Formation of highly ordered porphyrin adlayers induced by electrochemical potential modulation

Molecular self-assembly of porphyrin derivatives formed with intermolecular hydrogen bonding on the surface of Au(111) electrode in acidic solution can be controlled by varying the number of peripheral carboxy groups and the applied electrochemical potential.     

Use of vitamin B2 for fluorescence detection of thymidine-related single-nucleotide polymorphisms

In combination with abasic site (AP site)-containing DNAs, potential use of a biotic fluorescence compound, Vitamin B₂ (riboflavin), is demonstrated for the fluorescence detection of the thymine (T)-related single-nucleotide polymorphisms. Our method is based on construction of the AP site in DNA duplexes, which allows small ligands to bind to target nucleotides accompanied by fluorescence signaling: an AP site-containing probe DNA is hybridized with a target DNA so as to place the AP site toward a target nucleobase, by which hydrophobic microenvironments are provided for ligands to recognize target nucleotides through stacking and hydrogen-bonding interactions. In 10 mM sodium cacodylate buffer solutions (pH 7.0) containing 100 mM NaCl and 1.0 mM EDTA, Vitamin B₂ is found to selectively bind to T (K₁₁ = 1.8 × 10⁶ M⁻¹ at 5 °C) over other nucleobases, and this is accompanied by significant quenching of its fluorescence. While the sensing functions depend on the flanking sequences to the AP site, Vitamin B₂ is applicable to the detection of T/C (cytosine), T/G (guanine) and T/A (adenine) mutation sequences of the CYP2A6 gene, where the flanking nucleobases are guanines in both positions (-GXG-, X = AP site).     

Influence of confinement on the fragility of antiplasticized and pure polymer films

We investigate by molecular dynamics simulation how thin film confinement modifies the fragility of a model glass-forming liquid characterized previously in the bulk. Film confinement is found to reduce the relative fragility of the polymer fluid, leading to effects similar to simulations of the addition of an antiplasticizer additive. A reduction of fragility is not observed for the antiplasticized polymer film. These effects are interpreted in terms of variation in the string (cooperatively moving segments) concentration with film confinement and the addition of antiplasticizing additives.     

Synthesis and characterization of radioiodinated MD-230254: a new ligand for potential imaging of monoamine oxidase B activity by single photon emission computed tomography

A series of iodinated analogues of MD-230254 was synthesized and evaluated for inhibitory potency and selectivity toward monoamine oxidase B (MAO-B). Among them, 5-[4-(2-iodobenzyloxy)phenyl]-3-(cyanoethyl)-1,3,4-oxadiazole-2(3H)one (2-IBPO) was found to have high inhibitory potency and selectivity toward MAO-B (IC50=2.0 nM, MAO-A/MAO-B >50000). Analysis of the inhibition kinetics indicated that 2-IBPO acts in a two-step mechanism as a competitive, slow, and tight-binding inhibitor of MAO-B with a Ki value of 2.4 nM and an overall Ki* value at an equilibrium of 3.8 nM. The new radioligand for MAO-B, [125I]2-IBPO was conveniently synthesized from a tributylstannyl precursor by an iododestannylation reaction using sodium [125I]iodide and hydrogen peroxide with high radiochemical yield. The in vivo tissue distribution studies of [125I]2-IBPO demonstrated its high initial uptake and prolonged retention in the brain. A selective interaction of [125I]2-IBPO with MAO-B was confirmed by the pretreatment experiment with well known MAO specific inhibitors, l-deprenyl, Ro-16-6491, clorgyline, and Ro-41-1049. These very desirable characteristics of [125I]2-IBPO suggested that a 123I-labeled counterpart, [123I]2-IBPO, would have great potential in in vivo studies of MAO-B in the human brain with single photon emission computed tomography (SPECT).     

