As our initial test case, we consider four alanine polypeptides as idealized models for different secondary structure elements. The test set comprises (Ala) 10 in a 3 10 -helix conformation, as an α-helix, and as a β-strand, as well as (Ala) 11 featuring a turn between two antiparallel strands, as model of a β-sheet (see insets in Fig. ). Each of these models was constructed by assuming idealized backbone angles for the respective secondary structure element. These model polypeptides have previously considered in Ref. 61.