Then,
the middle layer in the tube (0.15 mL) was removed, and the
bottom layer in the tube (0.6 mL) was transferred to another
tube. For HDL separation, 0.3 mL of 1.478-kg/L sodium
bromide density solution was added to the 0.6 mL solution
in the tube, mixed, and ultracentrifuged at 100000g at 128C
for 4 hours, and the HDL layer was removed from the top