Fig. 2. Testing the selective decoupling pulse using real time and constant-time ¹H–¹³C HMQC on MBP.

a Overlay of a section of a real-time 2D ¹H–¹³C methyl HMQC experiment with (orange) and without (black) the selective decoupling pulse on a 500 µM MBP (42.5 kDa) protein. The leucine peaks remain as doublets, whereas the valine peaks collapse into singlets. b Constant-time ¹H–¹³C HMQC experiment with indirect constant-time period set to T = 28 ms (1/¹J_CC) and shaped pulse applied at time T/2. Valine resonances are positive (blue) whereas leucine peaks are negative (red). c A version of the experiment with constant-time evolution period is set to T = 42 ms (3/(2 ¹J_CC)) completely eliminates the leucine peaks from the spectrum with positive valine peaks remaining (blue). Full spectra are in Supplementary Fig. 5.