Synthesis of uniform anatase TiO2 nanoparticles by gel-sol method. 4. Shape control

Uniform anatase-type TiO(2) nanoparticles of different shapes have been formed by phase transformation of a Ti(OH)(4) gel matrix in the presence of shape controllers. For example, triethanolamine (TEOA) was found to change the morphology of TiO(2) particles from cuboidal to ellipsoidal at pH above 11. The shape control can be explained in terms of the specific adsorption of TEOA onto the crystal planes parallel to the c-axis of the tetragonal system in the alkaline range, as supported by the observation of preferential adsorption of TEOA onto the crystal planes parallel to the c-axis at pH 11.5 and by the pH dependence of the adsorption onto ellipsoidal particles. Diethylenetriamine (DETA) also modified the particle shape to ellipsoidal above pH 9.5 and the aspect ratio was much higher than with TEOA. The mechanism of the shape control could be explained in the same way as with TEOA, since analogous specific adsorption was observed with DETA as well. Similar shape control to yield ellipsoidal particles of a high aspect ratio was also achieved with other primary amines, such as ethylenediamine (ED), trimethylenediamine (TMD), and triethylenetetramine (TETA). However, secondary amines, such as diethylamine, and tertiary amines, such as trimethylamine and triethylamine, acted as a complexing agent of Ti(IV) ions to promote the growth of ellipsoidal particles of a low aspect ratio, rather than a shape controller to produce ellipsoids of a high aspect ratio. Sodium oleate and sodium stearate were found to modify the particle shape from round-cornered cubes to sharp-edged cubes. The mechanism was explained in terms of the reduction of the specific surface energies of the [001] and [100] planes of the tetragonal crystal system by the preferential adsorption of oleate or stearate ion onto these planes, based on the adsorption experiment using ellipsoidal and cubic particles.     

Structure of gentiodelphin,an acylated anthocyanin isolated from Gentiana Makinoi, that is stable in dilute aqueous solution

Structure of gentiodelphin is determined to be 5, 3′-d8-O-(6-O-$\text{trans}$-caffeoylβ-D-glucosyl)-3-O-(β-D-glucosyl)delphinidin. The anthocyanin is stable in dilute neutral aqueous solution. This stabilization may be caused from intramoleculaur hydrophobic interactions among the aromatic nuclei; the anthocyanidin being sandwiched win between two caffeic acids.     

Essential structure of co-pigment for blue sepal-color development of hydrangea

Blue sepal-color of Hydrangea macrophylla might be due to a supramolecular metal-complex pigment consisting of delphinidin 3-glucoside (1), co-pigments (5-O-caffeoylquinic acid (2), and/or 5-O-p-coumaroylquinic acid (3)) and Al³⁺ in an aqueous solution around pH 4.0. To clarify the mechanism of blue sepal-color development of hydrangea, we tried to reproduce the blue color in vitro by mixing 1 with designed synthetic co-pigments in the presence of Al³⁺ at pH 4.0. We at first succeeded in clarifying the essential functional structure in the co-pigment that could form the stable blue solution. Here, we present the structure of the blue pigment caused by an Al-complex coordinating of 1 at ortho-dihydroxyl groups of the B-ring, 1-hydroxy, 1-carboxylic acid, and the carbonyl residue in the ester at 5-position of 2 and/or 3. The hydrophobic interaction between the aromatic acyl residue at 5-position and the nucleus of 1 may also contribute to stabilize the complex.     

Contributions of the distance-dependent reorganization energy and proton-transfer to the hole-transfer process in DNA

A kinetic study of the single-step hole transfer in DNA was performed by measuring time-resolved transient absorption. DNA molecules with various sequences were designed and conjugated with naphthalimide (NI) and phenothiazine (PTZ) to investigate the sequence and distance dependence of the single-step hole transfer between guanines (Gs). Hole injection into DNA was accomplished by excitation of the NI site with a 355 nm laser pulse, and the kinetics of the hole-transfer process were investigated by monitoring the transient absorption of the PTZ radical cation (PTZ.+). Kinetic analysis of the time profile of PTZ.+ based on the kinetic model showed that the distance dependence of the hole-transfer process was significantly influenced by the DNA sequence. Results of temperature- and isotope-effect experiments demonstrated that the activation energy increased as the number of bridge bases separating the Gs increased. This is because of the distance-dependent reorganization energy and contribution of the proton-transfer process to the hole transfer in DNA.     

A novel photochemical reaction of 2-alkoxynicotinates to cage-type photodimers

Irradiation of a benzene solution of 2-alkoxynicotinic acid alkyl esters gave cage-type photodimers in good yields, the structure of which was established by X-ray single-crystal analysis. The maximum quantum yield was 8.0 x 10(-)(2) when a 5.0 M (almost neat) solution was used. Photolysis of phenyl 2-methoxynicotinate promoted photo-Fries rearrangement to give 1,3- and 1,5-rearranged products. Excimer emission of methyl 2-methoxynicotinate was observed at 77 K.     

