Static CP 31P NMR multilamellar bilayer broadlines in the absence and presence of the bioactive dipeptide β-Ala-Tyr or Glu

Static CP 31P-1H NMR experiments of DPPC/H2O multilamellar bilayers in the absence or presence of the dipeptide β-Ala-Tyr or the amino acid Glu were performed. The broadline 31P spectrum of the DPPC bilayers was perturbed more in the Glu-containing samples than those with β-Ala-Tyr. A novel simulation approach of the NMR broadline shapes simplifying the dynamical framework of the system was applied in order to compare the conformation of the gel and the liquid crystalline phases of DPPC bilayers alone or after the incorporation of either the dipeptide β-Ala-Tyr or Glu. The experimental NMR spectra were in agreement with fast overall rotational diffusion of the phospholipid macromolecules about an axis tilted with respect to the normal of the bilayer, and immobilized lamellar structures. Comparison of the structural parameters obtained from the simulations of the experimental NMR spectra of the DPPC bilayer samples without and with Glu showed that it interacts strongly with the headgroup. The dipeptide was on the other hand not interacting as strongly with the phosphate as the Glu, indicating that it was not located in the vicinity of the phosphate group.