Studies on the surface structure of very low density lipo-proteins

Very Low Density Lipoproteins (VLDL) were incubated with 5 different pure phospholipases. From the results the following conclusions were drawn. (1) The phospholipids ,re localized in a monomolecular layer on the outside of the VLDL particles. This supports the lipid core model proposed by several groups. (2) A minor fraction of the phospholipids (ranging from 3 to 10%) cannot be degraded by the enzymes and probably have a strong interaction with apoproteins. (3) The average surface pressure of VLDL is probably low, and comparable with a lateral surface pressure of 15 dynes/cm at the air--water interface, as concluded from experiments with two phospholipases A(2). Calculations of the thickness of the surface coat and protein coverage on the basis of this value agree very well with values reported in literature.