Synthesis of a star-shaped polymer via coordination of ester-linked pyridyl-terminated poly(oxyethylene) with ru(II)

The star-shaped polymer with trans-tetrapyridyl complex of Ru(II) as a core was prepared by complexation of ester-linked pyridyl-terminated poly(oxyethylene) (M̄_n = 2000) with a Ru₅Cl₁₂²⁻ cluster. The unimodal peak of the star-shaped polymer in the gel-permeation chromatogram was shifted to a higher molecular weight region than that of the starting prepolymer. The electron-withdrawing ester substituent in para position of the pyridine ring shifted the metal-to-ligand charge transfer (MLCT) band into the visible region.     

Influence of hydrofluoric acid on extraction of thorium using a commercially available extraction chromatographic resin

The dependence of Th recovery on hydrofluoric acid (HF) concentration in nitric acid (HNO₃) solutions (1–5 mol/dm³) containing 1 × 10⁻⁶ mol/dm³ of Th and various concentrations of HF and the elution behavior were studied using a commercially available UTEVA (for uranium and tetravalent actinide) resin column. Thorium recovery decreased with an increase in HF concentration in the sample solutions. The concentration of HF at which Th recovery started to decrease was ∼1 × 10⁻⁴ mol/dm³ in 1 mol/dm³ HNO₃ solution, ∼1 × 10⁻³ mol/dm³ in 3 mol/dm³ HNO₃ solution, and ∼1 × 10⁻² mol/dm³ in 5 mol/dm³ HNO₃ solution. When Al(NO₃)₃ (0.2 mol/dm³) or Fe(NO₃)₃ (0.6 mol/dm³) was added as a masking agent for F⁻ to the Th solution containing 1 × 10⁻¹ mol/dm³ HF and 1 mol/dm³ HNO₃, Th recovery improved from 1.4 ± 0.3% to 95 ± 5% or 93 ± 3%. Effective extraction of Th using UTEVA resin was achieved by selecting the concentration of HNO₃ and/or adding masking agents such as Al(NO₃)₃ according to the concentration of HF in the sample solution.     

Tuning of Electronic Properties of Single‐Walled Carbon Nanotubes under Homogenous Conditions

Reversible and non‐bonding interaction between SWNTs and ODCB is observed from the analyses of visible near‐infrared absorption data and Raman spectroscopies (see spectra). The solvent effect on SWNTs effectively controls the electronic structure of SWNTs under homogeneous conditions.

     

Enantioselective visualization of <Emphasis Type="SmallCaps">D</Emphasis>-alanine in rat anterior pituitary gland: localization to ACTH-secreting cells

The cellular localization of D-alanine (D-Ala) in the rat pituitary gland, the tissue containing the highest amount of D-Ala, has been clarified for the first time by enantioselective visualization of D-Ala using our own established mouse monoclonal antibody against D-Ala. D-Ala immunopositive cells were present predominantly in the anterior lobe, while no intense staining was observed in the intermediate and posterior lobes. The anterior pituitary gland contains five types of cells secreting specific hormones (growth hormone, adrenocorticotropic hormone (ACTH), gonadotropic hormone, prolactin, and thyroid-stimulating hormone), and the double staining results indicated that D-Ala is localized to the ACTH-secreting cells. The localization of D-Ala is clearly different from that of D-aspartic acid (D-Asp), which is observed in the prolactin cells. Considered together with our previous findings that D-Ala is localized to the insulin-secreting beta-cells in the pancreas, and both ACTH and insulin are typical regulatory hormones of blood glucose, D-Ala is suggested to have some functional relationships to blood glucose level regulation in mammals.     

Heterocyclic quinol-type fluorophores: synthesis, X-ray crystal structures, and solid-state photophysical properties of novel 5-hydroxy-5-substituent-benzo[b]naphtho[1,2-d]furan-6-one and 3-hydroxy-3-substituent-benzo[kl]xanthen-2-one derivatives

Novel heterocyclic quinol-type fluorophores (4 a-c) and (5 a-c) that contain substituents (R = Me, Bu, Ph) with nonconjugated linkages to the chromophore skeleton have been synthesized and their photophysical properties have been investigated in solution and in the solid state. Considerable differences in the absorption and fluorescence spectra were observed between the two states. Quinols 4 a-c and 5 a-c exhibited almost the same absorption and fluorescence spectra in solution; however, their solid-state fluorescence excitation and emission spectra in the crystalline state were quite different. We performed X-ray crystallographic analyses to elucidate the dramatic effect of the substituents of the nonconjugated linkage on the solid-state fluorescence excitation and emission spectra. The relationships between the solid-state photophysical properties and the chemical and crystal structures of 4 a-c and 5 a-c are discussed on the basis of the X-ray crystal structures.     

