Effect of encaged aromatic guests on the shape and connectivity of molecular cavity in crystalline polystyrene evaluated by molecular simulations

The delta form of crystalline syndiotactic polystyrene is a clathrate molecular compound in which various aromatic molecules are encaged. We have investigated the size, shape, and connectivity of the molecular cavity in the crystal using a molecular dynamics simulation. The effects of the guest species on the cavity structure were investigated in detail. In order to systematically vary the guest structure, various aromatic guests, e.g., benzene, toluene, p-xylene, m-xylene, o and mesitylene were examined. The interstitial spaces between the guests and the polymer chains were analyzed by cluster analysis of the free volumes. The individual cavity volumes into which the guests are clathrated were also evaluated. It was found that the guest molecules can greatly affect not only the cavity size and shape but also the connectivity of the cavities. The transport of small molecules in the crystal is discussed in connection with the cavity structure.     

Phenolic constituents of licorice. III. Structures of glicoricone and licofuranone, and inhibitory effects of licorice constituents on monoamine oxidase

Two new phenolic compounds, glicoricone (3) and licofuranone (4), were isolated from a species of licorice brought from the northwestern region of China, and their structures were assigned. Among the twelve licorice constituents examined for the inhibition of monoamine oxidase (MAO), six compounds, 3, 4, genistein (6), licopyranocoumarin (7), licocoumarone (14) and glycyrrhisoflavone (15), inhibited the enzyme with the IC50 (concentration required for 50% inhibition of the enzyme activity) values of 6.0 x 10(-5)-1.4 x 10(-4) M. Glycyrrhizin (1) also inhibited MAO with the IC50 value of 1.6 x 10(-4) M.     

FLUORESCENCE LIFETIME OF ACRIDINE ORANGE IN SODIUM DODECYL SULFATE PREMICELLAR SOLUTIONS

Abstract— The absorption and fluorescence spectra, and the fluorescence lifetime of acridine orange (AO) were measured in a wide range of the sodium dodecyl sulfate (SDS) concentration below and above the critical micelle concentration (cmc). The fluorescence consisted of two components with different lifetimes; short (<3 ns) and long (>3 ns). The short and long lifetime components are attributed to the AO monomer and dimer associated with detergent, respectively. The lifetime of the dimer increased with increasing the SDS concentration just below the cmc. It decreased suddenly to a constant value just above the cmc. The lifetime of the monomer showed only a slight increase in the concentration range of SDS employed.     

Determination of fluorine in standard rocks by photon activation analysis

A highly sensitive determination of fluorine in standard rocks by photon activation using the¹⁹F(,n)¹⁸F reaction combined with pyrohydrolysis for the separation of¹⁸F has been reported. The irradiation energy was operated at 20 MeV to avoid the interference from Na, because Na is one of the major element in rocks and¹⁸F is also produced from Na via²³Na(,n)¹⁸F reaction above its threshold energy, 20.9 MeV. After irradiation, fluorine was extracted by pyrohydrolysis and separated as LaF₃ precipitate. It was ascertained that the average recovery of fluorine in standard rocks was about 90% and the precipitate was of high radiochemical purity. This method was applied to the analysis of ten GSJ rock reference samples and two USGS standard rocks issued by the Geological Survey of Japan and the United States Geological Survey, respectively. The detection limit of this method was 0.02 g/g, and the results obtained by this method were in good agreement with the recommended values. This method was easily applied to the determination of a few ppm level of fluorine in rock samples, such as ultrabasic rock and feldspar.     

Synthesis and pharmacology of 3,4-dihydro-3-oxo-1,4-benzoxazine-8-carboxamide derivatives, a new class of potent serotonin-3 (5-HT3) receptor antagonists.

A series of 3,4-dihydro-3-oxo-1,4-benzoxazine-8-carboxamide derivatives was synthesized and evaluated for serotonin-3 (5-HT3) receptor antagonistic activity assessed by their ability to antagonize the von Bezold-Jarish (BJ) effect in rats. Derivatives bearing 1-azabicyclo[2.2.2]oct-3-yl moiety as a basic function attached to the carboxamide at position 8 showed more potent antagonistic activity than those bearing the other three basic moieties. Structure-activity relationships of this series showed that methyl and chloro groups were more effective as substituents at positions 4 and 6, respectively. The representative compound 15 (Y-25130) in this series showed potent antagonistic activity on the BJ effect (ED50 = 1.3 micrograms/kg i.v.), high affinity for 5-HT3 receptor (Ki = 2.9 nM) and complete protection against cisplatin-induced emesis in dogs at a dose of 0.1 mg/kg i.v.     

Carbon dioxide fixation by microalgae photosynthesis using actual flue gas discharged from a boiler

To mitigate CO₂ discharged from thermal power plants, studies on CO₂ fixation by the photosynthesis of microalgae using actual exhaust gas have been carried out. The results are as follows.

NMR and quantum chemical study on the OH...pi and CH...O interactions between trehalose and unsaturated fatty acids: implication for the mechanism of antioxidant function of trehalose

Trehalose is a disaccharide that attracts much attention as a stress protectant. In this study, we investigated the mechanism of the antioxidant function of trehalose. The spin-lattice relaxation times (T(1)) of (1)H and (13)C NMR spectra were measured to investigate the interaction between trehalose and unsaturated fatty acid (UFA). We selected several kinds of UFA that differ in the number of double bonds and in their configurations (cis or trans). Several other disaccharides (sucrose, maltose, neotrehalose, maltitol, and sorbitol) were also analyzed by NMR. The T(1) values for the (1)H and (13)C signals assigned to the olefin double bonds in UFA decrease with increasing concentration of trehalose and the changes reaches plateaus at integer ratios of trehalose to UFA. The characteristic T(1) change is observed only for the combination of trehalose and UFA with cis double bond(s). On the other hand, from the (13)C-T(1) measurements for trehalose, the T(1) values of the C-3 (C-3') and C-6' (C-6) are found to change remarkably by addition of UFA. (1)H[bond](1)H NOESY measurements provide direct evidence for complexation of trehalose with linoleic acid. These results indicate that one trehalose molecule stoichiometrically interacts with one cis-olefin double bond of UFA. Computer modeling study indicates that trehalose forms a stable complex with an olefin double bond through OH...pi and CH...O types of hydrogen bonding. Furthermore, a significant increase in the activation energy is found for hydrogen abstraction reaction from the methylene group located between the double bonds that are both interacting with the trehalose molecules. Therefore, trehalose has a significant depression effect on the oxidation of UFA through the weak interaction with the double bond(s). This is the first study to elucidate the antioxidant function of trehalose.     

Asymmetric construction of quaternary carbon stereocenter by Pd-hemilabile ligand-catalyzed allylic substitution

The catalyst comprised [PdCl(η³-C₃H₅)]₂ and a simple chiral hemilabile ferrocene ligand, 1′,2-bis(diphenylphosphinoethyl)ferrocenyl alcohol, provides synthetically acceptable results for an enantioselective Pd-catalyzed allylic alkylation of cyclohexanone derivatives bearing an electron-withdrawing group at the α-position to form the quaternary carbon with up to 90% enantioselectivity under mild reaction conditions.