Fabrication of platy apatite nanocrystals loaded with TiO2 nanoparticles by two-step emulsion method and their photocatalytic activity

Nanometer-sized TiO(2) island structure on the platy hydroxyapatite nanocrystals (HAp) has been accomplished by two-step emulsion process. At the first step, platy HAp nanocrystals, of which size was in the range of 70-200 nm after heat-treatment at 1078 K for 1 h, were prepared using the W/O emulsion system. Before the second step, HAp nanocrystals were immersed in NaH(2)PO(4) solution for the formation of hydroxyl group on their surface. In the following, titanium tetraisopropoxide reacted with the hydroxyl group of HAp surface to form TiO(2) nanoparticles on the surface of HAp nanocrystals, which were dispersed in the micrometer-sized methanol droplets of polyethylene cetylether-cyclohexane mixture (methanol/oil emulsion). The resulting hydroxyapatite nanocrystals loaded with TiO(2) nanoparticles showed the high photocatalytic activity comparing to the commercial TiO(2) catalyst.     

Dynamical visualization of "coffee stain phenomenon" in droplets of polymer solution via fluorescent microscopy

In the drying process of polymer solution droplets, we propose an experimental procedure for visualizing the solute concentration profile by combining the fluorescent microscopy with the lateral profile observation. We have conducted a dynamical observation of the transport process of the solute polymer toward the edge that causes the "coffee stain phenomenon". We have found that the polymer concentration increases sharply near the edge, while it remains almost constant in the central region until the last stage of drying. The method is useful to understand the dynamical process that occurs near the contact line.     

Highly effective and reversible control of the rocking rates of rotaxanes by changes to the size of stimulus-responsive ring components

We have designed and synthesized rotaxanes whose rates of rocking motion (pendular motion) were switched reversibly through changes to the size of the ring component in response to external stimuli. The ring molecules of the rotaxanes incorporate a metaphenylene unit, which swings like a pendulum, and a dianthrylethane unit, which undergoes reversible isomerization in response to photo- and thermal stimuli and changes the size of the ring component. The rocking rates were estimated quantitatively by variable-temperature (VT) NMR spectroscopy and saturation transfer experiments, which revealed substantial changes in the rates between the open and closed forms, particularly in the case of rotaxanes with an isopropoxy group attached to a phenylene unit.     

Combinatorial synthesis of RGD model cyclic peptides utilizing a palladium-catalyzed carbonylative macrolactamization on a polymer support

A combinatorial synthesis of 24-member RGD models was accomplished on polymer-support. Ortho-, meta-, and para-iodobenzylamines loaded on an aldehyde linker by reductive amination were coupled with RGD sequences and various omega-amino acids by a split-and-pool method. Palladium-catalyzed carbonylative macrolactamization of the polymer-supported cyclization precursors, followed by acid cleavage, provided conformationally restricted RGD model cyclic peptides.     

A synthesis of RGD model cyclic peptide by palladium-catalyzed carbonylative macrolactamization

Cyclic peptidic RGD models were efficiently synthesized by Pd(P(t-Bu)3)2-catalyzed carbonylative macrolactamization in the presence of 4 A molecular sieves under 10 atm of carbon monoxide.     

Preparation of highly photosensitizing liposomes with fullerene-doped lipid bilayer using dispersion-controllable molecular exchange reactions

Fullerene-containing liposomes with high photosensitization ability were prepared. Disaggregated fullerenes were efficiently injected into the bilayer of liposomes by a phototriggered molecular exchange reaction. These liposomes showed far higher photoreactivity than liposomes thermally produced by heating and microwave irradiation. This result indicates that control of self-aggregation of fullerene leads to a high quantum yield for the photoreaction because of the suppression of self-quenching of photoexcited fullerenes.     

Rational design of proteolytically stable, cell-permeable Peptide-based selective mcl-1 inhibitors

Direct chemical modifications provide a simple and effective means to "translate" bioactive helical peptides into potential therapeutics targeting intracellular protein-protein interactions. We previously showed that distance-matching bisaryl cross-linkers can reinforce peptide helices containing two cysteines at the i and i+7 positions and confer cell permeability to the cross-linked peptides. Here we report the first crystal structure of a biphenyl-cross-linked Noxa peptide in complex with its target Mcl-1 at 2.0 ? resolution. Guided by this structure, we remodeled the surface of this cross-linked peptide through side-chain substitution and N-methylation and obtained a pair of cross-linked peptides with substantially increased helicity, cell permeability, proteolytic stability, and cell-killing activity in Mcl-1-overexpressing U937 cells.     

DNA-templated assembly of naphthalenediimide arrays

π-Stacked naphthalenediimide (NDI) arrays are of interest as charge-transport materials. We have designed and synthesized an NDI derivative with two Zn(II)-cyclens that act as receptors for the thymine base in DNA. UV/Vis and CD spectroscopy, gel filtration, and molecular-modeling studies have shown that the bis(Zn(II)-cyclen)-NDI can be assembled in the presence of oligo-dT to form π-stacked NDI arrays. The assembly of the NDI arrays was found to be dependent on the length of the oligo-dT and the temperature. The NDI-oligo-dT assembly on a gold substrate exhibits photocurrent responses due to electron transfer through the π-stacked array.     

Use of dimethyl carbonate as a solvent greatly enhances the biaryl coupling of aryl iodides and organoboron reagents without adding any transition metal catalysts

The coupling reaction of aryl iodides with arylboronic acids to give biaryl compounds can be efficiently performed without adding a transition metal catalyst. The key to success is the use of dimethyl carbonate as a solvent. This finding provides a new strategy for constructing a biaryl linkage.     

Photo-triggered generation of a free thiol group on DNA: application to DNA conjugation

DNA oligomers possessing a 2-nitrobenzyl (NB) protected thiol group have been prepared. The photo-remove of the NB to generate a free thiol group in DNA has been analyzed by using reverse-phase HPLC and denaturing gel electrophoresis. The photo-triggered generation of the thiol function in DNA was applicable in the light-initiated ligation of thiol-modified DNA oligomers and Au–DNA conjugation.