I happened to start Fmoc removal of Peptide using 18,6% Piperidine in DMF before next coupling when the peptide was not well washed after acetylation by acetic anhydride. Could there be any undesired reaction(s) of the Piperidine and the remained acetic anhydride due to the incomplete washing? How will it affect the coupling of next amino acids? Thank you guys.
The piperidine could act as a nucleophile and the base would rather abstract the acidic proton from acetic anhydride. The reaction you mentioned could happen in case you have more piperidine than acetic anhydride, for example if you have not washed out completely the acetic anhydride after acetylation. The piperidine-acetic anhydride would be removed by the next washing step and would not affect the next aa coupling to the growing peptide.
Hi Carmine Pasquale Cerrato and Isaya John Bususu ,
I am running a similar experiment where I want to deprotect a Fmoc-GGGGGK-dye of the Fmoc protection group. I want to use 20% piperidine in NMP. My challenge is to find a suitable means to remove the GGGGGK-dye from the PIP/NMP after the deprotection step, and still have the protein functional for subsequent experiment. I've thought of vacuum evaporation but that has got its own problems.
May I know how best I can approach this? Any suggestion will be appreciated.
Thank you
Hi Eugene, after deprotection of your peptide resin, you can always use NMP to wash out piperidine by performing several washes, where the peptide will remain in the reaction container and the solvents go away though the filter.
I would prefer to use 20%PIP/DMF as the deprotection mixture and then use DMF to wash out piperidine AFTER deprotection.
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