Small letters: D-isoform;
O: Ornithine;
Ahx: 6-aminohexanoic acid; 
B: Beta-Alanine;
U: α-amino isobutyric acid (Aib);
Φ: L-2-naphthylalanine;
J: l-2,3-diaminopropionic acid;
X: other molecules (α-amino isobutyric acid, 1-aminocyclopentane-1-carboxylic acids (Ac5c), aeDP, aminoethylpropyl, 4-amino-butanoic acid, aeLP, aminoethylpropyl, aminohexyl residue, apDP, aminopropylpropyl, apLP, aminopropylpropyl, etc.)