De-esterification of cholesteryl esters in human plasma [alpha]-lipoprotein (HDL) by preparations of staphylococcal alpha toxin

SummaryChemical extraction and analysis of reaction mixtures of preparations of staphylococcal alpha toxin and human plasma [alpha]-lipoprotein (HDL) indicated that the cholesteryl esters which form an integral part of the lipoprotein molecules were de-esterified by the toxin preparations with no apparent destruction of the cholesterol moiety.This report is the first of cholesterol esterase produced by staphylococcus. This activity is closely associated with alpha toxin and may be a manifestation of alpha toxin itself. In addition it is shown that soluble plasma lipoproteins are useful substrates for biological reactions involving lipids.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22210/1/0000643.pd

A method of measuring protein dry weight in solutions of unknown salt concentration and an application to lipoproteins

The dialysis bag dry weight method was developed for the measurement of dry weights of lipoproteins subfractionated on density gradients where total recovery of lipoprotein in the gradient was to be determined. Use of the conventional method for dry weight determination was precluded because of inconsistent concentration changes which would occur in the dialysis step due to differences in both the lipoprotein and salt concentration among gradient fractions. The method described consists of transfer of measured undialyzed samples into previously weighed bags followed by dialysis against water, lyophilization of the protein-bag combination and calculation of the protein dry weight as the difference between the bag weight and the total weight.Since the method described incorporates dialysis in the assay, it is capable of giving an accurate protein dry weight measure of a non-predialyzed sample, whereas the conventional dry weight method gives an accurate value only of a previously dialyzed sample. The increase in the standard deviation of the overall dialysis bag method was shown to be less than double that of the conventional method for a sample of known salt concentration and there is no distinguishable difference in the central values obtained by the two methods.The particular usefulness of this method for lipoprotein solutions was presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33887/1/0000152.pd

Studies on the heterogeneity of human serum Lp lipoproteins and on the occurrence of double Lp lipoprotein variants

Lp lipoproteins have been prepared by a mild method from the serum of a large number of individuals. Approximately 25% of the individuals tested showed the presence of a double Lp peak in analytical ultracentrifuge diagrams. These double peaks were designated Lp(a)-1 and Lp(a)-2 to distinguish them from the single Lp(a) peak. The mean viscosity-corrected sedimentation coefficient, S 1.004, 20 C and density of the single Lp(a) peak were 15.8±1.8 s ( n =32) and 1.076±0.01 g/ml, of the Lp(a)-1 peak were 13.5±1.1 s ( n =14) and 1.064±0.007 g/ml, and of the Lp(a)-2 peak were 16.8±1.7 s ( n =14) and 1.074±0.009 g/ml. Absorption tests using a double and single Lp preparation showed that both Lp peaks in the double variants possess Lp(a) specificity. Evidence is lacking as yet for individual specificities for either Lp(a)-1 or Lp(a)-2. Interand intra-individual heterogeneity among Lp lipoproteins is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44186/1/10528_2004_Article_BF00485737.pd