Organic Memory Device Based on Carbazole‐Substituted Cellulose

A novel functionalized cellulose derivative, 6‐O‐[4‐(9H‐carbazol‐9‐yl)butyl]‐2,3‐di‐O‐methyl cellulose, has been synthesized and characterized. The photoluminescence spectrum of the as‐cast film of the cellulose derivative exhibits sharp peaks with a well‐defined vibronic structure, which indicates that the interaction between carbazole groups is rather weak. This is in contrast to the broad spectrum of a poly(N‐vinylcarbazole) thin film. A thin‐film device, where the cellulose derivative is sandwiched by two different metals, shows a drastic transition between low‐ and high‐conductivity states upon the forward and backward sweeping of an external electric field. This reversible current density transition behavior demonstrates a typical memory characteristic, with the ON/OFF (high‐ and low‐conductivity) states exhibiting a current ratio of about four orders of magnitude. The cellulose derivative with a functional group such as a carbazole moiety will be a candidate for organic electronic materials.

     

Photo-Deformation of Syndiotactic Polystyrene Gels

We report a usual and novel phenomenon that an excitation light beam of a spectrofluorometer produced a black mark in gels of syndiotactic polystyrene (SPS). This mark whose shape is identical with that of an excitation light beam was found to appear in SPS/chloroform gel just after only irradiation at 260 nm for 5 to 10 min. The heating of the gel with the mark at 80°C diminished the mark and recovered uniformly the gel to be as it had been before irradiation. We discuss what the black mark is and why it is produced by light irradiation.     

Stereocontrolled Synthesis of (11Z)-Retinal and Its Analogues

Suzuki coupling of stereochemically pure (Z)-bromotetraene 1 —which is extremely unstable but can be kept in frozen benzene in the presence of a small amount of PPh₃ at &sminus 01;20°C—and (Z)-alkenylboronic acid 2 provides the stereocontrolled synthesis of (11Z)-retinal 3 . The 11Z configuration, which is introduced by selective catalytic debromination of the corresponding dibromo precursor of 1 , is retained in this step. TBDMS = tBuMe₂Si.     

Organic Solvent‐Free Enzymatic Transformation of Poly(ϵ‐caprolactone) into Repolymerizable Oligomers in Supercritical Carbon Dioxide

The enzymatic transformation of poly(ϵ‐caprolactone) (PCL) into repolymerizable oligomers in supercritical carbon dioxide (scCO₂) using an enzyme was carried out in order to establish a sustainable chemical recycling system for PCL, which is a typical biodegradable synthetic plastic. The enzymatic conversion of PCL beads having an M̄_n of 110 000 using Candida antarctica lipase (lipase CA) in scCO₂ containing small amounts of water quantitatively afforded CL oligomers at 40°C. The CL oligomers were readily repolymerized using the same enzyme to produce high‐molecular weight PCL.     

Efficient Multiple Domain Ligation for Proteins Using Asparaginyl Endopeptidase by Selection of Appropriate Ligation Sites Based on Steric Hindrance

Three domain fragments of a multi-domain protein, ER-60, were ligated in two short linker regions using asparaginyl endopeptidase not involving denaturation. To identify appropriate ligation sites, by selecting several potential ligation sites with fewer mutations around two short linker regions, their ligation efficiencies and the functions of the ligated ER-60s were examined experimentally. To evaluate the dependence of ligation efficiencies on the ligation sites computationally, steric hinderances around the sites for the ligation were calculated through molecular dynamics simulations. Utilizing the steric hindrance, a site-dependent ligation potential index was introduced as reproducing the experimental ligation efficiency. Referring to this index, the reconstruction of ER-60 was succeeded by the ligation of the three domains for the first time. In addition, the new ligation potential index well-worked for application to other domain ligations. Therefore, the index may serve as a more time-effective tool for multi-site ligations.