Short, Solubilized Polyalanines Are Conformational Chameleons: Exceptionally Helical If N-and C-Capped with Helix Stabilizers, Weakly to Moderately Helical If Capped with Rigid Specers

摘要

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.