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Kazutami Sakamoto

Publications and source records attributed to Kazutami Sakamoto.

9 recordsLinked to original sources
PubMed2006

Depth dependence of stratum corneum lipid ordering: a slow-tumbling simulation for electron paramagnetic resonance.

We investigated the structural ordering of stratum corneum (SC) lipid by means of electron paramagnetic resonance (EPR) slow-tumbling simulation in conjunction with spin probe studies. The SC of human mid-volar forearm was stripped consecutively from three to six times. The EPR probe method detected a characteristic peak of sebaceous matter in the first SC stripping. The order parameter values obtained by the slow-tumbling simulation (S(0)) showed significant differences between each layer compared with those indicated by the conventional order parameter (S) using hyperfine couplings. Although the conventional S values were in the range of 0.56 (outermost layer) to 0.61 (bottom layer), the S(0) values by the simulation changed from 0.22 to 0.96. The present results suggest that the structural ordering of the outermost SC layer is less tight, whereas the structure of inner layers becomes more rigid. Therefore, we concluded that the EPR probe method recognizes sebaceous matters, whereas EPR in conjunction with the simulation allows quantitative evaluation of SC lipid ordering in relation to skin depth.

Computer Simulation↗
PubMed2004

Synthesis and characterization of chiral mesoporous silica.

Chirality is widely expressed in organic materials, perhaps most notably in biological molecules such as DNA, and in proteins, owing to the homochirality of their components (d-sugars and l-amino acids). But the occurrence of large-scale chiral pores in inorganic materials is rare. Although some progress has been made in strategies to synthesize helical and chiral zeolite-like materials, the synthesis of enantiomerically pure mesoporous materials is a challenge that remains unsolved. Here we report the surfactant-templated synthesis of ordered chiral mesoporous silica, together with a general approach for the structural analysis of chiral mesoporous crystals by electron microscopy. The material that we have synthesized has a twisted hexagonal rod-like morphology, with diameter 130-180 nm and length 1-6 micro m. Transmission electron microscopy combined with computer simulations confirm the presence of hexagonally ordered chiral channels of 2.2 nm diameter winding around the central axis of the rods. Our findings could lead to new uses for mesoporous silica and other chiral pore materials in, for example, catalysis and separation media, where both shape selectivity and enantioselectivity can be applied to the manufacturing of enantiomerically pure chemicals and pharmaceuticals.

Journal Article↗
PubMed2003

A novel anionic surfactant templating route for synthesizing mesoporous silica with unique structure.

Anionic surfactants are used in greater volume than any other surfactants because of their highly potent detergency and low cost of manufacture. However, they have not been used as templates for synthesizing mesoporous silica. Here we show a templating route for preparing mesoporous silicas based on self-assembly of anionic surfactants and inorganic precursors. We use aminosilane or quaternized aminosilane as co-structure-directing agent (CSDA), which is different from previous pathways. The alkoxysilane site of CSDA is co-condensed with inorganic precursors; the ammonium site of CSDA, attached to silicon atoms incorporated into the wall, electrostatically interacts with the anionic surfactants to produce well-ordered anionic-surfactant-templated mesoporous silicas (AMS). These have new structures with periodic modulations as well as two-dimensional hexagonal and lamellar phases. The periodic modulations may be caused by the coexistence of micelles that differ in size or curvature, possibly owing to local chirality. These mesoporous silicas provide a new family of mesoporous materials as well as shedding light on the structural behaviour of anionic surfactants.

Anions↗
PubMed2002

Intracellular redox regulation by a cystine derivative suppresses UV-induced NF-kappa B activation.

Nuclear factor (NF)-kappa B pathways are influenced by the intracellular reduction-oxidation (redox) balance. While NF-kappa B is activated through inhibitor (I)-kappa B degradation by oxidative stress, its DNA binding is accelerated in the reduced state. We found that N,N'-diacetyl-L-cystine dimethylester (DACDM) suppressed the UVB-induced NF-kappa B binding activity at a much lower concentration (50-100 microM) than N-acetyl-L-cysteine (NAC, 10-30 mM). While NAC suppressed the I-kappa B degradation but not the DNA binding, DACDM prevented the activated NF-kappa B from binding DNA, without influencing the I-kappa B degradation. These properties of DACDM make it possible to effectively regulate the intracellular redox balance.

