ABSTRACT
The success of the Edman method for the sequential degradation of peptides has led to the synthesis of modified isothiocyanate reagents designed to improve the ease and sensitivity of the procedure. One such reagent, 4-N,N-dimethylaminoazobenzene-4‱-isothiocyanate (DABITC) is capable of the stepwise degradation of minute quantities of peptides, producing colored 4-N,N-dimethylaminoazobenzene-4‱-thiohydantoin (DABTH)-amino acids. 1 The use of DABITC as a substitute for phenylisothiocyanate in the Edman degradation has several advantages. DABTH-amino acids have an absorption maximum at 436 nm. This obviates interference from UV-absorbing impurities and baseline rise due to alterations of the solvent gradient during HPLC. Moreover, the extinction coefficients are about twice those of PTH amino acids.
