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James,

Dima is right.  One of the protocols for protein-refolding with sarcosyl uses cyclodextrins to remove it.   However, sarcosyl is an anionic detergent above pH 5.5 under most conditions, so any ion exchange platform should work well to markedly reduce its presence in a preparation.  Also, it is extremely insoluble in the presence of divalent cations (as SDS is) and crystallizes readily.  I probably wouldn't try removing it with an IMAC column as it will bind to some extent and lead to continued contamination (something we have seen).  It is possible that hydroxyapatite column might be a good matrix for removing it.  

As sarcosyl is anionic, it is slower to dialyze across most membranes. However, we have had good results for detergent removal just using a standard spin-desalting column with G-25 Sephedex.  It is not absolutely quantitative detergent removal, but 100x decreases are easily reached in less than 20 min.  For sarcosyl, you could set up the column with G-25 DEAE-Sephedex at a pH where your protein doesn't bind and comes out in the flow-through.  After 1-2 centrifugations, your protein should be free of sarcosyl.

Regards,

Michael

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R. Michael Garavito, Ph.D.

Professor of Biochemistry & Molecular Biology

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Michigan State University      

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On Aug 28, 2009, at 1:24 AM, James Stroud wrote:

Hello All,

I dug around on the net and found this method to remove lipids from proteins:

"Wessel & Fluegge (1984), Anal. Biochem. 138:141-143. Itīs a methanol/chloroform precipitation and gives you a pellet that is easily redissolved. The method was especially devised for removing lipids or detergents, so it should be perfect for you."

 -- http://www.bio.net/bionet/mm/methods/1996-December/052513.html

Is this still the preferred way? I do not want to use reagents that are *themselves* likely to denature my protein. Has anyone tried cyclodextrins? I'm specifically trying to strip sarcosyl. I want to do it completely.

James