Lipids, positively charged

General anesthetics are usually small solutes with relatively simple molecular structure. As overviewed before, Meyer and Overton have proposed that the potency of general anesthetics correlates with their solubility in organic solvents (the Meyer-Overton theory) almost a century ago. On the other hand, local anesthetics widely used are positively charged amphiphiles in solution and reversibly block the nerve conduction. We expect that the partition of both general and local anesthetics into lipid bilayer membranes plays a key role in controlling the anesthetic potency. Bilayer interfaces are crucial for the delivery of the anesthetics. 

Figure 7. Lipophilicity profile of propranolol in liposomes composed of zwitterionic and charged lipids (phosphatidyl ethanolamine (PE), oleic acid (OA), phosphatidyl inositol (PI)). Conditions of measurements are described in [113]. The dotted line indicates the partitioning profile of propranolol in the egg PC liposome system. The bars show the pH-dependent charge profile of propranolol (hatched bars positively charged propranolol) and the lipids in the membrane (black bars negatively charged lipids). Reprinted from [113] Kramer, S. (2001). Liposome/water partitioning , In Pharmacokinetic Optimization in Drug Research, eds. Testa, B. et al. Reproduced by permission of Verlag Helvetica Chimica Acta, Zurich...

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