Nanotubes from hydrophobic dipeptides: pore size regulation through side chain substitution

The crystal structures of L-Ala-L-Ile, L-Ile-L-Ala, L-Val-L-Val, L-Val-L-Ile and L-Ile-L-Val are presented. Together with L-Ala-L-Val and L-Val-L-Ala they constitute a unique group of seven isostructural dipeptides with hydrophobic pores and identical three-dimensional hydrogen bond networks. Hydrophobic side chains form the inner surfaces of channels parallel to the hexagonal axes in these structures. By changing the bulk of the side chains the van der Waals' diameter of the channels can be regulated within the interval 3.3 to 5.2 Angstrom.