Time resolved small angle neutron scattering (TR-SANS) was used with a stopped-flow apparatus to probe the equilibration kinetics of water across lipid membranes, with and without AMPs. This was done at the D22 instrument at the Institut Laue-Langevin (ILL), in Grenoble, France (doi:10.5291/ILL-DATA.9-13-1096). As neutrons are scattered by the atomic nucleus they can be used to differentiate between isotopes. In particular, neutrons are scattered very differently by hydrogen ( the contrast between the vesicle core and the exterior is gradually lost with a corresponding timedependent diminishing in the total scattering intensity. The time dependence of the total scattering intensity, which reaches a minimum at complete equilibration of the buffer across the membrane, is conveniently expressed using the relaxation function R(t) defined as: