Dispersion stability of TiO2 nanoparticles covered with SiOx monolayers in water

The repetition of a two-step route consisting of chemisorption of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) and its subsequent photooxidation has formed SiOx monolayers on the surfaces of TiO2 particles layer by layer (SiOx(n < or = 4)/TiO2, n = repeated number). The trace of these processes using diffuse reflectance FT-IR and solid-state 29Si NMR spectroscopy reveals that TMCTS is chemisorbed on TiO2 through Ti-O-Si bonds followed by growth of Si-O-Si networks via dehydration-condensation of the Si-OH groups generated by TiO2 photocatalytic oxidation of the Si-H and Si-CH3 groups. The point of zero charge of the TiO2 particles decreases from 6.5 to 5.4 at n = 1, reaching 4.9 at n2. As a result of coverage with the SiOx monolayers, the dispersion stability of TiO2 particles in neutral water is significantly improved without changing their optical properties. The dispersion stability further increases with accumulation of SiOx monolayers.     

Synthesis of N-protected staurosporinones

We report a method for the synthesis of N-protected staurosporinones, which are useful for the synthesis of indolo[2,3-a]pyrrolo[3,4-c]carbazole alkaloids and related compounds. An interaction of gramine methiodide (2) with 3-(N-benzyl)indolylacetonitrile (3) in the presence of t-BuLi, followed by a CF3COOH-catalyzed intramolecular indole-indole coupling and dehydrogenation with DDQ, produced 5-cyanoindolo[2,3-a]carbazole 6 almost quantitatively. Reduction of its cyano group followed by N-benzylation produced N-benzylaminomethylindolo[2,3-a]carbazole 8b, which was subjected to Pd(OAc)2-catalyzed direct aromatic carbonylation to give N-protected staurosporinone 9b. Treatment with AlCl3 in anisole removed N-benzyl groups to afford staurosporinone quantitatively.     

Filter paper degrading ability of a Trichoderma strain with multinucleate conidia

The multinucleate conidia were produced from the green mature conidia of Trichoderma reesei Rut C-30 strain by colchicine treatment. The strain with higher Filter paper degrading ability was selected among those conidia using a double layer selection medium. The selected strain, JS-2 was able to collapse the filter paper within 15 min but the original strain took 25 min to collapse it completely. Moreover, the amount of reducing sugar in the L-type glass tube of the strain, JS-2 was greater than that of the original strain. The Avicel, CMC-Na, and Salicin hydrolyzing activity of the strain, JS-2, increased 2.1 times, 1.2 times, and 3.6 times higher than that of the original strain.     

Hydration changes of poly(2-(2-methoxyethoxy)ethyl methacrylate) during thermosensitive phase separation in water

Hydration changes of poly(2-(2-methoxyethoxy)ethyl methacrylate) (PMoEoEMa) during thermosensitive phase separation in water have been investigated by infrared spectroscopy. The C=O stretching band can be separated into three components assigned to non-hydrated carbonyl groups and singly and doubly hydrogen-bonded carbonyl groups (1728, 1709, and 1685 cm-1, respectively). Relatively large parts of the carbonyl groups (50% in 30 wt % solution) do not form hydrogen bonds even below the transition temperature (Tp) probably because they possess crowded positions near the backbone. The fraction of hydrogen-bonding carbonyl groups decreased during phase separation by approximately 0.2. Among five nu(C-H) bands, the highest- and the lowest-frequency bands (nu(C-H)A and nu(C-H)E) exhibited relatively large red shifts of 8 and 11 cm(-1), respectively. DFT calculations indicate that the formation of a H-bond between the ether oxygen and water leads to blue shifts of nu(C-H) of adjacent alkyl groups and has a larger effect than a direct H-bond to the alkyl groups, namely, C-H...O H-bonds. The fraction of hydrogen-bonding methoxy oxygens estimated from the position of the nu(C-H)A is 1 at Tp. This result indicates that the methoxy oxygens and the carbonyl are more favorably hydrated than the other at Tp, respectively.     

