Phospholipids isolation from mammalian cells

In the past decade a number of physical techniques have been used to evaluate the unique barrier properties of mammalian skin [1]. This chapter deals with the use of another physical technique, fluorescence spectroscopy, to study the barrier properties of the human stratum corneum (SC), specifically with respect to the transport of ions and water. The SC is the outermost layer of the human epidermis and consists of keratinized epithelial cells (comeo-cytes), physically isolated from one another by extracellular lipids arranged in multiple lamellae [2]. Due to a high diffusive resistance, this extracellular SC lipid matrix is believed to form the major barrier to the transport of ions and water through the human skin [3-5]. The objective of the fluorescence studies described here is to understand how such extraordinary barrier properties are achieved. First the phenomenon of fluorescence is described, followed by an evaluation of the use of anthroyloxy fatty acid fluorescent probes to study the physical properties of solvents and phospholipid membranes. Finally, the technique is applied to the SC to study its diffusional barrier to iodide ions and water. 

Finally, I introduce the naturally occurring protein surfactant originated from plants, called oleosin [75,76], In plant seeds, oils are stored in discrete organelles called oil bodies. Oil bodies are small spherical particles approximately 1 p,m in diameter. Notice in Fig. 14 the difference in size between plant oil bodies and mammalian lipoproteins (from approximately 10 nm to 80 nm in diameter) despite the similarity in structure. Each oil body has a core of triglycerides surrounded by a layer of phospholipids (Fig. 16) [76]. Oil bodies inside the cells of mature seeds or in isolated preparations are remarkably stable and do not aggregate or coalesce. This stability cannot be attained by only a layer of phospholipids. Seed oil bodies are stable because, in addition to the phospholipid layer, a layer of unique proteins, termed oleosin shields their surface. 

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