Practice question

Sensitivity in ELISA often enhanced via avidin biotin system without losing specificity. Primary antibody binds antigen, biotinylated secondary antibody binds primary, then streptavidin conjugated enzyme with four biotin binding sites attaches. Each secondary can carry multiple biotins, recruiting many enzyme molecules, amplifying signal dramatically. HRP and ALP alone give single enzyme per antibody. Direct detection lacks amplification steps. Biotinylation preserves antibody specificity because antigen recognition remains unchanged, while enzyme loading increases. This approach lowers detection limit for low abundance proteins and improves signal to noise ratio.