Interaction of liposomes with cultured cells: possible involvement of lipid peroxidation in cell growth inhibition

Systematic analyses of the interaction between liposomes and cells were examined. Liposomes were found to affect the growth of mouse NIH 3T3 cells depending upon their size, net charge, and cholesterol content. Among the charged compounds, stearylamine was the most inhibitory and showed complete inhibition of cell growth at 100 microM. The cholesterol-rich and small unilamellar vesicles were more suppressive compared to the cholesterol-poor and multilamellar ones, respectively. The binding assay of liposomes to the cells showed a positive correlation between liposome binding and the extent of growth inhibition. Suppression of liposome uptake by inhibitors of the cytoskeletal system and energy metabolism were suggestive of an endocytotic mechanism for the cellular uptake of liposomes. The growth inhibitory effect seemed secondary to the intracellular uptake of liposomes, and peroxidation of incorporated lipids would lead to cellular damage. Therefore, it is highly recommended that potential growth inhibitory effects associated with the particular composition and other properties of liposomes should be carefully assessed in any human studies, especially for long-term use.     

Viscosity of polydimethylsiloxane–pentamer systems

Viscosities of polydimethylsiloxane–pentamer systems were measured over the whole range of concentration. Twelve samples having molecular weights from about 1000 to 5 × 10⁵ were studied. The empirical reduction scheme, plots of log η versus log _cM^0.68, suggested by Ferry and co-workers is applicable to samples of M?_v ≥ 22,000 over the entire concentration. Such satisfying superposition of data may be attributed to the systems being the homologous mixtures in which glass temperatures of polymers are very low. On the basis of the treatment of Fox and Allen, the effects of the number and weight-average molecular weight on viscosity were examined, and the friction coefficient ζ per chain atom at constant M?_n was calculated over a wide range of M?_n. The value ζ is almost constant (ζ = 7.4 × 10^?9 dyne-sec./cm.) in the region of M?_n ≥ M_c, and where otherwise it decreases rapidly with decreasing M?_n. The length of the chainend segment was tentatively calculated.     

Sensitive analysis of alkyl alcohols as decomposition products of alkyl nitrites in human whole blood and urine by headspace capillary GC with cryogenic oven trapping

The abuse of alkyl nitrites is becoming a serious social problem worldwide. In this report, a simple and sensitive method is presented for the determination of n-butyl alcohol, isobutyl alcohol, and isoamyl alcohol as decomposition products of alkyl nitrites in human whole blood and urine samples using capillary gas chromatography (GC) with cryogenic oven trapping. After heating a whole blood or urine sample containing each alkyl alcohol and t-butyl alcohol [the internal standard (IS)] in a 7-mL vial at 55 degrees C for 15 min, 5 mL of the headspace vapor is drawn into a gas-tight syringe and injected into a GC inlet port. The vapor is introduced into an Rtx-BAC2 medium-bore capillary column in the splitless mode at 0 degrees C oven temperature in order to trap the entire analytes, and then the oven temperature is programmed up to 240 degrees C for the GC measurements by flame ionization detection. These conditions give sharp peaks for each compound and the IS and low background noise for whole blood or urine samples. The detection limits of the analytes are 10 ng/mL for whole blood and 5 ng/mL for urine. Linearity and precision are also tested to confirm the reliability of this method. Isobutyl alcohol and methemoglobin could be determined from the whole blood samples of three male volunteers who had sniffed isobutyl nitrite.     

Rearrangement approach to the formal displacement of the bridgehead methoxyl group of bicyclo[3.2.2]non-6-en-2-ones with alkyl alkenyl and aryl groups

A preferential trasformation of the C₂ -substituted 1-methoxybicyclo[3.2.2]non-6-en-2-ols, derived from 1-methoxybicyclo[3.2.2]non-6-en-2-ones, into the C₁-substituted bicyclo[3.2.2]non-6-en-2-ones was accomplished by utilizing TsOH in toluene (85°C) or boiling benzene.     

Kinetic aspects in the drying dissipative crack patterns of colloidal crystals

Kinetics of the dissipative structure formation in the course of drying the colloidal crystals of silica spheres (103 nm in diameter) in aqueous deionized suspension on a rinsed cover glass has been studied by the close-up video observation. The patterns of the broad ring of the hill accumulated with the spheres coexisted with the many spoke-like cracks. The characteristic convection flow of the spheres and the interactions between the spheres and substrate were important for the pattern formation. Cracks formed suddenly in the course of drying along the outside edge first, then toward the center, and stopped around the middle point between the outside edges and the frontier of suspension area. The further growth of the cracks took place at the adjacent place of the previous crack side by side and cooperatively. After the fast formation of these cooperative spoke-like cracks was completed, then all the crack lines further developed very slowly and simultaneously toward the center with the similar rate as that of the movement of the drying frontier of the suspension area toward center. Rates of the fast and slow modes of crack formation were 6.2 mm/s and 0.0098 mm/s, respectively, at the sphere concentration of 0.033 in volume fraction.