Oleic acid allows more apoprotein A-1 to bind with higher affinity to large emulsion particles saturated with cholesterol.
Apoprotein (apo) A-1 binding to large triolein-rich emulsion particles saturated with cholesterol has been examined as a function of the oleic acid content. Six emulsion systems were formed containing 0.3-1.0% (by weight) oleic acid, 82.9-86.3% triolein, 10.6-7.2% egg yolk phosphatidylcholine, and 6.7-5.5% cholesterol. The average emulsion particle diameters calculated from these lipid compositions ranged between 84 and 116 nm. Negative stain electron microscopy of an emulsion containing 1% oleic acid showed a polydisperse population of only large spherical particles with a mean diameter of 116 +/- 54 nm. The calculated cholesterol concentrations of the particles surface and core for the six emulsions were 43.3 +/- 1.1 and 5.6 +/- 0.2 mol%, respectively, and were rather constant. Therefore, when the surface oleic acid concentrations increased from 2.6 to 10.1 mol%, the phospholipid concentration decreased from 55.1 to 45.9 mol%. In the core, oleic acid increased at the expense of triolein. In the range studied a nearly 4-fold increase in the surface oleic acid content produces a similar increase in the binding capacity (N) and reduces the dissociation constant (Kd). The changes in the Kd and N values were linearly dependent on the surface oleic acid concentration. These data show that oleic acid allows more apoA-1 to bind with higher affinity to large emulsion particles saturated with cholesterol.
Derksen
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A
Department of Medicine, Boston University School of Medicine, Massachusetts 02118-2394.
Ekman
S
S
Small
D M
DM
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002784:Cholesterol; D002914:Chylomicrons; D004655:Emulsions; D019301:Oleic Acid; D009829:Oleic Acids; D013329:Structure-Activity Relationship; D013499:Surface Properties; D014304:Triolein / Q000378:metabolism
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D002914:Chylomicrons; D004655:Emulsions; D009829:Oleic Acids; D014304:Triolein; D019301:Oleic Acid; D002784:Cholesterol