
The physical chemistry of hydrated and compositionally well defined lipids has been studied for more than half a century, yet the phase behavior of even superficially simple model membranes can be controversial. Relying heavily on the fact that solid state deuterium NMR spectroscopy is sensitive to the dynamics of deuterated lipids, we have explored the characteristics of membranes composed of a variety of sterols and phospholipids. Apart from the lamellar liquid crystalline phases commonly known as "liquid ordered"or "liquid disordered", quasi-solid "gel" phases are frequently observed. Recently we have been asking: How does ceramide affect sphingomyelin/cholesterol membranes? What determines whether large (i.e. micron scale) domains form in ternary membranes? and finally, what adventures lie beyond phase diagrams? Cholesterol plays a big but poorly understood part in lipid-mediated drug delivery. Biopharmaceuticals can be shepherded to their sites of action by cholesterol-containing lipid nanoparticles. To successfully deliver these drugs to the cytosol, the endosome-encased lipid nanoparticle must be destabilized. What is cholesterol's contribution to the formation of the non-bilayer lipid phases thought to be involved in this process?

The physical chemistry of hydrated and compositionally well defined lipids has been studied for more than half a century, yet the phase behavior of even superficially simple model membranes can be controversial. Relying heavily on the fact that solid state deuterium NMR spectroscopy is sensitive to the dynamics of deuterated lipids, we have explored the characteristics of membranes composed of a variety of sterols and phospholipids. Apart from the lamellar liquid crystalline phases commonly known as "liquid ordered"or "liquid disordered", quasi-solid "gel" phases are frequently observed. Recently we have been asking: How does ceramide affect sphingomyelin/cholesterol membranes? What determines whether large (i.e. micron scale) domains form in ternary membranes? and finally, what adventures lie beyond phase diagrams? Cholesterol plays a big but poorly understood part in lipid-mediated drug delivery. Biopharmaceuticals can be shepherded to their sites of action by cholesterol-containing lipid nanoparticles. To successfully deliver these drugs to the cytosol, the endosome-encased lipid nanoparticle must be destabilized. What is cholesterol's contribution to the formation of the non-bilayer lipid phases thought to be involved in this process?