Optimization of HPLC-ECD conditions for determination of catechins with precision and efficiency based on the FUMI theory.

A chemometric tool based on the Function of Mutual Information (FUMI) theory can provide a relative standard deviation (RSD) without repetitive measurements in high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Two parameters: precision (= information content) phi and efficiency (= information content/time) theta, which were calculated from predicted RSD based on the FUMI theory, were used to optimize HPLC-ECD conditions, such as applied potential, flow rate, column length, and size of ODS porous packing. We selected catechins as analytes, and found that the most optimum applied potential and flow rate were +600 mV vs. SCE and 0.9 mL/min, respectively, because they gave the largest phi and theta values. Buffer concentration in mobile phase is less effective for giving large phi and theta values. Since the FUMI theory makes it possible to predict RSD without repetitive measurements, the present method saves considerable amounts of chemicals and experimental time, and was found to be useful for the optimization of experimental conditions for determination by HPLC-ECD.     

Radiation-induced polymerization at high dose rate. II. α-Methylstyrene in bulk

Bulk polymerization of α-methylstyrene was carried out in a wide dose rate range, 7.6–256 rad/sec by γ rays and 8.5 × 10³–2.1 × 10⁵ rad/sec by electron beams. At high dose rate by electron beams, cationic polymerization took place along with formation of oligomeric product of DP _n = ～4. At low dose rate by γ rays, radical polymerization was found to occur in water-saturated monomer. The cationic polymerization at high dose rate proceeds with essentially the same mechanism as was already known in γ-ray polymerization of dry monomers. Relatively low reaction rate of the cationic polymerization compared with that of styrene is explained with the fact that the propagation of α-methylstyrene is much more easily inhibited by a slight amount of water.     

Analysis by partial reflection spectrometry of protonated tetraphenylporphyrin adsorbed at a liquid-liquid interface

Visible reflection spectra of diprotonated meso-tetraphenylporphyrin adsorbates spontaneously formed at a dodecane-aqueous sulfuric acid interface have been measured using a home-made device comprising a prism-cell and variable-angle optics. The tilt angle of the pyrrole ring plane was estimated to be 47 degrees from the interface normal by use of an experimentally evaluated molecular density (1.20x10(-10) mol cm(-2)) of the diprotonated molecule in a monolayer form at the liquid-liquid interface. Positive and negative bands have been observed in the p-polarized partial internal reflection (p-PIR) spectra, whose band locations correspond to those in p-polarized external reflection (p-ER) spectra. Nevertheless, the bands in the p-PIR exhibited reversed sign to those of p-ER spectra. These suggest that the surface selection rule of the p-PIR spectrometry has a reversal rule of p-ER and p-PIR can also be used for the analysis of molecular orientation.     

Crossed molecular beam chemiluminescence study of the metastable mercury reaction: Hg(3P)+Br2 → HgBr(B) + Br

Chemiluminescence from HgBr(B) formed in the reaction of Hg(6³P_o with Br₂ has been observed using a N₂-seeded nozzle beam of metastable Hg³P_o) atoms. The cross section has been estimated to be 3⁺³_?2 at a collission energy of 0.33 eV. This value is smaller by more than an order of magnitude than the corresponding value for Hg(³P₂) atoms measured by Krause et al., in accordance with their inference based on less direct evidence.     

Adsorption of gaseous formaldehyde and carboxylic acids by ammonium-ion-exchanged alpha-zirconium phosphate

Ammonium-ion-exchanged alpha-Zr(HPO(4))(2)H(2)O (alpha-ZrP) was obtained as a single phase with the interlayer distance of 9.4 A by the ion-exchange of proton with ammonium ion. The ammonium ion-exchanged alpha-ZrP could adsorb ill-smelling gases, such as formaldehyde and carboxylic acids (formic acid, acetic acid, propionic acid, and butyric acid). The adsorption amounts of carboxylic acids increased in the order, butyric acid相似文献   

Total synthesis of (+)-macquarimicin A

The first total synthesis of (+)-macquarimicin A (1), a novel inhibitor of neutral sphingomyelinase (N-SMase) with antiinflammatory activity, has been accomplished. The present work determined the absolute configuration of (+)-1 and revised the C(2)-C(3) geometry to be Z. The synthesis features a transannular Diels-Alder reaction, which constructed the tetracyclic framework stereoselectively, and a convergent and efficient synthetic pathway, which afforded (+)-macquarimicin A (1) in 27 steps (longest linear sequence) with 9.9% overall yield.     

Reversed-phase liquid chromatographic retention and membrane activity relationships of local anesthetics

The chromatographic retention and membrane activity relationships of local anesthetics were studied to address the possible mechanisms for structure specificity and inflammation-associated decrease of their effects. Five representative drugs (3 mM for each) were reacted with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine liposomes in 25 mM potassium phosphate buffer (pH 5.9-7.9, containing 100 mM NaCl and 0.1 mM EDTA) for 10 min at 37 degrees C and the membrane fluidity changes were analyzed by measuring fluorescence polarization with 1,6-diphenyl-1,3,5-hexatriene. Their capacity factors were determined on octadecyl-, octyl- and phenyl-bonded silica columns with a mobile phase consisting of 25 mM potassium phosphate buffer (pH 5.9-7.9, containing 100 mM NaCl and 0.1 mM EDTA)-methanol (30:70, v/v) at a flow rate of 1.0 ml/min and at a column temperature of 37 degrees C and diode-array detection. Mepivacaine, prilocaine, lidocaine, ropivacaine and bupivacaine fluidized membranes in increasing order of intensity, which agreed with their clinical potency. The relative degree of membrane fluidization correlated with that of retention on an octadecyl stationary phase more significantly than the other phases. Both membrane-fluidizing effects and capacity factors decreased by lowering the reaction and mobile phase pH, being consistent with the hypothesis that anesthetic potency is reduced in inflammation because of tissue acidity. Reversed-phase liquid chromatography appears to be useful for estimating the structure-specific and pH-dependent membrane-fluidizing effects of local anesthetics.     

Reductive activation of dioxygen by a myoglobin reconstituted with a flavohemin

We successfully converted myoglobin, an oxygen-storage hemoprotein, into an oxygen-activating hemoprotein like cytochrome P450s by replacing the native hemin with the artificially created flavohemin. The reconstituted myoglobin, rMb(1), was chacterized by ESI-TOF-mass, UV-vis, and fluorescence spectra. The 1H NMR spectrum of cyanomet rMb(1) indicates that two hemin conformers are present in a ratio of 1:1. Upon the addition of NADH to the buffer solution of rMb(1) in the presence of SOD and catalase, the oxymyoglobin was rapidly formed. As compared with the formation of the oxygenated native myoglobin in the presence of 10-N-(acetylaminoethyl)isoalloxazine, the rate constant of the oxyheme formation in rMb(1) is 6 times larger. This is because the flavin covalently linked to the terminal heme propionate functions as an effective mediator of an electron transfer from NADH to the hemin in rMb(1). Furthermore, rMb(1) shows the deformylation activity, when 2-phenylpropionaldehyde (2-PPA) was employed as a substrate. This result indicates that the oxyheme is reductively activated to Fe(III)-peroxoanion (Fe(III)-O22-). The result in this report is the first example of the activation of dioxygen by myoglobin. This study shows the utility of the replacement of the native hemin with a chemically modified one for the functionalization of myoglobin.