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Thermodynamic Scale of β-Amino Acid Residue Propensities for an α-Helix-like Conformation
- Fisher, Brian F., Hong, Seong Ho, Gellman, Samuel H.
- Journal of the American Chemical Society 2018 v.140 no.30 pp. 9396-9399
- amino acids, nitrogen, thermodynamics, thioesters
- A thiol-thioester exchange system has been used to measure the propensities of diverse β-amino acid residues to participate in an α-helix-like conformation. These measurements depend on formation of a parallel coiled-coil tertiary structure when two peptide segments become linked by thioester formation. One peptide segment contains a “guest” site that accommodates diverse β residues and is distal to the coiled-coil interface. We find that helix propensity is influenced by side chain placement within the β residue [β³ (side chain adjacent to nitrogen) slightly favored relative to β² (side chain adjacent to carbonyl)]. The previously recognized helix stabilization resulting from five-membered ring incorporation is quantified. These results are significant because so few quantitative thermodynamic measurements have been reported for α/β-peptide folding.