Replacement of ProB28 by pipecolic acid protects insulin against fibrillation and slows hexamer dissociation

Non‐canonical amino acid mutagenesis was used to examine the biophysical consequences of changing ring size and structure at the single proline site in insulin. Addition of a methylene spacer to the prolyl ring (by replacement of proline by pipecolic acid at position B28) led to an increase in stability and a decrease in the rate of hexamer dissociation. The results of this work illustrate the power of non‐canonical amino acid mutagenesis in the engineering of macromolecular aggregation and protein therapeutics.