Lipoprotein Classification:
Lipoprotein Classification:
Lipoprotein can be classified based
on
- Hydrated density: Gofman in 1954 separated lipoproteins by ultracentrifugation into five major density classes.
- Eletrophoretic mobility: Teselius (1947), Frederickson and colleagues (1967) reported existence of two lipoprotein classes separated by moving boundary electrophoresis.
- Apo-Lipoprotein content: Alaupovic and colleagues
As the proportion of lipid to proteins in lipoprotein
complexes increases, the
density of the macromolecule
decreases. This property
is used in separating the various
lipoproteins in the plasma by ultracentrifugation .The rate at which
each lipoprotein floats through a solution of sodium chloride
(sp.gravity-1.063) is expressed as “Svedberg”
(Sf) unit of floatation. One Sf unit is equal to 10-13
cm/s/dyne/g at 260C.
Relatively high content of triglycerides in chylomicron and VLDL is a reflection
of their principal roles in the transport of triglycerides from intestines to liver and from liver to other tissues. There is also evidence
indicating that LDL is formed from VLDL fraction by the removal of
triglycerides.
LDL (about 20nm) carries most (about 2/3rd) of the cholesterol in normal plasma.
The clinical laboratory usually analyze only for total cholesterol
content and total
triglycerides content of the plasma. Knowing the general composition
of the lipoproteins one can draw useful inference about lipoprotein patterns.
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