Nondenaturing two-dimensional electrophoretic analysis of loop-sheet polymerization of serpin, squamous cell carcinoma antigen-2

Two homologous serine proteinase inhibitors (serpins), squamous cell carcinoma (SCC) antigen-1 and -2 were separated by nondenaturing two-dimensional electrophoresis combined with immunostaining to acquire further information on these proteins under physiological conditions. Polymers of SCC antigen-2 were detected in cytosolic extracts prepared from tumor tissues. The polymer formation of SCC antigen-2 was apparently decreased and the SCC antigen-2-synthetic peptide binary complexes were newly formed by the addition of synthetic peptide with sequences corresponding to residues from P14 to P2 in the reactive center loop of SCC antigen-2. On the other hand, the incubation with synthetic peptides having the sequence of the reactive center loop of SCC antigen-1 or antithrombin had no effect on polymerization of SCC antigen-2. These data suggest that the polymerization of SCC antigen-2 may occur spontaneously in vivo by the loop-sheet mechanism of serpin.     

Highly regioselective ring opening of epoxides with alcohols catalyzed by organotin phosphate condensates

Organotin phosphate condensates proved to catalyze the ring opening reaction of epoxides with alcohols in a highly regioselective manner.     

Regenerated protein fibers. I. Research and development of a novel solvent for silk fibroin

An alcoholic–aqueous solution of LiBr·H₂O is a useful solvent for silk fibroin, if the ratio of alcohol content to water content therein is 1 or more. The mixed solvents consisting of ethanol, water, and LiBr·H₂O showed a higher solubility if they contained a lesser amount of water. They further proved able to easily dissolve more than 20% by weight of silk fibroin. Solvents poorer in water content and richer in LiBr·H₂O showed a higher value of [η]; Huggins' coefficient of said solutions varied within a range 0.5–1.0, the minimum appearing at a water content of about 10% weight. Fibroin molecules remained stable in those solutions. The novel solvents for silk fibroin that have been developed by us are named “MU solvents,” by taking the initials in the names of Matumoto/Uejima. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1949–1954, 1997     

Solvent-induced crack growth in rubbery block polymers

The rapid cracking of lightly stressed rubbery block polymers of styrene and isoprene in certain liquids and vapors has been examined experimentally, by using model test pieces containing a single crack. Solvents which preferentially dissolve the rigid molecular end blocks rather than the rubbery center blocks are efficient cracking agents. The stress required for crack growth to occur is shown to be in accord with a simple energy criterion: the stored elastic energy must be sufficient to provide a characteristic energy for the newly formed surface. This characteristic energy ranges from values close to the surface energy of simple liquids up to about 100 times this value for thicker test pieces or slowly diffusing vapors, when some tearing of an incompletely swollen core is inferred. “Induction times,” before the initial crack starts to grow, are shown to be due to a progressive increase in stored energy under a constant stress as the material absorbs solvent and softens until the critical energy criterion is met. Thus, a timedependent fracture process is shown to be in accord with a constant energy criterion. Above the critical condition the rate of crack growth depends strongly upon stress, like tearing of amorphous elastomers, and the crack then accelerates rapidly.     

In vivo participation of artificial porphyrins in electron-transport chains: electrochemical and spectroscopic analyses of microbial metabolism

The effects of artificial porphyrins on the electron-transport chains of living microbes were investigated. The participation of porphyrins in the microbial electron-transport chains was demonstrated by spectroscopic and current-generation measurements. Large enhancement of the microbial current generation was accomplished by adding a cationic water-soluble manganese porphyrin as an electron mediator.     

Electronic state observation of inner organic thin films beneath electrodes: Fluorescence-yield X-ray absorption spectra of pentacene derivative films

The electronic states of inner organic thin films have been investigated by X-ray absorption spectroscopy (XAS) in a bulk-sensitive fluorescence-yield (FY) mode with theoretical analysis. The thin films of the synthesized pentacene derivative, i.e., 6,13-dihydrodiazapentacence (C₂₀N₂H₁₄), on SiO₂-covered Si substrates were fabricated and their morphology and crystallinity were characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis, respectively. The observed N K-edge FY-XAS spectra were different from the surface-sensitive XAS spectra measured in a partial-electron-yield (PEY) mode. The peaks on the FY-XAS spectra were well reproduced by the theoretical calculation of the unoccupied states of an HAPn molecule. In addition, the incident angle dependence of the FY-XAS spectra was consistent with the expected molecular orientation in the thin films. As a result, we successfully obtained the N and C K-edge FY-XAS spectra of the inner HAPn thin films even beneath Au electrodes.     

Electron transport and shell structures of single InAs quantum dots probed by nanogap electrodes

We have investigated electron transport and electron filling in single InAs quantum dots (QDs) using nanogap electrodes. Elliptic InAs QDs with diameter of 60/80 nm exhibited clear shell filling up to 12 electrons. Shell-dependent charging energies and level quantization energies for the s, p, and d states were determined from the addition energy spectra. Furthermore, it is found that the charging energies and the tunneling conductances strongly depend on the shell, reflecting that the electron wave functions for higher shells are more extended in space.     

A stable dialkylphosphinyl radical

Dialkylphosphinyl radical 1 was synthesized as thermally stable yellow crystals and found to be monomeric both in solution and in the solid state. EPR spectrum showed that the spin density of 1 is mainly localized on the 3p orbital of the dicoordinated phosphorus atom. A distinct absorption band due to the electronic transition from nonbonding electron pair orbital to singly occupied 3p orbital on the phosphorus atom of 1 was observed at 445 nm in solution. Phosphinyl radical 1 underwent facile reaction with carbon tetrachloride, hydrogen abstraction, and a unique reaction with a persistent radical, galvinoxyl, giving a cyclic phosphaalkene and a silylether.     

Kinetics of Spontaneous Bimetallization between Silver and Noble Metal Nanoparticles

A physical mixture of polymer‐protected Ag nanoparticles and Rh, Pd, or Pt nanoparticles spontaneously forms Ag‐core bimetallic nanoparticles. The formed nanoparticles were smaller than the parent Ag nanoparticles. In the initial process of this reaction, the surface plasmon absorption of Ag nanoparticles diminished and then almost ceased within one hour. Within several minutes, the decrease in Ag surface plasmon absorption could be analyzed by second‐order reaction. This reaction was accelerated with an increase of temperature and the energy gap in the Fermi level between Ag and the other metals. The activation energy (E_a) of this reaction could be determined. An electron transfer reaction from Ag to other metal nanoparticles was proposed as the initial interaction between these metal nanoparticles because the Fermi level of Ag is relatively high, and the electron transfer is possible in terms of energy. The Marcus plot between the rate constant and the driving force, roughly estimated from the work function of metals, and the observed E_a values reasonably explained the proposed electron transfer mechanism.