Incorporating the BEST methodology in experiments for measuring paramagnetic relaxation enhancements

Band-selective excitation short-transient (BEST) sequences are widely used for protein NMR experiments that start with amide proton magnetization, such as ¹H-¹⁵N HSQC, ¹H-¹⁵N TROSY, and multidimensional backbone assignment experiments, because the optimization of amide proton longitudinal relaxation afforded by the BEST methodology allows for much greater sensitivity when using short scan times. Here we show that the BEST methodology can be easily incorporated in sequences for measuring proton transverse relaxation rates (¹H R₂), which are typically used to determine paramagnetic relaxation enhancements (PREs). The resulting BEST-HSQC-PRE and BEST-TROSY-PRE experiments afford similar or better sensitivity for measuring PREs compared to previous methods, provide equally accurate measurements of transverse relaxation rates (and therefore PREs), and allow shorter scan times to be used.