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101.
The optical properties of reaction systems composed from a pseudoisocyanine (PIC) solution and dispersed layered silicates were studied using visible spectroscopy. Two series of reduced-charge montmorillonites were used as the silicate materials. Each series consisted of eight samples with different layer charges, which were prepared from one parent material. Observed trends were verified with another series of dioctahedral and trioctahedral smectites of different layer charges, structure, and origin. The layer charge density of the silicates significantly affected the aggregation of PIC cations. In addition to the formation of J-aggregates, dye spectral bleaching was also observed. Silicates with very low charge densities induced neither significant aggregation nor spectral bleaching of the dye. The highest levels of PIC J-aggregate formation were found in dispersions of the layered silicates with a medium surface charge. However, reversible spectral bleaching was also observed in some cases. PIC dye cations probably change their conformations during the adsorption process, due to the tension resulting from the large size of the cations and the relatively high charge density at the silicate surface. The bleached dye recovers, at least partially, with the rearrangement and redistribution of the dye cations over the time. In contrast, the presence of silicates with very high charge densities (synthetic taeniolite and fluorohectorite) led to the very fast and irreversible decomposition of the PIC. Perhaps, the tension in adsorbed dye cations, induced by the high charge density at the silicate surface, resulted in significant destabilization and a decomposition reaction of the chromophore. 相似文献
102.
Masahiro Fujita Hiroshi Egawa Katsumi Chiba Jun-Ichi Matsumoto 《Journal of heterocyclic chemistry》1997,34(6):1731-1735
The one-pot reaction of ethyl 1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxoquinoline-3-carboxylate ( 6 ) with tert-butyl acetoacetate gave 3-tert-butyl 7-ethyl 9-cyclopropyl-4-fluoro-6,9-dihydro-2-methyl-6-oxofuro[3,2-h]quinoline-3,7-dicarboxylate ( 5 ). This regioselective cyclization was rationalized by the Hard and Soft Acids and Bases principle. By use of a similar furan-forming reaction, we prepared 2-(amino-methyl)furo[3,2-h]quinoline-7-carboxylic acid 4 . Compound 4 showed weak antibacterial activity. 相似文献
103.
Shinsaku Fujita 《Journal of mathematical chemistry》2007,42(2):215-263
The concepts of double coset representations and sphericities of double cosets are proposed to characterize stereoisomerism, where double cosets are classified into three types, i.e., homospheric double cosets, enantiospheric double cosets, or hemispheric double cosets. They determine modes of substitutions (i.e., chirality fittingness), where homospheric double cosets permit
achiral ligands only; enantiospheric ones permit achiral ligands or enantiomeric pairs; and hemispheric ones permit achiral
and chiral ligands. The sphericities of double cosets are linked to the sphericities of cycles which are ascribed to right
coset representations. Thus, each cycle is assigned to the corresponding sphericity index (a
d
, c
d
, or b
d
) so as to construct a cycle indices with chirality fittingness (CI-CFs). The resulting CI-CFs are proved to be identical
with CI-CFs introduced in Fujita’s proligand method (S. Fujita, Theor. Chem. Acc. 113 (2005) 73–79 and 80–86). The versatility
of the CI-CFs in combinatorial enumeration of stereoisomers is demonstrated by using methane derivatives as examples, where
the numbers of achiral plus chiral stereoisomers, those of achiral stereoisomers, and those of chiral stereoisomers are calculated
separately by means of respective generating functions. 相似文献
104.
Tetsuro Fujita 《中国化学快报》2007,18(2):175-177
A new highly conjugated alkaloid of veratramine type, 225,25S,5α-veratramine-7(8),12(14)-diene-3β,13β,23β-triol-6-one (1), was isolated from the bulbs of Fritillaria hupehensis Hsiao et K.C. Hsia. Its structure was determined on the basis of spectroscopic evidences. 相似文献
105.
