If we now return to the 5 HDL particle subfractions that we routinely work with, from the small dense HDL3 through to the larger HDL2, and we analyze the total phospholipids, the free cholesterol and the triglycerides, contained in these particles, we can quickly see that the relative numbers or ratios of the molecules of these lipids in the different particles is actually quite different.
Looking especially at the 2 boxes that have been added in the Figure, the ratio of phospholipid to free cholesterol is only 2.5 in the small dense HDL3c particles, whereas it is >4:1 in the larger HDL3a particles. The clear implication of this is that the structural lipids, or even functional lipids, within HDL particles may be organized differently and in different proportions going across the different subpopulations of HDL particles within plasma.
J Clin Lipidol. 2011; 5(6).