Spectral width Spin-echo measurements

The measurement of one-bond coupling constants from the distance between the multiplet components in HSQC spectrum becomes unreliable for large proteins due to the differential relaxation that can severely broaden one of the components, and even make it undetectable. Luy and Marino proposed to overcome this problem by introduction of J-modulation to the sharp TROSY component. The JE-TROSY experiment starts with a spin-echo J-evolution period, which is followed by a traditional TROSY detection sequence. As the result the resonances are independently modulated by the single-bond coupling, which leads to the displacement of the cross-peak in the independent spectral dimension after the 3D Fourier transformation. This displacement is measured either relative to zero frequency if real FT is used in the J-dimension, or as the splitting between the pseudo multiplet components if the complex FT is applied. The spectral width in the J-dimension is normally set to twice the value of the... 

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