Peptides containing cysteine: the role of scavengers in cleavage cocktail

Since the development of Fmoc-based solid phase peptide synthesis, a wide variety of cleavage cocktails have emerged.  Each cleavage cocktail contains a unique combination of scavengers designed to prevent either side reactions mediated by the released protecting groups or the side chains themselves, or both during the peptide cleavage reaction.  As the number of scientists performing peptide synthesis grows, the question “which cleavage cocktail should I use?” comes up more often than not.

In today’s post, I’ll highlight the role of of scavengers for peptides containing cysteine residues.

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2 thoughts on “Peptides containing cysteine: the role of scavengers in cleavage cocktail”

  1. This is really interesting – despite everything I’ve read in the literature and been told by other peptide chemists, I still find that there is no difference between the purity of my crude peptides when I use EDT in the cleavage mixture and when I don’t. Others in my group have noticed this too and we often don’t use it simply because it causes more work as it’s so smelly! Any suggestions on why we’re not seeing any difference?

    1. Hello Jo,
      I rarely use EDT in my cleavage cocktails, but I also rarely synthesize peptides that contain Cys or Met, the two most oxidation prone amino acids. I typically use a more standard, odorless, 95:2.5:2.5 TFA:water:TIPS cocktail and have even used this recipe before for peptides that only contain a single Cys residue. The peptides in this post though are highly enriched with Cys, which I think exacerbated the challenges described.

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