title: Structure modification in hen egg yolk low density lipoproteins layers between 30 and 45 mN/m observed by AFM.
abstract: We have studied the structure of films made by low density lipoproteins (LDL) from hen egg yolk, which are composed of apoproteins, neutral lipids and phospholipids. These LDL have been deposited on air-water interface to form a monolayer which has been compressed to measure an isotherm using Langmuir balance. This isotherm presented three transitions (neutral lipid (surface pressure, pi=19 mN/m), apoprotein-lipid (pi=41 mN/m) and phospholipid (pi=51 mN/m) transitions). We have studied only the apoprotein-lipid transition. In order to observe the LDL film structure before (pi=30 mN/m) and after (pi=45 mN/m) the apoprotein-lipid transition, the formed films were transferred and visualised by atomic force microscopy (AFM). Our results have shown that the structures observed in the LDL film were different depending on the surface pressure. The apoproteins and neutral lipids appeared to be miscible up to the apoprotein-lipid transition, when demixing occurred. The structures observed after the apoprotein-lipid transition should be due to the demixing between apoproteins and neutral lipids. On the other hand, apoproteins and phospholipids seemed miscible whatever the surface pressure. Hence, the first transition (pi=19 mN/m) should be attributed to the free neutral lipid collapse; the second transition (pi=41 mN/m) should be attributed to the demixing of apoprotein-neutral lipid complexes; and the last transition (pi=51 mN/m) should be attributed to phospholipid collapse or to demixing of apoprotein-phospholipid complexes.
authors.affiliation: Institut National de la Recherche Agronomique, BIA, ISD, BP 71627, 44316 Nantes Cedex 3, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Dauphas
authors.forename: Valérie
authors.initials: V
authors.lastname: Beaumal
authors.forename: Paul
authors.initials: P
authors.lastname: Gunning
authors.forename: Alan
authors.initials: A
authors.lastname: Mackie
authors.forename: Peter
authors.initials: P
authors.lastname: Wilde
authors.forename: Véronique
authors.initials: V
authors.lastname: Vié
authors.forename: Alain
authors.initials: A
authors.lastname: Riaublanc
authors.forename: Marc
authors.initials: M
authors.lastname: Anton
mesh_terms: D000818:Animals; D002645:Chickens; D004527:Egg Proteins / Q000737:chemistry*; D004530:Egg Yolk / Q000737:chemistry*; D005260:Female; D008077:Lipoproteins, LDL / Q000737:chemistry*; D018625:Microscopy, Atomic Force
chemical_list: D004527:Egg Proteins; D008077:Lipoproteins, LDL