Hi Alex, I disagree with you even though GF is always the last step in my purifications. Because it involves concentration before and after the GF so during the concentration you can already be doing the buffer exchange. You use GF when you want to purify other protein impurities if they are different sizes. Of course it has other uses too. But not quite practical for just changing buffer also considering the amount of protein you could be loosing along the process. If one is careful, centripreps are best for concentrating and changing the buffer. I tell you this from experience with large hard to express proteins.
Best of luck, Remie > On Aug 19, 2014, at 10:45 AM, Alexander Aleshin <aales...@sanfordburnham.org> > wrote: > > Remie, > Actually, concentrating of a protein solution is not the best approach to > removing low MW impurities, gel filtration chromatography is more reliable > and ... faster. > > Regards, > Alex > >> On Aug 19, 2014, at 7:03 AM, Remie Fawaz-Touma wrote: >> >> Hi Reza, I had to do this before. >> >> This protocol works for any PEG and any chemical to be removed from a >> solution: buffer exchange into the new buffer you want your protein to be >> in. There are ways to do that by 15 mL Amicon concentrators from millipore >> for large volumes, or if your protein is already concentrated, there are >> some small 0.5 mL concentrators from millipore as well. >> >> The key is to keep your spinning at low speeds (concentrators manuals will >> tell you) so you don’t precipitate or loose your protein. Check your protein >> concentration every 2 hours just to make sure you are not loosing it on >> concentrator surfaces and so on. >> >> Good Luck, >> Remie >> >>> 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 >
