Solid-State NMR of Membrane-Active Proteins and Peptides

Membranes are commonly perceived as little more than a simple canonical bilayer formed by the obvious orientation-preference of the constituent amphiphilic lipid molecules. Hydrophilic head groups, such as the zwitterionic phosphatidylcholine (PC), line the interface with aqueous environments on both sides of the membrane, while the aliphatic fatty acid chains of varying lengths and degree of unsaturation meet tail-to-tail to fill the region flanked by the head groups. The common perception of membrane-associated peptides and proteins is that they generally span the membrane with simple secondary structures, usually α-helices, but include the occasional β-sheet structure. These secondary structures are frequently regarded as trivial anchors to be removed so that the more interesting soluble domains may be studied by conventional approaches.