The best of both worlds: A new lipid complex has micelle and bicelle-like properties

Abstract

The utility of detergent micelle and bicelle systems has been demonstrated to be a valuable tool for the study of membrane protein interactions and in structural studies. Bicelles are distinguished from micelles in that they contain a lipid bilayer that mimics the plasma membrane of cells making it more native-like than its detergent micelle counter-part. Bicelles are typically comprised of a long-chain phospholipid such as 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and either a short-chain phospholipid, typically 1,2-dihexanoyl-sn-glycero-3phosphocholine (DHPC), or a bile-salt derivative such as CHAPS or CHAPSO. In solution DMPC and DHPC bicelles assume a discoidal structure comprised of a heterogeneous arrangement where the short-chain lipids gather around the rim of the disk and the long-chain lipids form the flat, bilayer region of the bicelle. Aside from DHPC, CHAPS and CHAPSO few other detergents have reportedly been investigated for their ability to form bicelles with DMPC. In this study, the detergent, C8E5, was used to prepare mixtures with DMPC to determine if it adopts properties similar to DMPC-DHPC bicelles. Mixtures were evaluated using sedimentation equilibrium, 31 Pphosphorus NMR, and light scattering and compared to DMPC-DHPC bicelles. Interestingly, mixtures of DMPC and C8E5 assumed a spherical-shaped micellar structure, not the predicted discoidal shape. DMPC-C8E5 mixtures retain interesting properties rendering them particularly advantageous in studies of membrane protein interactions and hold promise as vehicles for drug delivery.

Versatile formation of supported lipid bilayers from bicellar mixtures of phospholipids and capric acid

“…In particular, 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC 6 ) 29-32 and 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC 7 ) 28,30 are the two main short-chain phospholipids that have been examined in most SLB fabrication-related studies despite the practical need to find natural substitutes with high abundance. Since it has been possible to form solution-phase bicelles by replacing short-chain phospholipids with detergents and detergent-like molecules [39][40][41][42] , we recently demonstrated the ability to fabricate SLBs using bicellar mixtures composed of long-chain 1,2-dioleoyl-snglycero-3-phosphocholine (DOPC) lipid and detergent-like molecules consistent of a saturated fatty acid called lauric acid (LA) with a 12-carbon long chain 43 or a saturated monoglyceride called monocaprin (MC) with a 10-carbon long chain 44 . At a q-ratio of 2.5, DOPC/LA bicelles were able to form SLBs across a wide range of lipid concentrations, however, SLB formation was less successful at a q-ratio of 0.25 and only worked at very low lipid concentrations 43 .…”