title: Helix propensities of basic amino acids increase with the length of the side-chain.
abstract: Helix formation in a 17-residue alanine-lysine peptide and analogous peptides with specific lysine --> X substitutions, where X is 2,3-diamino-L-propionic acid, 2, 4-diamino-L-butyric acid or L-ornithine, have been examined using circular dichroism measurements. The dependence of helix content on X, its position in the sequence, and the number of lysine --> X substitutions are reasonably well described by using the Lifson-Roig theory modified to include N-capping, without explicitly considering charge-helix dipole interactions. The helix propensities for these basic amino acids increase with the length of the side-chain in the rank order 2,3-diamino-L-propionic acid < 2,4-diamino-L-butyric acid < ornithine < lysine. This parallels the increase in helix propensities with side-chain length of other polar and charged amino acids.
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, CA 94305, USA.
authors.forename: S
authors.initials: S
authors.lastname: Padmanabhan
authors.forename: E J
authors.initials: EJ
authors.lastname: York
authors.forename: J M
authors.initials: JM
authors.lastname: Stewart
authors.forename: R L
authors.initials: RL
authors.lastname: Baldwin
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D011506:Proteins