Antibody' specifity

Dr Engelbert Buxbaum engelbert_buxbaum at
Wed Jul 23 05:54:48 EST 2003

Nikolai Scherbak wrote:

> Dear colleagues!
> I am wondering how specific antibodies are? I am working with transgenic
> plants (A. thaliana) and using polyclonal antibodies raised against protein
> that I would like to overexpress in transgenes. Unfortunately, my antibody
> binds even for non-transformed control plants. I know. That there is another
> protein i Arabidopsis with up to 50% identity to my recombinant protein. Can
> this be an explanation to the positive result in negative control? Or, by
> another words: can antibodies raised against one protein bind also to
> another protein with the 50% similarity to the first one? Mol.weight of
> proteins is almost the same...

There are two kinds of antibodies: sequence specific and fold-specific.
The former recognise a sepcific segment of about 5-6 amino acids, thee
latter a particular three-dimensional fold, which may include amino
acids from quite different parts of the primary structure. 

As you are working with a polyclonal serum, you will probably have both
types of antibody present. Yu may have to capture the interfering
antibodies with the cross-reacting protein (affinity chromatography or
batch operation), the flow through (or supernatant) should be specific
for your protein.

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