Optimizing the removal of an Acm protecting group

Disulfide rich peptides have gained significant attention recently due to their incredible biological stability and tolerance to epitope grafting.  This class of peptides is often folded in solution, assuming the desired disulfide bond pattern correlates with the most thermodynamically stable structure.  Sometimes though, especially for chemically synthesized cysteine rich peptides, this is not the case.  The result is a complex mixture of peptides with varying disulfide bonding patterns and identical mass.

Using pairs of cysteine residues with matched orthogonal side chain protecting groups during chemical synthesis allows for precise regioselective control of the disulfide bond pattern on-resin, simplifying final purification steps.  In today’s post, I’ll explore conditions for removing acetamidomethyl (Acm) protecting groups with simultaneous disulfide bond formation.

Continue reading Optimizing the removal of an Acm protecting group

How long should I let my cleavage reaction stir at room temperature?

As the rules for cell permeability continue to be elucidated, peptides are increasingly being used to deliver either themselves or cargo to the cell’s interior.  One thing is clear, increasing the overall cationic charge of the peptide enhances it’s delivery to not only the cytoplasm, but also the nucleus or other subcellular compartments.  To achieve the positive charge, large numbers of arginine residues are most often incorporated into the peptide sequence.

This begs the question though, should I change my cleavage protocol?  In today’s post, I’ll evaluate several lengths of time used to cleave and fully deprotect an Arg-rich peptide sequence. Continue reading How long should I let my cleavage reaction stir at room temperature?