The Effects of Side-Chain Configurations of a Retro–Inverso-Type Inhibitor on the Human T-Cell Leukemia Virus (HTLV)-1 Protease

In this study, the effects of side-chain configurations of D-Ile residues of a retro–inverso (RI)-type inhibitor on the human T-cell leukemia virus type 1 (HTLV-1) protease containing a hydroxyethylamine dipeptide isostere were clarified. Prior to evaluation using the RI-type inhibitor, the effects of side-chain configurations of Ile residues of the substrate peptide on the HTLV-1 protease were examined to estimate the influence of side-chain configurations on enzyme activity. Based on the estimation of the influence of side-chain configurations on protease affinity, the RI-type inhibitors containing a D-allo-Ile residue in the corresponding substrate sequence, instead of a D-Ile residue, were synthesized via 9-fluorenylmethoxycarbonyl-based solid-phase peptide synthesis. Refolded recombinant HTLV-1 protease (1-116, L40I) was used for the simple and short evaluation of the inhibitory activities of the synthesized RI-type inhibitors. The results clearly indicated that mimicking the whole topology, comprising both the main- and side-chain structures of the parent inhibitor, is effective for the design of potent RI-modified protease inhibitors.     

A deprotection procedure using SO3H silica gel to remove non-silyl protecting groups

Protecting groups are indispensable in organic synthesis and there is a great need for a variety of deprotection methods. Here, we investigated the scope of the application of a deprotection procedure using SO₃H silica gel, which we have previously reported as a desilylation procedure. Under these conditions, -OMOM, -OSEM, -OTHP, and -OAc groups and dimethyl acetal were cleaved. Pivaloyloxy, benzyloxy and methoxy carbonyl groups remained intact and selective deprotection of TBS groups in the presence of other protecting groups was accomplished. We succeeded in cleaving an acetyl group on a secondary alcohol in a highly polar nortropine derivative. Our findings here provide another deprotection option and would be helpful in the synthesis of multifunctional compounds.     

N-Arylated pyridinium salts having reactive groups

The pyridinium salts having reactive amine and/or pyridyl groups were obtained by the reaction using Zincke salts. Optical properties and anion exchange behavior of the obtained pyridinium salts were investigated.     

A design for pseudo-Anosov braids using hypotrochoid curves

We make use of hypotrochoid curves to propose mixing devices with simple mechanism, which gives pseudo-Anosov mixings. We exhibit some experiments to see the efficiency of the device.     

The Effect of Lithium Doping in Solution-Processed Nickel Oxide Films for Perovskite Solar Cells

The effect of substitutional Li doping into NiO_x hole transporting layer (HTL) for use in inverted perovskite solar cells was systematically studied. Li doped NiO_x thin films with preferential crystal growth along the (111) plane were deposited using a simple solution-based process. Mott-Schottky analysis showed that hole carrier concentration (N_A) is doubled by Li doping. Utilizing 4 % Li in NiO_x improved the power conversion efficiency (PCE) of solar devices from 9.0 % to 12.6 %. Photoluminescence quenching investigations demonstrate better hole capturing properties of Li:NiO_x compared to that of NiO_x, leading to higher current densities by Li doping. The electrical conductivity of NiO_x is improved by Li doping. Further improvements of the device were made by using an additional ZnO layer onto PCBM, to remove shunt paths, leading to a PCE of 14.2 % and a fill factor of 0.72.     

Theoretical investigation of the excited states of coumarin dyes for dye-sensitized solar cells

Using time-dependent density functional theory (TD-DFT), configuration interaction single (CIS) method, and approximate coupled cluster singles and doubles (CC2) method, we investigated the absorption spectra of coumarin derivative dyes (C343, NKX-2388, NKX-2311, NKX-2586, and NKX-2677), which have been synthesized for efficient dye-sensitized solar cells. The CC2 calculations are found in good agreement with the experimental results except for the smallest coumarin dye (C343). TD-DFT underestimates the vertical excitation energy of the larger coumarin dyes (NKX-2586 and -2677). Solvents (methanol) are found to induce a red shift of the vertical excitation energies, and their effects on the molecular geometry and the electronic structure are examined in detail. The deprotonated form of coumarin is also investigated, where a blue shift of the vertical excitation energies is observed.     

Synthesis of (±)-cyclic dehypoxanthine futalosine, the biosynthetic intermediate in an alternative biosynthetic pathway for menaquinones

The first synthesis of (±)-cyclic dehypoxanthine futalosine (cyclic DHFL), a biosynthetic intermediate in the futalosine pathway for menaquinones operating in microorganisms, has been achieved. Efficient growth of the Streptomyces coelicolor mutant, which lacks the cyclic DHFL synthetase gene (mqnC gene) was observed in the presence of synthetic (±)-cyclic DHFL.     

Hydrodynamic control of droplet division in bifurcating microchannel and its application to particle synthesis

We describe herein a microfluidic system for active and precise control of droplet division at a bifurcation point in a microchannel. Water-in-oil or oil-in-water droplets, which were initially formed at a T-junction, were introduced into the bifurcation point, and then divided into two daughter droplets. By continuously introducing 'tuning flow' into the downstream of one of the branch channels, and by controlling the flow rates distributed into the two branch channels, the sizes of the daughter droplets could be precisely tuned. The ratio of the volumetric flow rates into the branch channels was estimated by regarding the microchannel network as a resistive circuit. In addition, we performed synthesis of monodispersed polymer particles with controlled sizes utilizing the presented system. The ability to hydrodynamically control the droplet sizes will open new possibilities not only for producing useful emulsions, but also for conducting controlled chemical and biochemical reactions in a confined space.     

Conformational effects in acid-mediated ring opening of epoxides: a prominent role of the oxirane Walsh orbital

A kinetic study has been made of the BF(3)-mediated ring opening of two rigid conformers (alpha and beta) of m- and p-dimethyl-substituted homobenzoquinone epoxides spiro-linked with a twist-boat dibenzocycloheptene ring as compared with the conformationally mobile epoxides bearing diphenyl groups. The rates of the regioselective ring opening were dependent on the topological alignment of the dibenzocycloheptene ring as well as the substitution pattern of the quinone dimethyl groups, indicating pi-aryl participated orbital interaction with the vacant Walsh orbital of the oxirane ring.     

Mechanistic evidence for remote pi-aryl participation in acid-catalyzed ring opening of homobenzoquinone epoxides

The acid-induced reaction of bis(p-chlorophenyl)homobenzoquinone epoxide gave the dual ipso/ortho intramolecular S(E)2-Ar products associated with pi-aryl participated oxirane ring opening, whereas bis(p-tolyl)- and diphenyl-substituted homologues provided only the ortho products.