The terpene trilactones (TTLs), ginkgolides and bilobalide, are structurally unique constituents of Ginkgo biloba extracts, which exhibit various neuromodulatory properties. Although the TTLs are believed to be responsible for some of these effects, the specific interactions with targets in the central nervous system remain to be elucidated on a molecular level. Ginkgolides are known antagonists of the platelet-activating factor (PAF) receptor. Herein, we describe the first examination of the binding of native TTLs and their derivatives to the cloned PAF receptor, confirming that of the TTLs, ginkgolide B is the most potent PAF receptor antagonist. Ginkgolide derivatives carrying photoactivatable and fluorescent groups for the purpose of performing photolabeling have been prepared and evaluated using the cloned PAF receptor. These studies have shown that ginkgolide derivatives with aromatic photoactivatable substituents are potent PAF receptor antagonists with K i values of 0.09-0.79 µM and hence excellent ligands for clarifying the binding of ginkgolides to PAF receptor by photolabeling studies. Ginkgolide derivatives incorporating both fluorescent and photoactivatable groups still retained binding affinity to the PAF receptor and hence should be promising ligands for photolabeling and subsequent sequencing studies.

The Amphibacillus xylanus NADH oxidase, which catalyzes the reduction of oxygen to hydrogen peroxide with ␤-NADH, can also reduce hydrogen peroxide to water in the presence of free flavin adenine dinucleotide ( We have reported previously on a new group of facultatively anaerobic bacteria isolated from alkaline compost (17). Since the bacteria have unique phenotypic and chemotaxonomic characteristics (18), as well as bioenergetic properties (13), we named one of the isolate Amphibacillus xylanus (18). A. xylanus, which lacks a respiratory system and heme proteins, including catalase, grows well and has the same growth rate and cell yield under strictly anaerobic and aerobic conditions (18). This is due to the presence of anaerobic and aerobic pathways producing similar amounts of ATP (19). We purified NADH oxidase from aerobically grown A. xylanus (20) and found that hydrogen peroxide is formed during the reaction of the NADH oxidase. We have also found that the enzyme reduces hydrogen peroxide in the presence of additional free flavin adenine dinucleotide (FAD); this may be of physiological relevance because of the presence of 13 M free FAD in aerobically growing cells. Such behavior indicates that the A. xylanus NADH oxidase has unique functional properties that are different from those of other known NADH oxidases (8,10,12,27,(31)(32)(33).The amino acid sequence of A. xylanus NADH oxidase exhibits up to 51.2% identity to the alkyl hydroperoxide reductase F-52a flavoprotein component (AhpF) from Salmonella enterica (36), but the ability of the latter to reduce hydrogen peroxide was not reported (11). We have shown that both enzymes reduce not only alkyl hydroperoxides but also hydrogen peroxide in the presence of the 22-kDa protein component (AhpC) of the alkyl hydroperoxide reductase from Salmonella enterica, and the turnover numbers of the reactions catalyzed by the NADH oxidase are extremely high compared with those of known peroxide-reducing enzymes (21). Complete reduction of the NADH oxidase by dithionite required 6 electron equivalents/mol of enzyme-bound flavin (25,26). Such behavior indicated the presence of redox centers in addition to the FAD, and these were shown to be two disulfides, Cys128-Cys131 and Cys337-Cys340. To provide information about the relationship between such high turnover numbers and the three redox centers of the enzyme, the reductive half-reactions of the wild-type and the mutant (C337S/C340S) NADH oxidase were investigated and have been reported in a previous publication (22).Hydrogen peroxide is presumed to be accumulated in aerobically growing cells of A. xylanus, which lack catalase and a respiratory chain (18), because the NADH oxidase should regenerate NAD ϩ from NADH formed in the aerobic pathway and produce hydrogen peroxide from oxygen. The ability to get rid of hydrogen peroxide must be high for the cells to be able to survive under aerobic conditions. In the presence of free FAD or the AhpC protein, the NADH oxidase shows scavenging activity for hydrogen peroxide (21,2...

Aseries of assembled Pt II complexes comprising Nheterocyclic carbene and cyanide ligands was constructed using different substituent groups,[ Pt(CN) 2 (R-impy)] (R-impyH + = 1-alkyl-3-(2-pyridyl)-1H-imidazolium, R = Me (Pt-Me), Et (Pt-Et), i Pr (Pt-i Pr), and t Bu (Pt-t Bu)). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51-0.81 in the solid state at room temperature,originating from the triplet metal-metal-toligand charge transfer (3 MMLCT) state.Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt-t Bu.I mportantly, Pt-t Bu is the first example that exhibits blue 3 MMLCT emission. The 3 MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties.T he wide-range color tuning of luminescence using the 3 MMLCT emission presents an ew strategy of superfine control of the emission color.

