New picrotoxane terpenoids from Picrodendron baccatum

Two new picrotoxane norditerpenoid lactones, picrodendrins X (1) and Y (2), and four new picrotoxane sesquiterpenoid lactones, picrodendrins Z (3), α (4), β (5) and picrodendrioside A (6) were isolated from the bark and leaves of Picrodendron baccatum. Their structures were determined by spectral analysis and X-ray crystallographic analysis.     

Study on interactions of endocrine disruptors with estrogen receptor using fluorescence polarization

In this study, we examined the affinities of many (21) compounds such as hormones, pharmaceuticals, industrial chemicals, and phytoestrogens to the estrogen receptor (ER) by ER binding assay using fluorescence polarization (FP). This method is based on the competitive binding assay using fluorescein-labeled estradiol (F-E2), in which the polarization values decreased with the addition of the compounds (competitors). The obtained sigmoidal inhibition curves were transformed into the pseudo-Hill plots, and the concentrations at 50% inhibition (IC50) and Hill coefficients were obtained from the regression equations. We examined the relationship between the chemical structures and estrogenic activities, and finally classified the tested compounds into three categories, agonists, partial agonists and antagonists based on their Hill coefficients.     

Synthesis of 5-ethylpyrimidine nucleoside analogs

This paper describes the synthesis of acyclic, cyclic, and deoxy sugar nucleosides of 5-ethylpyrimidine, i.e., i) 1-(2-hydroxyethoxymethyl), 1-(2-methoxyethoxymethyl), and 1-ethoxyethyl derivatives of 5-ethyl-uracil and 5-ethylcytosine, ii) 5-ethyl-1-(tetrahydro-2H-pyran-2-yl)- and -1-(tetrahydrofuran-2-yl)uracils, and iii) 5-ethyl-2′-deoxyuridine.     

A New Method of Calculating Pore Size Distribution: Analysis of Adsorption Isotherms of N(2) and CCl(4) for a Series of MCM-41 Mesoporous Silicas

The adsorption isotherms of N(2) gas at 77 K and CCl(4) vapor at 283.1(5), 298.1(5), and 308.1(5) K were measured for six samples of the mesoporous silicas having uniform cylindrical pores (MCM-41). The pore radii of the six samples (r(p)), which were evaluated from the alpha(s) plots of the N(2) isotherms, were 1.13, 1.29, 1.50, 1.65, 1.90, and 2.53 nm. The CCl(4) adsorption isotherms show that the capillary condensation occurs at the very narrow P/P(0) range. The core radii of the six adsorbents (r(c)), which were estimated from a comparison plot of the CCl(4) isotherm, were 0.90, 1.01, 1.28, 1.37, 1.60, and 2.17 nm. In the comparison plot, the standard CCl(4) isotherm for nonporous silica was used as the reference isotherm. It has been clarified that the Polanyi adsorption potential of capillary condensation is proportional to the reciprocal of the core radii: RT ln(P(0)/P)=5.37r(c)(-1) nm(-1), ln(P(0)/P)=2.17r(c)(-1) nm(-1) at 298.1(5) K, [A]. The statistical thickness of adsorbed CCl(4) on the curved surface (t((pore))), which was estimated from the difference between the pore radii and the core radii, was given by Eq. [B]: t((pore))=0.188+0.336(P/P(0))+0.382(P/P(0))(2) nm [B], (0.08

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A highly potent non-nucleoside adenosine deaminase inhibitor: efficient drug discovery by intentional lead hybridization

We disclose herein the rapid discovery of the first highly potent (Ki = 7.7 nM) non-nucleoside adenosine deaminase (ADA) inhibitor based on the rational hybridization of two structurally distinct leads. Two micromolar inhibitors were discovered by a parallel rational design and random screening program, and individual crystal structures of bovine ADA in complexation with these inhibitors revealed several unknown binding sites and distinct binding modes. Using this information as the starting point, highly effective lead hybridization was achieved in only two structure-based drug design iterations. The conceptual approach illustrated by this example promises to be broadly useful in the search for new chemical entities and can contribute greatly to improve the overall efficiency and speed of drug discovery.     

