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Electron paramagnetic resonance (EPR) in conjunction with a slow-tumbling simulation was utilized for defining stratum corneum (SC) lipid structure. SC from the back of hairless mouse (HOS:HR-1) was stripped consecutively from one to three or four times using a glass plate coated with a cyanoacrylate resin. Aliphatic spin probes, 5-doxylstearic acid (5-DSA) and 3β-doxyl-5α-cholestane (CHL), were used to evaluate the SC ordering. EPR spectrum of 5-DSA incorporated in the SC demonstrated a characteristic peak for the first strip. A slow-tumbling simulation for 5-DSA showed clear differences in EPR intensities as well as ordering values (S 0) of the SC for control and terpenes treated SC. The α-terpineol enhanced the permeation of the single chain 5-DSA about three times more than that of the control. However, EPR spectra of CHL in the SC did not show a clear difference for each strip, except for the signal intensity. The results imply that CHL permeates into SC lipid differently from 5-DSA. The enhancement of the 5-DSA is more significant than that of CHL. Therefore, the present results can be useful for various drug administrations via the skin.

Electron paramagnetic resonance (EPR) in conjunction with a slow-tumbling simulation was utilized for defining stratum corneum (SC) lipid structure. We found that ordering calculated from the simulation is an appropriate index for evaluating SC lipids structure. The SC from two sites (mid-volar forearm and lower-leg) of human volunteers was stripped consecutively from one to three times using a glass plate coated with a cyanoacrylate resin. Aliphatic spin probes, 5-doxylstearic acid (5-DSA) and 3beta-doxyl-5alpha-cholestane (CHL), were used to monitor SC ordering. EPR spectrum of 5-DSA incorporated in the SC demonstrated a characteristic peak for the first strip. However, EPR spectra of CHL in the SC did not show a clear difference for each strip, except for the peak intensity. The results imply that CHL is not incorporated into the lipid phase as easily as 5-DSA is. A slow-tumbling simulation of the EPR spectrum was performed to analyze the detailed lipid structure. The simulation results for 5-DSA show differences in values of the SC ordering as a function of depth. Thus, these results along with the simulation analysis provide a detailed SC layer structure.

A simple rapid method was worked out for studying the physical and structural state of lipids by measuring the refractive indices of a layered lipid film. Melting processes of n-paraffins and phase transitions of phospholipids and the lecithin-cholesterol system also can be followed as a function of temperature. In accordance with data from the relevant literature, the measured refractive indices show that cholesterol lowers the phase transition temperature of lecithin. By isorefraction curves, the most ordered structure of the layers is indicated to occur at the equimolar ratio of cholesterol and lecithin. The method may be applied to study the effect of lipid-soluble agents upon lipid structure and is applicable for routine investigations and industrial purposes as well.

Methyl-branched derivatives of methyl 8,11,14-eicosatrienoate form stable liquid-expanded monolayers. Surface areas are expanded by the methyl branch. The expansion effect is a function of surface pressure. At high surface pressure, the greatest expansion occurs with a mid-point methyl branch. At low surface pressure, surface area increases continuously as the methyl group is moved along the carbon chain from carbon 19 to carbon 5. Desaturase activity varies inversely with surface area, and a linear correlation exists between surface area at low surface pressure and the desaturation rate. These data support the concept that lipid structure and its effect on short range forces between molecules is an important factor in desaturase activity.