Enantioselective total synthesis of convolutamydines B and E

[reaction: see text] The first enantioselective total synthesis of convolutamydines B and E has been achieved using our vinylogous Mukaiyama aldol reaction. The synthesis features highly diastereoselective vinylogous Mukaiyama aldol reaction with isatin instead of aldehydes to construct a chiral center of convolutamydines. Additionally, the absolute configuration of natural convolutamydine B has been determined as R by its CD spectrum.     

Novel chiral selectors anchored on polydimethylsiloxane as stationary phases for separation of derivatized amino acid enantiomers by capillary gas chromatography

Six chiral selectors of S-(-)-t-Leu-cyclopropylamide, S-(-)-t-Leu-cyclopentylamide, S-(-)-t-Leu-cyclohexylamide, S-(-)-t-Leu-cycloheptylamide, S-(-)-t-Leu-cyclooctylamide, S-(-)-t-Leu-cyclododecylamide have been prepared and anchored individually through amide bonding to a polydimethylsiloxane functionalized with 2,2,2-trifluoroethyl ester groups by way of nucleophilic displacement reaction. The resulting chiral polysiloxanes have been provided as stationary phases for the separation of amino acid enantiomers by capillary GC. Amino acids were derivatized into N(O)-trifluoroacetyl isopropyl esters. Especially, polydimethylsiloxane anchored with S-(-)-t-Leu-cyclooctylamide was found to be efficient for the separation of aspartic acid (Asp) enantiomers. The method was applied to the estimation of ages from the extent of Asp racemization in human dentines.     

In situ observation of cell-detachment process initiated by femtosecond laser-induced stress wave

When a stress wave generated by focusing a femtosecond laser is loaded on an animal cell adhered on a substrate, the cell is detached from the substrate. There are two possible mechanisms for the cell detachment: (a) The cell is detached from a scaffold coated on a glass plate, and (b) the cell is detached from the glass plate with the scaffold. In this work, we have studied the cell-detachment mechanism by visualizing the scaffold with a fluorescence probe of quantum dots. When the cell was detached from the substrate, fluorescence from the scaffold simultaneously disappeared from the glass plate, although the scaffold was not irradiated by the laser. This indicates that detachment due to the stress wave is attributed to mechanism (a). On the other hand, when the cell was detached from the substrate by a trypsin treatment, the fluorescence from the scaffold remained, suggesting mechanism (b). By comparing both results, it is considered that physiological damage of the cell membrane during the detachment process by femtosecond laser-induced stress wave is less than that due to the trypsin treatment.     

Structure and excitation relaxation dynamics of dimethylanthracene dimer in a gamma-cyclodextrin nanocavity in aqueous solution

Dimethylanthracene (DMA), which exhibits almost no self-association in bulk organic solvents, forms a dimer and emits excimer-like fluorescence in a gamma-cyclodextrin nanocavity in a dilute aqueous solution. The 1Bb and 1La electronic transitions of the DMA dimer split by 2230 and 344 cm(-1), respectively, in a fluorescence excitation spectrum obtained with the excimer-like emission. From these energy splits, the structure of dimer in relation to a dielectric constant inside gamma-CD was discussed on the basis of atom-atom Lennard-Jones potential calculations including Coulombic interactions. Excitation relaxations of DMA in the presence of alpha-, beta-, and gamma-CDs in aqueous solutions were investigated by time-resolved fluorescence. The results suggest that both the hydrated and anhydrated species exist in the alpha- and gamma-CD complexes, while only the anhydrated species exists in the beta-CD complex.     

Local structural analysis of In-doped Bi2Se3 topological insulator using X-ray fluorescence holography

We performed X-ray fluorescence holography measurements on an In-doped Bi₂Se₃ topological insulator and obtained an in-plane atomic image in the vicinity of In. We found that atomic images at the positions of the first nearest neighbors (NNs) are very weak whereas those at the positions of the second and the third NNs are relatively strong. On the basis of the fact that In is half of the atomic number of Bi, we attributed the origin of this feature to the clustering of the In atoms in the Bi plane. We calculated the intensity of the atomic images and confirmed that the formation of In cluster results in a decrease by 30% in the first NN atomic image intensity. However, the decrease in the magnitude is not enough to explain the experimental results, suggesting another contribution such as the lattice distortions. The effect of the lattice distortion on the atomic image intensity is discussed on the basis of the simulation including the positional fluctuation of In atoms.     

Diode-pumped 65 fs Kerr-lens mode-locked Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramic laser

Diode-pumped Kerr-lens mode-locked laser operation of Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramics has been achieved; 65 fs pulses with an average power of 320 mW under 5 W of pump power were obtained at the center wavelength of 1032 nm. The spectral bandwidth and the time bandwidth product were 18.9 and 0.345 nm, respectively. To our knowledge, this is the first demonstration of a Kerr-lens mode-locked laser operation based on Yb(3+):Lu(2)O(3) ceramic.     

Investigation of the cosmetic ingredient distribution in the stratum corneum using NanoSIMS imaging

In order to understand the mechanisms of action of cosmetic ingredients, it is important to establish the distribution of the component agents within the epidermis of the skin. To date, time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been used to detect cosmetic ingredients in the skin. However, it is technically difficult to investigate the distribution of the agents in the stratum corneum using TOF-SIMS. Therefore, an analytical method with higher spatial resolution is required. In this study, we investigated an imaging analysis technique based on NanoSIMS to detect cosmetic ingredients in the skin. Pig skin was used as a model for human skin. The sample was treated with a cosmetic formulation containing ¹⁵N-labelled pseudo-ceramide (SLE). The sample was frozen with liquid nitrogen and cross-sections were cut using a cryomicrotome. As a result, the fine layer structure of the corneocytes was clearly observed by using NanoSIMS. Our studies indicate that SLE penetrates into the stratum corneum via an intercellular route. We conclude that application of NanoSIMS analysis can contribute to a better understanding of the function of cosmetic ingredients in the skin.