Method for obtaining structure and interactions from oriented lipid bilayers

Precise calculations are made of ;he scattering intensity I(q) from an oriented stack of lipicl bilayers using a realistic model of fluctuations. The quantities of interest include the bilayer bending modulus K_c, Ins interbiiaycr interaction modulus B, and bilayer structure through the form factor F(q_z). I; is shown how K_c and B may be obtained from data at large q. where fluctuations dominate. Good estimates of F(q.) can be made over wide ranges of q. by using 7(q) in q regions away from the peaks and for q ≠ 0 where details of the scattering domains play little role. Rough estimates of domain sizes can also be ma Je from smaller q. data. Resuits are presented for data taken on fully hydrated. oriented DOPC bilayers in the L_u phase. These results illustrate the advantages of oriented samples compared to powder samples.