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521.
Suparpun?Chungcharoenwattana Hiroshi?Kashiwagi Masaharu?UenoEmail author 《Colloid and polymer science》2005,283(11):1180-1189
An addition of oleate micellar solution to two original sizes (180 nm and 50 nm) of preformed vesicles was studied using gel
exclusion chromatography, dynamic light scattering and freeze fracture electron microscopy. The effect of molar ratios of
phospholipid and oleate on size distribution of newly formed vesicles was investigated by varying molar concentrations of
these two components. After adding an equiamount of oleate to 180 nm-preformed vesicles or 50 nm-preformed vesicles, a relatively
monodisperse population of newly formed vesicles was detected. For the high amount of oleate addition to two original sizes
of preformed vesicles, the results were quite different. New large vesicles and a number of new small vesicles were observed
in samples of mixed EggPC/oleate suspension in the presence of preformed vesicles with 180 nm of size, whereas, only some
new large vesicles were detected in samples of mixed EggPC/oleate suspension in the presence of preformed vesicles with 50 nm
of size. We assumed that the number of new small vesicles, with size close to preformed vesicles, increased in the latter
case. The transformation of mixed EggPC/oleate micelles to mixed vesicles was investigated. The results showed that transformation
of mixed EggPC/oleate micelles to vesicles was remarkably faster than transformation of mere oleate micelles to vesicles.
The above findings suggested that new mixed EggPC/oleate vesicles with small size were presumably formed by partial solubilization. 相似文献
522.
YOSHIYUKI Nishio KENSUKE Matsuda YOSHIHARU Miyashita NORITAKA Kimura HIDEMATSU Suzuki 《Cellulose (London, England)》1997,4(2):131-145
Cellulose alkyl esters, CELL- OCOCnH2n+1(n = 1 6), were synthesized by a homogeneous reaction of cotton cellulose with different acyl chlorides in N,N-dimethylacetamide--lithium chloride solution. The miscibility of the esterified celluloses with poly(-caprolactone) (PCL) was investigated, mainly through thermal analysis by differential scanning calorimetry (DSC). A polymer pair, cellulose butyrate (CB)/PCL, showed the highest miscibility of all the binary blends examined here; this is usual when relatively high-substituted esters (DS 2.0) are used as the respective component. The butyl ester derivatives with DS 1.5 showed poor miscibility with PCL 相似文献
523.
Takahashi O Kohno Y Saito K Nishio M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(3):756-762
Ab initio MO calculations were carried out to examine the conformational energies of various benzylic compounds C(6)H(5)CH(2)XR (X=O, CH(2), CO, S, SO, SO(2); R=CH(3), C(2)H(5), iC(3)H(7), tC(4)H(9)) at the MP2/6-311G(d,p)//MP2/6-31G(d) level. Rotamers with R/Ph in gauche relationship are generally more stable than the R/Ph anti rotamers. In these stable geometries, the interatomic distance in the interaction of alpha- or beta-CH in the alkyl group and the ipso-carbon atom of the phenyl ring is short. The computational results are consistent with experimental data from supersonic molecular jet spectroscopy on 3-n-propyltoluene and NMR and crystallographic data on structurally related ketones, sulfoxides, and sulfones. In view of this, the alkyl/phenyl-congested conformation of these compounds has been suggested to be a general phenomenon, rather than an exception. The attractive CH/pi interaction has been suggested to be a dominant factor in determining the conformation of simple aralkyl compounds. 相似文献
524.
Shunsaku Ohta Kentaro Sato Ikuo Kawasaki Yuko Yamaguchi Satoko Nishio Masayuki Yamashita 《Journal of heterocyclic chemistry》2004,41(3):335-341
Reaction of 2‐(1‐chloro‐2,2‐dimethylpropyl)‐1‐methyl‐1H‐irnidazoles with diethyl methylmalonate in the presence of NaH gave a normal SN product, 2‐[(1,1‐diethoxycarbonylethyl)‐2,2‐dimethylpropyl]‐1‐methyl‐1H‐imidazole (2a) , and two tele‐reaction products, 5‐(1,1‐diethoxycarbonylethyl)‐1‐methyl‐2‐(2,2‐dimethylpropyl)‐1H‐imidazole (3a) and trans‐4,5‐di‐(1,1‐diethoxycarbonylethyl)‐4,5‐dihydro‐1‐methyl‐2‐(2,2‐dimethylpropyl)‐1H‐imidazole (4a) in 5, 17 and 70% yields, respectively. The scope and mechanism of this reaction are discussed. 相似文献
525.
Sadao Fujikura Masaharu Inoue Kiitiro Utimoto Hitosi Nozaki 《Tetrahedron letters》1984,25(19):1999-2002
Reaction of 6-bromo-1-trimethylsilyl-1-hexyne with magnesium affords the corresponding Grignard reagent whose C-Mg bond intramolecularly adds to the trimethylsilylacetylene moiety in 5-Exo-Dig manner and suprafacially. The reaction can be applied to the synthesis of some cycloalkanes having stereo-defined alkylidene substituents. 相似文献
526.
