title: Small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) studies of amide phospholipids.
abstract: Varying chemically the structure of phospholipids in the region between hydrophobic and hydrophilic segments is expected to have a strong influence on the interaction with water and the phase behavior. This is studied in this work with the motivation to investigate these lipids as potential inhibitors of phospholipase A2. Thus the amide phospholipids L-ether-amide-PC (1-O-hexadecyl-2-N-palmitoyl-2-amino-2-deoxy-sn-glycero-3-phosphocholine), L-ester-amide-PC (1-palmitoyl-2-N-palmitoyl-2-amino-2-deoxy-sn-glycero-3-phosphocholine) and L-ether-amide-PE (1-O-hexadecyl-2-N-palmitoyl-2-deoxy-sn-glycero-3-phosphoethanolamine) have been synthesized and characterized. The phase behavior and thermal transitions in buffer dispersions are examined by a combination of high-sensitivity differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) experiments between 10 and 80 degrees C at pH 8.9. The onset temperatures determined from DSC measurements agree well with the starting temperatures of changes in the repeat distance obtained by SAXS measurements. The phases observed are lamellar both below and above the main phase transition. The phase transition temperatures and enthalpies depend strongly on the substitutions in sn-1 position and head group structure. The lamellar repeat distance in gel and liquid-crystalline phases increases with increasing temperature for L-ester-amide-PC and L-ether-amide-PC, whereas the temperature dependence is opposite for the L-ether-amide-PE. The observed behavior is discussed and compared with that of DPPC and DPPE, indicating the strong dependence of hydration and phase behavior on head group structure.
authors.affiliation: International Joint Lab, Key Lab of Colloid and Interface Science, The Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Zhong Guan Cun, Beijing 100080, China.
authors.forename: Xiuhong
authors.initials: X
authors.lastname: Zhai
authors.forename: Markus
authors.initials: M
authors.lastname: Bartel
authors.forename: Gerald
authors.initials: G
authors.lastname: Brezesinski
authors.forename: Bernd
authors.initials: B
authors.lastname: Rattay
authors.forename: Helmuth
authors.initials: H
authors.lastname: Möhwald
authors.forename: Junbai
authors.initials: J
authors.lastname: Li
mesh_terms: D000577:Amides / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D008954:Models, Biological; D015394:Molecular Structure; D010713:Phosphatidylcholines / Q000032:analysis / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000032:analysis / Q000737:chemistry; D010743:Phospholipids / Q000032:analysis* / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D000577:Amides; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010743:Phospholipids; C483858:phosphatidylethanolamine