Measurement of sugar depletion from uncharged lamellar phases by SANS contrast variation

We applied small-angle neutron scattering (SANS) contrast variation to samp les where a microphase separation occurred. The samples contain multilamell ar vesicles in equilibrium with excess "solvent" that produce a very common powder pattern in SANS: a Debye-Sherrer ring produced by the regular bilay er packing superposed to a sharply decaying Porod behaviour. These two feat ures of the SANS pattern have distinct contrast match points (CMP). We expl oit here the small angle signal to determine the partition of sugars betwee n two coexisting microphases. The net result is an exclusion of small sugar molecules from the liquid crystalline domains of the sample. We discuss th is exclusion in relation with the observed maximum swelling, headgroup hydr ation and bilayer softening induced by the presence of the sugar molecules.