First-derivative EPR spectra of forms of Trg containing a nitroxide side chain R1 at the indicated positions. The spectra are scaled vertically for convenience of presentation. The magnetic field scan width was 98 G. The line width of the central resonance (ΔH) is indicated on the top spectrum. For spectra that appear to have contributions from two or more components, the less-mobile components are marked by arrows. ΔH−1 values for the spectra shown were: 46, 0.294; 45, 0.284; 44, 0.400; 43, 0.380; 42, 0.345; 41, 0.345; 40, 0.351; 39, 0.286; 38, 0.250; 31, 0.286; 30, 0.394; 26, 0.353; 25, 0.333; 23, 0.312; 21, 0.426; 18, 0.455; 17, 0.455.