348 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) Measurements," in Be&ore Biomechanics, J. M. Cowden and J. T. Scales, Eds. (Macmillan Ltd., London, 1976) pp 103-108. (4) J. Ferguson and J. C. Barbenel, "Skin Surface Patterns and the Directional Mechanical Properties of the Dermis," in Bioengineering and the Skin, R. Marks, Ed. (MTP Press, Lancaster, 1981), pp 83- 92. (5) P. F. F. Wijn, A. J. M. Brakee, J.P. Kuiper, and A. J. H. Vendrik, "The Alinear Viscoelastic Properties of Human Skin In Vivo Related to Sex and Age," Ibid., pp 135-145. (6) S. Dikstein and A. Hartzshtark, "In Vivo Measurement of Some Elastic Properties of Human Skin," Ibid., pp 45- 53. A. Tosti, G. Compagno, M. L. Fazzini, and S. Villardita, A ballistometer for the study of the plastoelastic properties of skin, J. Invest. Dermatol., 69, 315-317 (1977). R. Grahame and P. J. L. Holt, The influence of aging on the in vivo elasticity of human skin, Gerontol., 15, 121-139 (1969). H. Alexander and T. H. Cook, Accounting for natural tension in the mechanical testing of human skin, J. Invest. Dermatol, 69, 310-314 (1977). S. Dikstein, A. Hartzshtark, and P. Bercovici, The dependence of low-pressure indentation, slackness, and surface pH on age in forehead skin of women, J. Soc. Cosmet. Chem., 35, 221-228 (1984). H. Alexander and T. Cook, "Variations With Age in the Mechanical Properties of Human Skin In Vivo," reference 3, pp 109-117. D. E. Thompson, H. Mg. Hussen, and R. Q. Perritt, "Point Independence Characterization of Soft Tissues In Vivo," reference 4, pp 103-111. R. M. Dahlgren and W. H. Elsnau, Measurement of skin condition by sonic velocity,J. Soc. Cosmet. Chem., 35, 1-19 (1984). R. O. Potts, D. A. Chrisman, Jr., and E. M. Buras, Jr., The dynamic mechanical properties of human skin in vivo, J. Biomech., 16, 365-372 (1983). R. O. Potts, E. M. Buras, Jr., and D. A. Chrisman, Jr., Changes with age in the moisture content of human skin, J. Invest. Dermatol., 82, 97-100 (1984). J. De Rigal and J-L. Leveque, In vivo measurement of the stratum corneum elasticity, Bioeng. Skin, 1, 13-23 (1985). M. S. Christensen, C. W. Hargens III, S. Nacht, and E. H. Gans, Visco-elastic properties of intact human skin: Instrumentation, hydration effects, and the contribution of the stratum corneum, J. Invest. Dermatol., 69, 282 (1977). C. W. Hargens, III, "The Gas Bearing Electrodynamometer (GBE) Applied to Measuring Mechanical Changes in Skin and Other Tissues," in Bioengineering and the Skin, R. Marks and P. A. Payne, Eds. (MTP Press, Hingham, MA, 1981), pp 113-122. M. S. Christensen, S. Nacht, and E. W. Packman, Facial oiliness and dryness: Correlation between instrumental measurements and self-assessment, J. Soc. Cosmet. Chem. 34, 241 (1983). D. Maes, J. Short, B. A. Turek, and J. A. Reinstein, In vivo measuring of skin softness using the gas bearing electrodynamometer, Intern. J. Cosmet. Sci., 5, 189 (1983). J. D. Ferry, Viscoelastic Properties of Polymers, 3rd ed. (Wiley, New York, 1980), pp 11-12. O. H. Lowry, N. J. Rosenbrough, A. L. Farr, and R. J. Randall, Protein measurement with the folin phenol reagent, J. Biol. Chem., 193, 265 (1951). S. Onogi, T. Masuda, and T. Matsumoto, Non-linear behavior of viscoelastic materials. I. Disperse systems of polystyrene solution and carbon black, Trans. Soc. Rheol., 14, 275-294 (1970). W. Philippoff, Vibrational measurements with large amplitudes, Ibid., 10, 317-334 (1966). M. Kobayashi, S. Ishikawa, and M. Samejima, Application of nonlinear viscoelastic analysis by the oscillation method to some pharmaceutical ointments in the Japanese pharmacopea, Chem. Pharm. Bull. Jpn., 30, 4468-4478 (1982). (26) P. Drout, A. Rochefort, C. Oytana, and P. Agache, In vitro stress relaxation tests of human stratum corneum, Bioeng. Skin 1, 141-156 (1985).

j. Soc. Cosmet. Chem., 36, 349-354 (September/October 1985) X-ray diffraction study of human stratum corneum STIG E. FRIBERG and DAVID W. OSBORNE, Chemistry Department UMR, Rolla, MO 65401, and THOMAS L. TOMBRIDGE, Pathology Department, St. John's Regional Health Center, Springfield, MO 65804-2263. Received December 17, 1984. Synopsis A study of human thin skin stratum corneum was made using small-angle x-ray diffraction. This study elucidated how a new type of skin softener, 2-(alkoyloxy)-l-[(alkoyloxy)methyl]-ethyl-7-(4 heptyl-5,6- dicarboxy-2-cycloheoxene-l-yl ) heptanoate (G2), interacts with the stratum comeurn. A broad diffraction peak from 50-80 A, assigned to the lipid content of the stratum comeurn, was characteristic of untreated normal stratum corneurn. Washing of the specimen with a 0.1% soap solution removed the 50-80 • peak, while treatment with G2 caused the occurrence of a diffuse diffraction peak from 30-45 • for both unwashed and prewashed stratum comeurn. Treatment with a triglyceride oil gave no change in the diffraction pattern. It appears obvious that G2 has a penetrative action on stratum comeurn that is not present for unmodified triglycerides. INTRODUCTION Small-angle x-ray diffraction studies to determine the structure of human stratum corneum were first carried out by Swanbeck in the late 1950s (1,2). This landmark work provided a model that depicted the stratum corneum as being composed of 250 fk protein bundles surrounded by 80 fk thick lipid layers. Since this study, small-angle x-rays have been used by other investigators to examine the stratum corneum and the epidermal lipid it contains (3,4). These studies have mainly used stratum corneum samples obtained from thick skin. However, as has been demonstrated (5), the barrier function and physical properties of thick skin stratum corneum are significantly different from those of thin skin stratum corneum. Since thin skin covers most of the body, especially those parts targeted by ß cosmetics, investigation of the properties of its stratum corneum are of obvious signif- icance. In addition, it is reasonable that information gained from investigations on thick skin may not be totally applicable to the thin skin counterpart, since thin skin provides a much greater barrier function through its different structure. Earlier diffraction studies concentrated on structural elucidation of the stratum corneum for both healthy skin and diagnosed dermatological conditions. However, there is no reported use of low-angle x-ray diffraction to study the effects of external treatments on the stratum corneum. Even the effect of washing upon the epidermal lipids has not been studied, despite the use of thorough washing with Ivory © soap by sebum donors two hours prior to collection (6). It was such experiments by Downing and co-workers 349