Figure 4.

1H and ¹⁵N lineshapes predicted for the broad and narrow multiplet components of ¹H^N and ¹⁵N of the ¹⁵N–¹H moiety in a [¹⁵N,¹H]COSY experiment of the type of Fig. 3 b1 and b2 for large proteins in H₂O solution at 20°C and a ¹H frequency of 750 MHz. (a1 and a2) Spherical protein of size 150 kDa. For the calculation a rotational correlation time of 60 ns, Δσ_H = −16 ppm and Δσ_N = −160 ppm were used, and all nonlabile protons were replaced with deuterons. Relaxation due to DD coupling with other labile protons was modeled by placing two protons at a distance of 0.29 nm from ¹H^N. The full linewidths at half height are indicated. (b1 and b2) Spherical protein of size 800 kDa. The calculation used τ_c = 320 ns and otherwise the same parameters as in a.