Theory and Applications of Nitroxide-based Paramagnetic Cosolutes for Probing Intermolecular and Electrostatic Interactions on Protein Surfaces

作者：Yusuke Okuno, Charles D. Schwieters, Zhilin Yang, G. Marius Clore · 发表于：Journal of the American Chemical Society · 年份：2022 · DOI：10.1021/jacs.2c10035 · 被引用次数：21 · 研究领域：Lanthanide and Transition Metal Complexes、Electron Spin Resonance Studies、Advanced MRI Techniques and Applications

Solvent paramagnetic relaxation enhancement (sPRE) arising from nitroxide-based cosolutes has recently been used to provide an atomic view of cosolute-induced protein denaturation and to characterize residue-specific effective near-surface electrostatic potentials (ϕ ENS ). Here, we explore distinct properties of the sPRE arising from nitroxide-based cosolutes and provide new insights into the interpretation of the sPRE and sPRE-derived ϕ ENS . We show that: (a) the longitudinal sPRE rate Γ 1 is heavily dependent on spectrometer field and viscosity, while the transverse sPRE rate Γ 2 is much less so; (b) the spectral density J (0) is proportional to the inverse of the relative translational diffusion constant and is related to the quantity ⟨ r –4 ⟩ norm, a concentration-normalized equilibrium average of the electron–proton interspin separation; and (c) attractive intermolecular interactions result in a shortening of the residue-specific effective correlation time for the electron–proton vector. We discuss four different approaches for evaluating ϕ ENS based on Γ 2, J (0), Γ 1, or ⟨ r –6 ⟩ norm . The latter is evaluated from the magnetic field dependence of Γ 1 in conjunction with Γ 2 . Long-range interactions dominate J (0) and Γ 2, while, at high magnetic fields, the contribution of short-range interactions becomes significant for J (ω) and hence Γ 1; the four ϕ ENS quantities enable one to probe both long- and short-range electrostatic interactions. The experimental ϕ ENS p...