Methyl 13C CPMG Relaxation Dispersion

Relaxation dispersion experiments report on ms-µs timescale exchange processes. Methyl ¹³C CPMG relaxation dispersion experiments were performed on a [1-¹³C, ¹⁵N] hE:FOL:NADP⁺ sample at multiple temperatures (280 K, 300 K, and 310 K) using a Bruker DRX 800 MHz spectrometer and the pulse schemes described by Skrynnikov et al.^{24 (link)} and Lundström et al.^{25 (link)} Using [1-¹³C] glucose as the sole carbon source leads to isolated ¹³C enriched methyls for most methyl side chains; however, the presence of ¹³C-¹³C_methyl labeling for Thr-γ2 and Ile-δ1 methyls can interfere with accurate spin-relaxation measurements due to the one bond C-C coupling.^{18 (link)} Experiments were performed using a total relaxation period T_CPMG of 40 ms and refocusing delays 1/τ_cp of 100, 200, 400*, 600, 1000, 1400*, 1800, and 1900 s⁻¹ where * denotes experiments completed in duplicate. Dispersion curves were fit using the program GLOVE.^{26 (link)}