and cholesteryl esters is surrounded by a phospholipid (monolayer) membrane. Apolipoprotein
A-I is modeled here as a long amphipathic -helix, with the nonpolar face of the helix
embedded in the hydrophobic core of the lipid particle and the polar face of the helix
exposed to solvent. (b) A ribbon diagram of apolipoprotein A-I. (Adapted from Borhani, D. W.,
Rogers, D. P., Engler, J. A., and Brouillette, C. G., 1997. Crystal structure of truncated human apolipoprotein A-I suggests
a lipid-bound conformation. Proceedings of the National Academy of Sciences 94:12291–12296.)