Cleavage of vinyl carbon-silicon bond with tetrabutylammonium fluoride

Dimethylphenylsilyl group is removed from a vinyl carbon with tetrabutylammonium fluoride. The presence of phenyl group on silicon atom plays a critical role. The cleavage of allyldimethylsilyl- and alkoxydimethylsilyl groups also proceeds very easily.     

Terahertz time-domain attenuated total reflection spectroscopy in water and biological solution

We demonstrate time-domain attenuated total reflection spectroscopy in terahertz frequency region. Geometry of the reflection measurement is well optimized to obtain accurate optical constants of water or aqueous biomolecular system. We determine the dielectric constants of distilled water and sucrose solutions with this technique. This technique will open new aspects in the research field of biological systems in water.     

Periodic-orbit bifurcation and shell structure at exotic deformation

We have investigated the semiclassical origin of superdeformed shell structure and also of reflection-asymmetric deformed shapes by means of the periodic orbit theory and the deformed cavity model. Systematic analysis of the quantum-classical correspondence reveals that bifurcation of equatorial orbits into three-dimensional ones play predominant role in the formation of these shell structures. Presented by K. Matsuyanagi at the International Conference on “Atomic Nuclei and Metallic Clusters”, Prague, September 1–5, 1997.     

Horse liver alcohol dehydrogenase-catalyzed enantioselective reduction of cyclic ketones: The effect of the hydrophobic side chain of the substrate on the stereoselectivity of the reaction

Horse liver alcohol dehydrogenase (HLADH)-catalyzed enantioselective reductions of alkyl 3-oxocyclopentanecarboxylates, endo-5-acyloxybicyclo[2.2.1]heptan-2-ones and exo-5-acyloxybicyclo[2.2.1]heptan-2-ones gave the corresponding homochiral alcohols and ketones and the interaction between the hydrophobic side chain of the substrate and the hydrophobic zone in the active site played an important role in the specificity of the reduction. The stereoselectivities of the reactions were interpreted on the basis of the cubic space section model and a new rule, which contributes to development of a specificity analysis on the basis of the model, is introduced.     

Almost Total Elementary Maps

A partial map f of a structure M is called almost total if |M — dom(f)| = |M — ran(f)| < ω. We study a difference between an almost total elementary map and an automorphism.     

Switching characteristics of the triggered vacuum gap for ahigh-repetition-rate pulse-power source

Switching characteristics of sealed-off triggered vacuum gaps (TVGs) were examined from the viewpoint of a high repetition rate at high current discharge. With a triggered energy of 11 J, it was possible to fire the main gap in both the anode and cathode modes of operation. In repetitive discharge experiments, the TVG-tube was put in the center of the cylindrical conductor and the switching tube inductance was about 27 nH. The TVG-tube was confirmed to have capabilities for 1000 shots with a pulse current of 120 kA and a high repetition rate of 5 Hz. These experimental results indicated that the TVG-tube is a potential repetitive closing switch for the plasma X-ray source     

Pd(O) promoted transformation of N-tosyl-2-(1,3-butadienyl)-aziridine into N-tosyl-2-vinyl-3-pyrroline

1,3-Butadienylaziridines activated by N-tosyl group smoothly rearrange to vinylpyrrolidine derivatives in the presence of a catalytic amount of Pd(PPh₃)₄. Transformation of dienylazetidines into vinylpiperidine derivatives is also described.     

Electron transfer reaction in a single protein molecule observed by total internal reflection fluorescence microscopy

To observe an electron transfer (ET) process in a single protein molecule, we constructed a model system, Alexa-HCytb5, in which cytochrome b5 (Cytb5) is modified with a fluorescent probe, Alexa Fluor 647 dye. In this model system, intramolecular transfer of an electron from the Alexa dye to heme in Cytb5 is supposed to oxidize the probe and quench its fluorescence, and the ET reaction at the single-molecule level can be monitored as the intermittent change in the fluorescence intensity. Alexa-HCytb5 was fixed on the glass surface, and illumination of laser light by the total internal reflection resulted in blinking of the fluorescence from the single Alexa-HCytb5 molecule in the time scale of several hundred milliseconds. Each Alexa-HCytb5 molecule is characterized by its own rate constant of the blinking, corresponding to the ET rate constant at the single-molecule level, and its variation ranges between 1 and 10 s(-1). The current system thus enables us to visualize the ET reaction in the single protein molecule, and the protein ET reaction was found to be explained by the distribution of the rate constants. On the basis of the Marcus theory, we suggest that the origin of this rate distribution is the distance change associated with the structural fluctuation in the protein molecule.