[Show abstract][Hide abstract]ABSTRACT: Regioselectively hetero-labeled hosts, 6A-pyrenebutylate-6X-tosyl-modified gamma-cyclodextrins (X = B or H, C or G, D or F, and E for gamma-1, gamma-2, gamma-3, and gamma-4, respectively), were synthesized in order to investigate their chemo-sensor properties for applications to organic compounds, such as bile acids and terpenes. The hosts (gamma-1, gamma-2, gamma-3, and gamma-4) exhibit pure monomer fluorescence. The guest-induced fluorescence emissions of these hosts were suppressed in the presence of guests. The extent of fluorescence variations of these hosts with guests was recognized as a manifestation of the sensing ability of the hosts. A sensing parameter (deltaI/I0, where I and I0 are the fluorescence intensities in the presence and absence of a guest and deltaI = I0-I) was used to describe the sensing ability of these hosts. Host gamma-analogs were able to detect progesterone, ursodeoxycholic acid, chenodeoxycholic acid, and (-)-borneol with high sensitivity. The behaviors of the appended moieties of these hosts during the formation of host-guest complexes were studied using induced circular dichroism (ICD) spectra, fluorescence spectra and the MM2-energy-minimized structure. The host gamma-analogs exhibited different ICD spectra patterns before and after the addition of ursodeoxycholic acid. The guest-induced variations of ICD and the fluorescence spectra and MM2-minimized structures suggest that the pyrene and tosyl moieties move by altering the spatial relationship between them, in which the pyrene moiety works as a hydrophobic cap and the tosyl moiety is speculated to act as a spacer.
No preview · Article · Mar 2002 · Analytical Sciences
[Show abstract][Hide abstract]ABSTRACT: The discharge property in the solid state has been utilized for ceramics processing and printer technology. The charge of particles has to be controlled in these fields because it affects the particle filling process in ceramics processing and the print quality of a printer. Fine silica particles are used to refine ceramics or resin particles for optimization of flowability, the discharge ability and the wettability. However, it is difficult to understand these properties, because critical factors ``affecting'' for these properties have not been elucidated yet. For example, the discharge property has not been examined in connection with the surface chemical structure of particles. In this study, we report the electron accepting or electron donating ability of chemicals and find that the discharge property is significantly influenced by that ability. Work function values are measured for polystyrene resin particles covered by different kinds of silica particles. In addition, we suggest a simple evaluation method for solid discharge through the measuring of pH in solution form. The relationships among the discharge, pH and work function values are examined. As a result, we arrive at some results to elucidate these phenomena.
No preview · Article · Dec 2001 · Japanese Journal of Applied Physics
[Show abstract][Hide abstract]ABSTRACT: The effect of dansyl modified -cyclodextrin (1)on the chaperone activity of heat shock proteins such as HSP70 and HSP90 hasbeen studied. The fluorescence intensity of 1 was decreased when HSP70 and HSP90 were added to the host solution. This phenomenon suggested that host–guest complexation was occuring. The binding constants of 1 were obtained using a 1:1 complex formation type equation by employing the guest-induced fluorescence variations. Host 1 exhibited a higher binding ability forHSP70 than for HSP90. The effects of 1 on the chaperone activity and degradation of HSP70 and HSP90 were studied by measuring the absorption of aggregation of citrate synthase (C.S.) and sodium dodecyl sulfate (SDS)polyacrylamide gel electrophoresis of trypsin degradation, respectively. Host1 can contribute to regulate C.S. aggregation andpromote trypsin degradation of HSP70 and HSP90.
No preview · Article · May 2001 · Journal of Inclusion Phenomena
[Show abstract][Hide abstract]ABSTRACT: A fluorescent molecular sensing for endocrine-disrupting chemicals and their analogs has been investigated by fluorescence spectral change of regio-selective 1-pyrene-ρ-cyanobenzene-modified γ-cyclodextrins on the addition of a guest. These host compounds showed both monomer and exciplex fluorescence at around 378 and 397 nm, and 468nm, respectively. On accommodation of the guests such as dioxin analogs, p-nonylphenol, 2, 4-dichlorophenoxyacetic acid, bisphenol A, and diethylphthalate, the intensities of the guest-induced monomer fluorescence increased or decreased, and those of the guest-induced exciplex emission decreased. The extent of the fluorescence variations with the guest was employed to display the sensing abilities of these hosts. The sensing parameters, ΔIm/I0m and ΔIex/I0ex, were used to describe the sensing ability of the hosts, where Im and I0m, and Iex and I0ex were fluorescence intensities of monomer and exciplex emission, respectively, in the presence and absence of the guest, and ΔIm=I0m-Im, and ΔIex=I0ex-Iex. These hosts particularly exhibited high sensitive and selective molecular recognition ability for 2, 4, 6-trichlorophenol, p-nonylphenol and bisphenol A.
[Show abstract][Hide abstract]ABSTRACT: Flexible regioselectively hetero-substituted hosts, 6A-O-4-pyrenylbutanoyl-6X-O-p-cyanobenzoyl-modified γ-cyclodextrins (X = B or H, C or G, D or F, and E for γ-1, γ-2, γ-3, and γ-4, respectively) have been synthesized in order to investigate their fluorescence sensing properties for application to organic compounds such as bile acids and cyclic alcohols. The hosts, γ-1, γ-2 and γ-3, exhibit both monomer and exciplex fluorescence, whereas γ-4 exhibits only monomer emission. In guest-induced emission of γ-1, γ-2 and γ-3, exciplex emission is suppressed while monomer emission is increased. However, γ-4 exhibits only a negligible change in monomer fluorescence in the presence of guests. The extent of exciplex fluorescence variation of γ-1, γ-2 and γ-3 with guests is recognized as the manifestation of the sensing ability of the hosts. A sensing parameter (ΔIex/I0ex) was used to describe the sensing ability of three hosts. Host γ-analogs, γ-1, γ-2 and γ-3, are able to detect ursodeoxycholic acid, deoxycholic acid, chenodeoxycholic acid, and (−)-borneol with high sensitivity by exciplex emission. The sequence of the binding ability of these hosts is γ-2 > γ-1 > γ-3. The behaviors of the appended moieties of these hosts during the formation of host–guest complexes were studied using induced circular dichroism (ICD) and fluorescence spectra. The host γ-analogs γ-1–γ-3 exhibit different ICD patterns to γ-4 before and after addition of ursodeoxycholic acid. The guest-induced variations of ICD and fluorescence spectra changes suggest that the pyrene and cyanobenzene moieties move, altering the spatial relationship between them.
No preview · Article · Jan 2001 · Journal of the Chemical Society Perkin Transactions 2