Short model peptides having a high α‐helical tendency: Design and solution properties

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Abstract
Secondary structure is not typically observed for small peptides in solution. Several of the properties of α‐helical peptides are known which lead to the stabilization of the structure. The utilization of all the known factors important for α‐helical stabilization in the design of model α‐helical peptides (MAP) is reported. The peptides are based on the repeating eleven amino acid sequence, Glu‐Leu‐Leu‐Glu‐Lys‐Leu‐Leu‐Glu‐Lys‐Leu‐Lys (MAP1–11). The CD spectra of these peptides give evidence for more α‐helical content than has been reported for any short peptide (< 18 amino acids) to date. This α‐helical tendency does not require the presence of lipid or reduced temperature. For instance, Suc‐[Trp9]MAP9‐3″ amide (5), a seventeen amino acid peptide has 100% and 80% α‐helical contents at 1.7 × 10−4 M and 1.7 × 10−5 M, respectively. Suc‐[Trp9]MAP2‐11 amide (3), merely ten amino acids in length, is 51% α‐helical at 1.7 × 10−4 M in 0.1 M phosphate buffer at room temperature. In the presence of lipid or trifluoroethanol, the α‐helical content of these peptides is increased. This series of peptides demonstrates the complimentarity of various secondary structure design principles and the extent to which structure can be induced in small linear peptides.