Preparation and Characterization of SiO2-MxOy(M = V, Sn, Sb) Thin Films from Silicic Acid and Metal Chlorides

The preparation of SiO₂-M _x O _y (M = V, Sn, Sb) binary oxide thin films by sol-gel method was investigated. The reaction of silicic acid with metal chloride (M = Sn and Sb) or oxychloride (M = V) formed homogeneous solutions. The dip-coating of slide glass and silicon wafer followed by heat treatment gave oxide films having Si—O—M bond. The changes of FT-IR spectra as a function of heat treatment temperature and molar composition confirmed the Si—O—M bonds. The sheet resistance of films increased with an increase on heat treatment temperature and decrease in the content of metal oxide M _x O _y . X-ray diffraction peaks were observed for the SiO₂-V₂O₅ films with high V₂O₅ contents and heat-treated above 250°C, while the others were amorphous. Oxide films heat treated at 500°C had a thickness between 340–470 nm.     

NON-CLOTTABLE FIBRINOGEN BY PHOTOOXIDATION IN BLOOD PLASMA

Abstract— Bovine blood plasma anticoagulated with acid-citrate dextrose was irradiated with an incandescent lamp in the presence of methylene blue and oxygen. Thrombin-induced clotting activity of plasma was rapidly reduced and was lost completely in only 10 min of irradiation. This is due to the very rapid photooxidation of fibrinogen regardless of the presence of other proteins.     

High-molecular-weight polyterephthalamide by direct polycondensation reaction in the presence of poly(ethylene oxide)

Polyterephthalamides of high molecular weight (η_inh up to 1.9) were obtained by the direct polycondensation reaction of terephthalic acid and aromatic diamines in the presence of poly(ethylene oxide) (PEO) with triphenyl phosphite in a N-methylpyrrolidone (NMP)–pyridine solution that contained lithium chloride. The molecular weights of the polymers produced varied with the amount and molecular weight of PEO, which showed maximum values when PEO with a molecular weight of 2.0 × 10⁴?5.0 × 10⁵ was used in a concentration of about 0.5 wt % in the solvent. The polycondensation reaction was significantly affected by the level of pyridine in a mixed solvent of NMP and pyridine and by the concentration of the lithium chloride added.     

Preparation and properties of polysilsesquioxanes: Polysilsesquioxanes and flexible thin films by acid‐catalyzed controlled hydrolytic polycondensation of methyl‐ and vinyltrimethoxysilane

Polymethylsilsesquioxane (PMS) and polyvinylsilsesquioxane (PVS) were prepared by acid‐catalyzed controlled hydrolytic polycondensation of methyl‐ and vinyltrimethoxysilane (MTS and VTS), respectively. The spinnabilities and molecular weights of polysilsesquioxanes were easily controlled by the reaction conditions, such as the molar ratios of water, hydrochloric acid, and methanol to MTS or VTS; nitrogen flow rate; temperature; and stirring rate. PMS and PVS showed spinnability of more than 200 cm when their molecular weights were up to 42,000 (PMS) and 19,000 (PVS) M_w. Transparent, colorless, and flexible films of 0.02–0.10 mm thick were prepared by casting a 20 wt % acetone–methanol (V/V = 1) solution of PMS and PVS on a polymethylpentene shale, followed by heating at 80°C for 3 weeks. The tensile strength of the films, approximately 26 (PMS) and 17 (PVS) MPa, was found to be correlated with the structure of the polysilsesquioxanes. The surface contact angle and electroconductivity of films were also measured. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1017–1026, 1999     

Characteristics of InAlGaAs/InAlAs Superlattice Avalanche Photodiodes for Ultra-low Optical Power Detection in the Near Infrared

Static characteristics of two different structured InAlGaAs/InAlAs superlattice avalanche photodiodes (SLAPDs) cooled by liquid nitrogen were evaluated at a wavelength of 1.5 μm. The dark current of the SLAPD having a thick superlattice layer of 0.504 μm was 5 × 10⁻¹³ A. This was successively reduced by four orders of magnitude compared to that of the thin layer SLAPD of 0.231 μm at a breakdown voltage of around 20 V. The thickened layer was effective in suppressing tunneling dark current. An output current of 1.7×l0⁻¹² A at a bias voltage of 15 V was measured for an optical input with a wavelength of 1.5 μm and a signal power of 1 × 10⁻¹² W. This showed a sharp distinction from the dark current.