Accurate Determination of 1H‐15N Dipolar Couplings Using Inaccurate Settings of the Magic Angle in Solid‐State NMR Spectroscopy

Abstract

AbstractMagic‐angle spinning (MAS) is an essential ingredient in a wide variety of solid‐state NMR experiments. The standard procedures to adjust the rotor angle are not highly accurate, resulting in a slight misadjustment of the rotor from the magic angle ( ) on the order of a few millidegrees. This small missetting has no significant impact on the overall spectral resolution, but is sufficient to reintroduce anisotropic interactions. Shown here is that site‐specific 1H‐15N dipolar couplings can be accurately measured in a heavily deuterated protein. This method can be applied at arbitrarily high MAS frequencies, since neither rotor synchronization nor particularly high radiofrequency field strengths are required. The off‐MAS method allows the quantification of order parameters for very dynamic residues, which often escape an analysis using existing methods.