Epitope Degradation
Definition
The destruction or alteration of the molecular site on an antigen that an antibody recognises, caused by hydrolysis, oxidation, UV radiation, or microbial proteolysis. Epitope degradation reduces effective sensitivity and can produce false negatives in aged forensic samples even when the target protein was originally present.
- Causes
- Hydrolysis, oxidation, UV exposure, microbial proteolysis
- Effect
- Reduced immunoassay sensitivity
- Main risk
- False negatives in aged or degraded samples
- Common substrates affected
- Blood, semen and saliva stains after heat or humidity
Common questions
How can epitope degradation cause a false negative even though the target protein was originally present?+
The antibody used in the assay recognises a specific structural region, and once that region is chemically altered or cleaved the antibody can no longer bind it, even though other parts of the protein or its DNA may still be detectable.
Does epitope degradation affect DNA recovery from the same stain?+
Not directly. DNA and protein degrade through different chemical pathways at different rates, so a stain can still yield a DNA profile after its epitopes have degraded past the point of giving a positive immunoassay.
Related terms
- Cross-Reactivity
- The capacity of an antibody raised against one analyte to bind structurally related compounds. In RIA, cross-reactivity is the main driver of...
- Limit of Detection (LOD)
- The lowest concentration of analyte that produces a signal reliably distinguishable from the instrument noise, conventionally three times the standard deviation of...
- Limit of Quantitation (LOQ)
- The lowest concentration at which the assay can produce a quantitative measurement with acceptable precision and accuracy, typically defined as the concentration...
- Negative Control
- A sample known not to contain the target antigen. Run alongside case samples to detect contamination or non-specific background reactivity. A reactive...
- Positive Control
- A sample of known composition containing the target antigen at a concentration that should produce a defined signal. Run alongside case samples...