17-21. The iron-binding site of transferrin in Figure 17-7 can ac- commodate certain other metal ions besides Fe and certain other anions besides CO. Data are given in the table for the titration of transferrin (3.57 mg in 2.00 mL) with 6.64 mM Ga presence of the anion oxalate, C20, and in the absence of a suit- able anion. Prepare a graph similar to Figure 17-10, showing both sets of data. Indicate the theoretical equivalence point for the bind- ing of one and two Ga ions per molecule of protein and the ob- served end point. How many Ga+ ions are bound to transferrin in the presence and in the absence of oxalate? 3+ solution in the Titration in presence of C,0 Titration in absence of anion Total pl Ga" added 241 nm Total pl. Ga added 241 nm Absorbance at Absorbance at 0.0 0.044 0.0 0.000 2.0 0.143 2.0 0.007 4.0 0.222 0.306 6.0 0.012 6.0 10.0 0.019 8.0 10.0 0.381 14.0 0.024 18.0 0.452 0.508 0.030 0.035 12.0 22.0 14.0 0.541 26.0 0.037 16.0 0.558 0.562 18.0 21.0 0.569 24.0 0.576 Aspartic acid 80 Protein Histidine 253 " Positively Tyrosine charged arginine 121 r 192 Carbonate anion