Enhancing effect of phenylboronic acid compounds and their interactions with the diol groups of saccharides in a capillary electrophoresis-chemiluminescence detection system.

In our previous study, we proposed molecular recognition of mono- and disaccharides making use of the interaction between their diol groups and p-iodophenylboronic acid in capillary electrophoresis with a chemiluminescence detection system. Here, to extend our knowledge of molecular recognition, we first examined the enhancing effects of four phenylboronic acid compounds other than p-iodophenylboronic acid i.e., 4-biphenylboronic acid, 4-octyloxyphenyl-boronic acid, 3-octyloxyphenylboronic acid, and 4-dodecyloxyphenylboronic acid, for luminol-hydrogen peroxide-horseradish peroxidase reaction in the capillary electrophoresis-chemiluminescence detection system. Only 4-biphenylboronic acid showed an enhancing effect similar to that of p-iodophenylboronic acid; the effect was determined over the range of 0.5-10 microM in this system. Second, we estimated the apparent stability constants between the diol groups of saccharides (1-methyl-D-glucoside, D-saccharose, and D-fructose) and the boronic acid moieties of the two enhancers, p-iodophenylboronic acid and 4-biphenylboronic acid. The apparent binding constants obtained here provided insight to confirm the principle of molecular recognition for the saccharides examined here.     

Detecting a sodium chloride ion pair in ice using terahertz time-domain spectroscopy.

The hydrogen bond resonance of a sodium chloride (NaCl) ion pair trapped in aqueous ice has been observed by transmission terahertz time-domain spectroscopy. The absorption peak of a sodium chloride ion pair in ice is 1.65 THz at 83 K. By investigating the interaction of the cation and anion with other chemical compounds, we deduce that the absorption peak originates from the hydrogen bond resonance of sodium chloride and water molecules. The charge redistribution that occurs when other ion pairs are added to aqueous salt solution changes the absorption spectrum. Furthermore, the results also indicate that simple molecules such as sodium halides have fingerprints in the terahertz region when the ions are trapped in ice. NaCl ion pairs in seawater and in Ringer's solution were examined.     

Solubility enhancement for poly(amic acid)s by rapid hydrolysis of the polymer main chain during alkaline development

In an alkaline developer carboxyl containing polymer films possess a higher critical carboxyl group concentration (CGC₀) below which dissolution does not occur, compared with novolac resins; therefore, it is difficult to obtain the polymer film with a lower dissolution rate and less swelling. We describe herein a new approach for reducing CGC₀ of carboxyl containing polymers by introducing an ester group which is labile in the alkaline developer within the time‐scale of development to obtain the polymers with moderate dissolution rates and less swelling. The rapid hydrolysis that leads to polymer degradation is clearly verified by gel permeation chromatography (GPC).     

Facile Multiple Alkylations of C60 Fullerene

The reduction of fullerene (C₆₀) with sodium dispersion in the presence of an excess amount of dipropyl sulfate was found to yield highly propylated fullerene, C₆₀(nC₃H₇)_n (max. n = 24), and C₆₀(nC₃H₇)₂₀ was predominantly generated as determined by mass spectroscopy.     

Determination of oxytetracycline in blood serum by high-performance liquid chromatography with direct injection.

A direct injection analysis by high-performance liquid chromatography has been developed for oxytetracycline in serum of animals and fish. A Hisep shielded hydrophobic phase column (15 cm x 4.6 mm I.D.) and a mobile phase of methanol-0.2 M oxalic acid (10:90, v/v, pH 7.0) with ultraviolet detection at 360 nm were used. The standard calibration curves in serum of chicken, hog, cattle and rainbow trout were linear over the range 0.1-20 micrograms/ml. The recoveries of oxytetracycline from all serum samples determined at two different concentrations (0.5 and 2.0 micrograms/ml) were 88-103%. The detection limit was 0.05 micrograms/ml for every serum sample.     

Electrical resistance of a monatomic step on a crystal surface

We have succeeded in measuring the resistance across a single atomic step through a monatomic-layer metal on a crystal surface, Si(111)(sqrt[3]xsqrt[3])-Ag, using three independent methods, which yielded consistent values of the resistance. Two of the methods were direct measurements with monolithic microscopic four-point probes and four-tip scanning tunneling microscope probes. The third method was the analysis of electron standing waves near step edges, combined with the Landauer formula for 2D conductors. The conductivity across a monatomic step was determined to be about 5 x 10(3) Omega(-1) m(-1). Electron transport across an atomic step is modeled as a tunneling process through an energy-barrier height approximately equal to the work function.