Oxidative decarboxylative synthesis of 2-H-imidazolines from glyoxylic acid and 1,2-diamines

A novel method to prepare 2-H-imidazolines from glyoxylic acid monohydrate and 1,2-diamines is described; the key reaction of this method is the oxidative decarboxylation of the 2-carboxy imidazolidines by NBS.     

Decelerated chirality interconversion of an optically inactive 3(10)-helical peptide by metal chelation

A dynamically optically inactive 3(10)-helical peptide possessing metal chelating ability between the side-chains at the i and i + 3th residues was synthesized, and its metal complexes were shown to stabilize the peptide structure and the helical sense.     

Temperature-sensitive nonionic vesicles prepared from Span 80 (sorbitan monooleate)

Different types of nonionic vesicles were prepared from commercial Span 80 (also called sorbitan monooleate), as an inexpensive, biocompatible alternative to conventional phospholipid-based vesicles (liposomes). The vesicles were characterized by different techniques and comparison was made with vesicles formed from POPC (1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine) or DOPC (1,2-dioleoyl- sn-glycero-3-phosphocholine). Dynamic light scattering measurements, electron microscopy analyses, and two types of fusion assays indicate that Span 80 vesicles are stable for at least 7 days at 4 or 25 degrees C, while storage at 42 degrees C causes irreversible vesicle fusion. This indicates that Span 80 vesicles are thermoresponsive with vesicle fusion occurring at elevated temperature. This property may be related to headgroup dehydration and is certainly not directly linked to the phase transition temperature (Tm) of the vesicles, since the Tm is below -30 degrees C, as determined by differential scanning calorimetry (DSC). The measured Tm value for Span 80 vesicles is lower than in the case of DOPC or POPC, correlating with a higher fluidity of Span 80 vesicles as compared to POPC or DOPC vesicles, as determined with DPH (1,6-diphenyl-1,3,5-hexatriene) as fluorescent membrane probe. High fluidity correlates with increased leakage of entrapped water-soluble dye molecules. Addition of cholesterol and soybean phosphatidylcholine lowers the extent of leakage, allowing a tuning of the bilayer permeability.     

Nanoscale assemblies of gigantic molecular {Mo154}-rings: (dimethyldioctadecylammonium)20[Mo154O462H8(H2O)70

Clusters based on the mixed-valence gigantic inorganic ring [Mo154O462H14(H2O)70]14- ({Mo154}-ring) and dimethyldioctadecylammonium (DODA) were combined to form novel molecular assemblies of an inorganic-organic hybrid molecular system as Langmuir-Blodgett (LB) and cast films. (DODA)20[Mo154O462H8(H2O)70] (2) was prepared by cation exchange and was characterized by a combination of thermogravimetry, IR, UV-vis-NIR, 1H NMR, and XRD measurements. The salt 2 was soluble in common organic solvents, and the chemical stability of {Mo154}-ring encapsulated by DODA cationic surfactants in CHCl3 was found to be higher than that of the "native" sodium salt of the {Mo154}-ring in H2O. Uniform spherical vesicle-like molecular assemblies of (DODA)20[Mo154O462H8(H2O)70] were observed in dilute THF, whose average diameter of 95 nm and a normalized variance of 5.7% were confirmed by a X-ray small-angle scattering. Deposition of 2 as a cast film showed circular domains with a typical diameter of approximately 100 nm, indicating possible similarities between solution and surface-deposited structures. The resulting LB films of salt 2 were transferred from an acidic buffer subphase with pH = 1.5 onto mica, giving a two-dimensional film surface with a unity transfer ratio. Further, the electronic absorption spectra of the LB multilayer were consistent with the classic type II mixed-valence MoV/MoVI electronic state well know for molybdenum blue {Mo154}-ring systems, and it appears that on the surface the plane of the {Mo154}-ring is approximately parallel to the substrate surface, as indicated by polarized electronic spectra, while the alkyl chains of DODA were relatively normal to the substrate surface. Therefore, the layer between the {Mo154}-rings and DODA cations was alternately stacked along the direction of film propagation. Finally, it was found that the surface morphology of the cast and LB films was determined by the molecular assembly of (DODA)20[Mo154O462H8(H2O)70] in solution and the air-water interface, respectively.     

