Enzyme-linked immunosorbent assay for Met-enkephalin using unconjugated enkephalin as a solid phase antigen

This paper presents a competitive enzyme-linked immunosorbent assay for Met-enkephalin, in which there is no need for preparing any special derivative of Met-enkephalin for its optimal function as a solid-phase antigen. Immunoplate wells were first coated with free Met-enkephalin, and then incubated with antiserum and free Met-enkephalin. The antibodies bound to the solid-phase Met-enkephalin were determined by using anti-IgG conjugated to horseradish peroxidase. The detection limit of the assay was 44 fmol Met-enkephalin per well. The results also showed that Met-enkephalin bound to the solid phase can be titrated directly.