Figure 4.

Experimental (black solid lines) and simulated (red dotted lines) ¹⁵N σ₁- (right) and σ₂- (left) CSA line shapes of [¹⁵N]-N-acetyl-valine generated by the various R-symmetry sequences: R18₂⁵ (a), R10₁³ (b), R12₁⁴ (c), R8₁³ (d), R10₁⁴ (e), and R12₁⁵ (f). The sample was spun at an MAS frequency of 10 kHz. The rf field strength applied during the recoupling period was 45, 50, 60, 40, 50, and 60 kHz for (a)–(f), respectively. The best-fit ¹⁵N CSA parameters measured by each symmetry sequence are listed in Table 2.