The inverse contrast variation in small-angle neutron scattering: a sensitive technique for the evaluation of lipid phase diagrams

Small-angle neutron scattering experiments have been performed with aqueous dispersions of binary lipid mixtures. One component was protonated, the other was partly deuterated. By varying the mole fraction of the deuterated species the mean scattering-length density of the lipid lamellas and hence the contrast between liposomes and the solvent was changed. It is shown that this inverse contrast variation has the advantage of (i) a simpler data analysis, (ii) an increased resolution of homogeneous and heterogenous lipid distributions and (iii) a considerably increased sensitivity for the evaluation of phase diagrams in segregated lipid mixtures. Phase boundaries can now be determined to an accuracy of better than 1 mol%.