Short, solubilized polyalanines are conformational chameleons: exceptionally helical if N- and C-capped with helix stabilizers, weakly to moderately helical if capped with rigid spacers.
Isolating spacers introduced between solubilizing lysine regions and a polyalanine core permit rigorous characterization of context-free alanine helices. The preferred building blocks for isolating spacers are amino acids with rigid, extended conformations such as proline, isonipecotic acid, and tert-leucine. Replacing isolating spacers by conventional N- and C-caps dramatically increases the helicity of dodecaalanine. Solubilized, isolated polyalanines provide optimal tools for testing polypeptide helicity algorithms, central to resolution of the protein folding problem.
Miller
J S
JS
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Kennedy
R J
RJ
Kemp
D S
DS
D000409:Alanine / Q000737:chemistry*; D002942:Circular Dichroism; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012995:Solubility
D010446:Peptide Fragments; D010455:Peptides; C011083:polyproline; C019529:polyalanine; C011080:polyglycine; D000409:Alanine