Estimation of surface area in very-low-density human serum lipoproteins

The surface area of very-low-density lipoproteins (VLDL) from the serum of 15 healthy donors, as well as the surface of artificial lipid particles, ha ve been estimated. The artificial particles were prepared as a mixture of e gg phosphatidylcholine and triolein. Two fluorescent probes - energy donor and acceptor - were placed on the surface, and Forster's nonradiative energ y transfer was measured; the transfer efficiency is a function of the surfa ce area. The fluorescent probe K-68 (4-[5-(phenyloxazolyl-2)-1-pentadecyl)p yridinium) was used as a donor, and DSP-12 (4-p-(dimethylamino)styryl-N-dod ecylpyridinium) was used as an acceptor. The specific surface area of the artificial lipid particles was estimated t o be 0,585 +/- 0,015 nm(2) per one phosphatidylcholine molecule, which is b y 15% less then in lipid bilayers. The specific area of VLDL particles was 259 +/- 65 nm(2) per 1 g of total V LDL. This value is close to the specific area of low-density lipoproteins ( LDL), and corresponds to the area of a spheric particle 10-12 nm in radius. However, VLDL are assumed as much more large particles as compared with LD L. Therefore, the new data of the VLDL surface area raise a problem of revi sion of existing VLDL models.