Retention behavior of bile acid derivatives using cyclodextrin in the mobile phase in high-performance liquid chromatography

The retention behavior of 3-(1-anthroyl)bile acids together with bile acid glucuronides, sulfates, and 12-dehydro derivatives is examined by the addition of cyclodextrin to the mobile phase in reversed-phase high-performance liquid chromatography. The data suggest that the functional group at the 12 position of the steroid moiety may be the important factor for the formation of the inclusion complex from the solute and cyclodextrin. The separation of these bile acid derivatives is much improved by this inclusion chromatography.     

Procedure for increasing the detection responses of estrogens in LC–MS based on introduction of a nitrobenzene moiety followed by electron capture atmospheric pressure chemical ionization

A practical procedure for determining estrogens in biological fluids has been studied using liquid chromatography–electron capture atmospheric pressure chemical ionization–mass spectrometry combined with derivatization. Among the commercially available reagents (4-nitrobenzoyl chloride, 2,4-dinitrofluorobenzene, 4-nitrobenzenesulfonyl chloride and 4-nitrobenzyl bromide), 4-nitrobenzenesulfonyl chloride was of the most practical use; it rapidly and quantitatively reacted with estrogens and increased the detection responses by 8–23 times. The derivatization method allowed the reproducible and accurate quantification of serum and urine estrone and estradiol of a pregnant woman, which is useful for diagnosis of the fetoplacental function, with small amounts (10 μl) of sample and a simple pretreatment procedure. Tatsuya Higashiis Associate Professor of the Laboratory of Clinical Analytical Sciences (Professor Kazutake Shimada’s research group) at the Graduate School of Natural Science and Technology of Kanazawa University. He received the Japan Society for Analytical Chemistry Award for Young Scientists in 2003 and the Pharmaceutical Society of Japan Award for Young Scientists in 2006. His current research interests are the development of methods for increasing sensitivity in LC-MS to detect and characterize trace amounts of biologically active steroids, such as estrogens, androgens and neuroactive steroids.     

Electronic spectra of hydrogen-bonded 2-fluoropyridine clusters with water in a supersonic free jet

Fluorescence excitation, multiphoton ionization, and dispersed fluorescence spectra of bare and hydrogen-bonded 2-fluoropyridine with water were measured in a supersonic free jet. For bare 2-fluoropyridine, fluorescence quantum yield decrease in the higher vibronic levels was observed even under collision-free conditions. The inter-system crossing channel was probed experimentally by two color R2PI and found to be negligible. The non-radiative relaxation process of 2-fluoropyridine is mainly governed by the relaxation to the electronic ground state. Electronic spectra of 2-fluoropyridine-(water)(n) (n=1 approximately 3) were also obtained. The hydrogen bond formation with water increases the quantum yield in the higher vibronic levels. Rather low frequency vibrations were observed in the hole burning spectrum of bare 2-fluoropyridine; however, these vibronic bands disappeared with the hydrogen bond formation with water. The appearance of low frequency vibronic bands observed for bare 2-fluoropyridine is ascribed to the existence of closely lying (n,pi) state.     

Mechanism of the CO oxidation reaction on O-precovered Pt(111) surfaces studied with near-edge x-ray absorption fine structure spectroscopy

The mechanism of CO oxidation reaction on oxygen-precovered Pt(111) surfaces has been studied by using time-resolved near-edge x-ray absorption fine structure spectroscopy. The whole reaction process is composed of two distinct paths: (1) a reaction of isolated oxygen atoms with adsorbed CO, and (2) a reaction of island-periphery oxygen atoms after the CO saturation. CO coadsorption plays a role to induce the dynamic change in spatial distribution of O atoms, which switches over the two reaction paths. These mechanisms were confirmed by kinetic Monte Carlo simulations. The effect of coadsorbed water in the reaction mechanism was also examined.     

Rhodium-catalyzed cyclization of 1,6-enynes triggered by addition of arylboronic acids

1,6-Enynes reacted with arylboronic acids in the presence of a catalytic amount of a rhodium(I) complex under mild conditions to give (Z)-1-(1-arylethylidene)-2-vinylcyclopentanes. The regioselective addition of an arylrhodium(I) species across the carbon-carbon triple bond triggered the cyclization process. Intramolecular carborhodation onto the pendent alkene in a 5-exo mode furnished a five-membered ring. Finally, the rhodium(I) methoxide generated by beta-methoxy elimination reacted with the arylboronic acid to promote the next catalytic cycle.     

A Flow System Based on a Fluorometer and a Luminometer to Monitor the Correlation of Protein Conformation and Function

A flow system to monitor the reactions in solutions was constructed, which connected a fluorometer and a luminometer in series. Using a stream through it, the correlation of fluorescence and luminescence was measured. The system was tested with actin. The fluorescence emission gave the signal of polymerization of labeled actin and the luminescence gave that of ATP hydrolysis by actin. The observations showed the correlation between ATP hydrolysis and polymerization. Applications of other proteins to this system will give insights into the characteristics of proteins.     

Flow-injection spectrophotometric determination of acetyl-coenzyme A with immobilized phosphotransacetylase

Phosphotransacetylase (PTA) is immobilized on AF-Tresyl TOYOPEARL 650 gel and used on-line in a stainless-steel column (10 × 4 mm i.d.). CoA-SH liberated enzymatically from acetyl-CoA is reacted with Ellman's reagent [5,5′-dithiobis(2-nitrobenzoic acid)] in the carrier stream. The calibration graph for acetyl-CoA is linear from 4 × 10^?6 to 4 × 10^?4 M and the detection limits is 8 × 10^?7 M. The immobilized enzyme can be employed for over 4 months without any significant decrease in activity. The enzyme retains its activity in methanol even though the initial rate of reaction is decreased.     

Self-shaping of bioinspired chiral composites

Self-shaping materials such as shape memory polymers have recently drawn considerable attention owing to their high shape-changing ability in response to changes in ambient conditions, and thereby have promising applications in the biomedical, biosensing, soft robotics and aerospace fields. Their design is a crucial issue of both theoretical and technological interest. Motivated by the shape-changing ability of Towel Gourd tendril helices during swelling/deswelling, we present a strategy for realizing self-shaping function through the deformation of micro/nanohelices. To guide the design and fabrication of selfshaping materials, the shape equations of bent configurations, twisted belts, and helices of slender chiral composite are developed using the variation method. Furthermore, it is numerically shown that the shape changes of a chiral composite can be tuned by the deformation of micro/nanohelices and the fabricated fiber directions. This work paves a new way to create self-shaping composites.     

Twist decompositions of gluing homeomorphisms of planar Heegaard diagrams of genus two

We will give a very simple algorithm to decompose a gluing homeomorphism of a planar Heegaard diagram of genus two into Dehn twists associated with the canonical base.