Formation of the long-periodicity phase in model membranes of the outermost layer of skin (Stratum corneum)
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Formation of the LongPeriodicity Phase in Model Membranes of the Outermost Layer of Skin (Stratum Corneum) M. A. Kiseleva, E. V. Ermakovaa, A. Yu. Gruzinovb, and A. V. Zabelinb a
Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia email: [email protected] b National Research Centre “Kurchatov Institute”, pl. Akademika Kurchatova 1, Moscow, 123182 Russia Received April 9, 2013
Abstract—Model SC membranes (lipid membranes fabricated from the main components of the lipid matrix of the outermost layer of mammalian skin (stratum corneum (SC)) are used to study the general regularities of the nanostructurization of SC lipid matrix. A model membrane from the outermost layer of skin SC with a composition ceramide 1/ceramide 6/cholesterol/palmitic acid/cholesterol sulfate and a component weight ratio of 30/30/20/15/5 has been investigated by Xray diffraction. It is shown that the membrane structure at pH = 7.2 consists of two shortperiodicity phases with repeat distances d = 47 and 35.7 Å and a longperiod icity phase with d = 127 Å. An increase in pH to 9.0 leads to destruction of the longperiodicity phase, while the shortperiodicity phase is retained with d = 48.3 Å. DOI: 10.1134/S106377451306014X
INTRODUCTION The outermost layer of mammalian skin (stratum corneum (SC)) consists of dead and keratinized cells (corneocytes) and a lipid matrix, which contains flat tened corneocytes (Fig. 1). This structure resembles a brick wall, in which corneocytes play the role of bricks and the lipid matrix cements them. The SC lipid matrix is the main barrier preventing penetration of small molecules through human skin. Thus, it plays a decisive role in the diffusion of drugs through the cuta neous covering and takes part in the control of water balance in the body owing to water diffusion through SC [1]. Ceramide molecules are the main component (up to 47 wt %) of SC lipid matrix.
A general statement is that the size of a multilayer LM unit cell depends on the length of hydrocarbon tails of ceramide molecules entering the composition of the membrane. On the basis of these general prop erties, molecules of longchain ceramides 1, 4, 9 (Fig. 2) should form multilayer membranes with a large repeat distance d ~ 120–130 Å (longperiodicity phase (LPP)), while molecules of other shortchain ceramides should form membranes with a repeat dis tance of 50–60 Å (shortperiodicity phase (SPP)). Experimental studies aimed at searching for LPP and SPP in native and model membranes yield contradic
To date, the question about the function each cera mide plays in the formation of the nanostructure and properties of SC lipid matrix cannot be answered unambiguously [2]. Despite the absence of exact experimental data on the role of each ceramide in the formation of SC lipid matrix properties at the molec ular level, the range of application of ceramides in the production of products by major cosmetics firms is constantly increasing. Study of model SC membranes with a known lipid composition yields infor
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