Human milk fat globules: Polar lipid composition and in situ structural investigations revealing the heterogeneous distribution of proteins and the lateral segregation of sphingomyelin in the biological membrane

▶ Human milk fat globules are unique colloidal assemblies: mean diameter: 4-5 μm; surface area: 2 m2/g fat; apparent zeta potential: −7 mV (37 °C). ▶ In the membrane surrounding fat globules, sphingomyelin is laterally segregated in liquid-ordered phase domains of various sizes and shapes. Proteins are heterogeneously distributed. ▶ Cytoplasmic remnents are connected to human milk fat globules ▶ A new model for the structure of the human milk fat globule membrane is proposed.