DETERGENT SOLUBILIZATION OF PHOSPHOLIPID-BILAYERS IN THE GEL STATE - THE ROLE OF POLAR AND HYDROPHOBIC FORCES

Testing the solubilisation of phosphatidylcholine (PC) bilayers by Tri ton X-100 reveals that in the gel state, but not in the fluid state, t he amount of detergent required to solubilise the phospholipid is high ly dependent on the chain length. Saturated C16 and C18 PC are virtual ly insoluble at 4 degrees C. However, addition of water-soluble reagen ts that perturb hydrogen bonding, e.g, urea, or of small proportions o f non-bilayer lipids, make the bilayers amenable to detergent solubili sation, even at low temperatures. These results are relevant in the ex planation of the origin of detergent-resistant membrane fragments as f ound, e.g. in caveolae or 'rafts'. (C) 1998 Elsevier Science B.V. All rights reserved.