Supplemental_Data

1. To demonstrate the specificity and affinity of ALFR for the folate receptor, we examined the fluorescence intensity of KB cells treated with folate-rhodamine (25 nM; an established FR-specific ligand) in the presence of increasing concentrations of ALFR (0-200 nM). Co-incubation with ALFR reduced cell-associated rhodamine fluorescence in a concentration-dependent manner, resulting in >90% blockade of folate-rhodamine binding at 200 nM ALFR. Analysis of the binding data from this competition study yielded a Kd of ALFR for the folate receptor of ~17 nM (95% confidence intervals: 8.9-34 nM, R2=0.98).