Unexpected resin binding of tagged proteins

Dear colleagues,

When trying to confirm in vitro some protein-protein
interactions by pull-down assays, I am experiencing
repeated unspecific binding of his-tagged proteins
expressed in and purified from E. coli to different
matrices, like amylose resin and protein A-sepharose.
And viceversa, I have got binding of an MBP(maltose-
binding protein) fusion to nickel agarose. Could any
of you give me a hint of what may be happening?

Thanks in advance.

Greetings,

Jose

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Jose L. Carrasco, Ph.D.
Instituto de Biologia Molecular y Celular de Plantas
Universidad Politecnica de Valencia
Avenida Los Naranjos, s/n
46022 Valencia (Spain)
Email: [Only registered users see links. ]
Phone: 34-963877864
Fax: 34-963877859
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Historians believe that in newspost
<[Only registered users see links. ].es> on Wed, 1
Oct 2003, Jose Luis Carrasco <[Only registered users see links. ].es> penned the
following literary masterpiece:

Hydrophobic interaction between the sepharose backbone and your protein?
I've seen it reported before over the years.

Duncan
--
I love deadlines. I especially like the whooshing noise they make as
they go flying by.

Duncan Clark
GeneSys Ltd.