Stability and reproducibility of gel-suspension samples for the liquid scintillation counting of14C using N-lauroyl-L-glutamic-α,γ-dibutylamide

Stability and reproducibility of gel-suspension samples were investigated in order to evaluate the characteristic feature of the gel-suspension method for¹⁴C activity measurement. Commercially available gelling agent, N-lauroyl-L-glutamic-α,γ-dibutylamide, was used for the gelformatio of the samples. No change of the counting rate for the gel-suspension sample was observed for more than 2 years after the sample preparation. Four samples used for checking the reproducibility of the sample preparation method. The same values were obtained for the counting rate of¹⁴C activity within the counting error. No change of the counting rate was observed for the “re-gelated” sample. These results show that the gel-suspension method is appropriate for the¹⁴C activity measurement by the liquid scintillation method and is useful for a long-term preservation of the sample for repeated measurement.     

Synthesis of both enantiomers of cyclic methionine analogue: (R)- and (S)-3-aminotetrahydrothiophene-3-carboxylic acids

A method of synthesizing an optically active cyclic methionine analogue, 3-aminotetrahydrothiophene-3-carboxylic acid (At₅c), is described. A Bucherer–Bergs reaction of 4,5-dihydro-3(2H)-thiophenone and the subsequent alkaline hydrolysis of a hydantoin, followed by Cbz protection of the amine, afforded racemic Cbz-At₅c (±)-3 in excellent yield. Diastereomeric esters derived from Cbz-At₅c (±)-3 and (R)-BINOL could be separated by column chromatography to give both diastereomers with >99% de. X-ray crystallographic analysis revealed the absolute configuration of the synthesized amino acid derived from the less polar diastereomeric ester to be (S).     

Photonic bandgap fiber with a silica core and multilayer dielectric cladding

A new technique for fabricating a photonic bandgap fiber is proposed. A multilayer Si--SiO2 film is deposited upon a silica glass fiber, and a clear bandgap is observed in the loss spectrum. The properties of the bandgap are easily controlled by adjustment of the thickness and the refractive index of the multilayer film.     

Photo-induced reactions of hemin (DMSO) n clusters (n = 0-3) produced with electrospray ionization

Photo-induced reaction of [Fe(III)-protoporphyrin]⁺ (hemin⁺) ions solvated with dimethylsulfoxide (DMSO) is investigated by using a tandem mass spectrometer with electrospray ionization. We measure the photodissociation yields of mass-selected hemin⁺(DMSO)_n clusters for n = 0-3 in the energy region of 15 800-28 200 cm^-1. The mass spectra of the fragment ions show the β-cleavage of carboxymethyl groups in addition to the evaporation of solvent molecules. Yield of the β-cleavage reaction is found to depend strongly on the excitation energy and the number of solvent molecules. We also examine the metastable decomposition of the clusters following primary mass selection and determine the incremental solvent binding energies and internal energies for the clusters using evaporative ensemble model. From these results, we investigate the reaction mechanism of β-cleavage of hemin⁺ ion.     

Diketopyrrolopyrrole J‐Aggregates Formed by Self‐Organization with DNA

Bis(2‐thienyl)diketopyrrolopyrrole with two Zn^II‐cyclens (ZnCyc‐DPP) was designed and synthesized to evaluate the selective binding of Zn^II‐cyclen with thymine base in single‐strand DNA as a tool for the construction of a highly ordered multichromophore system on DNAs. Through UV/Vis titrations, gel filtration chromatography, and circular dichroism spectroscopy, ZnCyc‐DPP formed J‐type DPP aggregates with oligo‐dT_n DNAs. The DPP aggregates absorbed on a gold electrode exhibited good photocurrent responses. The present results show that binding Zn^II‐cyclen–chromophore conjugates and thymine bases together is a powerful tool for preparing DNA‐templated multichromophoric systems with specific functions.     

Potential oscillations in galvanostatic electrooxidation of formic acid on platinum: a mathematical modeling and simulation

We have modeled temporal potential oscillations during the electrooxidation of formic acid on platinum on the basis of the experimental results obtained by time-resolved surface-enhanced infrared absorption spectroscopy (J. Phys. Chem. B 2005, 109, 23509). The model was constructed within the framework of the so-called dual-path mechanism; a direct path via a reactive intermediate and an indirect path via strongly bonded CO formed by dehydration of formic acid. The model differs from earlier ones in the intermediate in the direct path. The reactive intermediate in this model is formate, and the oxidation of formate to CO2 is rate-determining. The reaction rate of the latter process is represented by a second-order rate equation. Simulations using this model well reproduce the experimentally observed oscillation patterns and the temporal changes in the coverages of the adsorbed formate and CO. Most properties of the voltammetric behavior of formic acid, including the potential dependence of adsorbate coverages and a negative differential resistance, are also reproduced.     

Infrared-laser delivery system based on polymer-coated hollow fibers

Infrared Er : YAG laser delivery systems based on hollow fibers with an internal polymer layer has been developed. The system consists of a hollow fiber as the delivery medium, a launching coupler for effective coupling between the laser beam and the fiber, and a sealed hollow-fiber tip attached at the output end of the fiber. Fabrication process of the fiber and attachment of the delivery system is reported.     

Fabrication Techniques and Characteristics of Ultra-Thin Optical Polarizing Films Using Gold Island Films

Fabrication techniques of ultra-thin optical polarizing films using gold island films have been investigated for the near-infrared region. The polarizing films are fabricated by stretching the periodic multilayers consisting of gold island layers and glass layers. We have experimentally investigated the optimum fabricating conditions necessary to induce large optical anisotropy into the gold island layers and have formed submicrometer-thick polarizing films with an extinction ratio of ≥20 dB in a near-infrared region longer than 800 nm. These polarizing films could be useful micro-polarizers for fiber-embedded in-line optical devices, micro-optics, and hybrid integrated optics.     

Development of sensitive derivatization method for aldosterone in liquid chromatography-electrospray ionization tandem mass spectrometry of corticosteroids

A highly sensitive quantification method of aldosterone by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) was investigated in a positive mode using recently developed picolinyl derivatization. Aldosterone was smoothly and quantitatively converted to the ethyl ether-picolinyl derivative by treatment with HCl-ethanol followed by the esterification with picolinic acid in the presence of 2-methyl-6-nitrobenzoic anhydride and 4-dimethylaminopyridine. The positive ion-ESI mass spectrum of the ethyl ether-picolinyl derivative was characterized by an appearance of protonated molecule ([M+H](+)) as a base peak. The ethyl ether-picolinyl derivatization gave a successful result in a separation of aldosterone from corticosterone, dehydrocorticosterone and cortexolone, and also provided an approximately 10-fold higher ESI response in the positive-LC-ESI-MS/MS (selected reaction monitoring; SRM) when compared to that of underivatized molecule (negative mode). The limit of quantification of aldosterone by SRM using ethyl ether-picolinyl derivatization (m/z 494-->m/z 448) was 1 pg/0.2 ml serum with accuracy and precision of 92.6% and 5.6%, respectively.