Electrophoretic mobility: which lipoprotein shows pre-beta mobility?

• A. Chylomicrons
• B. VLDL
• C. LDL
• D. HDL

Answer: (B)

In electrophoresis of lipoproteins, mobility is determined by particle size, density, and surface apolipoproteins which affect net charge. The paths run from near the origin toward more mobile fractions in this order: chylomicrons at the origin, pre-beta lipoproteins, beta-lipoproteins, and then alpha-lipoproteins. The lipoprotein that shows pre-beta mobility is the one that migrates just ahead of the origin but before the beta region, due to its triglyceride-rich, relatively large particles and its apolipoprotein composition (Apo B-100 with Apo E/C). This makes it move between origin and the LDL (beta) fraction. Chylomicrons stay at origin because of their large size and minimal charge; LDL migrates to the beta region; HDL to the alpha region. So, pre-beta mobility corresponds to VLDL.