Using multiple quantum coherence to increase the 15N resolution in a three-dimensional TROSY HNCO experiment for accurate PRE and RDC measurements

We present a new version of the 3D TROSY HNCO pulse scheme, referred to as HR-TROSY HNCO, with comparable resolution in the 15N dimension to a 2D 1H-15N HSQC experiment. In the conventional 3D TROSY HNCO, the constant time period (1/2JNC ∼ 32 ms) severely limits the maximum resolution in the 15N dimension. In the HR-TROSY HNCO experiment presented here, both constant time periods (∼32 ms each) for coherence forward and backward transfer between 15N and 13C′ are utilized to double the 15N evolution time. This leads to a dramatic enhancement in peak separation along the 15N dimension, making the HR-TROSY HNCO an ideal pulse scheme for accurate paramagnetic relaxation enhancement and residual dipolar coupling measurements.