We are currently doing papain digests of monoclonal antibodies in order
to make F(ab) fragments. In a recent experiment we have noticed
something strange when running non-reducing SDS-PAGE to check the final
product (after digestion and cleanup on a Protein A column). In the
lane with 0.5 uL of the F(ab) we see a strong band at about 45K as
expected. In the lane with 1.0 uL of the F(ab) the 45K band is weaker
and we see a strong band of about 30-32K. The only difference being the
amount loaded on the gel.
We have seen this 30K band before but much weaker. There is no obvious
correlation with the type of Mab used to make the F(ab), or with the
final concentration of the F(ab) prep.
Any ideas? Thanks in advance.
Allison
