The Avidin-Biotin System

Engineering New Forms of Avidin

The avidin-biotin system (ABS) is used extensively as a mediator in a broad range of biological applications, including isolation, localization, cytochemistry, immunoassay and diagnostics (Wilchek & Bayer, 1990). The alkaline properties and oligosaccharide content of the avidin isolated from egg white – which at least appear to be responsible for some nonspecific interaction at biological levels – had originally given the preference to the use of the bacterial biotin-binding analog, ie Streptavidin. However, the nonspecific absorption properties of avidin have been corrected to the extent that the bioengineered neutral & deglycosylated avidin, ie NeutraLite Avidin, exhibits very low levels of nonspecific absorption to biological materials while at the same time leaving a large number of lysine residues readily available for chemical derivatization & conjugation.

The Wilchek & Bayer Group at the Weizmann Institute are to be credited with the merit & success of developing innovative molecular probing / targeting techniques – sometimes coined “bio-recognition” – using the Avidin-Biotin System (ABS): (Weizmann Institute Web Site).

The general approach in avidin-biotin technology

A target molecule in an experimental system is labeled with a biotinylated binder molecule. The biotinylated binder is in turn labeled with an avidin-conjugated probe. Alternatively, the biotinylated binder can be labeled with free avidin followed by a biotinylated probe.