Efficient polarization transfer between spin-1/2 and N nuclei in solid-state MAS NMR spectroscopy.

Abstract: Polarization transfer between spin-1/2 nuclei and quadrupolar spin-1 nuclei such as N in solid-state NMR is severely challenged by the typical presence of large quadrupole coupling interactions. This has effectively prevented the use of the abundant N spin as a probe to structural information and its use as an element in multi-dimensional solid-state NMR correlation experiments for assignment and structural characterization. In turn, this has been a contributing factor to the extensive use of isotope labeling in biological solid-state NMR, where N is replaced with N. The alternative strategy of using the abundant N spins calls for methods enabling efficient polarization transfer between N and its binding partners. This work demonstrates that the recently introduced CP transfer method can be optimized to achieve efficient H N polarization transfer under magic angle spinning conditions. The method is demonstrated numerically and experimentally on powder samples of NH4NO3 and l-alanine. [Copyright &y& Elsevier]