Peptide B, the N-terminal fragment of thioredoxin obtained by cyanogens bromide treatment was aminoethylated and digested with pepsin. Eight peptides were separated by high voltage paper electrophoresis and chromatography and characterized with respect to amino acid sequence. The results account for all 37 residues peptide B. The N-terminal sequence of peptide B was determined as: Ser-Asp-Lys-Ile-Ile-His-Leu-Thr-Asp-Asp-Ser-Phe. [ABSTRACT FROM AUTHOR]