Titanocene dichloride, ( -C5H5)2TiCl2, is a potential antitumor drug thought to be

Chapter 20, Problem 20-25

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Titanocene dichloride, ( -C5H5)2TiCl2, is a potential antitumor drug thought to be carried to cancer cells by the protein transferrin (Figure 17-7). To measure the Ti(IV) binding capacity of transferrin, the protein was treated with excess titanocene dichloride. After allowing time for Ti(IV) binding to the protein, excess small molecules were removed by dialysis (Demonstration 26-1). The protein was then digested with 2 M NH3 and used to prepare a series of solutions with standard additions for chemical analysis. All solutions were made to the same total volume. Titanium and sulfur in each solution were measured by inductively coupled plasmaatomic emission spectrometry, with results in the table. Each transferrin molecule contains 39 sulfur atoms. Find the molar ratio Ti/transferrin in the protein. Added Ti ICP-AES Added S ICP-AES (mg/L) signal (mg/L) signal 0 0.86 0 0.017 4 3.00 1.10 37.0 0.022 1 6.00 1.34 74.0 0.026 8 12.0 1.82 148.0 0.036 2