Theoretical investigations into the variability of the 15N solid-state NMR parameters within an antimicrobial peptide ampullosporin A.

摘要

The solid-state NMR measurements play an indispensable role instudies of interactions between biological membranes andpeptaibols, which are amphipathic oligopeptides with a highabundance of α-aminobutyric acid (Aib). The solid-state NMRinvestigations are important in establishing the molecular modelsof the pore forming and antimicrobial properties of peptaibols,but rely on certain simplifications. Some of the underlyingassumptions concern the parameters describing the 15N NMRchemical shielding tensor (CST) of the amide nitrogens in Aib andin conventional amino acids. Here the density functional theory(DFT) based calculations were applied to the known crystalstructure of one of peptaibols, Ampullosporin A, in order toexplicitly describe the variation of the 15N NMR parameters withinits backbone. Based on the DFT computational data it waspossible to verify the validity of the assumptions previously madeabout the differences between Aib and other amino acids in theisotropic part of the CST. Also the trends in the magnitudes andorientations of the anisotropic components of the CST, asrevealed by the DFT calculations of the full periodic structure ofAmpullosporin A, were thoroughly analyzed, and may beemployed in future studies of peptaibols.