Aggregation of amphiphilic pyranines in water: facile micelle formation in the presence of methylviologen

Four amphiphilic pyranines in which the acidic hydrogen of pyranine was replaced by an octyl, dodecyl, hexadecyl, and eicosyl group, POCn (n=8, 12, 16, and 20), were prepared, and their spectroscopic properties and aggregation behaviors in water were investigated. The critical micelle concentration (cmc) of the amphiphilic pyranines was found to be relatively large even in POC20 having a long hydrophobic alkyl chain (ca. 3x10(-3) M). 1H NMR studies revealed that POC16 and POC20 exist in the compact structure with the pyranine nucleus wrapped with a long methylene chain in water. As in the case of parent pyranine, the addition of methylviologen (MV2+) to an aqueous solution of POCn resulted in the absorption spectral change and efficient quenching of POCn fluorescence. In the case of POC8 and POC12, these spectral changes induced by the MV2+ addition were thoroughly explained in terms of the formation of the electrostatic complex POCn/MV2+ with a complexation constant of approximately 3x10(4) M(-1). On the other hand, an unexpectedly large dependence of the absorption spectral change, as well as fluorescence quenching, on the total concentration of MV2+ was observed in POC16 and POC20. The Stern-Volmer plot for quenching of the fluorescence of POC16 and POC20 gave a curve deviating largely upward from a straight line. The plot was successfully analyzed by the equation induced by assuming the aggregate formation of the complex POCn/MV2+, which revealed the considerably small cmc values of the complexes, 3.6x10(-7) and 3.6x10(-8) M for POC16/MV2+ and POC20/MV2+, respectively. Experimental evidence in support of the aggregate formation was obtained by 1H NMR and dynamic light scattering studies.     

Entrapping desired amounts of actin filaments and molecular motor proteins in giant liposomes

We have successfully prepared cell-sized giant liposomes encapsulating desired amounts of actoHMM, a mixture of actin filament (F-actin) and heavy meromyosin (HMM, an actin-related molecular motor), in the presence of 5 mM MgCl 2 and 50 mM KCl. We employed a spontaneous transfer method to prepare those liposomes. In the absence of HMM, F-actin was distributed homogeneously inside the liposomes. In contrast, when F-actin was encapsulated in liposomes together with HMM, network structures were generated. Such network structures are attributable to the cross-linking of F-actin by HMM.     

Fullerene nanowires: self-assembled structures of a low-molecular-weight organogelator fabricated by the Langmuir-Blodgett method

Fullerene derivative C60TT, which is substituted with the low-molecular-weight organogelator tris(dodecyloxy)benzamide, formed nanowire structures on application of the Langmuir-Blodgett (LB) method. The surface morphology of the C60TT LB film was dependent on the holding time before deposition at a surface pressure of 5 mN m(-1); it changed from a homogeneous monolayer to a bilayer fibrous structure via a fibrous monolayer structure, which was estimated to have dimensions of 1.2 nm in height, 8 nm in width, and 5-10 microm in length. From the structural and spectroscopic data, it is inferred that close packing of the fullerene moiety occurs along with intermolecular hydrogen bonding within the monolayer fibrous structure. The morphological changes in the LB film are explained kinetically by the Avrami theory, based on the decrease in the surface area of the monolayer at the air/water interface. The growth of the quasi-one-dimensional fibrous monolayer structures at holding times from 0 to 0.2 h is considered to be an interface-controlled process, whereas the growth of the quasi-one-dimensional bilayer fibrous structures from 0.2 to 18 h is thought to be a diffusion-controlled process.     

A viscosity self-oscillation of polymer solution induced by the Belousov-Zhabotinsky reaction under acid-free condition

We succeeded in measuring a viscosity self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction for a polymer solution on the constant temperature condition under acid-free condition. The polymer chain is consisted of N-isopropylacrylamide, ruthenium complex as a catalyst of the BZ reaction, and an acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and the solubility control site. The viscosity self-oscillation for the AMPS-containing polymer solution was attributed to the difference between viscosities for the polymer solution in the reduced and oxidized states. The effects of the polymer concentration and the temperature of the polymer solution on the viscosity self-oscillation were investigated. As a result, the viscosity self-oscillating behavior significantly depended on the polymer concentration and the temperature of the polymer solution. The period of the viscosity self-oscillation decreased with increasing temperature in accordance with the Arrenius equation.     

Local existence and blow-up criterion for the Euler equations in Besov spaces of weak type

We introduce Besov type function spaces, based on the weak L ^p -spaces instead of the standard L ^p -spaces, and prove a local-in-time unique existence and a blow-up criterion of solutions in those spaces for the Euler equations of perfect incompressible fluid in . For the proof, we establish the Beale-Kato-Majda type logarithmic inequality and commutator type estimates in our weak spaces. Abbreviate title: Euler equations in Besov spaces of weak type