Fig. 1.
Schematic representation of the potential cross-reactivity of anti-Met-enkephalin and anti-β-endorphin polyclonal IgG antibodies. The amino acid sequence of Met-enkephalin (five amino acids corresponding to only one epitope, gray box) is identical to the first five amino acids of the β-endorphin and may be recognized by immune serum IgG specifically raised against Met-enkephalin () or β-endorphin (
)