Order-disorder transition in bilayers of diphytanoyl phosphatidylcholine

A comparative study on bilayers of diphytanoyl phosphatidylcholine (DPhPC) and bilayers of dimyristoyl phosphatidylcholine (DMPC) was made by X-ray la mellar diffraction as a function of temperature and the degree of hydration . An order-disorder phase transition of DPhPC reveals an interesting contra st to the standard model of DMPC. Electron density profiles allow us to ded uce the conformational changes which occur in the headgroup-glycerol region and in the chain region. The important conclusion is that the lipid headgr oup may have different conformational energetics in lipids of different cha ins. We explain why this is important to protein-membrane interactions. (C) 2000 Elsevier Science B.V. All rights reserved.