Fig 2.
The accessibility of diffusible spin relaxers provide a measure of the hydrophobicity of the spin-labeled side chain environment. Top: The contrast function (Φ), which is the logarithmic value of the ratio between the hydrophobic (O2) and the hydrophilic (CrOx) paramagnetic relaxers, is a relative measure of the hydrophobicity of the local microenvironment of the labeled side chain, and is plotted as a function of residue number. Bottom: the accessibility parameter of the hydrophilic relaxer (ΠCrOx), a measure of the relative hydrophilicity of the local microenvironment of the labeled side chain, is plotted as a function of residue number. Larger contrast function values and lower accessibility values of the hydrophilic relaxer indicate greater hydrophobicity. Solid and dashed black lines indicate consecutive and missing data points, respectively. A sinusoidal-shaped periodicity of 3.6 residues per cycle indicates an α-helical structure (orange), whereas an alternating periodicity indicates a β-strand structure (blue). Data for residues 88–173 are plotted, wherein residues 99–163 are from the current study.