We demonstrate a novel 3D NNC magic angle spinning NMR experiment that generates ¹⁵N–¹⁵N internuclear contacts in protein systems using an optimized ¹⁵N–¹⁵N proton assisted recoupling (PAR) mixing period and a ¹³C dimension for improved resolution. The optimized PAR condition permits the acquisition of high signal-to-noise 3D data that enables backbone chemical shift assignments using a strategy that is complementary to current schemes. The spectra can also provide distance constraints. The utility of the experiment is demonstrated on an M₀Aβ₁₋₄₂ fibril sample that yields high-quality data that is readily assigned and interpreted. The 3D NNC experiment therefore provides a powerful platform for solid-state protein studies and is broadly applicable to a variety of systems and experimental conditions.National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant EB-001960)National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant EB-002026
