Hello everyone.

In my project, I am dealing with a siderophore binding protein and I need to calculate the dissociation constant of the protein with various siderophores and its precursors with and without the iron ion.

Even though I thoroughly dialyzed the protein and dissolved the required ligand compounds with the dialysis buffer, I got a signal like this when conducting ITC with Fe-siderophore.

I am pretty sure the ligand itself does not bother since bare ligand was also conducted and it did not make any problem, but I used FeCl3 anhydrous for adding Fe ion into the ligand.

So I wonder whether Cl- ion was too much (I applied [FeCl3] to have the final concentration to be ~100 mM) or something else.