title: Structural polymorphism of hydrated ether-linked dimyristyl maltoside and melibioside.
abstract: The structural polymorphism of two selected disaccharide glycolipids with a maltose (DMMA) and a melibiose (DMME) carbohydrate headgroup linked to dimyristyl alkyl chains were investigated by FTIR-spectroscopy, differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and film-balance measurements. The compounds displayed thermotropic multilamellar phases. In the gel phase, DMMA formed also a crystalline phase of orthorhombic symmetry, and DMME an interdigitated phase. The gel to liquid crystalline phase transition temperature T(c) of DMMA depended on the storage and hydration conditions, a precooled sample having a T(c) around 45 degrees C, and a freshly prepared sample around 33 degrees C. In contrast, the phase transition temperature for the gel to liquid crystalline phase of DMME was always found at 24 degrees C. Surface pressure isotherms of the lipids on water and buffer showed that DMMA covers only a small surface area (approximately 35A(2)) whereas DMME requires 50 A(2) of space on the surface. Films of DMMA can be compressed up to a maximum compressibility Pi(max) of 54 mN m(-1) whereas the tilted DMME forms less stable films with Pi(max) of 34 mN m(-1). These different structural characteristics reflect the different conformations of the disaccharide head groups. The presence of the alpha1-->4 linked maltose head group in DMMA and an alpha1-->6 linked melibiose head group in DMME induces geometrical structures ranging from a slightly wedge-shaped towards a more tilted structure, and as a consequence of Israelachvilis packing model, to the formation of different phases. In addition, the structural constraints of DMME allow the formation of a phase with interdigitated hydrocarbon chains.
authors.affiliation: Martin-Luther-Universität Halle-Wittenberg, Institut für Physikalische Chemie, Mühlpforte 1, Halle/Saale, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Garidel
authors.forename: Jörg
authors.initials: J
authors.lastname: Howe
authors.forename: Götz
authors.initials: G
authors.lastname: Milkereit
authors.forename: Manfred
authors.initials: M
authors.lastname: Rössle
authors.forename: Sebastian
authors.initials: S
authors.lastname: Linser
authors.lastname: Sven Gerber
authors.forename: Regine
authors.initials: R
authors.lastname: Willumeit
authors.forename: Thomas
authors.initials: T
authors.lastname: Gutsmann
authors.forename: Volkmar
authors.initials: V
authors.lastname: Vill
authors.forename: Klaus
authors.initials: K
authors.lastname: Brandenburg
mesh_terms: D002152:Calorimetry, Differential Scanning; D004187:Disaccharides / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry*; D053838:Scattering, Small Angle; D017550:Spectroscopy, Fourier Transform Infrared; D053835:Unilamellar Liposomes; D014961:X-Ray Diffraction
chemical_list: D004187:Disaccharides; D006017:Glycolipids; D053835:Unilamellar Liposomes; C527512:dimyristoyl melibioside; C527513:dimyristyl maltoside