where, b l is the scattering length of the DSPC, the value of which is available in Table , and V l is the volume of DSPC; taken in this work as 1189.9 Å3 , based on a PC head group volume of 339.5 Å3 and tail group volume of 850.4 Å3 . This value of the tail group volume agrees well with the expected compression of ∼12 %, as discussed in detail by Campbell et al.. Model 2 is essentially the same as model 1, however, an interfacial roughness is now present at the airphospholipid and phospholipid-water interfaces, which is conformal in nature, such that it has the same thickness at all interfaces. This roughness is modelled with an error function , the width of which is taken as 2.9 Å, in agreement with the work of Campbell et al.. In this model, the volume fraction of the layer was kept constant at a value of 1 while the layer thickness, d was the single variable parameter with a uniform prior probability from Å.