sodium-dodecyl-sulfate and octanoic-acid

A novel method for preparing a finely dispersed oil-in-water emulsion is proposed. Octanoic acid dissolved in water at a high temperature of 220 or 230 degrees C at 15 MPa was combined with an aqueous solution of a surfactant and then the mixture was cooled. When a nonionic surfactant, decaglycerol monolaurate (ML-750) or polyoxyethylene sorbitan monolaurate (Tween 20), was used, fine emulsions with a median oil droplet diameter of 100 nm or less were successfully prepared at ML-750 and Tween 20 concentrations of 0.083% (w/v) and 0.042%, respectively, or higher. The diameters were much smaller than those of oil droplets prepared by the conventional homogenization method using a rotor/stator homogenizer. However, an anionic surfactant, sodium dodecyl sulfate, was not adequate for the preparation of such fine emulsions by the proposed method. Although the interfacial tensions between octanoic acid and the surfactant solutions were measured at different temperatures, they were not an indication for selecting a surfactant for the successful preparation of the fine emulsion by the proposed method.

Topics: Caprylates; Emulsions; Glycerol; Hot Temperature; Laurates; Oils; Particle Size; Polysorbates; Sodium Dodecyl Sulfate; Surface Tension; Surface-Active Agents; Water

The variability in human skin irritation responses has been well documented and can confound our ability to accurately assess differences in skin reactivity between human subpopulations. In the current analysis, results were compiled from nine acute irritation patch test studies, conducted at three test facilities over a 5-year period. Four irritant test chemicals, 20% sodium dodecyl sulphate, 100% decanol, 100% octanoic acid and 10% acetic acid, were tested in sufficient numbers of test subjects to enable the stratification of results for different human subpopulations. An increased reactivity was noted for Asian versus Caucasian subjects for each of three test chemicals, in contrast to the previously described individual study results from which these data were drawn. Male subjects were directionally or significantly more reactive to each of the test chemicals than female subjects. The oldest age cluster of subjects (56-74 years of age) was directionally or significantly less reactive than younger age clusters. There was virtually identical reactivity between self-assessed 'sensitive' and normal skin groups. Lastly, there was little correlation between the results from individual subjects tested in two or more studies with the same chemicals. These results add to our general understanding of population differences in skin reactivity and the potential implications for ingredient and product skin safety testing and risk assessment.

Topics: Acetic Acid; Adult; Age Factors; Aged; Asian; Caprylates; Dermatitis, Allergic Contact; Fatty Alcohols; Female; Humans; Irritants; Linear Models; Male; Middle Aged; Patch Tests; Risk Factors; Sex Factors; Sodium Dodecyl Sulfate; White People

It is well-known that humans show a wide range of variation in skin reactivity to irritant chemicals. This has been established through population studies, through the examination of inter-subject variability, and (to a limited extent) through studies of skin site variation in response within subjects. However, simple response variability within individual test subjects has not been examined as carefully, and this has implications for our ability to predict irritant reactivity. Some key questions are: (i) how consistently do human beings respond, even within a given study, to different equally irritating chemicals, or to the same chemical when comparing different concentrations or durations of exposure, and, (ii) Do individual test subjects' responses to one chemical (or exposure scenario) correlate with their responses to another? To examine these questions in some detail, we reexamined individual study subjects' responses from earlier published studies involving both acute and cumulative irritation patch test protocols. Acute irritation responses were compared across chemicals with similar irritation profiles. Cumulative irritation responses were compared across different concentrations of the anionic surfactant, sodium dodecyl sulfate (SDS). Acute (high concentration) and cumulative (low concentration) patch test responses to SDS were also compared. The analysis showed that, as might be expected, response correlations were greatest within test types, either when comparing chemicals of similar overall irritancy, or when comparing similar concentrations of a single chemical. However, individually divergent responses were also frequent, reinforcing the conclusion that a given individual's response to one chemical or exposure condition does not always predict their response to another. This has important ramifications for other questions related to population differences in skin reactivity.

