title: Collapsed bipolar glycolipids at the air/water interface: effect of the stereochemistry on the stretched/bent conformations.
abstract: This article describes a comparative study of several bipolar lipids derived from tetraether structures. The sole structural difference between the main two glycolipids is a unique stereochemical variation on a cyclopentyl ring placed in the middle of the lipids. We discuss the comparative results obtained at the air/water interface on the basis of tensiometry and ellipsometry. Langmuir-Blodgett depositions during lipid film compressions and decompressions were also analyzed by AFM. The lactosylated tetraether (bipolar) lipid structures involved the formation of highly stable multilayers, which are still present at 10 mN m(-1) during decompression. This study suggests also that the stereochemistry of a central cyclopentyl ring dramatically drives the conformation of the corresponding bipolar lipids. Both isomers (trans and cis) adopt a U-shaped (bent) conformation at the air/water interface but the trans cyclopentyl ring induces a much more frustration within this type of conformation. Consequently, this bipolar lipid (trans-tetraether) undergoes a flip of one polar head-group (lactosyl) leading to a stretched conformation during collapse.
authors.affiliation: Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France; Université européenne de Bretagne, France.
authors.forename: Alicia
authors.initials: A
authors.lastname: Jacquemet
authors.forename: Nolwenn
authors.initials: N
authors.lastname: Terme
authors.forename: Thierry
authors.initials: T
authors.lastname: Benvegnu
authors.forename: Véronique
authors.initials: V
authors.lastname: Vié
authors.forename: Loïc
authors.initials: L
authors.lastname: Lemiègre
mesh_terms: D000388:Air / Q000032:analysis*; D006017:Glycolipids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D008968:Molecular Conformation; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry*
chemical_list: D006017:Glycolipids; D014867:Water
keywords: AFM; Bipolar lipid; Bolaamphiphile; Cyclopentyl ring; Glycolipid; Langmuir film; Stereochemistry