Acetylcysteine↗
PubMed2001

Solubilization of Polar Oils in Surfactant Self-Organized Structures.

The cloud temperature of 2 wt% C(12)EO(8) aqueous solutions decreases upon addition of sarcosinate-lauroyl isopropyl (SLIP), 1-dodecanol, and m-xylene, whereas it increases in glycerol tris(2-ethylhexanoic) ester (TEH), isopropyl myristate (IPM), and saturated hydrocarbon systems. A three-phase microemulsion is formed at equal weights of water and oil in the IPM system, but a lamellar liquid crystal (L(alpha)) is present in the SLIP system at the balanced temperature. The effect of added oil on the phase transition of the hexagonal (H(1)) phase was also investigated by means of SAXS study. The H(1)-L(alpha) transition occurs upon addition of SLIP or 1-dodecanol whereas the H(1)-I(1) (discontinuous micellar cubic) phase transition takes place in TEH or IPM systems. These differences in phase behavior are attributed to the placement of solubilized oil in micelles: In the former systems, oil tends to penetrate in the surfactant palisade layer and induces the surfactant layer curvature in micelles to be less positive, while the penetration tendency is small and the opposite effect on the curvature is induced upon addition of the latter oils. Copyright 2001 Academic Press.

Journal Article↗
PubMed2000

Electron paramagnetic resonance: a new techniquein skin research.

BACKGROUND/AIM: Electron paramagnetic resonance (EPR) spectra of nitroxide spin probes have been used for studying biological membranes and chemical-membrane interaction. We have investigated the influence of surfactants on the intercellular lipid structure of cadaver stratum corneum and the possibility of EPR spectral measurements on the stripped stratum corneum utilizing cyanoacrylate resin, which might reflect the actual skin lipid conditions. CONCLUSION: EPR spectra are useful in evaluating the fluidity measurement of stratum corneum of cadaver skin and stripped stratum corneum.

Journal Article↗
PubMed2000

Electron paramagnetic resonance study utilizing stripping method on normal human stratum corneum.

BACKGROUND/AIM: Electron paramagnetic resonance (EPR) spectra of nitroxide spin probes are useful for studying biological membranes, and chemical-membrane interaction. The objective of this study was to assess the fluidity of stripped stratum corneum (SC) of normal human skin with EPR. METHODS: We quantified the fluidity of stripped SC (S-SC) by a single stripping with cyanoacrylate onto quartz glass, cover glass or transparent film. Spectra were compared with those of the SC of cadaver skin (C-SC). RESULTS: All S-SC spectra were similar to those of C-SC. There were no statistical differences in the order parameters S between C-SC and those on quartz cell and cover glass, but those of transparent film were significantly higher. Spectra after a month storage at room temperature at 5 degrees C and at -20 degrees C were unchanged. The order parameter S had decreased after a 3-month storage in all conditions. CONCLUSION: This method is useful for the evaluation of the fluidity measurement utilizing EPR spectra of S-SC.

Journal Article↗
PubMedDate not supplied

Protective effects of an antioxidant derived from serine and vitamin B6 on skin photoaging in hairless mice.

The generation of reactive oxygen species (ROS) by ultraviolet radiation (UVR) accelerates skin aging, which is known as photoaging. Because cutaneous iron catalyzes ROS generation, sequestering iron by chelating agents is thought to be an effective approach toward preventing photoaging. Previously, N-(4-pyridoxylmethylene)-l-serine (PYSer) was designed as an antioxidant to suppress iron-catalyzed ROS generation by its iron-sequestering activity. In this study, PYSer showed protective effects against skin damage in hairless mice irradiated with ultraviolet B (UV-B). Topical application of PYSer to the skin significantly delayed and/or decreased the visible wrinkle formation induced by chronic UV-B irradiation. A histological study indicated that UV-B-induced epidermal hypertrophy and lymphocytic infiltration were suppressed by PYSer. Moreover, PYSer showed suppressive activity against the UV-B-induced increase in glycosaminoglycans (GAG). These results indicate that PYSer is a promising antioxidant for the prevention of chronic skin photoaging by its iron-sequestering activity.

Animals↗