Influence of the alkyl chain length of alkyl glucosides on their ability to solubilize phosphatidylcholine liposomes

The solubilizing alterations caused by a series of alkyl glucosides (alkyl chain length ranging from C-8 to C-12) in neutral and electrically charged phosphatidylcholine (PC) liposomes were investigated. The surfactant to pho spholipid molar ratios (Re) and the bilayer/aqueous phase partition coeffic ients (K) were determined by monitoring the changes in the static light sca ttering (SLS) of the system during solubilization. Liposomes were formed by PC, to which phosphatidic acid (PA) or stearylamine (SA) was added when re quired to increase the negative or positive surface charge. The fact that a t the two interaction levels investigated (100 and 0% of SLS of the surfact ant/PC systems), the free surfactant concentration for each surfactant was always comparable to its critical micelle concentration (CMC) indicates tha t the liposome solubilization was mainly ruled by the formation of mixed mi celles. The rise in the surfactant CMC (decrease in its alkyl chain length) led to an increase in the surfactant ability to saturate or solubilize lip osomes and inversely in an abrupt decrease in its bilayer affinity, regardl ess of the electrical charge of liposomes. The overall balance of these opp osite tendencies shows that the octyl glucoside showed the highest ability to saturate and solubilize liposomes (lowest Re values), whereas the dodecy l glucoside exhibited the highest degree or partitioning into liposomes or affinity with these bilayer structures (highest K values). The use of C-9-G lu reduced approximately 2.5 times the concentration needed to saturate and solubilize 1.0 mM PC liposomes with respect to that needed for C-8-Glu, re gardless of the type of electrical charge present in bilayers. (C) 2001 Els evier Science B.V. All rights reserved.