Comparative behavior of sterols in phosphatidylcholine-sterol monolayer films

The ability of sterols other than cholesterol (CHOL) to support membrane fu nctions in membranes that normally contain CHOL as the primary. if not sole , sterol may be due, in part, to how well such sterols can mimic CHOL's beh avior and physical properties in membranes. We compared the mixing properti es of CHOL, 7-dehydrocholesterol (7DHC), and desmosterol (DES) in egg phosp hatidylcholine-sterol monolayer films containing 10, 20, and 30 mol percent sterol, measuring pressure-area isotherms on a Langmuir-Blodgett trough wi th the aqueous, buffered subphase maintained at 37 degreesC. Under the cond itions employed, the pressure-area isotherms for all three sterols were sim ilar, with 7DHC exhibiting slightly larger molecular areas on the water sur face at all compositions. These results are discussed in the context of the ability of sterols such as 7DHC and DES 10 substitute structurally and fun ctionally for CHOL in biological membranes. (C) 2001 Published by Elsevier Science B.V.