15N-(13CO)-13CX 2D spectra of (a) IL-bo3 collected on a 500 MHz spectrometer (1H frequency) with 30 ms DARR mixing for 35 hrs, processed with 20 Hz (F1, 15N) and 15 Hz (F2, 13C) net Gaussian-to-Lorentzian line broadening and (b) IY-bo3 collected on a 750 MHz spectrometer (1H frequency) with 50 ms DARR mixing for 75 hrs, processed with 35 Hz (F1, 15N) and 20 Hz (F2, 13C) net Gaussian-to-Lorentzian line broadening.