Scheme 1.

(A) Sequence of the AK peptide, where the grey region indicates the helical residues; (B) coarse-grained model derived based on 14 helical amide units in the gray region of (A); (C) definition of the three different regions; (D) definition of the signal region, where the underline indicates the ¹³C=O labeled amide units; (E) representative conformational states, where “^*” denotes a helical nucleus; and (F) definition of the nucleation and propagation steps and the respective rate constants.