A novel lipid-polymer system with unique properties has potential in drug delivery and biotechnology applications

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-3-phosphocholine (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, 31P-phosphorus 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.

On the Interaction of Ionic Liquid 1-Butyl-3-Methylimidazolium Hexafluorophosphate with β-Cyclodextrin in Aqueous Solutions

The formation of inclusion complex of β-cyclodextrin (β-CD) with the hydrophobic room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) in aqueous solutions was studied at 298.15 K using 1H, 13C, 19F and 31P NMR spectroscopy and isothermal titration calorimetry (ITC). Currently, there is a disagreement in the literature concerning the structure of the complex formed. In contrast to some results published recently in the literature, we found no reasonable support for β-CD to form an inclusion complex with 1-butyl-3-methyl-imidazolium cation of bmimPF6 in water. Our measurements on bmimPF6, the ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl), and the inorganic salt potassium hexafluorophosphate (KPF6) consistently support the formation of a weak 1:1 inclusion complex of β-CD with hexafluorophosphate anion instead of the bmim+ cation. The thermodynamic parameters of the respective complexation were calculated. The binding constant was evaluated from ITC and proton, fluorine and phosphorus NMR measurements, and the complex formation enthalpy and entropy were obtained from ITC.