Imject™ Maleimide-Activated Ovalbumin (Thermo Scientific™)

Thermo Scientific Imject Maleimide-Activated Ovalbumin is sulfhydryl-reactive ovalbumin (OVA) for hapten-carrier conjugation with cysteine-containing peptides and other thiolated antigens.

Features of Imject Maleimide-Activated Ovalbumin:

• Maleimide-Activated Ovalbumin, supplied lyophilized in PBS (pH 7.2) with stabilizer
• Activated with 5 to 15 moles of maleimide per mole of ovalbumin
• Ideal for conjugating cysteine-containing peptide antigens to make immunogen or screening target
• Conjugation reaction complete in 2 hours; results in stable, covalent thioether bonds
• Single polypeptide protein with molecular mass of 45,000 Daltons
• Contains 14 aspartic acid and 33 glutamic acid residues whose carboxyl groups account for the net negative charge (pI 4.63) of OVA
• Not as immunogenic as keyhole limpet hemocyanin (KLH) but more soluble in DMSO (dimethyl sulfoxide) for applications that require this solvent
• Useful as an irrelevant protein carrier for antibody screening and immunoassays after using KLH as the carrier protein to generate the immune response against the hapten

This product consists of purified, carrier-grade ovalbumin that has been modified with SMCC crosslinker to attach maleimide groups capable of forming covalent crosslinks with sulfhydryl (-SH) moieties on cysteine residues of peptides and other molecules. Immunogens are easily prepared from peptide antigens that have been engineered with a terminal cysteine residue as a precise conjugation point. Several antigen molecules can be attached per carrier protein molecule without blocking intended epitopes by crosslinking to primary amines or carboxylates within the peptide sequence.

Carrier proteins are large, complex molecules capable of stimulating an immune response upon injection. Successful production of antibodies specific to small antigens (i.e., peptides or drug compounds) requires that these haptens be covalently conjugated to a larger, more complex molecule (usually a protein) to make them immunogenic. Carrier proteins are chosen based on immunogenicity, solubility, and whether adequate conjugation with the carrier can be achieved.

Ovalbumin (OVA), the most abundant protein in chicken egg whites, is a convenient protein for a variety of uses in the laboratory. The 45kDa protein is sufficiently large and complex to be mildly immunogenic. Consequently, OVA can be used as a carrier protein for conjugation to haptens and other antigens to make them more immunogenic for immunization. If not commonly used to prepare the primary immunogen, OVA is a popular carrier protein to make antigens more amenable to analysis (e.g., screening assays involving plate coating) of antibodies that were produced using KLH or other more immunogenic carrier protein.

Imject Ovalbumin is not as immunogenic as other proteins, such as keyhole limpet hemocyanin (KLH). However, OVA's independent structure make it especially useful as a carrier for peptides and other small antigens that by themselves are difficult to manipulate in typical screening assays such as ELISA. Although it is more hydrophobic and less soluble in aqueous buffers than BSA, ovalbumin remains soluble in up to 70% DMSO, making it useful for conjugation with haptens that require DMSO for solubility. Ovalbumin contains numerous primary amines, some of which have been modified to make Maleimide-Activated Ovalbumin.

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Imject™ Ovalbumin (in PBS)