J-modulated TROSY experiment extends the limits of homonuclear coupling measurements for larger proteins

This paper describes the use of a TROSY experimental scheme and its variant extended with a scaled J-modulation spin-echo sequence for accurate and se nsitive measurement of homonuclear (3)J(HNHalpha) coupling constants in lar ger proteins with uniform N-15 labeling. Exclusive selection of the most sl owly relaxing component of a N-15-H-1 multiplet by the TROSY approach leads to substantial improvement in resolution; this is a prerequisite for accur ate measurement of couplings from the H-1 multiplets directly along the H-1 frequency dimension or from the J-scaled doublets along the N-15 frequency dimension. (C) 2001 Academic Press.