Fig. 3
From: Bioinformatics tools and data resources for assay development of fluid protein biomarkers
Potential matrix-dependent obstacles of successful antibody binding to fluid protein biomarkers. Several circumstances can arise within an immunoassay that hide the epitope (blue) from its corresponding antibody. (A) Fluid biomarkers that are located inside EVs are not accessible for antibodies. (B) A PTM (red) that lies on or close to the epitope might mask it from the antibody. (C) If the interface of a protein interaction with another present molecule (green) is close or on the epitope, the antibody cannot recognize its binding region. (D) If a protein is accumulating, its altered structure might hide the epitope within the aggregate