Figure 2. SP-A enhances the sedimentation velocity of [³H]Rb-LPS micelles in the presence of calcium.

[³H]Rb-LPS (10⁻⁷ M) was preincubated with or without SP-A (195 μg/ml) for 45 min at 37 °C in the presence of either 2 mM Ca²⁺ or 2 mM EDTA. Afterwards, linear (5–50%) sucrose density gradients were performed as described in the Experimental section. Sedimentation direction is from right to left. The radioactivity of each fraction is presented as percentage of total recovered radioactivity.