In an effort to compare the impacts of small (i.e., Ala), medium-sized (i.e., Z-Abu), and bulky AAs (i.e., Val) on peptide structure and stability, we synthesized AA-containing analogs 2a-c and 3a-c of Balaram's incipient 310-helical peptide 1. The different types of AAs exerted similar effects on conformation according to NOE-restrained structural calculations. Variants 2a-c possessing a AA in place of Aib-1 all preferred the 310-helical shape of the original peptide, whereas analogs 3a-c with a AA replacing Aib-3 all adopted a -sheet-like orientation instead. Thus, the location of the AA in the backbone played a larger role than the size of the residue in determining the structures of the peptides.