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The Final Step of Peptide Synthesis: Cleavage, Scavengers and Cold Ether
Once the last amino acid is attached, the peptide is still stuck to the resin and wrapped in protecting groups. The final step handles both problems at once.
The cocktail
The resin is treated with a mixture based on trifluoroacetic acid (TFA), a strong acid. TFA cuts the peptide from the bead and strips the side-chain protecting groups.
Why scavengers
Removing those groups releases reactive positively charged fragments that can attack sensitive residues such as tryptophan, methionine and tyrosine. Scavengers such as water and triisopropylsilane mop them up first.
Cold ether precipitation
The mixture is dripped into ice-cold diethyl ether. The peptide is insoluble in ether and falls out as a white solid, while leftover reagents stay dissolved. It is spun down and washed.
What comes next
- Purification by HPLC.
- Mass spectrometry to confirm identity.
- Freeze-drying (lyophilization).
A side effect
Because TFA is the acid used, the final peptide often carries trifluoroacetate as its counter-ion. Long sequences such as Tesamorelin 10mg have many basic residues that pair with it, which is why net peptide content is lower than the vial weight. Keep reading.
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For laboratory research use only. Not for human or veterinary use, and not intended to diagnose, treat, cure or prevent any condition. This article is educational and is not medical advice.