SDS-PAGE protein processing

Chris Chang cchang at
Thu Oct 24 15:22:08 EST 2002

Is your "p2xy protein" sample in the first case a purified protein, or an
extract from some tissue? Also, are you using monoclonal or polyclonal
antibodies? Do you use identical extraction and/or gel sample processing
procedures with the rat and human brain samples?

You might try running all 4 samples (p2xy, cell culture, rat brain, human
brain) on the same gel, just to rule out sample handling differences between
2 experiments possibly done on two different days. If the size difference
persists, maybe your protein exists in a tight complex from human brain and
cell culture, but not in rat brain. Handling of samples (purification, etc.)
will affect the persistence of any complex, as well.

Good luck,


<mdsgshl2 at> wrote in message
news:20021021130849.25108.qmail at
> I am looking at p2xy protein using an antibody plus rat brain control. I
find that I am getting one molecular weight for the rat brain which is also
seen in my protein samples. This specific band disappears with
preabsorption. However, when I run a different protein sample from cultured
cells using a human brain control I also get matching bands in my control
and test proteins but they are at a much higher molecular weight, using the
same antibody. All the bands also disappear using preabsorption.
> can anyone explain what might be happening as I am looking for the same
protein in the cultured and other samples using the same antibody but
getting different molecular weights?
> Thanks

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