Melan-A/MART-1 analog ([Leu27]-Melan-A, MART-1 (26-35)) is a biological active peptide. (This Melan-A (26-35) analog, Leu substituted for Ala at position 27, shows better HLA-A*0201 binding properties as well as better immunogenicity and antigenicity than the natural Melan-A (26-35).Pyroglutamyl (pGlu) peptides may spontaneously form when either Glutamine (Q) or Glutamic acid (E) is located at the sequence N-terminus. The conversion of Q or E to pGlu is a natural occurrence and in general it is believed that the hydrophobic γ-lactam ring of pGlu may play a role in peptide stability against gastrointestinal proteases. Pyroglutamyl peptides are therefore considered a normal subset of such peptides and are included as part of the peptide purity during HPLC analysis.)