Comparison of 7-deydrocholesterol and desmosterol in ternary sterol/phsopholipid mixed Langmuir monolayers

COLL 192

Kimberly Borrenpohl and Alexa Serfis. Department of Chemistry, Saint Louis University, 3501 Laclede Ave., St. Louis, MO 63103
Cholesterol supports and initiates membrane functions in biological membranes, but it has been found that other sterols may have the capability of replacing cholesterol in natural membranes, with detrimental effects. Membrane accumulation of the cholesterol (CHOL) derivative 7-dehydrocholesterol (7DHC) has been implicated as a causative factor in the Smith Lemli Opitz Syndrome. We have previously reported that 7DHC and a second cholesterol derivative desmosterol (DES) exhibit behavior similar to CHOL when incorporated into binary phosphatidylcholine (PC)/sterol mixed Langmuir monolayers. The current study compares the physical characteristics of ternary mixtures of DHC/CHOL/PC and DES/CHOL/PC monolayers on water. Pressure-area isotherms for the mixed monolayers show a large condensing effect which is maximized at 30 mol percent sterol. The sterols behave very similarly at all DHC and DES compositions, indicating that DHC and DES may substitute for cholesterol in natural membranes.