Nanostructured lipid aggregates offer enormous potential as tools for membrane structural biology and biophysics. Poly(Styrene-Maleic Acid) stabilized lipid nanodiscs have a number of attractive characteristics including ease of preparation and low cost. In this proposal we wish to probe the effects of lipid tail length on determining disc size, shape and stability. In previous experiments we have probed DMPC/DMPG or DPPC/DPPG discs which have different regions of thermal stability and disc sizes. Here we propose to investigate the effect of mixing the lipid tail lengths to more closely approximate real biological membranes and to study the effects on the nanodisc size and shape for lipids with charged, uncharged and mixed headgroup compositions, and also, using contrast, to highlight the location and any potential phase separation of the lipids in the mixed lipid nanodiscs.