Figure 6.

Conjugations of DA quinones (DAQ) to phenolic hydroxyl groups of synthesized peptides. Three peptides synthesized react with DA under tyrosinase catalysis in the presence or absence of l-cys. After reaction, peptides are precipitated and analyzed by SDS-PAGE, visualized by nitroblue tetrazolium (NBT), silver, and CBB R-250 staining respectively. (A) Peptide Y with 5 phenolic hydroxyl groups (tyrosine residues) can react with DAQ well in solutions, (B) peptide S with 5 non-phenolic hydroxyl groups (serine residues) have poor capability to react with DAQ. (C) Peptides G with no hydroxyl groups (glycine residues) have poor capability to react with DAQ in solutions. (D) Comparison of reactions capability of 3 peptides with DAQ.