Conformational dynamics detected by nuclear magnetic resonance NOE values and J coupling constants

Conformational relevant NMR parameters such as NOE values and coupling constants depend in a nonlinear way on distances and dihedral angles. This may be misleading in the determination of molecular conformations when a conformational equilibrium exists with rates that are fast on the NMR time scale: short nuclear distances are overemphasized when distances obtained by NOEs are used as a tool for modelling the conformation in solution. Antamanide, a cyclic decapeptide, is shown to be such a case. However, molecular dynamics calculations with NOE constraints can be used to identify crucial NOE values and prove the evidence of a conformational equilibrium. In addition, homonuclear and heteronuclear coupling constants provide additional support for the existence of “the” conformation or the conformational equilibrium, respectively.