• Peptide synthesis emerged as a dominant methodological paradigm, with general procedures, novel bond-forming strategies, and applications to dipeptides and gramicidin-related sequences [4] [7] [12] [15] [6] [8].

• Analytical methods for detecting, separating, and identifying peptides, from paper chromatography to hydrolysate sequencing, enabling mapping of peptide components in complex systems [1] [10] [17] [16].

• Peptide metabolism and enzymatic processing, including aminopeptidases, trypsin activities, carboxypeptidases, and metal-peptidases; exploring specificity, inhibition, and mechanisms [2] [11] [18] [14] [13] [20].

• Early structural and sequence analyses linking peptide sequence, terminal segments, and optical configuration to function, exemplified by insulin, gramicidin S, and related peptides [17] [19] [8] [6].