Takeshi Yoshimi

Involvement of Arg-328, Arg-334 and Arg-342 of DnaA protein in the functional interaction with acidic phospholipids

We reported previously that three basic amino acids (Arg-360, Arg-364 and Lys-372) of DnaA protein are essential for its functional interaction with cardiolipin. In this study, we examined the effect of mutation of some basic amino acids in a potential amphipathic helix (from Lys-327 to Ile-345) of DnaA protein on this interaction. ATP binding to the mutant DnaA protein, in which Arg-328, Arg-334 and Arg-342 were changed to acidic amino acids, was less inhibited by cardiolipin than that of the wild-type protein, as was the case for mutant DnaA protein with mutations of Arg-360, Arg-364 and Lys-372. A mutant DnaA protein with mutations of all six basic amino acids showed the most resistance to the inhibition of ATP binding by cardiolipin. These results suggest that Arg-328, Arg-334 and Arg-342, like Arg-360, Arg-364 and Lys-372, are also involved in the functional interaction between DnaA protein and acidic phospholipids.

Orientational Behavior of Ionic Liquid Crystal Polymers and Their Nonionic Family

Multilayered Langmuir-Blodgett (LB) films were prepared from the monolayers of an ionic liquid crystalline azo-polymer (IP-4) and a nonionic liquid crystalline azo-polymer (NP-4). The multilayer structures in the LB films were completely disturbed by UV light irradiation. However, the periodic layer orderings in the LB films were rebuilt upon a subsequent visible light irradiation. Although NP-4 exhibits a nematic phase in the bulk state at room temperature, the consequent double layered structure with a homeotropic alignment in the LB film of NP-4 was very similar to the smectic layered structures of IP-4.

Photorefractive effect of liquid crystalline polymers possessing azobenzene chromophores

A series of liquid crystalline polymers possessing azobenzene chromophores were synthesized, and in each polymer the photorefractive effect of the isotropic phase was investigated. The photorefractive effect was evaluated by a four-wave mixing experiment. The diffraction efficiency of a side-chain liquid crystalline polymer possessing chiral moieties was measured and compared with that of a polymer possessing achiral chromophores. Chiral polymers exhibited unusual electric-field dependence on diffraction efficiency. The effects of liquid crystallinity and chiral substituents on photorefractivity are discussed.

Second Harmonic Generation of Side Chain Polymer Liquid Crystals Possessing Asymmetric Carbon without Poling Treatment

Side-chain polymer liquid crystals that possess mesogenic donor-π-acceptor chromophores (azobenzene and stilbene derivatives) and a chiral unit were synthesized, and the efficiencies of the second harmonic generation (SHG) of these polymers were investigated. It was found that these polymers exhibited SHG susceptibility without the application of high voltage.

Hyperpolarizabilities and second harmonic generation of side-chain polymer liquid crystals possessing alkylsulfone-substituted stilbene and azobenzene chromophores

Abstract Side-chain polymer liquid crystals that possess mesogenic donor-π-acceptor chromophores (azobenzene and stilbene derivatives) were synthesized, and the efficiencies of second harmonic generation (SHG) were investigated. SHG susceptibility was found to be stabilized in liquid crystalline polymers. Hyperpolarizabilities (β) of chromophores of the polymers were also investigated by the hyper Rayleigh scattering method, and it was found that the β value of the polymers was nearly twice of that of the corresponding monomers. The magnitude of the β of polymers was affected by the length of the spacer unit that connects the chromophore (mesogen) to the polymer main chain.