Kinetics of opacification of apo-enriched HDL. Opacification kinetics of HDL (0.5 mg/mL) treated with increasing concentrations of (A) apos A-I and (B) A-II. The concentrations of added apos were 0.0, 0.11, 0.23 and 0.67 mg/mL for curves a, b, c and d respectively. Grey points are raw data, black lines are fits to the data using the equation given in the Methods. C. Effect of increasing apo concentration on the rate constant for opacification. For 0.0 to 0.23 mg/mL added apo, the reduction in opacification rate was −7.2 × 10−3 sec−1mg−1 for apo A-II and −3.8 × 10−3 sec−1mg−1 for apo A-I. D. Maximum opacification of HDL in the presence of added apo A-I or A-II relative to control HDL. For C and D, open circles are addition of apo A-I, closed circles are apo A-II.