Anti-biofouling properties of polymers with a carboxybetaine moiety

The resistance of random copolymers of BMA and CMB against biofouling was evaluated. The amount of proteins adsorbed onto the CMB copolymers was smaller than that onto other polymers (non-ionic polymers and copolymers of ordinary ionic monomers and BMA) and decreased with an increase in the content of CMB residues. Furthermore, there was a dramatic decrease in the number of cells (platelets and fibroblasts) that adhered to the CMB copolymers compared with that to other polymers. In contrast with this, CMB copolymers were slightly perturbative to both complement and coagulation systems. However, the overall results suggest that zwitterionic moieties are effective for making polymer materials biocompatible due to their excellent anti-biofouling property.     

Oxygen reduction reaction activities of Ni/Pt(111) model catalysts fabricated by molecular beam epitaxy

Oxygen reduction reaction (ORR) activities were evaluated for clean Pt(111) and Ni/Pt(111) model catalysts fabricated by molecular beam epitaxy. Exposure of clean Pt(111) to 1.0 L CO at 303 K produced linear-bonded and bridge-bonded CO-Pt IR bands at 2093 and 1858 cm^? 1. In contrast, 0.3-nm-thick Ni deposited on Pt(111) at 573 K (573 K-Ni_0.3 nm/Pt(111)) produced broad IR bands for adsorbed CO at around 2070 cm^? 1; the separation of reflection high-energy electron diffraction (RHEED) streaks is slightly wider for 573 K-Ni_0.3 nm/Pt(111) than for the clean Pt(111). For 823 K-Ni_0.3 nm/Pt(111), the separation of the RHEED streaks is the same as that for the Pt(111), and a single sharp IR band due to adsorbed CO is located at 2082 cm^? 1. The results suggest that for the 823 K-Ni_0.3 nm/Pt(111), a Pt-enriched outermost surface (Pt-skin) was formed through surface segregation of the substrate Pt atoms. ORR activities for the 573 K- and 823 K-Ni_0.3 nm/Pt(111) as determined from linear sweep voltammetry curves were five times and eight times higher than that for clean Pt(111), respectively, demonstrating that Pt-skin generation is crucial for developing highly active electrode catalysts for fuel cells.     

Isolation of four new flavonoids from Melicope triphylla

Four new flavonoids, 3,5-dihydroxy-7,8-dimethoxy-3',4'-methylenedioxyflavone (1), 3,5-dihydroxy-7-methoxy-3',4'-methylenedioxyflavone (2), 3,5-dihydroxy-7-isopentenyloxy-8-methoxy-3',4'-methylenedioxyflavone (3) and 5-hydroxy-3-isopentenyloxy-7-methoxy-3',4'-methylenedioxyflavone (4), were isolated from the leaves of Melicope triphylla. In addition, two known flavonoids were detected including 5-hydroxy-3,7-dimethoxy-3',4'-methylenedioxyflavone (5) and 5-hydroxy-7-isopentenyloxy-3,8-dimethoxy-3',4'-methylenedioxyflavone (6). The structures of the new compounds were established by spectroscopic methods.     

Application of a wavelength-dispersive particle-induced X-ray emission system to chemical speciation of phosphorus and sulfur in lake sediment samples

The chemical speciation of phosphorus and sulfur in lake sediment was performed by analyzing Kα X-ray spectra recorded with a high-resolution wavelength-dispersive particle-induced X-ray emission (WD-PIXE) system. The concentrations of phosphorus and sulfur in the sediment were 2500 and 7000 ppm, respectively. To measure both minor elements in a reasonable measurement time, a 2-MeV proton beam with a high current density (6 nA/mm²) was used for the chemical speciation. The possible chemical state change caused by the proton irradiation was studied in order to determine the maximal irradiation time without significant change. We found that the chemical states of phosphorus and sulfur were stable under a beam current density of 6 nA/mm² and a measurement time of 60 min (phosphorus) and 90 min (sulfur). The chemical states of phosphorus and sulfur were determined to be P⁵⁺ and a mixture of S²⁻ and S⁶⁺, respectively.     

High‐Resolution Crystal Structure of a Silver(I)–RNA Hybrid Duplex Containing Watson–Crick‐like CSilver(I)C Metallo‐Base Pairs

Metallo‐base pairs have been extensively studied for applications in nucleic acid‐based nanodevices and genetic code expansion. Metallo‐base pairs composed of natural nucleobases are attractive because nanodevices containing natural metallo‐base pairs can be easily prepared from commercially available sources. Previously, we have reported a crystal structure of a DNA duplex containing T? Hg^II? T base pairs. Herein, we have determined a high‐resolution crystal structure of the second natural metallo‐base pair between pyrimidine bases C? Ag^I? C formed in an RNA duplex. One Ag^I occupies the center between two cytosines and forms a C? Ag^I? C base pair through N3? Ag^I? N3 linear coordination. The C? Ag^I? C base pair formation does not disturb the standard A‐form conformation of RNA. Since the C? Ag^I? C base pair is structurally similar to the canonical Watson–Crick base pairs, it can be a useful building block for structure‐based design and fabrication of nucleic acid‐based nanodevices.     