Topics: Acetic Acid; Acute Disease; Asian People; Caprylates; Chronic Disease; Dermatitis, Allergic Contact; Fatty Alcohols; Humans; Irritants; Patch Tests; Predictive Value of Tests; Severity of Illness Index; Sodium Dodecyl Sulfate; White People

Topics: Ammonium Sulfate; Animals; Antigens; Caprylates; Chemical Precipitation; Chromatography, Affinity; Chromatography, Agarose; Chromatography, Gel; Chromatography, Ion Exchange; Electrophoresis, Polyacrylamide Gel; Humans; Immunoglobulin G; Immunologic Techniques; Ligands; Mice; Polyethylene Glycols; Rabbits; Rats; Sodium Dodecyl Sulfate; Sulfates

Electrically silent hydrogen ion fluxes across a planar bilayer lipid membrane (BLM) induced by an addition of monocarboxylic acid at one side of BLM were studied by measuring pH changes in the unstirred layers near the BLM surface. The pH changes were assayed by recording protonophore-dependent potentials as well as by direct measurements of pH shifts in he unstirred layers close to the membrane by the pH microelectrode. It was shown that the mechanism of the acid transport changed qualitatively upon the increase of the hydrophobic chain length of the acid. In the case of short-chain acids at pH < pKa, the total transport was limited by diffusion of the anionic form of the acid across the unstirred layers, while at the alkaline pH (pH>>pKa) the transport was limited by diffusion of the neutral form across the membrane. In the alkaline pH range the pH shifts induced by short-chain acids were sensitive to the presence of cholesterol in the BLM as well as to the stirring conditions in the cell. However, in the case of long chain acids (more than 8 carbonic atoms) the transport was limited by diffusion of the anionic form of the acid in the whole range of pH studied. In the latter case, pH changes in the unstirred layers did not depend on the presence of cholesterol in the membrane, and moreover pH shifts were not dependent on the thickness of the unstirred layer. It was proposed that the peculiarities of the long-chain acid-induced proton transport were associated with the formation of micelles of the acid in bathing solutions.

Topics: Acetates; Acetic Acid; Butyrates; Butyric Acid; Caproates; Caprylates; Carboxylic Acids; Decanoic Acids; Hydrogen-Ion Concentration; Lipid Bilayers; Permeability; Sodium Dodecyl Sulfate; Structure-Activity Relationship

Dissociation constants and rate constants for the binding of 2-acetylpyridine-5-[(2-chloroanilino)thiocarbonyl]thiocar bonohydrazone (I, BW348U87), an agent that enhances the antiherpetic efficacy of acyclovir, to human serum albumin have been determined. I quenched the fluorescence of human serum albumin, whereas the absorbance of I at 370 nm increased upon binding to the protein. The absorbance change was attributed to preferential binding of anionic I (pKa 7.0). Titration data indicated multiple binding sites for I. The dissociation constant of the high-affinity site was 0.11 microM. The time course for binding of I to 100 nM human serum albumin was biphasic. The early and late phases were described by first-order rate constants that had maximal values of 100 and 11 sec-1, respectively. The rate constant for the dissociation of I from human serum albumin was estimated to be 6 sec-1. Dodecyl sulfate and octanoate displaced I from human serum albumin.I with rate constants of 4.5 and 7.3 sec-1, respectively. Since the fluorescence emission spectrum of human serum albumin and the absorption spectrum of I overlapped significantly (the spectral overlap integral, J, was 2.6 x 10(-14) M-1 cm3), the possibility of Förster dipole-dipole energy transfer was considered. However, a significant fraction of the fluorescence quenching by I resulted from a conformational change in the protein upon binding of I and was not the result of dipole-dipole energy transfer. Nonetheless, the distance between one of the binding regions for I on human serum albumin and a tryptophan residue in the protein was estimated to be 31 A by this method. The high affinity of I for albumin could be related to its low hematological toxicity.

Topics: Acyclovir; Antiviral Agents; Binding Sites; Caprylates; Humans; Hydrazones; Kinetics; Protein Conformation; Pyridines; Serum Albumin; Sodium Dodecyl Sulfate; Spectrophotometry, Ultraviolet; Thermodynamics; Tryptophan