Synthesis of a model compound for the photosynthetic electron transfer

In order to elucidate the role of special pair chlorophyll in photosynthetic electron transfer, a new model compound 1, where two etioporphyrins are covalently tied in a face-to-face orientation and further linked to a quinone with a polymethylene chain, was synthesized.     

Intramolecular excimer fluorescence,its solvent dependence,and photodimerization of 1,2-dianthrylethanes

Both 1,2-di(1-anthryl)ethane (I) and 1,2-di(9-anthryl) ethane (II) show two types of excimer fluorescence spectra under different conditions; one with peak at 460 nm (type-1) and the other with peak at 530 nm (type-2). Furthermore, the type-1 excimer emission shows a peculiar dependence upon the solvent polarity.     

Matching-Updating Mechanism: A Solution for the Stable Marriage Problem with Dynamic Preferences

We studied the stable marriage problem with dynamic preferences. The dynamic preference model allows the agent to change its preferences at any time, which may cause instability in a matching. However, preference changing in SMP instances does not necessarily break all pairs of an existing match. Sometimes, only a few couples want to change their partners, while others choose to stay with their current partners; this motivates us to find stable matching on a new instance by updating an existing match rather than restarting the matching process from scratch. By using the update mechanism, we try to minimize the revision cost when rematching occurs. The challenge when updating a matching is that a cyclic process may exist, and stable matching is never achieved. Our proposed mechanism can update a match and avoid the cyclic process.     

The synthesis of benzofuroquinolines. III. Two dihydroxybenzofuroquinolinones

Two dihydroxybenzofuroquinolinones, 3,9-dihydroxy-5H-benzofuro[3,2-c]quinolin-6-one (V) and 3,8-dihydroxy-6H-benzofuro[2,3-b]quinolin-11-one (VI), were obtained by the demethyl-cyclization of 3-(2,4-dimethoxyphenyl)-4-hydroxy-7-methoxy-1H-quinolin-2-one (IV). By the methylation with diazomethane, V gave a dimethylated compound (VII), while VI gave a trimethylated compound (VIII).     

A novel method for predicting disintegration time in the mouth of rapidly disintegrating tablet by compaction analysis using TabAll

A tableting process analyzer (TabAll) was used to predict disintegration time in the mouth of rapidly disintegrating tablet. Analyzer profiles recorded upper punch displacement and die wall force encountered during tablet processing. Changes in the mixing ratio of spherical sugar granules and microcrystalline cellulose or lactose affected upper punch displacement and die wall force profiles. Analysis of the compaction process revealed a strong association between disintegration time in the mouth and stationary time, relaxation time of upper punch displacement, and relaxation time of die wall force; disintegration time in the mouth decreased as the three parameters increased. Thus, analysis of the compaction process is useful for predicting disintegration time in the mouth of rapidly disintegrating tablet, which can assist the formulation of new rapidly disintegrating tablets.     

Stepwise charge separation and charge recombination in ferrocene-meso,meso-linked porphyrin dimer-fullerene triad

A meso,meso-linked porphyrin dimer [(ZnP)(2)] as a light-harvesting chromophore has been incorporated into a photosynthetic multistep electron-transfer model for the first time, including ferrocene (Fc), as an electron donor and fullerene (C(60)) as an electron acceptor to construct the ferrocene-meso,meso-linked porphyrin dimer-fullerene system (Fc-(ZnP)(2)-C(60)). Photoirradiation of Fc-(ZnP)(2)-C(60) results in photoinduced electron transfer from the singlet excited state of the porphyrin dimer [(1)(ZnP)(2)] to the C(60) moiety to produce the porphyrin dimer radical cation-C(60) radical anion pair, Fc-(ZnP)(2)(*+)-C(60)(*-). In competition with the back electron transfer from C(60)(*-) to (ZnP)(2)(*+) to the ground state, an electron transfer from Fc to (ZnP)(2)(*+) occurs to give the final charge-separated (CS) state, that is, Fc(+)-(ZnP)(2)-C(60)(*-), which is detected as the transient absorption spectra by the laser flash photolysis. The quantum yield of formation of the final CS state is determined as 0.80 in benzonitrile. The final CS state decays obeying first-order kinetics with a lifetime of 19 micros in benzonitrile at 295 K. The activation energy for the charge recombination (CR) process is determined as 0.15 eV in benzonitrile, which is much larger than the value expected from the direct CR process to the ground state. This value is rather comparable to the energy difference between the initial CS state (Fc-(ZnP)(2)(*+)-C(60)(*-)) and the final CS state (Fc(+)-(ZnP)(2)-C(60)(*-)). This indicates that the back electron transfer to the ground state occurs via the reversed stepwise processes,that is, a rate-limiting electron transfer from (ZnP)(2) to Fc(+) to give the initial CS state (Fc-(ZnP)(2)(*+)-C(60)(*-)), followed by a fast electron transfer from C(60)(*-) to (ZnP)(2)(*+) to regenerate the ground state, Fc-(ZnP)(2)-C(60). This is in sharp contrast with the extremely slow direct CR process of bacteriochlorophyll dimer radical cation-quinone radical anion pair in bacterial reaction centers.     

Zinc- and indium-promoted conjugate addition-cyclization reactions of ethenetricarboxylates with propargylamines and alcohol: novel methylenepyrrolidine and methylenetetrahydrofuran syntheses

A new zinc- and indium-promoted conjugate addition-cyclization reaction to afford nitrogen- and oxygen-containing five-membered heterocycles has been developed. Reaction of ethenetricarboxylates with propargylamines (1 equiv) in the presence of ZnBr2 or InBr3 afforded methylenepyrrolidines in high yields. The stoichiometric use of ZnBr2 or InBr3 at room temperature and the catalytic use of InBr3-Et3N at 80 degrees C were effective. Reaction of ethenetricarboxylates with propargyl alcohol in the presence of ZnBr2 or InBr3 afforded methylenetetrahydrofurans.     

Time-sliced ion-velocity imaging study of the reaction Y + O2 → YO + O

The oxidation reaction dynamics of the gas-phase yttrium atoms by oxygen molecules was studied under crossed-beam conditions. The product YO was detected using a time-of-flight mass spectrometer combined with laser single-photon ionization. An acceleration lens system designed for the ion-velocity mapping conditions, a two-dimensional (2-D) detector, and a time-slicing technique were used to obtain the velocity and angular distributions of the products. Two ionization wavelengths were used for the internal (vibrational and/or electronic) energy selective detection of YO. The single photon of the shorter wavelength (202.0 nm) can ionize all states of YO(X?(2)Σ, A'?(2)Δ, and A?(2)Π), while electronically excited YO(A' and A) are dominantly ionized at a longer wavelength (285.0 nm). Time-sliced images were converted to the velocity and angular distributions in the center-of-mass frame. The general features of the velocity distributions of YO, determined at two wavelengths, were well represented by those expected from the statistical energy disposal model. The forward-backward symmetry was also observed for two images. These results suggest that the reaction proceeds via long-lived intermediates, and that this mechanism is consistent with previous chemiluminescence/LIF studies.     

Structures of the dimeric and monomeric chromanones, gonytolides A-C, isolated from the fungus Gonytrichum sp. and their promoting activities of innate immune responses

Innate immunity is the front line of self-defense against microbial infection. After searching for natural substances that regulate innate immunity using an ex vivo Drosophila culture system, we identified a novel dimeric chromanone, gonytolide A, as an innate immune promoter from the fungus Gonytrichum sp. along with gonytolides B and C. Gonytolide A also increased TNF-α-stimulated production of IL-8 in human umbilical vein endothelial cells.