Journal of Lipid Research, Vol 35, 510-523, Copyright © 1994 by Lipid Research, Inc.
Ultracentrifugal subclasses of low and intermediate density lipoproteins
JJ Opplt and ES Holzberg
Case Western Reserve University, Cleveland State University, OH 44136.
Low density lipoprotein (LDL) and intermediate density lipoprotein (IDL)
classes have been shown to be composed of discrete metabolic entities or
subclasses. Present ultracentrifugal methods are unable to precisely
determine these subclasses. A new analytical micro- ultracentrifugal method
was developed that facilitates the determination of IDL and LDL subclasses
and their F1.21 flotation coefficient from ultracentrifugal scans. The
method is based on the modification of a published equation (Fujita, H.
1956. J. Chem. Phys. 24: 1084-1090) adapted to calculate concentration
gradient boundary curves for IDL and LDL that are approximately Gaussian in
form. Using an extension of this modified equation, theoretical
distributions of the gradient curves were calculated. By applying the
theoretical distributions, IDL and LDL subclasses were resolved from
absorbance scans as Gaussian concentration gradient boundary curves. Both
theoretically calculated and experimentally determined boundary curves for
IDL and LDL lipoproteins were plotted and found to be in excellent
agreement. Three subclasses of LDL and four subclasses of IDL were
determined. The mean flotation rates of the LDL subclasses were: LDL1 =
37.2 +/- 0.6, LDL2 = 31.1 +/- 0.9, and LDL3 = 26.7 +/- 0.7. The mean
flotation rates of the IDL subclasses were: IDL1 = 61.6 +/- 0.9, IDL2 =
53.9 +/- 1.0, IDL3 = 50.1 +/- 0.6, and IDL4 = 45.6 +/- 1.1.
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