I have a peptide dissolved in 50% DMSO. I wish to remove DMSO and get solid peptide, so I can dissolve it at a higher concentration. Is it possible to lyophilise 50% DMSO? Any other ideas? Thanks.
That will not work. DMSO has a high boiling point and you will probably destroy your peptide. I would try to precipitate it by adding Na-Acetate or -Citrate to increase salt levels and then use isopropanol (50-60% total) to precipitate the peptide. I'm not sure will this work for DMSO solutions but I use similar protocol to precipitate proteins isolated from tissues using TRIzol reagent or RIPA buffer.
What is the size of the peptide? You could use a reverse phase cartridge if the peptide has some hydrophobicity.
In addition to the above suggestions, you may set your peptide as ionic. Ion exchangers may work to isolate your peptide from the solvent environment if you can alter the charge of your peptide to gain a cationic or anionic form. Reduce the DMSO ingredient by diluting with the convenient buffer which pH establishes the peptide (pI dependent) as ionic and next, apply flash chromatography either by MPLC or gravity flow. At this point, reversed-phase or HIC may also be beneficial. You may test these in if the precipitation procedures won't work for that.
Omar Gonzalez-Ortega Thanks. The peptide is about 8 kDa. Since it's quite expensive, I wish to recover as much as possible.
Well, I think reverse phase chromatography is your best option. Again you will need some hydrophobicity in your peptide to reduce losses.
Although an 8k peptide may fold nicely in aqueous buffer due to solvent interactions, peptide properties and methods generally are sequence specific. Would you care to share your sequence?
Without seeing the sequence, I would recommend against chromatography, as it may never come off the column.
Actually, under high vacuum, you can remove DMSO on a rotovap under 100 C, albeit slowly. Afterward, you may never be able to dissolve the resulting film in anything other than DMSO. People don't usually use DMSO to dissolve a peptide unless it refuses to dissolve in more aqueous solutions.
You also can lyophilize DMSO, although you may need to repeat the process a few times, and the DMSO tends to offgas through the vacuum pump and stink like garlic. First dilute to ~1% DMSO by addition of 50% MeCN. Use more MeCN, if the peptide precipitates.
@Glumac has a decent idea, although I would precipitate with ether, which is arguably easier to remove after filtration. The problem with precipitation of a hydrophobic peptide is that you may obtain a sticky product and observe significant loss of mass.
You also can use old-fashioned dialysis. As @Akyildiz indicated, you should use buffer pH to maximize ionization and aqueous solubility. (Use the sequence to determine pI.) My favorite buffers are NH4OAc and NH4HCO3, as they are volatile in lyophilization. HOAc also works well on the freeze-dryer. But as above, you may obtain a sticky precipitate upon initial dilution.
- Badges
- Science topic
- Similar topics
- Linguistics
- Composition Studies
- Publications