This was derived by considering the geometry of hexagonally close-packed lipid tubules that characterise in the inverse hexagonal phase, with lmin = lc (~ 13 Å for phytantriol). Using the values outlined in Fig. E, water channel radii were calculated to be 9.3 Å, 25.5 Å, and 12 Å for phytantriol cubosomes, monoolein cubosomes and phytantriol/tocopherol acetate hexosomes respectively.