The iron-binding site of transferrin in Figure 17-7 can accommodate certain other metal

Chapter 17, Problem 17-21

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The iron-binding site of transferrin in Figure 17-7 can accommodate certain other metal ions besides Fe3 and certain other anions besides CO3 2. Data are given in the table for the titration of transferrin (3.57 mg in 2.00 mL) with 6.64 mM Ga3 solution in the presence of the anion oxalate, C2O4 2, and in the absence of a suitable anion. Prepare a graph similar to Figure 17-10, showing both sets of data. Indicate the theoretical equivalence point for the binding of one and two Ga3 ions per molecule of protein and the observed end point. How many Ga3 ions are bound to transferrin in the presence and in the absence of oxalate? Titration in presence of C2O3 2 Titration in absence of anion Total L Absorbance at Total L Absorbance at Ga3 added 241 nm Ga3 added 241 nm 0.0 0.044 0.0 0.000 2.0 0.143 2.0 0.007 4.0 0.222 6.0 0.012 6.0 0.306 10.0 0.019 8.0 0.381 14.0 0.024 10.0 0.452 18.0 0.030 12.0 0.508 22.0 0.035 14.0 0.541 26.0 0.037 16.0 0.558 18.0 0.562 21.0 0.569 24.0 0.576