¹⁵N CEST data and traditional model-free analysis capture fast internal dynamics of DJ-1

Previous studies have shown that relaxation parameters and fast protein dynamics can be quickly elucidated from ¹⁵N-CEST experiments [1]. Longitudinal R₁ and transverse R₂ values were reliably derived from fitting of CEST profiles. Herein we show that ¹⁵N-CEST experiments and traditional modelfree analysis provide the internal dynamics of three states of human protein DJ-1 at physiological temperature. The chemical exchange profiles show the absence of a minor state conformation and, in conjunction with ¹H-¹⁵N NOEs, show increased mobility. R₁ and R₂ values remained relatively unchanged at the three naturally occurring oxidation states of DJ-1, but exhibit striking NOE differences. The NOE data was, therefore, essential in determining the internal motions of the DJ-1 proteins. To the authors' knowledge, we present the first study that combines ¹⁵N CEST data with traditional model-free analyses in the study of a biological system and affirm that more 'lean' model-free approaches should be used cautiously.