title: Biophysics (and sociology) of ceramides.
abstract: In the past decade, the long-neglected ceramides (N-acylsphingosines) have become one of the most attractive lipid molecules in molecular cell biology, because of their involvement in essential structures (stratum corneum) and processes (cell signalling). Most natural ceramides have a long (16-24 C atoms) N-acyl chain, but short N-acyl chain ceramides (two to six C atoms) also exist in Nature, apart from being extensively used in experimentation, because they can be dispersed easily in water. Long-chain ceramides are among the most hydrophobic molecules in Nature, they are totally insoluble in water and they hardly mix with phospholipids in membranes, giving rise to ceramide-enriched domains. In situ enzymic generation, or external addition, of long-chain ceramides in membranes has at least three important effects: (i) the lipid monolayer tendency to adopt a negative curvature, e.g. through a transition to an inverted hexagonal structure, is increased, (ii) bilayer permeability to aqueous solutes is notoriously enhanced, and (iii) transbilayer (flip-flop) lipid motion is promoted. Short-chain ceramides mix much better with phospholipids, promote a positive curvature in lipid monolayers, and their capacities to increase bilayer permeability or transbilayer motion are very low or non-existent.
authors.affiliation: Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, P.O. Box 644, 48080 Bilbao, Spain. gbpgourf@lg.chu.es
authors.forename: Félix M
authors.initials: FM
authors.lastname: Goñi
authors.forename: F-Xabier
authors.initials: FX
authors.lastname: Contreras
authors.forename: L-Ruth
authors.initials: LR
authors.lastname: Montes
authors.forename: Jesús
authors.initials: J
authors.lastname: Sot
authors.forename: Alicia
authors.initials: A
authors.lastname: Alonso
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D002518:Ceramides / Q000737:chemistry* / Q000378:metabolism; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D012996:Solutions; D013816:Thermodynamics; D014867:Water
chemical_list: D002518:Ceramides; D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D010743:Phospholipids; D012996:Solutions; D014867:Water