Synthesis of novel cyclic 1-alkenylboronates is accomplished through the zirconium-mediated regio- and stereoselective double functionalization of 1-alkynylboronates and the subsequent ruthenium-catalyzed ring-closing metathesis (RCM). The obtained substituted cyclic 1-alkenylboronates are transformed into o-terphenyl and triphenylene derivatives.

X-ray absorption (XAS) and emission (XES) spectroscopy near B K and C K edges have been performed on metallic (ϳ0.1 at. % B, B-diamond) and semiconducting (ϳ0.03 at. % B and N, BN-diamond) doped diamond films. Both B K XAS and XES spectra show a metallic partial density of states (PDOS) with the Fermi energy of 185.3 eV, and there is no apparent boron-concentration dependence in contrast to the different electric property. In C K XAS spectrum of B-diamond, the impurity state ascribed to boron is clearly observed near the Fermi level. The Fermi energy is found to be almost same with the top of the valence band of nondoped diamond: E V = 283.9 eV. C K XAS of BN-diamond shows both the B-induced shallow level and N-induced deep and broad levels as the in-gap states, in which the shallow level is in good agreement with the activation energy ͑E a = 0.37 eV͒ estimated from the temperature dependence of the conductivity; namely, the change in C 2p PDOS of impurity-induced metallization is directly observed. The electric property of this diamond is ascribed mainly to the electronic structure of C 2p near the Fermi level. The observed XES spectra are compared with the discrete variational X␣ (DVX␣) cluster calculation. The DVX␣ result supports the strong hybridization between B 2p and C 2p observed in XAS and XES spectra, and suggests that the small amount of boron ͑ഛ0.1 at. % ͒ in diamond occupies the substitutional site rather than interstitial site.

Summary1. Studies using highly informative genetic markers (e.g. microsatellites) have revealed effective movement of genes through pollen grains from more distant sources into offspring than those inferred on the basis of physical pollen movement alone. In order to identify the factors that cause such effective pollen movement in tree populations, analyses of the genetic structure of reproductive trees and parentage analyses for seedlings and saplings were conducted in a 110-ha population of Aesculus turbinata , a tall deciduous tree species that is pollinated by insects and has large seeds that are dispersed by gravity and small mammals. 2. By analysing genotypes of seed coats, which are identical to those of the seed parents, and of leaves from seedlings, pollen donors and seed parents were identified for seedlings. Differences in size and dispersal mode between pollen and seeds caused a significant difference in dispersal distances. Reflecting the restricted seed dispersal (25.3 m on average), there was significant positive relatedness between reproductive trees standing within 150 m of each other. 3. The percentage of self-pollinated offspring decreased from 8.3% at the seedling stage to 0.56% at the sapling stage. The disappearance of out-crossed individuals during the stage between seedling and sapling seemed to be associated with the spatial distance separating their parents: the proportion of juvenile trees that died was higher for those that originated from out-crosses between adults standing within 100 m of each other, where positive relatedness was found between adult trees. Consequently, the deaths of individuals arising from self-pollination events and from crosses between reproductive trees that were spatially adjacent caused longer effective pollen movement for the offspring that survived. The distance between the two parents of a tree, which indicates the distance of effective pollen movement, increased from 179.9 m for seedlings to 288.9 m for saplings. 4. The genetic structure of the adult population of A. turbinata affected the survival of offspring through biparental inbreeding depression, and, then, removal of individuals resulting from crosses between related adults in turn promoted effective pollination over longer distances.

The synthesis, crystal structures, and photophysical properties of four anionic platinum complexes bearing N-heterocyclic carbenes (NHCs), 4)), are reported. The tetra-n-butylammonium salts afforded discrete Pt(II) complexes surrounded by the bulky cations in the crystalline states with no Pt−Pt, π−π, or solute−solvent interactions. As a result, the crystals exhibited strong phosphorescence with quantum yields of 0.24−0.72 at 298 K. The three isomeric complexes 2−4 with π-extended structures of 1 exhibited luminescence with different colors depending on the π-extension site. These complexes in a discrete and restricted space enabled the comparative investigation of the luminescent states and regioselective benzannulation effect using computational methods and luminescence spectroscopy. Blueemissive 1 and 2 exhibited lifetime changes at temperatures of 77−298 K, suggesting the influence of dark states located 2000− 3000 cm −1 above the emissive state. In contrast, yellow-and orange-emissive 3 and 4 showed no thermal deactivation effect at ambient temperature. The temperature dependence of the emission lifetimes in the low-temperature region of 4−77 K showed that blue-emissive 1 and 2 had a relatively large zero-field splittings (ZFSs) of 35 and 28 cm −1 , respectively, indicating the significant contribution of triplet metal-to-ligand charge transfer character to the 3 π−π* emission. On the other hand, the ZFS of 4 was less than 2 cm −1 , suggesting purer 3 π−π* character.

Luminescent ionic liquids are formed by the melting of tetranuclear rhenium(v) clusters.