Question on names of immunoglobins

Ken Frauwirth BioKen frauwirt at notmendel.Berkeley.EDU
Wed Nov 9 15:43:45 EST 1994

In article <1994Nov9.155909.1 at>,
 <mdcabl at> wrote:

>Also, how did we get the silly
>nomenclature for pepsin digests of IgG.  F(ab')2 looks like a calculus problem.
>I think F= fragment and ab=antigen binding but what's the prime symbol for?
>Allen Black
>Dept. of Pathology
>Univ. of Newcastle 

You are correct about the F and ab.  However, the nomenclature originated 
from the papain digest, in which there are 2 F(ab) fragments and one F(c)
fragment (for complement-binding fragment).  Because papain cleaves "above"
the disulfide linkage, the two F(ab) pieces are separate.  In the case of
pepsin, however, the cleavage is "below" the disulfide bond, so the F(ab)
pieces are covalently linked.  Therefore, technically, it is not really 2 
F(ab) fragments, but 2 slightly larger pieces, that are joined together. 
The prime simply indicates this difference.

I hope that clears it up,

Ken Frauwirth (MiSTie #33025)       _           _
frauwirt at       |_) *    |/ (_ |\ |
Dept. of Molec. & Cell Bio.        |_) | () |\ (_ | \|  
Univ. of Cal., Berkeley          I had a .sig, but I broke it.

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