Single transition-to-single transition polarization transfer (ST2-PT) in [15N,1H]-TROSY

This paper describes the use of single transition-to-single transition polarization transfer (ST2-PT) in transverse relaxation-optimized spectroscopy (TROSY), where it affords a root 2 sensitivity enhancement for kinetically stable amide N-15-H-1 groups in proteins. Additional, conventional improvements of [N-15,H-1]-TROSY include that signal loss for kinetically labile N-15-H-1 groups due to saturation transfer from the solvent water is suppressed with the 'water flip back' technique and that the number of phase steps is reduced to two, which is attractive for the use of [N-15,H-1]-TROSY as an element in more complex NMR schemes. Finally, we show that the impact of the inclusion of the N-15 steady-state magnetization (Pervushin et al., 1998) on the signal-to-noise ratio achieved with [N-15,H-1]-TROSY exceeds by up to two-fold the gain expected from the gyromagnetic ratios of H-1 and N-15.