Reza, If your protein is not too small (>20 kDa), use a spin-column (i.e., desalting column) with G-25 sephedex. It is CHEAP, fast, and the recovery is good. We have even used them to adjust buffer concentrations or to remove micellar detergents; we have used protein concentrations up to 10 mg/mL, prior to crystallization.
You will need a clinical centrifuge, G-25 Sephedex (reusable) equilibrated in your desired buffer, glass wool, 15 mL plastic conical centrifuge tube (reusable), 5 mL syringe barrel (reusable). Load the Sephedex into the 5 mL syringe barrel to make a gel bed ≥ 5x the sample volume Put into the 15 mL plastic conical centrifuge tube and spin for 2 min to remove excess buffer Remove the excess buffer from conical centrifuge tube Add your sample (0.2 mL to 1 mL) to the gel bed, then spin for 2 min to collect your cleaned sample. The sample will be slightly diluted by 10-20% depending on conditions. We have our students in our undergraduate biochem class do this all the time to remove ammonium sulfate from protein samples for assay. If they can do it..... Or you can buy premade stuff to do the same thing. Good luck, Michael **************************************************************** R. Michael Garavito, Ph.D. Professor of Biochemistry & Molecular Biology 603 Wilson Rd., Rm. 513 Michigan State University East Lansing, MI 48824-1319 Office: (517) 355-9724 Lab: (517) 353-9125 FAX: (517) 353-9334 Email: rmgarav...@gmail.com **************************************************************** On Aug 19, 2014, at 9:55 AM, Reza Khayat <rkha...@ccny.cuny.edu> wrote: > Hi, > > Does anyone have a protocol for getting rid of PEG3350 from a protein sample? > > Best wishes, > Reza > > Reza Khayat, PhD > Assistant Professor > The City College of New York > Department of Chemistry, MR-1135 > 160 Convent Avenue > New York, NY 10031 > Tel. (212) 650-6070 > www.khayatlab.org
