Precipitation technique

                         Immuno chemical technique-  Precipitation

                                       Made by- Vanie Singh

                                       Department of Botany

                                      Himachal  Pradesh university

·         Antigen reacts with antibodies to form the antigen-antibody complex.

·         Depending upon the size of nature of the complex and the nature of the antigen, two types of reactions are known

1.        Agglutination

2.        Precipitation

·         When a soluble antigen having at least 2 or more antibody binding sites react with the corresponding antibody in suitable concentration, it leads to the formation of large antigen-antibody complex which is visible to the naked eye as a precipitation reaction. Such reactions are called precipitation reactions.

·         On the other hand when the antigen is of particulate nature, its reaction with the antibody leads to visible clumping called agglutination. E.g., Routine blood grouping

 

Precipitins and Precipitation

v  Antibodies leading to precipitation reactions are called precipitins.

v  They are usually bivalent to polyvalent.

v  Both the antigen and antibody have to be in the optimal concentration so that the antigen and antibody molecule can react with many molecules to form a large complex appearing a precipitate.

v  In excess of either the antigen or antibody small are soluble complexes are formed that do not appear as precipitate.

v  For e.g., when antigen is in excess, most of it is present in the free unbound form in the supernatant.

v  Ony few antigen molecules are bound to the antibody forming small and soluble antigen-antibody complexes.

v  Similarly in antibody excess, only few antibodies are bound to antigen and most of them are again present in free form in the supernatant.

v  It is at the optimal concentration ratio of the antigen and antibody concentration, that the precipitation occurs.

 

Refrences:

1.       Kuby

2.       Dr. S.K Gupta

3.       Anil k. Sharma

4.       Dr. P. Madhavee Latha


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