FIGURE 4.

The effect of solution pH on ligand binding to WT and variant sLDLR. One μg of AEDANS-Trp-null apoE3-NT·DMPC and 4 μg of a given sLDLR were incubated in 50 mm Tris base or Tris succinate buffer, 2 mm CaCl₂, 100 mm NaCl, adjusted to the indicated pH values. Samples (300 μl final volume) were excited at 280 nm, and fluorescence emission intensity at 470 nm was determined. Values reported are the mean ± S.D. (n = 3); filled circles, LA5@2 sLDLR; open squares, LA2@5 sLDLR; and filled squares, LA5⇔2 sLDLR.