Alignment and structural analysis of membrane polypeptides by 15N and 31P solid‐state NMR spectroscopy

In contrast to solution NMR spectroscopy, where complete or almost complete averaging leads to isotropic values, the anisotropic character of nuclear interactions is apparent in solid‐state NMR spectra. The orientation dependence of chemical shift and dipolar or quadrupolar interactions has been used to obtain dynamic as well as angular information from polypeptides that strongly interact with phospholipid bilayers. This article illustrates the advantageous characteristics of the anisotropic 15N or 31P chemical shift interactions that in a direct manner allow one to obtain information on the alignment of helical polypeptides or of phospholipid head groups with respect to the membrane normal.