Human serum low density lipoprotein-sodium deoxycholate interaction.

The binding of sodium deoxycholate to low density lipoprotein (LDL) is a relatively fast process, as compared to the lipid displacement reaction and solubilization. The initial reaction has a bimolecular rate constant of approximately 539 M-1 S-1. In the presence of 1 mM sodium deoxycholate, below critical micelle concentration, 0.04 g of sodium deoxycholate was bound per g of LDL, resulting in an increase in particle radius from 102 to 128 +/- 0.3 A and an axial ratio of 5.6 for a prolate ellipsoid. Such increases were also observed using higher sodium deoxycholate concentrations and are apparently due to sodium deoxycholate-induced elongation or distortion of certain portions of LDL.