Caprylic acid precipitation antibody

For best results, plates should be coated with the IgG fraction of an antiserum, this can be conveniently prepared using caprylic acid precipitation [see Chapter 10 and ref. 15). Where this is not possible, indirect capture may be used, such as antispecies antibody on the plate, or the streptavidin-biotin system. Any indirect capture system must be compatible with the final label, e.g, labeled antigen or different species antisera with no crossreaction with die indirect coating antibody 11. Safety data (from ref. 16)... 

Temponi, M., Kekish, U., and Ferrone, S. (1988). Immunoreactivity and affinity of murine IgG monoclonal antibodies purified by caprylic acid precipitation. /. Immunol. Methods 115, 151-152. 

At moderately acidic pH values, the short chain fatty acid, caprylic acid, is an effective protein precipitant. It has found an application in immunoglobulin purification as conditions have been developed that result in the precipitation of the majority of non-immunoglobin proteins in the serum leaving the antibodies in solution. The concentration of caprylic acid required differs for the serum of different species as shown in Table 1 (see Note 12). 

Caprylic acid (also called octanoic acid) can also be used for the precipitation of antibodies from serum, ascites, or hybridoma culture supernatant.60"63 In terms of antibody purity, precipitation with caprylic acid is significantly less efficient than the chromatographic methods. Note also that precipitation with caprylic acid is associated with a reduction in the affinity properties of some antibodies and is not suitable to purify murine IgA and IgG3. 

A number of other precipitating agents have been used in the purification of proteins. In some instances, the use of sodium sulfate can result in a purer antibody preparation, but generally it does not offer advantages over ammonium sulphate. Caprylic (octanoic) acid, however, offers a different approach and also has a long history of use (5). Conditions can be created where this short chain fatty acid will effectively precipitate the majority of serum proteins with the exception of the immunoglobulins. 

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