“…Linear peptides form fl-sheets (Karle, Karle, Mastropaolo, Camerman & Camerman, 1983), 3,0-helices for short peptides (Toniolo et al, 1983), ahelices for longer peptides Fox & Richards, 1982), double helices (Benedetti, di Blasio, Pedone, Lorenzi, Tomasic & Gramlich, 1979;Langs, 1988) and mixed helices consisting of a 3,0/ahelix and a fl-ribbon twisted into a helix (Karle, Flippen-Anderson, Sukumar & Balaram, 1987;Karle, Flippen-Anderson, Agarwalla & Balaram, 1991). The latter has been established in Leu-zervamicin and a 16-residue apolar analog that contain in their sequences three Pro or Hyp (hydroxyproline) residues at positions 10, 13 and 15.…”