The same BE-code identification can be implemented or double-checked using the BE-CAcoNH data recorded using the pulse sequence shown in Figure . The CA-C' transfer was implemented by J-based INEPT-like manner , which yielded higher transfer efficiency than the dipolar coupling-based transfer using BSH-CP . Figure presents the read-out BE-codes derived from the BE-CAcoNH experiments, with theresult largely consistent with that given by BE-CANH, except for K4, K13 and K28. The errors for the K4 and K13 are discussed above. That for K28 is probably related to its Cβ chemical shift (32.6 ppm), which is near the edge of the BE-1 inversion profile, although this error did not happen for the BE-CANH data. As mentioned above, the error is readily identified as the code [110] is invalid, and since the BE-3 data clearly has no signal for K28, the correct code [010] can be deduced. The present method is more prone to give a false positive since the peak elimination relies on the perfect spin inversion, thus the unobserved peak provides stronger evidence in reading the BE-code. Similar logic is to be incorporated when automating the BEcode assignment procedure that will be described below. The error from the imperfect edge profile can be addressed by improving the OC design for a steeper cutoff profile. The generation of such pulses remains a subject for future investigation. Sequential signal assignment of the GB1. In Figure , we show an example of the sequential walk for the A 26 EKV 29 segment of GB1 (the superscripts show the residue number). We chose the CANH peak at [δCα, δN, δH] = [66. 3, 117.8, 7.47] ppm as the starting point (Figure ). This peak with the BE-code of [010] and δCα >60 ppm can readily be assigned to valine residue as described above. In the cognate slice taken from the BE-CAcoNH at δN = 117.7 ppm, we identified a residue with the BE-code of [010] for Group B. While GB1 has four valine residues, AV 21 , KV , GV and TV 54 , only lysine residue is to give the BE-code of [010], and thus the chosen peak is uniquely assigned to KV . It follows that the Cα chemical shift found in the BE-CAcoNH slice is for Lys28. To go on a step farther, we now look for a Cα peak matching to this K28 Cα peak in other CANH slices. As is seen in Figure , we found two candidate slices. To find out which is the correct one, we see again its cognate BE-CAcoNH spectra and look for the BE-code of [010] for Glu27 (Group B). The CAcoNH slice taken at δN = 116.2 ppm showed the BE-code of [010], while that at δN = 120.1 ppm showed [101], thus the former is assigned to EK 28 (the other slice was later assigned to FK with Phe in Group A for [101]). This process can be repeated as long as possible. Figure shows the walk for one more step down to A 26 EK 28 . The Cα peak of Glu27 matched three CANH slices, but only one of them taken at δN = 115.7 ppm had the cognate CAcoNH slice correctly exhibiting the code of [011] for Ala. The other slices were later assigned to K10 and Q32.