In situ conductance measurements for alignments of silica particles under alternating electric fields

The alignments of silica particles formed in sinusoidal electrical fields of 1 kHz were assessed using an optical microscope with measuring the electric conductance of a silica dispersion between two Pt electrodes in a vitreous silica glass cell. We confirmed that the electric conductance of the silica dispersion between the two electrodes in the cell reflected the surface conductance of the silica particles settling at the bottom of the cell. More interestingly, we observed that the electric conductance of the silica dispersion in the cell increased when pearl chains of the silica particle were formed along the direction of the electric field. However, no clear change in the electric conductance of the dispersion was observed at higher electric field strengths where a transition from pearl chains to zigzag band patterns and circulating movements of the silica particles in the zigzag bands formed.     

Thermoresponsive characteristics of fluoroalkyl end-capped co-oligomers in aqueous solutions and on the poly(methyl methacrylate) film surface

Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide--acryloylmorpholine co-oligomers were prepared by the co-oligomerizations of fluoroalkanoyl peroxides with the corresponding monomers. These fluorinated co-oligomers exhibited a lower critical solution temperature (LCST) characteristic in aqueous solutions. Of particular interest, a steep time dependence of contact angle values for dodecane was observed from 40 to 60 degrees C to decrease their values, effectively, on the modified PMMA [poly(methyl methacrylate)] film surface treated with fluorinated co-oligomer possessing the LCST: 36 degrees C (in water), although such a steep time dependence was not observed from 20 to 30 degrees C.     

Aplyronine A, a potent antitumor macrolide of marine origin, and the congeners aplyronines B and C: isolation, structures, and bioactivities

Aplyronine A (2), a potent antitumor macrolide was isolated from the sea hare Aplysia kurodai together with the congeners aplyronines B (3) and C (4). The absolute stereostructure of aplyronine A (2) was determined by the instrumental analysis (mainly NMR and MS) and the enantioselective synthesis of the fragments obtained from chemical degradation of aplyronine A (2). The structures of aplyronines B (3) and C (4) were also elucidated. Cytotoxicity and antitumor activity of aplyronine A (2) were evaluated.     

Selective Cadmium Fluorescence Probe Based on Bis-heterocyclic Molecule and its Imaging in Cells

Journal of Fluorescence - Fluorescence probes that selectively image cadmium are useful for detecting and tracking the amount of Cd2+ in cells and tissues. In this study, we designed and...     

Computation of high Reynolds number flow around a circular cylinder with surface roughness

Incompressible high-Reynolds-number flows around a circular cylinder are analyzed by direct integration of the Navier-Stokes equations using finite-difference method. A generalized coordinate system is used so that a sufficient number of grid points are distributed in the boundary layer and the wake. A numerical scheme which suppresses non-linear instability for calculations of high-Reynolds-number flows is developed. The computation of an impulsively started flow at Re = 1200 is compared with corresponding experimental observations, and excellent agreements are obtained.A series of computations are carried out on the flow around a circular cylinder with surface roughness. The height of the roughness in these computations is 0.5% of the diameter. The range of Reynolds numbers is from 10³ to 10⁵; no turbulence model is employed. Sharp reduction of drag coefficient is observed near Re = 2 × 10⁴, which indicates that the critical Reynolds number is captured in the present computation.     

Tuning of the methylimidazolium/imidazole balance in polycations for gene carrier

The chemical structure of methylated poly(1‐vinylimidazole) (PVIm‐Me) has been tuned for gene carrier properties, which are cell viability, the stability of its DNA polyion complexes, and gene expression. The resulting PVIm‐Me with lower methylation degree (6 and 20 mol%) exhibited no significant cytotoxicity, as compared with 40 mol% PVIm‐Me, in spite of the same concentration and chemical structure of positive charges. The DNA complex with 20 mol% PVIm‐Me stably retained the DNA, as compared with 6 or 40 mol% PVIm‐Me, which was examined by competitive exchange with dextran sulfate. As a result, the DNA complex with 20 mol% PVIm‐Me mediated most efficient gene delivery, where the resulting transfection activity was higher than that mediated by a positive control, poly(ethylenimine). These results suggest that the optimization of the balance of the methylimidazolium and the imidazole groups of PVIm‐Me is essential for gene carrier design. Copyright © 2014 John Wiley & Sons, Ltd.