With PEC you can achieve very high purities above 90%. However, the purity level can be strongly affected by three factors.

1. Every peptide (on resin) with a free N-terminus after Fmoc (or Boc) deprotection will be isolated. Therefore, the quality of synthesis is crucial for the success of PEC purification and sources of error such as amino acid contamination, incomplete Fmoc deprotection or incomplete capping must be avoided.
2. Cleavage from the synthesis resin is of great importance. Using proper quencher and sufficient volumes of high purity ether are crucial to avoid re-addition of protecting groups or aldehyde contamination to the linker-coupled target sequence. We recommend using the protocol given in your purification kit.
3. Sequence-dependent precautions might be relevant, especially if you have special amino acids or modifications containing azide groups or disulfides.

Re-use of filter material is not recommended.

Internal modifications are possible, however, take care no side reactions occur in either basic or reductive conditions when cleaving the peptide after purification. The effect of solubility must be considered too. N-terminal modifications are only possible, if they allow linker coupling. Please don’t hesitate to contact us and share your challenge.

A good quality peptide synthesis is crucial for good results with PEC. There are some general rules to adopt:

1. Take care to have complete Fmoc (Boc) deprotection before coupling the next amino acid.
2. Block your truncated sequences with acetic anhydride after each coupling cycle using our recommended protocol.
3. Avoid amino acid contamination. If you are using an automated synthesizer, take care your tubing’s are washed thoroughly between amino acids to prevent contamination.
4. Use high grade ether for precipitation after cleavage from the synthesis resin to avoid contamination with free aldehydes/ketones. They will imminently couple to the linker and thus reduce the yield. Follow the proposed protocol for cleavage of the peptide from the synthesis resin.

Unfortunately, not. The performance of the purification relies on the quality of synthesis and cleavage. That is: The target peptide sequence is isolated ‘as synthesized’ after cleavage. If aspartimide is present, it will be retained during purification or side products may form. However, using the reductive cleavable linker, any basic treatment can be circumvented to minimize possible post-formation of aspartimide or other base-induced side reactions. Also consider using preventive actions in sequence design.