Fractionation of alkaline phosphatase during adsoption of CR1-containing vesicles. Bound vesicles and unbound supernatants were resuspended in PBS containing 1% Triton X-100 and assayed for alkaline phosphatase using PNP substrate in sodium-barbital buffer, pH 10.5, as described in the Materials and Methods. () The material bound to either 25 μL or 100 μL beads conjugated to anti-CR1 peptide IgG (Immune) or to 25 μL or 100 μL beads conjugated to nonimmune rabbit IgG (Non-Imm). (▪) γ-Band and unbound material. All volumes were adjusted to equal the volume of the γ-band originally applied to allow direct comparisons. The results shown are the mean ± SEM of duplicate determinations from each of three separate experiments.