[Leu27]-Melan-A, MART-1 (26-35), is a biologically active peptide modified by substituting leucine for alanine at position 27, which enhances its HLA-A*0201 binding, immunogenicity, and antigenicity compared to the natural peptide. Pyroglutamyl (pGlu) peptides, arising from the spontaneous cyclization of glutamine (Q) or glutamic acid (E) at the N-terminus, are a recognized subset of peptides that may confer increased stability due to the hydrophobic γ-lactam ring of pGlu. These pGlu peptides are typically included during peptide purity assessments in HPLC analysis.