l‐Histidyl‐l‐serine 3.7‐hydrate: water channels in the crystal structure of a polar dipeptide

Dipeptides may form nanotubular structures with pore diameters in the range 3.2–10 Å. These compounds normally contain at least one and usually two hydrophobic residues, but l ‐His‐l ‐Ser hydrate, C₉H₁₄N₄O₄·3.7H₂O, with two hydrophilic residues, forms large polar channels filled with ordered as well as disordered water molecules.