Homonuclear chemical shift correlation in rotating solids via RNnu n symmetry-based adiabatic RF pulse schemes.

ABSTRACT

The efficacy of RN(nu) (n) symmetry-based adiabatic Zero-Quantum (ZQ) dipolar recoupling schemes for obtaining chemical shift correlation data at moderate magic angle spinning frequencies has been evaluated. RN(nu) (n) sequences generally employ basic inversion elements that correspond to a net 180 degrees rotation about the rotating frame x-axis. It is shown here via numerical simulations and experimental measurements that it is also possible to achieve efficient ZQ dipolar recoupling via RN(nu) (n) schemes employing adiabatic pulses. Such an approach was successfully used for obtaining (13)C chemical shift correlation spectra of a uniformly labelled sample of (CUG)(97) - a triplet repeat expansion RNA that has been implicated in the neuromuscular disease myotonic dystrophy. An analysis of the (13)C sugar carbon chemical shifts suggests, in agreement with our recent (15)N MAS-NMR studies, that this RNA adopts an Alpha-helical conformation.