Quick Definition
What is Normal Goat Serum (NGS)?: Normal Goat Serum (NGS) is serum from healthy goats used as a blocking reagent in IHC and IF when secondary antibodies are raised in goat. It saturates non-specific Fc receptor binding sites in tissue sections before the secondary antibody is applied, reducing background signal.
When NOT to use goat serum for blocking
Never use Normal Goat Serum when your primary antibody is raised in goat. Goat serum IgG will occupy the same epitope binding sites that your goat primary antibody targets — blocking binding and resulting in no signal. In this case use blocking serum from a different species (horse serum is a common alternative).
NGS vs NDS for multi-label experiments
For single-label IHC with a goat secondary, NGS is correct. For multi-label IF with primaries from rabbit, mouse, and goat hosts, switching all secondaries to donkey-raised allows a single Normal Donkey Serum (NDS) blocking step — simplifying the protocol significantly.
Key Facts
- Used when secondary antibody is goat-raised — e.g. goat anti-rabbit HRP, goat anti-mouse AF488
- Species matching rule: blocking serum species = species of secondary antibody host
- 5–10% NGS in PBS for 30–60 min — applied after antigen retrieval, before primary antibody
- Do not wash after blocking — drain excess and apply primary directly in 1–5% NGS/PBS
- NGS cannot be used when primary antibody is raised in goat — would block primary antibody binding sites
- Available from SeamlessBio: 50 mL, 100 mL, 500 mL; heat inactivated on request
Further Reading
SeamlessBio GmbH · Passau, Germany · info@seamlessbio.de
English 
Deutsch