Free amino acids and water soluble peptides in stratum corneum and skin surface film in human beings.

In recent years, increasing interest has been centered on the biochemistry and physiology of the skin surface, in particular, its potential for resisting physical, chemical, and microbiologic challenges. Morphologically, the skin surface is composed of the stratum corneum, sweat and sebaceous gland ducts, and hair follicles that open onto the surface through pores. The stratum corneum consists of dead, keratinized cells which act like a sponge in holding the surface film material. Surface film is derived primarily from sebaceous glands, sweat glands, and keratinizing epidermis. It is an extremely complex substance. Partly aqueous and partly lipid in nature, homogenized by cholesterol and wax alcohols, it contains proteins, carbohydrates, lipids, acids, salts and their derivatives. Surface film is the skin's first defense. It helps prevent overdrying and overwetting; it slows absorption of foreign chemicals from the skin surface; and it protects against some infections and infestations.' It supports the growth of some normal and some pathogenic skin organisms.2 The stratum corneum and its surface film are interdependent and are treated as one unit in this study. Literature on the origin, action, and composition of the stratum corneum and skin surface film has been increasing steadily, especially since Rothman's' monumental work on the physiology and biochemistry of the skin. We' have been concerned with several aspects of this work and, more recently, with the water soluble organic components of the stratum corneum-surface film complex. Knowledge of the water soluble components is basic to the study of normal and pathogenic skin organisms and patterns