylsulfoxide (1) was prepared by the selective oxidation of 4-methylthiostyrene with sodium metaperiodate in 87% yield. This monomer was readily homopolymerized in DMSO by AIBN at 60°C. The polymer obtained is soluble in ethanol, chloroform, DMSO, and DMF, but insoluble in water, benzene, and petroleum ether. The inherent viscosity of this polymer was 0.33 dL/g in DMSO. This sulfoxide monomer (1) was copolymerized with styrene, methyl methacrylate, acrylo-nitrile, and acrylamide under radical conditions. From the copolymerization with styrene, copolymerization parameters were obtained as follows; r¹ = 0.56, r_St, = 0.26, and Q¹ = 1.19, e¹ = 0.58. Similarly, methyl-4-vinylbenzylsulfoxide (2) was prepared, and the polymerizability of (2) was also investigated.     

Preparation of Polymeric Analogs of Tetramethylurea and Their Use as Liquid-Liquid Phase-Transfer Catalysts

Polymeric analogs of tetramethylurea were prepared by free-radical polymerization of N,N,N'-trimethyl-N'-p-vinylbenzylurea and copolym-erization of this monomer with styrene. These polymers are soluble in toluene and have the ability to extract alkali metal ions such as lithium, sodium, and potassium. Moreover, these polymers act as phase-transfer catalysts for typical S _N 2 reactions, although the monomeric analogs tetramethylurea and N,N,N'-trimethyl-N'-benzylurea do not. A plausible mechanism for these catalytic reactions is proposed.     

Development of sheath‐flow probe electrospray ionization (SF‐PESI)

Probe electrospray ionization (PESI) uses a sharp solid needle as electrospray emitter. This method was found to be applicable to the analysis of real‐world samples with high concentrations of salts and detergents without sample pretreatment. Since PESI is only applicable to wet samples but not to dry samples, sheath‐flow PESI (SF‐PESI) has been developed. The metal needle was inserted into the fine plastic capillary with a protrusion of 0.1–0.2 mm from the capillary terminus. The solvent was supplied continuously through the capillary. At the lowest position of the probe, solvent flowing out from the capillary makes the sample wet and extracts the analytes from the surface. The extracted analytes were electrosprayed at the highest position of the needle. SF‐PESI was successfully applied to samples such as narcotics, tablets, bill, fruits, potatoes, etc. Copyright © 2013 John Wiley & Sons, Ltd.     

Sonodynamic therapy using water-dispersed TiO2-polyethylene glycol compound on glioma cells: comparison of cytotoxic mechanism with photodynamic therapy

Sonodynamic therapy is expected to be a novel therapeutic strategy for malignant gliomas. The titanium dioxide (TiO(2)) nanoparticle, a photosensitizer, can be activated by ultrasound. In this study, by using water-dispersed TiO(2) nanoparticles, an in vitro comparison was made between the photodynamic and sonodynamic damages on U251 human glioblastoma cell lines. Water-dispersed TiO(2) nanoparticles were constructed by the adsorption of chemically modified polyethylene glycole (PEG) on the TiO(2) surface (TiO(2)/PEG). To evaluate cytotoxicity, U251 monolayer cells were incubated in culture medium including 100 μg/ml of TiO(2)/PEG for 3h and subsequently irradiated by ultraviolet light (5.0 mW/cm(2)) or 1.0MHz ultrasound (1.0 W/cm(2)). Cell survival was estimated by MTT assay 24h after irradiation. In the presence of TiO(2)/PEG, the photodynamic cytotoxic effect was not observed after 20 min of an ultraviolet light exposure, while the sonodynamic cytotoxicity effect was almost proportional to the time of sonication. In addition, photodynamic cytotoxicity of TiO(2)/PEG was almost completely inhibited by radical scavenger, while suppression of the sonodynamic cytotoxic effect was not significant. Results of various fluorescent stains showed that ultrasound-treated cells lost their viability immediately after irradiation, and cell membranes were especially damaged in comparison with ultraviolet-treated cells. These findings showed a potential application of TiO(2)/PEG to sonodynamic therapy as a new treatment of malignant gliomas and suggested that the mechanism of TiO(2)/PEG mediated sonodynamic cytotoxicity differs from that of photodynamic cytotoxicity.     

High-contrast, high-intensity laser pulse generation using a nonlinear preamplifier in a Ti:sapphire laser system

We report a high-contrast, high-intensity Ti:sapphire chirped-pulse amplification system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). By cooling the Ti:sapphire crystal in the final amplifier down to 77 K, the chirped-pulses are amplified to 2.9 J at a 10 Hz repetition rate without a thermal lensing effect. Pulse compression down to 19 fs duration obtained after amplification indicates a peak power of 80 TW. With the OPCPA, the temporal contrast is significantly improved to better than 7x10(-9) in a few picoseconds interval prior to the main laser pulse.     

蛋白质跨膜传输的飞秒和频振动光谱快速实时监测

Characterization of conformation kinetics of proteins at the interfaces is crucial for understanding the biomolecular functions and the mechanisms of interfacial biological action. But it requires to capture the dynamic structures of proteins at the interfaces with sufficient structural and temporal resolutions. Here, we demonstrate that a femtosecond sum frequency generation vibrational spectroscopy (SFG-VS) system developed by our group provides a powerful tool for monitoring the real-time peptide transport across the membranes with time resolution of less than one second. By probing the real-time SFG signals in the amide I and amide A bands as WALP23 interacts with DMPG lipid bilayer, it is found that WALP23 is initially absorbed at the gel-phase DMPG bilayer with a random coil structure. The absorption of WALP23 on the surface leads to the surface charge reversal and thus changes the orientation of membrane-bound water. As the DMPG bilayer changes from gel phase into fluid phase, WALP23 inserts into the fluid-phase bilayer with its N-terminal end moving across the membrane, which causes the membrane dehydration and the transition of WALP23 conformation from random coil to mixed helix/loop structure and then to pure α-helical structure. The established system is ready to be employed in characterizing other interfacial fast processes, which will be certainly helpful for providing a clear physical picture of the interfacial phenomena.     

Characterization of Hyaluronidase 4 Involved in the Catabolism of Chondroitin Sulfate

Hyaluronidases (HYALs) are endo-beta-N-acetylhexosaminidases that depolymerize not only hyaluronan but also chondroitin sulfate (CS) at the initial step of their catabolism. Although HYAL1 hydrolyzes both CS and HA, HYAL4 is a CS-specific endoglycosidase. The substrate specificity of HYAL4 and identification of amino acid residues required for its enzymatic activity have been reported. In this study, we characterized the properties of HYAL4 including the expression levels in various tissues, cellular localization, and effects of its overexpression on intracellular CS catabolism, using cultured cells as well as mouse tissues. Hyal4 mRNA and HYAL4 protein were demonstrated to be ubiquitously expressed in various organs in the mouse. HYAL4 protein was shown to be present both on cell surfaces as well as in lysosomes of rat skeletal muscle myoblasts, L6 cells. Overexpression of HYAL4 in Chinese hamster ovary cells decreased in the total amount of CS, suggesting its involvement in the cellular catabolism of CS. In conclusion, HYAL4 may be widely distributed and play various biological roles, including the intracellular depolymerization of CS.