Takehiko Nishio Hiroyuki Koyama Daigo Sasaki Masami Sakamoto 《Helvetica chimica acta》2005,88(5):996-1003
The photochemical reactions of different N‐(2‐acylphenyl)‐2‐bromo‐2‐methylpropanamides have been investigated. Irradiation of the N‐unsubstituted anilides 1a – 1c gave the corresponding dehydrobromination, cyclization, and bromo‐migration products 2, 3 , and 4 , respectively (Table 1). Irradiation of the N‐alkyl anilides 1e – 1g afforded the corresponding deacylation and cyclization products 5 and 6 , respectively, whereas irradiation of the N‐alkyl anilides 1i – 1k , carrying 2‐benzoyl groups on the aromatic rings, afforded the unexpected tricyclic lactams 7 (besides 2, 5 , and 6 ). The formation of the cyclization products 6 could be rationalized in terms of an electrocyclic ring closure of the 6π‐electron‐conjugated enamides 2 produced by dehydrobromination of 1 , followed by thermal 1,5‐acyl migration (Path B in the Scheme). The formation of the bridged lactams 7 probably follows a mechanism involving the 1,7‐diradical 8 generated by ζ‐H‐abstraction (1,8‐H transfer) by an excited acyl O‐atom (Path A). 相似文献
527.
The wavelength dependence of the photolysis of 7-methyl-β-ionone ((E)- 1 ) was investigated. Irradiation of (E)- 1 with light of λ > 347 nm leads primarily to (E/Z)-isomerization followed by transformation to the tricyclic enol ether 3 as the only secondary photoproduct. On photolysis of (E)- 1 with light of shorter wavelength (λ > 280 nm or λ = 254 nm), however, a series of other products was formed (via a) photocyclization of the dienone chromophore (→ 5 ), (b) photo-enolization (→ 8 ), and (c) a 1,5-sigmatropic H-shift (→ (E/Z)- 7 ). For the structure elucidation of the new products, 7-[13C]methyl-β-ionone ((E)-[7-methyl-13C]- 1 ) was prepared and irradiated furnishing the corresponding 13C-labelled photoproducts. 相似文献
528.
Liposomes containing distearoylphosphatidylethanolamine with covalently linked polyethylene glycol of molecular weight 2,000 (DSPE-PEG2000) covering a range of 0–30 mol% were prepared by a mechanical dispersion or detergent-removal method. The effects of DSPE-PEG2000 on particle sizes and lamellarity of liposomes were investigated. The average diameters of vesicles prepared from both methods decreased when the concentration of DSPE-PEG2000 was increased. The decrease in vesicle size with increase in DSPE-PEG2000 was ascribed to the steric hindrance of strongly hydrated PEG. The significant decrease in the sizes of DSPE-PEG2000-containing EggPC vesicles prepared by the detergent-removal method could be explained by the postvesiculation size growth in the process of micelle–vesicle transition. For DMPC vesicles prepared by the detergent-removal method, electron micrographs showed that inclusion of DSPE-PEG2000 promoted vesicle formation. Based on the results of investigation of calcein entrapment efficiency, we concluded that the lamellarity of liposomes is reduced as PEG lipid concentration is increased. Fragmentation of multilamellar vesicles into smaller unilamellar vesicles occurred more readily when the liposome suspension was subjected to repetitive freeze-thawing. After five cycles of freezing and thawing, vesicles containing more than 0.5 mol% DSPE-PEG2000 were fragmented into unilamellar vesicles with diameters smaller than 300 nm. 相似文献
529.
S. Goto D. Kaji I. Nishinaka Y. Nagame S. Ichikawa K. Tsukada M. Asai H. Haba S. Mitsuoka K. Nishio M. Sakama Y. L. Zhao K. Sueki K. Tanikawa K. Takamiya H. Kudo H. Nakahara 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(1):73-76
To study the correlation between fragment mass distributions and shell structures of fission fragments, fragment mass and energy distributions in proton-induced fission of 232Th and uranium isotopes, 233,235,238U, were precisely measured using a double-TOF method. It was found that the lighter side of the heavier wing of asymmetric mass distributions shifts to larger fragment mass number corresponding to the N/Z value of the fissioning nucleus. The results are explained qualitatively by the change of the most probable mass number of fission fragments of Z = 50 proton-shell. 相似文献
530.
Masaharu Oguni Prof. Dr. Satoshi Maruyama Kenji Wakabayashi Atsushi Nagoe 《化学:亚洲杂志》2007,2(4):514-520
The dynamic properties of water confined within nanospaces are of interest given that such water plays important roles in geological and biological systems. The enthalpy‐relaxation properties of ordinary and heavy water confined within silica‐gel voids of 1.1, 6, 12, and 52 nm in average diameter were examined by adiabatic calorimetry. Most of the water was found to crystallize within the pores above about 2 nm in diameter but to remain in the liquid state down to 80 K within the pores less than about 1.6 nm in diameter. Only one glass transition was observed, at Tg=119, 124, and 132 K for ordinary water and Tg=125, 130, and 139 K for heavy water, in the 6‐, 12‐, and 52‐nm diameter pores, respectively. On the other hand, two glass transitions were observed at Tg=115 and 160 K for ordinary water and Tg=118 and 165 K for heavy water in the 1.1‐nm pores. Interfacial water molecules on the pore wall, which remain in the noncrystalline state in each case, were interpreted to be responsible for the glass transitions in the region 115–139 K, and internal water molecules, surrounded only by water molecules in the liquid state, are responsible for those at 160 or 165 K in the case of the 1.1‐nm pores. It is suggested that the glass transition of bulk supercooled water takes place potentially at 160 K or above due to the development of an energetically more stable hydrogen‐bonding network of water molecules at low temperatures. 相似文献