1H NMR studies on cyclo[-Arg(Mtr)-Gly-Asp(But)-Ser(But)-Lys(Boc)-] and cyclo(-Arg-Gly-Asp-Ser-Lys-), cyclic analogues of the ‘adhesion’ domain of fibronectin

High-field 1H NMR techniques in DMSO solution, augmented by a comparison with calculated conformations based on cyclo(-Ala-Gly-Ala-Ala-Ala-), and restrained molecular dynamics calculations have revealed preferred conformations for both of the conformationally constrained-Arg-Gly-Asp-Ser-analogues studied. A type II′β-turn spanning Gly-Asp and a slightly less stable γ-turn at the Lys residue were revealed for both peptides.