Next, we experimentally validated the BE-block incorporating the BE-1/2/3 pulse using a powder mixture of uniformly 13 C, N labeled L-Ala, L-Leu (Group A) and L-Val (Group B), and the pulse sequence in Figure . The length of the BE-block 2𝜏 ) was set to 16 ms to minimize the Ala and Val Cα signals with the BE-1 pulse. For a convenience in the subsequent analysis and discussion, we here define a three-digits binary code, or BE-code, indicating the signal appearance (1) or disappearance (0) in the spectra incorporating the BE-1, -2, and -3 pulses in this order. Thus, each amino acid group is expressed in the BEcode as following: These errors are easily spotted out as the code [110] is invalid by design. Although the Cβ chemical shift for Q2 and E19 (29.9 and 30.7 ppm, respectively) are well within the inversion window of the BE-1 pulse, the signal appeared in the spectrum incorrectly. Considering the fact that the signal for V21, whose Cβ chemical shift (31.9 ppm) is also within the BE-1 inversion window, was correctly eliminated (Figure ), the error cannot be attributed to a malfunction of the BE-1 pulse, and thus attributed to the deviation of 𝐽 $%$& values for Q2 and E19 from the typical value. Even so, since the peak in the BE-1 data for these residues were much smaller than that in the BE-2 data, an intensity thresholding easily retrieve the correct code [010]. The one-bond 𝐽 $%$& couplings in proteins with typical fold is reported to distribute with a standard deviation of ~2.5 Hz 13 , i.e. 95% of the cases fall within ±5 Hz window around the typical value. Our calculation showed that this 10 Hz fluctuation in J coupling causes small false positive peak in the BE-1 inversion window of the magnitude ~0.2 or less, relative to the intensity in the BE-2 data (Figure ). Considering the imperfect edge profiles for the Cb spin inversion as well, a threshold at the onethird (~0.33) of the tallest peak in the BE-1/2/3 dataset typically provides a good result.