PubMed · 14825158
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T H JAMES. 1951. Developer activity of di- and trihydroxybenzoic acids.. https://doi.org/10.1021/j150487a012
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pH affects many processes on cell metabolism, such as enzyme kinetics. To enhance the understanding of the living cells, it is therefore indispensable to have a method to monitor the pH in living cells. To accomplish this, a dynamic intracellular pH measurement method applying low concentration benzoic acid pulse was developed. The method was thoroughly validated and successfully implemented for measuring fast dynamic intracellular pH of Saccharomyces cerevisiae in response to a glucose pulse perturbation performed in the BioSCOPE set-up. Fast drop in intracellular pH followed by partial alkalinization was observed following the pulse. The low concentration benzoic acid pulse which was implemented in the method avoids the undesirable effects that may be introduced by benzoic acid to cell metabolism.
Nitrogen-doped titanium dioxide powders were prepared by wet method, that is, the hydrolysis of acidic tetra-butyl titanate using aqueous ammonia solution, followed by calcination at temperatures about 350 degrees C. The catalysts exhibited photocatalytic activity in the visible light region owing to N-doping. The light absorption onset of TiO(2-x)N(x) was shifted to the visible region at 459 nm compared to 330 nm of pure TiO(2). An obvious decrease in the band gap was observed by the optical absorption spectroscopy, which resulted from N2p localized states above the valence band of TiO(2-x)N(x) (compared to TiO(2)). The TiO(2-x)N(x) catalyst was characterized to be anatase with oxygen-deficient stoichiometry by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and X-ray photoelectron spectroscopy (XPS). The binding energy of N1s measured by XPS characterization was 396.6 eV (TiN bonds, beta-N) and 400.9 eV (NN bonds, gamma-N(2)), respectively. The photocatalytic activity of TiO(2-x)N(x) under visible light was induced by the formation of beta-N in the structure. Photocatalytic decomposition of benzoic acid solutions was carried out in the ultraviolet and visible (UV-vis) light region, and the TiO(2-x)N(x) catalyst showed higher activity than pure TiO(2).
In-vitro human skin permeation and distribution of geranyl nitrile (GN) was determined using epidermal membranes following application (5 microl/cm(2)) in 70% ethanol, under non-occlusive conditions, at maximum in-use concentration (1%). Permeation was measured (12 time-points over 24 h) using 6% (w/v) Oleth-20 in pH 7.4 phosphate buffered saline as receptor. Permeation of reference benzoic acid was assessed using the same skin donors. Overall recovery of GN at 24 h was low (14.1+/-0.4%) due to evaporation. Evaporative loss of GN from polytetrafluoroethylene (PTFE) sheet, under the same conditions was rapid (93% over 24h) although this overestimated loss during permeation where evaporation competed with uptake. At 24 h, 1.89+/-0.15 microg/cm(2) GN, (3.74+/-0.30% of applied dose) (mean+/-standard error, SE, n=12), had permeated. Following rapid initial permeation, the absorption plateaued due to depletion. Levels of GN in the epidermis (plus any remaining stratum corneum after tape stripping), filter paper membrane support and receptor fluid were combined (as per SCCNFP guidelines) to produce a total absorbed dose value of 4.72+/-0.32%. Systemic exposure resulting from the use of GN as a fragrance ingredient, under unoccluded conditions, would be low based on the currently reported use levels.