Photoinduced reductive repair of thymine glycol: implications for excess electron transfer through DNA containing modified bases

Photoinduced reduction of thymine glycol in oligodeoxynucleotides was investigated using either a reduced form of flavin adenine dinucleotide (FADH(-)) as an intermolecular electron donor or covalently linked phenothiazine (PTZ) as an intramolecular electron donor. Intermolecular electron donation from photoexcited flavin (FADH(-)) to free thymidine glycol generated thymidine in high yield, along with a small amount of 6-hydroxy-5,6-dihydrothymidine. In the case of photoreduction of 4-mer long single-stranded oligodeoxynucleotides containing thymine glycol by *FADH(-), the restoration yield of thymine was varied depending on the sequence of oligodeoxynucleotides. Time-resolved spectroscopic study on the photoreduction by laser-excited N,N-dimethylaniline (DMA) suggested elimination of a hydroxyl ion from the radical anion of thymidine glycol with a rate constant of approximately 10(4) s(-1) generates 6-hydroxy-5,6-dihydrothymidine (6-HOT(*)) as a key intermediate, followed by further reduction of 6-HOT(*) to thymidine or 6-hydroxy-5,6-dihydrothymdine (6-HOT). On the other hand, an excess electron injected into double-stranded DNA containing thymine glycol was not trapped at the lesion but was further transported along the duplex. Considering redox properties of the nucleobases and PTZ, competitive excess electron trapping at pyrimidine bases (thymine, T and cytosine, C) which leads to protonation of the radical anion (T(-)(*), C(-)(*)) or rapid back electron transfer to the radical cation of PTZ (PTZ(+)(*)), is presumably faster than elimination of the hydroxyl ion from the radical anion of thymine glycol in DNA.     

Preparation and characterization of conducting trimetallic nickel-dithiolene complexes with bridging tetrathiooxalate ligands

Trimetallic nickel dithiolene complexes with two tetrathiooxalate (tto) ligands were obtained by a reaction monitored by ESI-mass spectrometry followed by HPLC separation and were characterized by elemental or crystal structural analysis, MO calculations, and electrical conductivity measurements.     

Liquid chromatographic analysis of cinchona alkaloids in beverages

A method for the determination of Cinchona extract (whose main components are the alkaloids cinchonine, cinchonidine, quinidine, and quinine) in beverages by liquid chromatography was developed. A beverage with an alcohol content of more than 10% was loaded onto an OASIS HLB solid-phase extraction cartridge, after it was adjusted to pH 10 with 28% ammonium hydroxide. Other beverages were centrifuged at 4000 rpm for 5 min, and the supernatant was loaded onto the cartridge. The cartridge was washed with water followed by 15% methanol, and the Cinchona alkaloids were eluted with methanol. The Cinchona alkaloids in the eluate were chromatographed on an L-column ODS (4.6 mm id x 150 mm) with methanol and 20 mmol/L potassium dihydrogen phosphate (3 + 7) as the mobile phase. Cinchona alkaloids were monitored with an ultraviolet (UV) detector at 230 nm, and with a fluorescence detector at 405 nm for cinchonine and cinchonidine and 450 nm for quinidine and quinine (excitation at 235 nm). The calibration curves for Cinchona alkaloids with the UV detector showed good linearity in the range of 2-400 microg/mL. The detection limit of each Cinchona alkaloid, taken to be the concentration at which the absorption spectrum could be identified, was 2 microg/mL. The recovery of Cinchona alkaloids added at a level of 100 microg/g to various kinds of beverages was 87.6-96.5%, and the coefficients of variation were less than 3.3%. A number of beverage samples, some labeled to contain bitter substances, were analyzed by the proposed method. Quinine was detected in 2 samples of carbonated beverage.