Development of calixarene-based host molecules for peptides in aqueous media

We synthesized a peptidocalix[4]arene library consisting of 1000 members that was suitable for peptide recognition in aqueous media. Some peptidocalix[4]arenes in the library were host molecules for guest peptides. Electrostatic interaction between the host and guest molecules was the most important factor for binding in aqueous media.     

A simple technique to measure regional cerebral blood flow during intravascular balloon clamping

A case of giant internal carotid ophthalmic aneurysm was presented. In order to clarify whether the patient could tolerate carotid occlusion, a balloon clamping test was performed. before surgery. The cerebral blood flow was measured using early imaging by single photon emission computed tomography (SPECT) with N-isopropyl-(iodine-123)-p-iodoamphetamine (123I-IMP). When the balloon clamping test was performed the tracer was injected, and scanning was performed 35 minutes after removing the catheter. This tracer enabled a "memory of blood flow" during temporary ischemia to determine the character of quick diffusion and slow wash out, that could not be performed by other methods of cerebral blood flow measurement. SPECT with 123I-IMP can simplify the measurement of cerebral blood flow during the balloon clamping test.     

Chemical reaction dynamics of PeCB and TCDD decomposition: A tight‐binding quantum chemical molecular dynamics study with first‐principles parameterization

The decomposition reaction dynamics of 2,3,4,4′,5‐penta‐chlorinated biphenyl (2,3,4,4′,5‐PeCB), 3,3′,4,4′,5‐penta‐chlorinated biphenyl (3,3′,4,4′,5‐PeCB), and 2,3,7,8‐tetra‐chlorinated dibenzo‐p‐dioxin (2,3,7,8‐TCDD) was clarified for the first time at atomic and electronic levels, using our novel tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization. The calculation speed of our new method is over 5000 times faster than that of the conventional first‐principles molecular dynamics method. We confirmed that the structure, energy, and electronic states of the above molecules calculated by our new method are quantitatively consistent with those by first‐principles calculations. After the confirmation of our methodology, we investigated the decomposition reaction dynamics of the above molecules and the calculated dynamic behaviors indicate that the oxidation of the 2,3,4,4′,5‐PeCB, 3,3′,4,4′,5‐PeCB, and 2,3,7,8‐TCDD proceeds through an epoxide intermediate, which is in good agreement with the previous experimental reports and consistent with our static density functional theory calculations. These results proved that our new tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization is an effective tool to clarify the chemical reaction dynamics at reaction temperatures. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Crystal structures and topochemical polymerizations of 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes

Highly conjugated monomers, 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes (methoxy (1a), ethoxy (1b), isopropoxy (1c), benzyloxy (1d), chloroethoxy (1e), and bromoethoxy (1f)), were synthesized. Recrystallizations of 1a, 1c, 1e, and 1f yielded two crystal forms (prisms (1a-A) and needles (1a-B), needles (1c-A) and plates (1c-B), prisms (1e-A) and plates (1e-B), and prisms (1f-A) and needles (1f-B)), which have different molecular packing modes by X-ray crystal structure analysis, indicating that the crystals are polymorphic. In the photopolymerizations of these monomer crystals in the solid state, 1a-A, 1e-A, and 1f-A polymerized topochemically to give crystalline polymers. For their thermal polymerizations in the solid state, in addition to 1a-A, 1e-A, and 1f-A, 1e-B and 1f-B polymerized, but polymers formed from the 1e-B and 1f-B were amorphous. The packing of quinodimethane molecules in the crystals was defined by four kinds of parameters, stacking distance (d(s)), the distance between the reacting exomethylene carbon atoms (d(cc)), the angles formed between the stacking axis and longer axis of the monomer molecule (theta(1)), and the shorter axis of the monomer molecule (theta(2)), and then the polymerization reactivity of these quinodimethanes in the solid state was discussed on the basis of these parameters.     

