N-Alkanes in the Skin

Mammals are not alone in their requirement to survive as an aqueous body in a terrestrial environment. Plants, arthropods, reptiles, and birds have all developed cellular mechanisms to regulate integumental water loss in an arid environment.1Although the details of the regulatory systems vary significantly among these divergent groups, all share a common requirement for integumental lipids for this function. Lipids by definition display minimal affinity for water, however, the degree of hydrophobicity varies among different lipid classes. Whereas the polar headgroups of phospholipids and glycosphingolipids exhibit considerable affinity for water, even such so-called polar lipids can display substantial hydrophobicity, depending on the chain length of their esterified fatty acids, and the presence or absence of hydroxyl groups. Among the traditional nonpolar or neutral lipids; ie, free fatty acids, triglycerides, sterol esters, and hydrocarbons; the latter, which are for the most part very long chain (C ≤ 20 species),