(A) Examples of lipids commonly used in membrane protein folding studies. Lipids such as those with PC headgroups tend to form bilayers, while non-bilayer forming lipids such as DOPE and cardiolipin (CL) adopt hexagonal phases. Single-chain lipids such as Lyso PC tend to form micelles. (B) Lipid composition determines the overall electrostatic and mechanical properties of mixed lipid bilayers. Introducing non-bilayer forming lipids alters the lateral pressure profile of a bilayer.