title: Hydration behaviour of POPC/C(12)-Bet mixtures investigated by sorption gravimetry, (31)P NMR spectroscopy and X-ray diffraction.
abstract: The hydration behaviour of mixtures of the zwitterionic phospholipid 1-palmitoyl-2-oleolyl-sn-glycero-3-phosphocholine (POPC) and the zwitterionic surfactant N,N-dimethyl-N-dodecyl-betain (C(12)-Bet) was investigated by sorption gravimetry, solid-state (31)P NMR-spectroscopy and small angle X-ray diffraction (SAXD). Negative excess hydration (dehydration) was found for almost all hydration degrees investigated. This behaviour is explained by the formation of an inner salt between the dipoles of phospholipid and surfactant headgroups that show a reverse sequence of partial charges with respect to the hydrocarbon backbone. The formation of an inner-salt most probably reduces potential water binding sites. Moreover, NMR data suggest that the incorporation of the zwitterionic surfactant into the phospholipid membrane is correlated with reorientation of the phosphate axis towards the membrane director as well as with reduced lateral and wobbling diffusion.
authors.affiliation: Katholieke Universiteit Leuven, Department of Metallurgy and Materials Engineering, Leuven, Belgium. Helge.Pfeiffer@mtm.kuleuven.be
authors.forename: H
authors.initials: H
authors.lastname: Pfeiffer
authors.forename: H
authors.initials: H
authors.lastname: Weichert
authors.forename: G
authors.initials: G
authors.lastname: Klose
authors.forename: K
authors.initials: K
authors.lastname: Heremans
mesh_terms: D001622:Betaine / Q000031:analogs & derivatives* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010713:Phosphatidylcholines / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D010713:Phosphatidylcholines; D013501:Surface-Active Agents; D014867:Water; D001622:Betaine; C081626:dodecylbetaine; C028694:1-palmitoyl-2-oleoylphosphatidylcholine