β-Casein–phospholipid monolayers as model systems to understand lipid–protein interactions in the milk fat globule membrane

Abstract

a b s t r a c tPhospholipideprotein monolayer films were studied as model systems to mimic the structure of the native bovine milk fat globule membrane (MFGM) and to understand lipideprotein interactions at the surface of the globule. Phospholipids extracted from bovine raw milk, raw cream, processed milk and buttermilk powder were spread onto the airewater interface of a Langmuir trough, b-casein was then added to the sub-phase, and LangmuireBlodgett films were studied by epifluorescence microscopy and atomic force microscopy. In all films, b-casein was responsible for clustering of the sphingomyelin-and cholesterol-rich microdomains into larger platforms. This suggests that the same phenomenon may happen at the surface of the milk fat globule, where specific MFGM proteins may cause aggregation of microdomains.

Potential health benefits of sphingolipids in milk and dairy products

“…This is highly complex biological membrane that surrounds the fat globule, hereby stabilizing it in the continuous phase of the milk, and preventing it from enzymatic degradation by lipases (Danthine et al, 2000). Many detailed investigations of the MFGM composition and structure ( Figure 1) as well as it's technological, nutritional and health properties have been recently performed and reported in scientific reviews (Dewettinck et al, 2008;Gallier et al, 2012). Organization of the MFGM as a trilayer structure is now well accepted, with the inner layer composed of proteins and polar lipids from the endoplasmic reticulum and the outer bilayer of polar lipids originating from specialized secretory regions of the apical plasma membrane of the mammary epithelial cells (Heid and Keenan, 2005).…”

Interactions of bioactive molecules & nanomaterials with Langmuir monolayers as cell membrane models

“…With the same idea in mind, the native bovine milk fat globule membrane (MFGM) was mimicked with lipid-proteins mixed monolayers [88]. Phospholipids extracted from bovine raw milk, raw cream, processed milk and butter milk powder were spread onto the air-water interface.…”

The Milk Fat Globule Membrane

“…LangmuireBlodgett films are obtained by the layerby-layer transfer of Langmuir monolayers onto a solid support (e.g., glass or mica slides) (Kaganer et al, 1999) and are easily studied with atomic force microscopy (AFM), a label-free technique to study surfaces in air or liquid. Phase images of monolayers can be acquired when using the AFM in tapping mode and reveal the viscoelastic properties of the monolayers (Gallier et al, 2012a). For example, AFM was used to show the orogenic displacement of proteins by surfactants at the oilewater and airewater interfaces and follow the digestion of interfacial proteins under simulated gastric conditions.…”

“…Thus, phospholipid Langmuir monolayers provide a basic understanding of the biophysics of the MFGM (Gallier et al, 2010b(Gallier et al, , 2012a. The MFGM is a trilayer of phospholipids with proteins, cholesterol, and other compounds.…”

“…The MFGM is a trilayer of phospholipids with proteins, cholesterol, and other compounds. In an attempt to understand the lateral organization of the MFGM, Gallier et al (Gallier et al, 2010b(Gallier et al, , 2012a extracted phospholipids from dairy products (raw milk, raw cream, pasteurized and homogenized milk, and buttermilk powder) and characterized the physical properties of these phospholipid monolayers with and without milk proteins at the airewater interface. Most studies are limited to single phospholipid monolayers or binary or ternary systems due to the complexity of monolayer model systems (Kaganer et al, 1999).…”