ESTIMATION OF AN INDEX OF HYDROPHOBICITY OF DNA INTERIOR USING 5-METHOXYPSORALEN AS A FLUORESCENT PROBE 总被引:1,自引:0,他引:1
Masako Sasaki Isao Nakasato Hiroyuki Sugiura Hitoshi Fujita Toshibumi Sakata 《Photochemistry and photobiology》1987,46(4):551-555
The index of hydrophobicity of DNA interior was estimated by measuring fluorescence spectra of psoralen derivatives associated with DNA. The environment around 5-MOP associated with DNA was as hydrophobic (Dk = 34) as methanol, suggesting that the molecules reside at the space between the base-pairs in B-form DNA. This is also true for 8-MOP. Thus, planar and aromatic molecules of 5- and 8-MOP are more stable in the interior of DNA than in aqueous medium due to hydrophobic affinity. 相似文献
106.
Position — Sensitive single-wire proportional counter for conversion electron Mössbauer spectroscopy
A position-sensitive single-wire proportional counter for the INS 2 air-core spectrometer has been improved to take conversion electron Mössbauer spectrum as a function of electron energy with a multichannel mode. The position resolution at 13.6 keV was found to become 1.6 mm with the counter gas pressure of 320 Torr. The position resolution was obtained as a function of energy between 7 and 60 keV for gas pressure of 40 Torr, 160 Torr and 320 Torr. The L, M and N conversion electron spectrum of the 14.4 keV transition in57Fe was taken with the present system. Overall momentum resolution was found to be 0.23% for the L1-line and 0.19% for the M1 line. 相似文献
107.
108.
Oyamatsu D Hirano Y Kanaya N Mase Y Nishizawa M Matsue T 《Bioelectrochemistry (Amsterdam, Netherlands)》2003,60(1-2):115-121
The enzymatic activity of diaphorase (Dp) immobilized on a solid substrate was characterized using a scanning electrochemical microscope (SECM) with shear force feedback to control the substrate-probe distance. The shear force between the substrate and the probe was monitored with a tuning fork-type quartz crystal and used as the feedback control to set the microelectrode probe close to the substrate surface. The sensitivity and the contrast of the SECM image were improved in the constant distance mode (distance, 50 nm) with the shear force feedback compared to the image in the constant height mode without the feedback. By using this system, the SECM and topographic images of the immobilized diaphorase were simultaneously measured. The microelectrode tip used in this study was ground aslant like a syringe needle in order to obtain the shaper topographic images. This shape was also effective for avoiding the interference during the diffusion of the enzyme substrates. 相似文献
109.
Cs2CO3 was found to efficiently catalyze the reaction of β-cyclodextrin and N-tosylimidazole. Stirring β-cyclodextrin and N-tosylimidazole in 1/1.2 molar ratio in DMF in the presence of catalytic amount of Cs2CO3 at rt for 1.5 h afforded 2A-mono(O-tosyl)-β-cyclodextrin in 32% yield. The 2A,2B-, 2A,2C- and 2A,2D-ditosylates were isolated in ca. 6-7% yields, respectively, when β-cyclodextrin and N-tosylimidazole were used in 1/2.5 molar ratio. The charge of excess (10 equiv) of N-tosylimidazole ensured a one-step direct (protection-free) synthesis of the per(2-O-tosyl)-β-cyclodextrin in 5% isolated yield. N-(m-Nitrobenzenesulfonyl)imidazole even allowed a much faster access to the corresponding persulfonate in only 1 h reaction. 相似文献
110.
Takashi Murashima Kazuyuki Hayata Jun Matsui Daisuke Miyoshi Takashi Yamada Naoki Sugimoto 《Tetrahedron letters》2007,48(48):8514-8517
The DNAs modified with tetraphenyl porphyrin at the center of 13mer oligonucleotide were synthesized using phosphoramidite chemistry and automated DNA synthesis. When the porphyrin modified oligonucleotide was annealed with its complementary strand, they formed a standard B-form duplex. The porphyrin moiety intercalated in the duplex, and moderately lowered the thermal stability. 相似文献