Figure 1.

Sorcin binds doxorubicin with high affinity in vitro. (a) SPR titration experiments in the presence of 500 μM CaCl₂ and (b,c) fluorescence titration experiments in the presence of 0.5 μM EDTA: Doxorubicin binding to Sorcin (b) and SCBD (c) monitored by intrinsic fluorescence quenching. Each protein was incubated for 3 min at 25 °C in the presence of increasing concentration of ligand. The bars indicate the standard deviation for three independent experiments. The insets show the whole emission peak for each sample from one representative experiment. Both Sorcin and SCBD contain two binding sites for doxorubicin, with affinities in the nanomolar and low micromolar range