Solubilization of Polar Oils in Surfactant Self-Organized Structures

The cloud temperature of 2 wt% C(12)EO(8) aqueous solutions decreases upon addition of sarcosinate-lauroyl isopropyl (SLIP), 1-dodecanol, and m-xylene, whereas it increases in glycerol tris(2-ethylhexanoic) ester (TEH), isopropyl myristate (IPM), and saturated hydrocarbon systems. A three-phase microemulsion is formed at equal weights of water and oil in the IPM system, but a lamellar liquid crystal (L(alpha)) is present in the SLIP system at the balanced temperature. The effect of added oil on the phase transition of the hexagonal (H(1)) phase was also investigated by means of SAXS study. The H(1)-L(alpha) transition occurs upon addition of SLIP or 1-dodecanol whereas the H(1)-I(1) (discontinuous micellar cubic) phase transition takes place in TEH or IPM systems. These differences in phase behavior are attributed to the placement of solubilized oil in micelles: In the former systems, oil tends to penetrate in the surfactant palisade layer and induces the surfactant layer curvature in micelles to be less positive, while the penetration tendency is small and the opposite effect on the curvature is induced upon addition of the latter oils. Copyright 2001 Academic Press.     

Creation and characteristics of phosphatidylcholine stationary phases for the chromatographic separation of inorganic anions

New stationary phases for chromatographic separation of anions, obtained by loading liposomes made from dimyristolyphosphatidylcholine (DMPC) onto reversed-phase packed columns (C18 and C30) are reported. Mono- and divalent anions were used as model analyte ions and retention data for these species were obtained using the DMPC stationary phases and used to elucidate the separation mechanisms involved in this chromatographic system. The DMPC stationary phases can separate anions by either a solvation-dependent mechanism or an electrostatic ion-exchange mechanism, depending upon the relative magnitudes of the negative electrostatic potential (Psi(-)) of the phosphate moiety (P-) and the positive electrostatic potential (Psi(+)) of the quaternary ammonium groups (N+) on the headgroup of DMPC. If Psi(+) > Psi(-), such as in case where Psi(-) has been reduced either by binding of eluent cations (e.g., H+ or divalent cations) onto the P- group of DMPC or by steric screening when a C30 reversed-phase material was used to support the DMPC, then the overall electrostatic surface potential (and hence also the effective anion-exchange capacity) was generally large and the anions were separated on the basis of an electrostatic mechanism. However, if Psi(+) was similar to Psi(-), such as in the case of using a C18 reversed-phase support and monovalent cations as eluent cations, then the overall electrostatic surface potential and the effective anion-exchange capacity were very small and the analyte anions were separated on the basis of a solvation-dependent mechanism. The DMPC stationary phases were found to be suitable for the direct determination of iodide and thiocyanate in highly saline water samples, such as seawater samples.     

One-directional crystal growth in charged colloidal silica dispersions driven by diffusion of base

Aqueous dispersions of charged colloidal silica particles showed a novel one-directional crystal growth by diffusion of a weak base, pyridine. The colloidal crystal consisted of pillar-shaped crystal grains whose height and width were in the order of centimeter and subcentimeter, respectively. The growth process was explainable in terms of (i) the diffusion of pyridine with neutralization reactions between weakly acidic silica surfaces, (ii) charging up of the silica particles, and (iii) the charge-induced crystallization of the dispersions.     

Immobilized aminoacylase on porous glass beads

Aminoacylase was immobilized on porous glass by two different coupling methods. One aminoacylase preparation was covalently bound to an alkylaminosilane derivative of porous glass with glutaraldehyde [alkylamino-porous glass-CVB-aminoacylase]; the other aminoacylase derivative was prepared by covalently binding the enzyme to arylaminosilane glass by diazotization [arylamino-porous glass-CVB-aminoacylase]. The enzyme activities of the immobilized aminoacylases were 3.2-13.0 U/ml glass for the former and 1.9-6.8 U/ml glass for the latter. The alkylamino-porous glass-CVB-aminoacylase showed excellent stability at pH 6-9 and at temperatures below 50°C. The derivative could be stored for more than 6 mo without appreciable loss of the activity. Continuous hydrolysis using the alkylamino-porous glass-CVB-aminoacylase packed in column was carried out for 54 days at 37°C, with a calculated half-life of 78 days. It was determined that alkylamino-porous glass-CVB-aminoacylase would be applicable in an industrial preparation of various l-amino acids from their dl forms.