Help with Gel Filtration

[p3p7id3]

>From the information provided I would not immediately assume dimerization
via a disulfide bond.  If you do come to this conclusion make sure you
dialyze or add neat EDTA to ~10-20 mM before trying to reduce your sample.

p3p7id3.

<kaj.stenberg at helsinki.fi.invalid> wrote in message
news:apf1dd$lhs$1 at oravannahka.helsinki.fi...
> dustjohn at hotmail.com wrote:
>
> > Trying to separate a 60kDa His-tagged protein from a ~26kDa Ecoli
> > protein that purifies along with it on the His-column.  Had no
> > luck separating the two with a Sephadex G-75 column (bed length
> > ~25cm, column diameter ~1.5cm).  Switched to G-50, same bed length
> > and, again, no separation.  Should I run a longer column (~90cm
> > bed length)?  Should I increase/decrease the filtration rate
> > (usually ~1ml/min).
>
> It is a dimer in your buffer system. If you insist, try Superdex-200, or
> depending on amounts needed, HPLC. Adding (fresh) 1-10mM DTT to the
> buffer could make wonders.
> Separating 56kd from 60kd is not a gel filtration aproach.
>
> --
> Kaj Stenberg