Fig. 2. Process to identify serine as the source of the NH(CH2)2 moiety. HYSCORE spectra of CrHydA1 Hox samples isolated from maturation reactions supplemented with different sets of 13C, 15N-amino acid mixtures. Amino acid codes follow their standard abbreviations. Cys and Tyr have been previously tested.17,25 Eight amino acids (Asp, Phe, His, Ilv, Asn, Gln, Thr, Trp) have not been individually tested. Spectrometer settings are as indicated in Fig. 1.
