In this study we will present a full biophysical characterization of the NFκB-IκBα tertiary complex with a focus on intrinsically disordered regions. The identification of the intrinsically disordered N-terminus domain of IκBα exhibits protection occurring at the side chain interface, but not at the backbone interface. This protection occurs at regions near IκBα’s phosphorylation sites S32 and S36. Here we will present hydrogen deuterium mass spectrometry, fast photochemical oxidation of proteins coupled with mass spectrometry and in silico frustration calculations to support our claims.