Detergent solubilisation of phospholipid bilayers in the gel state: the role of polar and hydrophobic forces.

Testing the solubilisation of phosphatidylcholine (PC) bilayers by Triton X-100 reveals that in the gel state, but not in the fluid state, the amount of detergent required to solubilise the phospholipid is highly dependent on the chain length. Saturated C16 and C18 PC are virtually insoluble at 4 degreesC. However, addition of water-soluble reagents that perturb hydrogen bonding, e.g. urea, or of small proportions of non-bilayer lipids, make the bilayers amenable to detergent solubilisation, even at low temperatures. These results are relevant in the explanation of the origin of detergent-resistant membrane fragments as found, e.g. in caveolae or 'rafts'.