Weak Signal from Inadequate Antibody-Antigen Interaction (ELISA (Signal Problems))

Question

Accepted Answer

Signal is present but consistently lower than expected. Positive controls show weak but detectable signal while samples are near background. Common causes: 1) Primary antibody concentration is too low for effective antigen binding 2) Incubation time is insufficient for antibody-antigen equilibrium 3) Target protein is absent or at very low concentration in the sample 4) Antibody affinity is lower than expected for the specific sample matrix Solutions: 1) Increase primary antibody concentration incrementally (e.g., 2-fold to 10-fold higher) 2) Extend antibody incubation time (e.g., overnight at 4°C instead of 1 hour at room temperature) 3) Run a positive control sample to verify antibody functionality 4) Verify target protein expression in sample type by checking scientific literature or using alternative detection methods