However, for the most cooperative complexes, α were remarkably lower than expected based on the reported values, especially for Brd4(2). This discrepancy was mainly attributed to the relatively high protein concentrations used in competitive F NMR experiments. While FP competition experiments can be performed at 15 nM of VBC, the F NMR titrations were performed at 1 µM. Therefore, for the most stable ternary complexes, the tight binding limit of the F NMR assay was reached, consequently overestimating their affinities. To overcome these issues, the titrations of MZ1 in absence and in presence of Brd4(2) were performed again at lower Please do not adjust margins Please do not adjust margins concentrations of VBC. Unfortunately, the lower signal-to-noise ratio and poor assay window introduced high deviations in the IC50 values, resulting in α values still not comparable to those previously reported. [a] Not determined.