H2 plasma development of X-ray imaged patterns on plasma-polymerized resists

An X-ray imaged pattern on a plasma-polymerized film was successfully developed by H₂ plasma etching. Plasma-polymerized MMA and 6FBMA were formed by using an inductively coupled argon flow type reactor. An X-ray imaged pattern on the film was attained through a knife-cut window of a gold plate. The X-ray was generated from a Cu target at 20 kV and main wavelength 1.54 Å. The pattern development was performed using a tubular type reactor with parallel plate electrodes. The quality of plasma-polymerized resists in an X-ray lithography was evaluated by comparing it with the conventional polymer in the dry and wet process, and the minimum dose rate for a visible pattern fabrication was measured to be 4.1 J/cm² for both resists in H₂ plasma etching development.     

Theoretical prediction of minima in association constants for complex formation between alkylviologens and indole derivatives in the presence of polyelectrolytes

Association constants K for the complexation between various alkylviologens (methyl, propyl, butyl, pentyl, and hexyl) and indole derivatives (acetate and butyrate) have been determined. The order of K values indicates the important role of hydrophobic interactions in aiding the formation of charge transfer complexes. Influences of two kinds of polyelectrolytes; i.e., potassium polystyrenesulfonate (KPSS, anionic) and 3,3-ionene (cationic) on the K values were also examined. KPSS decreased the K value but, interestingly, yielded a minimum, and the K value increased at high KPSS concentrations. The influence of the type of alkylviologen on the K versus [KPSS] plots was successfully understood by a theory of substrate partitioning between bulk water and the environment of the polymer.     

Reversible labeling of tyrosine residue in peptide using 4-fluoro-7-nitro-2,1,3-benzoxadiazole and N-acetyl-L-cysteine.

The reversible labeling of tyrosine (Tyr)-containing peptide, which involves detection and recovery, is described in this paper. The phenolic-OH in Tyr structure reacted with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) under a mild condition at room temperature in alkaline medium. The resulting derivative absorbed at around 280 nm and 380 nm. However, the fluorescence was very weak. The NBD moiety in the derivative was efficiently removed by the treatment of N-acetyl-L-cysteine (N-AcCys), and the original peptide before the labeling was completely recovered. The proposed procedure was successfully applied to the reversible labeling of N-terminal amine-blocked peptides, i.e., N-AcTyr-Val-Gly, Z-Glu-Tyr, Z-Phe-Tyr, N-Formyl-Met-Leu-Tyr, and N-AcArg-Pro-Pro-Gly-Phe-Ser-Pro-Tyr-Arg. Although the proposed method could not recover the N-terminal amine-free peptides without blocking, the selective detection and the recovery of Tyr-containing peptide fragments were possible by the combination with enzyme digestion. The reversible labeling of Tyr-containing peptide was demonstrated with [Tyr8]-bradykinin as a model for high-molecular-mass peptides and proteins. The peptide fragments containing NBD-O-Tyr moiety, obtained after the digestion, were easily discriminated from various peptides with the monitoring of UV and FL, because the target peptide did not fluoresce, but absorbed at both 280 nm and 380 nm. The peptide fragment containing Tyr was finally recovered from the de-labeling reaction with N-AcCys. The proposed method hence provides a novel technique for the reversible labeling of Tyr-containing peptides, which will enable the selective detection and the recovery of the original peptide.     

Intelligent drug delivery systems obtained by radiation

Radiation-induced polymerization of acryloyl-L-proline methyl ester, an -aminoacid-containing monomer, in the presence of a crosslinking agent and a hydrophilic monomer gave rise to polymer hydrogels whose water content at equilibrium was found to decrease as the swelling temperature increased. Some hydrogel samples were obtained with entrapped acetaminophen, an analgesic and antipyretic drug. It was ascertained that the release of the drug was controlled by both the hydrophilicity of the polymer matrices and the environmental temperature.     

Synthesis of 1-Substituted Benzimidazoles Using N,N'-Thionyldibenzimidazole or N-Chlorosulfinylbenzimidazole

N,N'-Thionyldiimidazole has been known as an imidazole transfer reagent^2–4 and form a new class of compound with a wide range of synthetic application. Continuing our studies on the imidazole transfer reaction, we succeeded with the benzimidazole transfer reaction using N,N'-thionyldibenzimidazole. The present communication deals with a new procedure providing 1-substituted benzimidazoles.     

Synthesis of thiosaccharides employing the Pummerer rearrangement of tetrahydrothiopyran oxides

The Pummerer rearrangement of 1-deoxy-5-thioglucopyranose derivatives carrying acetonides at the C3,4-positions proceeded regioselectively at the C1 position by treating with TFAA in the presence of pyridine. Studies employing deuterium-labelled derivatives revealed that the reaction was induced by E2 1,2-elimination of trifluoroacetic acid of the trifluoroacetoxy sulfonium intermediate. This methodology was applied to the synthesis of an isomaltotriose derivative consisting of 5-thioglucopyranoside units.     

A model calculation on the electronic structure of Ni-Cu and Pd-Ag alloys

The electronic structure of Ni-Cu and Pd-Ag alloy surfaces is investigated by the CNDO/2 tight-binding method. In both alloys, the VIIIB and IB metal atoms form the independent d sub-bands, which is qualitatively consistent with the calculations by the coherent-potential approximation and with photoemission spectroscopy experiments.     

A synthesis of (±)-brefeldin A

A macrolide antibiotic, brefeldin A, was synthesized from trans-4-oxocyclopentane-1,2-dicarboxylic acid in a stereoselective manner, the intermediary hydroxy acid being lactonized by the mixed 2,4,6-trichlorobenzoic acid anhydride—4-dimethylaminopyridine method.     

Oscillatory reactions in polymer systems

Modified Belousov–Zhabotinskii (BZ) oscillation reactions were studied in the systems of ferroin or tris(2,2′-bipyridyl)ruthenium(II) dichloride or the polymerized ruthenium complex as electron transfer agents and sulfuric acid or polyethylenesulfonic acid (HPES) as acidic media. HPES was a good acidic medium for the chemical oscillation in spite of a long induction period. Moreover, chemical oscillation was observed at low concentration of HPES, where no oscillation was observed in the solution of sulfuric acid. On the other hand, no oscillation was observed in the solution of polystyrenesulfonic acid (HPSS). These results were discussed from the standpoint of the nature of polyelectrolytes.