Panel A. INTOXSY pulse sequence highlighting the most salient features of the magnetization transfer pathway. The delay ε was set to 1.72 ms. The exchange time (Ex) was varied from 0 to 250 ms in 10, 20 or 50 ms increments. DIPSI-2 mixing time was set to 10 ms. 13C atoms frequency labeled when bearing OH are depicted in blue whereas 13C frequency labeled when bearing OD are in red. The pulse sequence is separated in sections: (a) HSQC; (b) Refocusing 1H magnetization; (c) Exchange time and (d) 1H,1H TOCSY transfer. Panel B. Plots showing that OH/OD exchange and 1H T1 modulate isotope-discriminated peak intensity, and yield the resulting INTOXSY exchange rate profiles.