Nitrogen-15 chemical shift anisotropy and 1H–15N dipolar coupling tensors associated with the phenylalanine residue in the solid state

Nitrogen-15 chemical shift anisotropy (CSA) and 1H–15N dipolar coupling tensors associated with the Phe-16 residue of the magainin2 peptide are reported in this Letter. The experimental results predict that the magnitudes of the 15N CSA tensor are σ11N=55±2, σ22N=80±2 and σ33N=220±2 ppm. The results also suggest that the least shielded element, σ33N, is in the peptide plane making an angle of 22±3° with the N–H bond vector whereas σ11N and σ22N are 45±15° away from the peptide plane and the normal to the peptide plane, respectively. The magnitudes of the principal elements of the 15N CSA tensors associated with 15N-Phe-16 and 15N-Gly-18 sites of the magainin2 peptide are significantly different while the orientation of the tensors in the molecular frame is the same.