“…The L-NAAA, L-NAVA, and L-NAIA molecules, instead, to better assemble themselves in the crystals, form alternate layers containing either group connected by networks of hydrogen bonds, or hydrophobic groups, so that the crystals are characterized by cleavage planes. (10,25,26) In the L-NALA crystals, the molecules form wrinkled polar sheets making concavities in the shape similar to a half-egg box, in which the twisted leucine side chains settle. (25) Moreover, in this case, only four hydrogen bonds, instead of six, are shared by each molecule.…”