Solid‐Phase Edman Degradation

A modification of the Edman degradation is described whereby peptides are degraded sequentially on a solid support by a machine, the solid‐phase peptide sequencer. Reagents are pumped through a column containing the resin‐bound peptide, and the amino acid thiazolinones released after each degradative cycle are collected on a fraction collector for subsequent analysis. A complete cycle requires 2 h, and all operations are controlled automatically by a programmer. An improved peptide resin is described, to which peptides can be attached in yields ranging from about 70% for the 30 amino acid insulin B‐chain to nearly 100% for smaller peptides. Of the 18 amino acids examined so far, glycine, alanine, phenylalanine, tyrosine, valine, leucine, isoleucine, proline, methionine, asparagine, glutamine, histidine, lysine, threonine, serine and cysteic acid are degraded normally; the phenylthiohydantion of threonine is partially dehydrated and that of serine is almost completely destroyed by trifluoroacetic acid, however. The phenylthiohydantion of glutamic acid is not detected, because it remains bound by its γ‐carboxyl group to the resin. When aspartic acid is encountered in peptides, furthe