[talderson]

• I am assuming you tried ITC, but were unable to acquire satisfactory results?

• If so, when you are titrating your unlabeled protein into the labeled sample, what molar concentration-fold do you typically see HSQC peak changes reach a maximum? That is, do you need 3-fold binding partner to elicit maximum decreases in HSQC peaks of the labeled protein? Or is binding tighter than that: sub-stoichiometric concentrations of unlabeled protein. That might give you a start/estimate of Kd...i.e. weak (mid to high uM) or tight binding in the low uM to high nM range.

• I myself would be interested in literature that discusses quantitative binding constants derived from NMR titration experiments. Alas, I haven't seen any specific papers on the topic.