Deviations of NOE ratios at 600 MHz over a wide range of proton offsets. (a) The difference with the NOE ratios measured in a reference experiment are displayed for all 15N-1H pairs in human ubiquitin with the proton carrier placed at 8.2 ppm (black); 4.7 ppm (blue); 0 ppm (green); -4 ppm (red); -8 ppm (magenta); and -100 ppm (orange). In this series of experiments, the interpulse delay was τ = 5 ms; the RF amplitude ω1/(2π) = 4 kHz. In the reference experiment, the RF amplitude during effective proton saturation was ω1/2π = 9 kHz, the interpulse delay,τ = 22 ms. In all experiments, the nominal flip angle was β = 180°, and the duration of saturation 4 s. (b) Simulations of the deviation from the correct NOE value. As in the experiments, the interpulse delay was τ = 5 ms and the RF amplitude ω1/2π = 4 kHz. The microdynamic parameters were S2 = 0.7 and τe = 60 ps.