Avanti provides L-a-phosphatidylinositol-4,5-bisphosphate (#840046) dissolved in chloroform:methanol:water (20:9:1, v/v) which we find provides better solubility at higher lipid concentrations. If methanol and/or water present a problem in your system, it has been reported that an aliquot of the above solution can be evaporated (using nitrogen) and dried under high vacuum for 30 minutes, and dissolved in chloroform (3mL chloroform per mg lipid) (personal communication from Dr. Stuart McLaughlin).