A method involving three computer programs is described for characterizing the major component of the Sf 0–12 low‐density lipoprotein class by its Sf rate, hydrated density and molecular weight. All necessary information is obtained from a standard low and high‐density lipoprotein ultracentrifugal analysis. Moving‐boundary flotation rates are measured in 1.061 g/ml sodium chloride and 1.200 g/ml sodium bromide solutions and are corrected to flotation at zero concentration. Hydrated densities are calculated from η Fo versus ρ plots and minimum hydrated molecular weights calculated using Stokes' frictional factor, assuming spherical molecules. Preliminary application of this procedure indicates higher Sfo rates, higher molecular weights, and lower hydrated densities in females than in males. Molecular weights and standard deviations of the principal Sf 0–12 component for non‐fasting normal adult females and males were 2.36±0.16 and 2.12±0.20 millions, respectively.
A comparison has been made of human serum lipoprotein analysis by agarose gel and paper electrophoresis with a standard method of analytical ultracentrifugation. Samples were obtained from 28 patients with various disorders of lipoprotein metabolism. Correspondence was shown between the following electrophoretic and ultracentrifugal fractions: β and Sf 0–20; pre‐β and Sf 20–400; α1 and total HDL. The deviations observed with the electrophoretic methods, though sizable, were smaller than the usual clinically significant abnormalities. Semiquantitative application is there fore justified. Agarose gel electrophoresis is slightly more difficult than paper electrophoresis, but gives improved resolution of pre‐β‐ and β‐lipoproteins and better densitometric scans. Evidence was also presented that the agarose method, when used in conjuction which ultracentrifugation, may be a valuable research technique for the study of lipoprotein properties.
Subfractionation of the total low density Sf 4-105, the low density Sf 4-20 and high density plasma (or serum) lipoproreins has been accomplished using a cumulative flotation rate procedure. Fractionation employs nonlinear salt gradients and high performance swinging bucket rotors. Subfractionation of the total low density lipoproteins with minimal contamination allows an extremely accurate lipoprotein mass measurement of Sf > 400, total very low density lipoproteins and low density lipoproteins (LDL) by elemental CHN analysis. Physical and chemical data on LDL and high density lipoprotein (HDL) subfractions are in general agreement with earlier data. Lower molecular weight data are obtained for HDL subfractions than reported earlier; however this may be the result of the different fractionation procedures used.
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