Noriyuki Kumazawa

Photoresponse of a titanium dioxide chemical sensor

Abstract A novel method for identification of chemical compounds using multiple parameters is proposed. An ac voltage was applied to a titanium dioxide (TiO 2 ) semiconductor gas sensor. The resulting conductance, surface potential and phase lag of the output current wave form with respect to the input voltage wave form in the dark and under illumination were recorded. It was found that the sensitivity of the sensor increases almost one order of magnitude under a monochromatic light (at 700 nm) intensity of 50 mW cm −2 . Three dimensional figures representing these three linear parameters enabled us to distinguish alcohol and benzene compounds at low concentration, with a single detector.

Electrical oscillation and fluctuation in phospholipid membranes: Phospholipids can form a channel without protein

Fluctuations and/or step-wise changes in membrane potential and electrical current were observed in bilayer membranes of dioleoylphosphatidylcholine (DOPC) in the absence of any channel protein. The DOPC membranes consisted of three types: black lipid membranes, pipette-clamp membranes and lipid membranes transferred to porous filter paper by conventional Langmuir-Blodgett techniques. This finding is significant since phospholipids are the main constituents of biomembranes. Lipid molecules with a cis double bond in their carbon skeleton are suggested to be important in the gating or excitation of biomembranes.

Titaniumdioxide chemical sensor working with AC voltage

Abstract A novel method to distinguish chemical compounds is proposed, based on multidimensional information, derived from simple linear response. An ac voltage was applied to a titaniumdioxide (TiO 2 ) semiconductor gas sensor. The resulting conductance, surface potential and phase difference of the input voltage-output current wave form were recorded. All the three parameters showed linear response to the concentration of the adsorbed chemical compounds in gaseous form and depended on their chemical structure. Three dimensional figure of these three linear parameters enabled us to distinguish alcohols and benzenes with a single detector.

Chemical sensor based on titanium dioxide thick film : Enhancement of selectivity by surface coating

Titanium dioxide chemical sensor working with AC voltage can be used to discern individual chemical compound, using a single detector. Two different types of molecules, i.e., alcohols and benzenes were used as the adsorbent on the surface of the sensor. Results showed that three parameters that were used to trace a single molecule, were also helpful to determine the existence of mixed gases and their ratio of mixture. It was also found that when the sensor surface was coated with a bilayer of polyion complex, it enhanced the selectivity of the sensor. In this case benzene molecules showed vivid response compared to the alcohols.

Skin surface electric potential as an indicator of skin condition: a new, non‐invasive method to evaluate epidermal condition

Abstract:  We previously demonstrated that the skin surface electric potential, which has been long recognized as a parameter of emotional or physiological state, is generated by epidermal keratinocytes and is strongly associated with the ion concentration gradient in the epidermis. Thus, at temperatures below the threshold of sweating, the potential provides a measure of the epidermal ion concentration gradient, which in turn is related to epidermal homeostasis and pathology. In the present study, we established a new, non‐invasive method to measure skin surface electric potential. In healthy skin, calcium ion was localized in the uppermost epidermis and the gradation disappeared by tape stripping. Skin surface potential was also disappeared by tape stripping. Moreover, environmental humidity affected the potential, whereas temporary hydration of the stratum corneum did not affect it. These results suggest that the skin surface electric potential may be an indicator of the pathophysiology of the living layer of epidermis, and thus may be useful as a new parameter to evaluate skin condition.

Molecular basis of the protonophoric and uncoupling activities of the potent uncoupler SF-6847 ((3,5-di-tert-butyl-4-hydroxybenzylidene)malononitrile) and derivatives. Regulation of their electronic structures by restricted intramolecular rotation

We reported recently (Yoshikawa, K. and Terada, H. (1982) J. Am. Chem. Soc. 104, 7644-7646) that the potent uncoupler of oxidative phosphorylation SF-6847 [3,5-di-tert-butyl-4-hydroxybenzylidene)malononitrile) shows unique intramolecular restricted rotation of the malononitrile moiety. In this study, values for the activation energy Ea of the restricted rotation of SF-6847 derivatives with the same alkyl chain R in both ortho positions of the phenolic hydroxyl group were determined from the temperature-dependent change in the 1H-NMR signals of their aromatic protons. The Ea values of the neutral forms of these derivatives were found to be the same irrespective of R, but those of the anionic forms increased with increase in the alkyl chain length of R. It was found that the restricted rotation of the malononitrile moiety regulates its electron-withdrawing ability in such a way as to keep the acid dissociability of these derivatives similar, overcoming the effect of steric hindrance by R. The protonophoric activity of these derivatives, in a phospholipid bilayer membrane and their uncoupling activity in rat-liver mitochondria were both found to depend on Ea of their anionic forms. The stability of the uncoupler anions regulated by the restricted rotation of the malononitrile group in a nonpolar membrane environment was found to be important for exhibition of these activities. The hydrophobicity of the anionic forms of these derivatives was suggested also to be affected by the intramolecular rotation.

Characteristic responses of a phospholipid molecular layer to polyols.

Polyols (sugar alcohols) are widely used in foods, pharmaceutical formulations and cosmetics, and therefore it is important to understand their effects on cell membranes and skin. To address this issue, we examined the effect of polyols (1,2-ethanediol (ethylene glycol), 1,3-butanediol, 1,2,3-propanetriol (glycerol), and 1,2,3,4-butanetetraol) on artificial membrane systems (liposomes, monolayers, or dry films) prepared from phospholipid (1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)). 1,2-Ethanediol and 1,3-butanediol had little effect on the size of the DMPC liposomes or the surface pressure (π)-surface area (A) isotherm of DMPC monolayers at an air-water interface, whereas 1,2,3-propanetriol or 1,2,3,4-butanetetraol increased both liposome size and surface pressure. Attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) and differential scanning calorimetry (DSC) were used to evaluate the interaction between DMPC and polyols. These experimental results suggest that the chemical structure of polyol plays an important role in the characteristic interaction between polyol and DMPC.

Transformation of Escherichia coli Mediated by Natural Phospholipids

Transformation system for Escherichia coli based upon introduction of plasmid DNA by natural phospholipids has been developed. Transformants are easily obtained by treatment with natural phospholipids such as phosphatidylethanolamine, phosphatidylcoline, and phosphatidylserine, where the presence of MgCl2 or CaCl2 is essential. This method of transformation is applicable not only for small plasmid pHSG399 (2.3 Kb) but also for giant plasmid R6K (100 Kb).

Effects of metals on skin permeability barrier recovery

Please cite this paper as: Effects of metals on skin permeability barrier recovery. Experimental Dermatology 2010; 19: e124–e127.

Skin surface electrical potential as an indicator of skin condition: observation of surfactant‐induced dry skin and middle‐aged skin

Abstract:  We previously reported that skin surface electrical potential might be a good parameter of skin pathophysiology. To examine the potential availability of skin surface electrical potential measurement for diagnostic purposes, we measured the change of the potential in surfactant‐induced dry skin and we compared the values of the potential in volunteers of different age groups. We also measured trans‐epidermal water loss (TEWL) in the same groups. The skin surface electrical potential was significantly increased after sodium dodecyl sulphate treatment, and the alteration was much more marked than that of TEWL. Further, a significant difference in skin surface electrical potential was observed between young‐ and middle‐aged volunteers, although there was no significant difference in TEWL between the two groups. These results suggest that skin surface electrical potential may be a good indicator of the pathophysiological state of the living layer of epidermis.