The Cyclopeptide spelled ALEXANDER is made from a sequence of Alanine ( A ), Leucine ( L ), Glutamic acid ( E ), Dimethylglycine ( X ), Alanine ( A ), Asparagine ( N ), Aspartic acid ( D ), Glutamic acid ( E ), Arginine ( R ). "X" usually designate any amino acid - here we used dimethylglycine, an unnatural aminoacid that looks like "X". Learn more about peptides and Amino Acids on Wikipedia! (https://en.wikipedia.org/wiki/Amino_acid)