Furopyridines. IV. Unexpected dimerization of 5-methyl-4,5,6,7-tetrahydrofuro[3,2-c]- and 6-methyl-4,5,6,7-tetrahydrofuro[2,3-c]pyridine by acidic hydrolysis

Reaction of 5-methyl-4,5,6,7-tetrahydrofuro[3,2-c]- ( 1 ) and 6-methyl-4,5,6,7-tetrahydrofuro[2,3-c]pyridine ( 2 ) with hydrochloric acid gave novel dimerized compounds 3a-d and 4a-d , respectively. The structures of 3a, 3b, 4a and 4b were determined by spectroscopic method, and 3c, 3d, 4c and 4d by single crystal X-ray analysis. The reaction courses for the formation of these compounds are proposed.     

One-pot reactions of bicyclic zinc enolate generated from Ni-catalyzed reductive cyclization to furnish octahydro-4,7-ethanobenzofuran-9-one derivatives

The one-pot reactions of catalytically generated bicyclic zinc enolate with various electrophiles are reported. The zinc enolate as a key intermediate is efficiently delivered from Ni-catalyzed reductive cyclization of alkynyl cyclohexadienone. Employing aldehydes, imine, nitroalkene, and α,β-unsaturated carbonyl compounds as electrophiles, this new class of one-pot reactions gave multi-functionalized cis-hydrobenzofurans and octahydro-4,7-ethanobenzofuran-9-one derivatives in moderate to good yields.     

Furopyridines. II. Bromination and nitration of furo[2,3-b]-, furo[3,2-b]-, furo[2,3-c]- and furo[3,2-c]pyridine

In order to reveal the reactivities of furopyridines, we undertook bromination and nitration of four furopyridines ( 1, 2, 3 and 4 ) whose chemical properties had been almost unknown. Bromination of 1, 2, 3 and 4 gave the corresponding trans-2,3-dibromo-2,3-dihydro derivatives 6, 8, 10 and 12 , respectively, which were converted to 3-bromofuropyridines 7, 9, 11 and 13 by treatment with sodium hydroxide in aqueous methanol. Nitration of 1 with a mixture of fuming nitric acid and sulfuric acid afforded a mixture of addition products 14a, 14b and 14c and 2-nitro derivative 15 . Both 14a and 14b were easily converted to 15 by treatment with sodium bicarbonate. Compound 2 was nitrated to give a mixture of cis- and trans-2-nitro-3-hydroxy-2,3-dihydro derivative 16a and 16b and 2-nitro derivative 17 . The cis isomer 16a was transformed to the trans isomer 16b by refluxing on silica gel in ethyl acetate. Compound 16b was dehydrated with acetic anhydride to give 17 . Nitration of 3 gave a nitrolic acid derivative 20 . Nitration of 4 gave a mixture of 2-nitro derivative 22 and 3-(trinitromethyl)pyridin-4-ol ( 23 ). The structures of 20 and 23 were established by single crystal X-ray analysis. The differences of behavior observed in these reactions are discussed in connection with the results of the determination of pKa values and the relative reactivities of deuteriodeprotonation of these furopyridines.     

Photocatalytic Activity of Radial Rutile Titanium(IV) Oxide Microspheres for Aerobic Oxidation of Organics

Radial rutile TiO₂ nanorod homomesocrystals (TiO₂-NR HOMCs) or the so-called “sea urchin-like TiO₂ microspheres” were synthesized by using a hydrothermal method. TiO₂-NR HOMCs show photocatalytic activity for aerobic oxidative degradation of 2-naphthol under irradiation of UV- and visible light. Furthermore, extremely small iron oxide clusters were formed on the surface of TiO₂-NR HOMCs (FeO_x/TiO₂-NR HOMCs) by the chemisorption-calcination technique to reduce the band gap. The FeO_x-surface modification gives rise to drastic enhancement of the UV- and visible-light activity. Reversed double-beam photoacoustic spectroscopy measurements were performed for TiO₂-NR HOMCs and FeO_x/TiO₂-NR HOMCs to obtain the ERDT (energy-resolved distribution of electron traps)/CBB (conduction-band bottom) patterns. The ERDT/CBB pattern of TiO₂-NR HOMCs consists of two components derived from rutile (C1) and amorphous TiO₂ (C2). In the pattern, the surface electron traps in C2 exist near the CBB to be removed by the FeO_x-surface modification. By taking this finding into consideration, the striking surface modification effect is ascribable to the electrocatalytic activity (or the action as an electron reservoir) of the FeO_x clusters for multiple ORR, the suppression of recombination, and the increase in the visible-light harvesting efficiency.