| 摘要 |
Cyclic homodetic peptides having a repeating D-L-chirality motif are shown to have a stable disk conformation with the amino acid side chains extending radially outward and the carbonyl and amino groups extending axially upward or downward. Such cyclic peptides can be employed as subunits in the assembly of molecular tubes. Cyclic peptides having a repeating D-L-chirality motif and lacking mutually repulsive side-chains are shown to stack atop one another in an anti-parallel fashion and are shown to be held together by the formation of beta-sheet hydrogen bonding. The stacked cyclic peptides form a molecular tube having a central channel. The diameter of the channel is determined by the size cyclic peptide. If the cyclic peptide includes ionizable amino acid residues, e.g. glutamic acid or lysine, assembly and disassembly of the molecular tubes can be controlled by varying the pH. If the cyclic peptide includes hydrophobic amino acid residues, the molecular tube will insert into a lipid membrane. In such instances, the molecular tube provides a transmembrane channel. The channel can be gated or ungated. Molecular tubes can be terminated with a terminal cyclic peptide having methylated amino groups in one orientation. Molecular tubes may be employed as drug carriers, molecular sieves, reaction vessels, membrane channels, and other uses.
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