Noncatalytic kinetic study on site-selective H/D exchange reaction of phenol in sub- and supercritical water

The site-selective H/D exchange reaction of phenol in sub- and supercritical water is studied without added catalysts. In subcritical water in equilibrium with steam at 210-240 degrees C, the H/D exchange proceeds both at the ortho and para sites in the phenyl ring, with no exchange observed at the meta site. The pseudo-first-order rate constants are of the order of 10(-4) s(-1); 50% larger for the ortho than for the para site. In supercritical water, the exchange is observed also at the meta site with the rate constant in the range of 10(-6)-10(-4) s(-1). As the bulk density decreases, the exchange slows down and the site selectivity toward the ortho is enhanced. The enhancement is due to the phenol-water interaction preference at the atomic resolution. The site selectivity toward the ortho is further enhanced when the reaction is carried out in benzene/water solution. Using such selectivity control and the reversible nature of the hydrothermal deuteration/protonation process, it is feasible to synthesize phenyl compounds that are deuterated at any topological combination of ortho, meta, and para sites.     

Studies on cardiotonic agents. I. Synthesis of some quinazoline derivatives

A series of quinazoline derivatives with various 4-heterocyclylpiperidino groups at the 4-position was synthesized and tested for cardiotonic activity in anesthetized dogs. Among them, several 6,7-dimethoxyquinazoline derivatives showed potent cardiotonic activity.     

Studies on cardiotonic agents. II. Synthesis of novel phthalazine and 1,2,3-benzotriazine derivatives

A series of phthalazine and 1,2,3-benzotriazine derivatives which have heterocyclylpiperidino groups was synthesized and tested for cardiotonic activity in anesthetized dogs. Several 6,7-dimethoxyphthalazine derivatives showed relatively potent cardiotonic activity comparable to that of amrinone.     

Synthesis, characterization, and photochemical properties of azobenzene-conjugated Ru(II) and Rh(III) bis(terpyridine) complexes

We synthesized azobenzene-conjugated bis(terpyridine) Ru(II) and Rh(III) mononuclear and dinuclear complexes and investigated their photochemical properties on excitation of the azo pi-pi band upon 366 nm light irradiation. The Ru mononuclear complex underwent trans-to-cis photoisomerization to reach the photostationary state with only 20% of the cis form, while the Ru dinuclear complex did not isomerize at all photochemically. On the other hand, the mononuclear and dinuclear Rh complexes showed almost complete trans-to-cis photoisomerization behavior. Cis forms of the Rh complexes thermally returned to the trans form at a much slower rate than those of organic azobenzenes, but they did not isomerize photochemically. The reduction potential of the cis forms was 80 mV more negative than that of the trans forms. The photoisomerization quantum yields of the Rh complexes were strongly dependent on the polarity, viscosity, and donor site of the solvents as well as the size of the counterions. We investigated the photoisomerization process of these complexes using femtosecond absorption spectroscopy. For the Rh complexes, we observed S(n) <-- S(2) and S(n) <-- S(1) absorption bands similar to those of organic azobenzenes. For the Ru complexes, we observed very fast bleaching of the MLCT band of the Ru complex, which indicated that the energy transfer pathway to the MLCT was the primary cause of the depressed photoisomerization. The electronic structures, which were estimated from ZINDO molecular orbital calculation, supported the different photochemical reaction behavior between the Ru and Rh complexes.     

Ionic liquid crystal as a hole transport layer of dye-sensitized solar cells

Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazolium cations, resulting in high conductivity of the electrolyte.     

Seven-membered vibsane-type diterpenes with a 5,10-cis relationship from Viburnum awabuki

New five seven-membered vibsane-type diterpenes named 5-epi-vibsanin C, 5-epi-vibsanin H, 5-epi-vibsanin K, 18-O-methyl-5-epi-vibsanin K and 5-epi-vibsanin E have been isolated from the leaves of Viburnum awabuki (Caplifoliaceae). Their structures have been elucidated by analyses of spectroscopic data and comparison of their spectral data with those of the previously known seven-membered vibsane-type diterpenes. The occurrence of these seven-membered vibsane-type diterpenes with a cis relationship on the C-5 and C-10 positions in nature have been predicted by conformational analysis of vibsanin B, an eleven-membered vibsane-type diterpene. Vibsanin C, 5-epi-vibsanin C and 5-epi-vibsanin H exhibited moderate cytotoxic activities on KB cells.