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An exceptionally stable peptide nanotube system with flexible pores

Acta Cryst. (2002). B58, 849-854

Carl Henrik Görbitz

[Figure 1] The unit cell and molecular packing of C8H16N2O3⋅ 0.35C2H3N(left) and C8H16N2O3⋅0.25C3H8O⋅0.22H2O (right) viewed along the c axis. Solvent guest molecules are shown in grey, positions for water molecules in C8H16N2O3⋅0.25C3H8O⋅0.22H2O appear as small crosses.
In a series of data collections on a selected single crystal of the dipeptide L-Ala-L-Val, space group P61, it is shown that small guest molecules like acetonitrile, methanol and acetone can be removed from hydrophobic channels parallel to the hexagonal axis without impairing the structure of the hydrogen-bonded peptide host structure. L-Ala-L-Val is one of the very first organic molecules with this property. Alcohol guests larger than methanol are also absorbed, but they induce a doubling of the a and b axes as well as a change in the shape and size of the pores. The observed structural modifications explain why these solvent molecules are more or less irreversibly trapped inside the channels.