Physicochemical Properties of Bovine Serum High Density Lipoprotein

Bovine high density lipoprotein, floating between densities of 1.063 g per ml and 1.125 g per ml, constitutes about 80% of all bovine serum lipoproteins. Preparations of this lipoprotein appear homogeneous by several criteria: electrophoresis, sedimentation velocity, sedimentation equilibrium, and NH2-terminal amino acid analysis. Bovine high density lipoprotein is a spherical protein-lipid aggregate, containing 32% protein and 68% lipid by weight; its molecular weight is 376,000. The protein component appears to consist of 4 subunits of molecular weight 28,100. Tryptophan fluorescence spectra of the native lipoprotein and of its delipidated form have maximum fluorescence wave lengths at 328 and 338 nm, respectively, an indication that on delipidation the environment of tryptophan residues becomes more polar.