PubMed · 5573790
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S Olerud, B Pontén. 1971-03-03. [A synthetic, absorbable suture thread].. https://pubmed.ncbi.nlm.nih.gov/5573790/
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Exposure to pesticides as a result of their use in agriculture will vary according to the type of formulation, the method of application and the protective measures used. Quantitation of external exposure does not on its own predict the amount absorbed nor does it allow the toxic hazard to be assessed; information on skin penetration is also required. With the use of a suitable generic database for exposure, the assessment of many compounds would only require the measurement of skin penetration. With the knowledge of human dermal pharmacokinetics a field study can be performed which measures the absorbed dose directly and avoids the need for exposure measurement.
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Proton concentration gradients across membranes are important for many biological energy transducing processes. The kinetics of proton dependent processes can be studied by pH-jump methods in which protons are photochemically released. In the following we describe the synthesis and the properties of photolabile 4-formyl-6-methoxy-3-nitrophenoxyacetic acid, a 'caged proton'. The synthesis is based on vanillin, which is alkylated with chloroacetic acid to give a carboxylic acid (pK = 2.72). In a second step a nitro group ortho to the formyl group is introduced. Photochemical proton release occurs by a reaction mechanism analogous to the well known photochemical formation of 2-nitrosobenzoic acid from 2-nitrobenzaldehyde. The pK values of the photoproduct are 0.75 and 2.76, respectively, thus allowing the use of the compound in a wide pH-range. The quantum yield is 0.18, lower than in the case of the 2-nitrobenzaldehyde/2-nitrosobenzoic acid system (phi = 0.5). The release of the proton in a flash photolysis experiment occurs within less than 1 microseconds. The spectrum of photolabile compound has absorption maxima at 263 nm and 345 nm, respectively. Its permeability across a lipid bilayer membrane is very low (permeability coefficient Pd approximately equal to 10(-9) cm.s-1 at pH 8) so that transmembrane proton concentration gradients can be generated.