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Avidin and streptavidin reagents are powerful tools in detection and purification applications of biotinylated proteins, nucleic acids and other macromolecules. Conjugated to enzymes, they are suitable for use in solid-phase assays, tissue/cell staining systems, and blotting applications. The fluorochrome conjugates can be employed in immunofluorescence, in situ hybridization detection, and flow cytometry. Agarose bound avidin and streptavidin are ideal for isolation of biotinylated macromolecules.

Unconjugated and Enzyme Conjugates

Avidin. Avidin is a 68 kDa glycoprotein with an extraordinarily high affinity (1015 M-1) for the small molecular weight vitamin, biotin. Because this affinity is over one million times higher than that of antibodies for most antigens, the binding of avidin with biotin (unlike antibody-antigen interactions) is essentially irreversible. In addition to this high affinity, the biotin/avidin system can be effectively exploited because avidin has four binding sites for biotin, and most proteins (including antibodies and enzymes) can be conjugated with several molecules of biotin. These aspects provide the potential for macromolecular complexes to be formed between avidin and biotinylated enzymes.

Over the years we have found that different methods employed in the preparation of avidin can result in distinct “forms” of avidin. These forms of avidin are optimized for use in different applications.

Avidin D – has very low non-specific binding properties. Fluorescent conjugates made with Avidin D are recommended for routine immunofluorescence applications.

Avidin DN – exhibits very low non-specific binding to nucleic acids. Conjugates of Avidin DN can be used to detect biotinlabeled DNA or RNA probes for in situ hybridization or nucleic acid blot techniques.

Avidin DCS – is a cell sorter grade with reduced nonspecific binding for use in cell sorting and other applications. Fluorescent conjugates of Avidin DCS have a high fluor/protein ratio with increased efficiency of fluorescence.