Friday, 2 May 2014

The Process Of Antibody Labeling

By Tracie Knight


Antibodies are broadly used in immunoassays particularly to identify and quantify antigens. In this case, the one that detects and recognizes the antigen is termed as the primary antibody, which specifies the assay. In addition, a label is incorporated into assay by either the direct or indirect methods of detection to enhance measurability. Antibody labeling has its own protocols, with critical parameters and procedures to be applied in any instance.

Immunoassay uses the two methods above in identifying an antigen. The direct method detects the antigen by means of detaching the label covalently. The covalent bond attaches it to the primary immunoglobulin. A single incubation of the antigen is executed that also demands only one wash step. Such a simplified assay depletes assay variability and increases the quality of the data.

Indirect detection attaches the label covalently to a secondary protein that is and allowed to bind to the corresponding primary protein at the time of immunoassay. In this detection, the assay entails two different parts. It begins with a period of incubation with the primary antigen detector that is not labelled. At this time, some minor antibodies fixes to the antigen.

The direct detection entails a single protein and completely eliminates the unspecified binding of secondary protein. These characteristics make the process quick. It however experiences the drawbacks of cutting down on the immunoreactivity of primary immunoglobulin which occurs due to labeling. The signal can rarely be amplified. The indirect method, on the other hand permits signal amplification that is enhanced by the presence of many epitopes in the primary antibodies. The epitopes increases sensitivity, an important factor in the amplification.

Buffers and additives are the key considerations when it comes to providing labels for the antibodies. Your antibody will certainly contain other substances, usually a buffer or salt, additives and other proteins. It is occasionally necessary to purify the antibody before performing the labeling reaction. The purification removes the stabilizing proteins such as BSA. It also removes the low molecule substances, including Tris buffer, acid and glycine.

The process of labeling depends to a large extent on the concentration and level of purity. The exercise requires that the protein be logically pure. The desirable level of purity is 95 percent but the range from 90 percent is acceptable. The concentration is also vital. For ease of providing the labels, the concentration of 0.255 mg/ml and above is ideal. Many antibodies that are commercially available are in a labeling form. However, this is not always the case. Some are impure and this makes purification an obligation.

There are multiple types of labels, with varied uses suitable for specific applications. It is worth knowing that the kind of label together with the strategy employed in providing the labels must be carefully analysed and tailored to each application. The different labels include biotin, enzyme conjugates, active sites probes and fluorescent probes.

The labeling kit to be used is, out of doubt, an important factor. The kit should be well chosen to enhance the exercise. It should be worth relying upon, convenient and complete. It should not result in the loss of material, scaling up issues and batch to batch variation. The conjugates resulting from the kit must be stable in terms of covalent bonding. When assessing the reliability and efficiency of the kit, consider the amount of antibody it consumes relative to the labels.




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