Spiral structures, phospholipids

Self-assembly of phospholipids, such as phosphatidylcholine, a nutritional supplement, in the presence of calcium creates 50-500 nm large, continuous, solid, lipid bilayer sheets rolled into a spiral structure termed nanocochleates.f These can be made to envelope a lipid-soluble drug, such as amphotericin B, to exclude water and protect against pH, oxidation, light, enzymatic attack, hydrolysis, and extremes in temperature. The nanocochleates will convert to liposomes at a pH greater than 6.5 in a calcium deficient environment as is found in the cell (typically less than 1-2... 

A key factor in formation of structures that are not compact is the line tension between the phases, which suppresses instabilities at an interface. The addition of cholesterol to a monolayer lowers the line tension and favors the formation of ramified structures. Complex lamellar structures of many types, including spirals (Fig. 22), are formed in the LE LC transition region of phospholipids doped with cholesterol. If the amphiphiles are chiral, the spirals have a unique sense of rotation. 

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