Integration of spin-state-selective excitation into 2D NMR correlation experiments with heteronuclear ZQ/2Q p rotations for 1JXH-resolved E.COSY-type measurement of heteronuclear coupling constants in proteins

Spin-State-Selective Excitation (S³E), which forexample selectively excites amide proton resonances corresponding toexclusively either the α or the β spin state of the covalentlybound ¹⁵N atom is employed for E.COSY-type extraction ofheteronuclear J coupling constants. Instead of having one spectrum with twopeaks (corresponding to the α or β spin state of¹⁵N), S³E generates two spectra, each with onlyone peak for each ¹⁵N nucleus. These two spectra are generatedfrom the same data set, so that there is no reduction in sensitivitycompared to conventional ¹J_NH-resolved methods.Another interesting feature in comparison with conventional methods is that¹J_NH can be suppressed during the evolutionperiod, meaning that no heteronuclear multiplet structure is visible in theω1 frequency dimension. The S³E pulsesequence element is combined with NOESY for measurement of³J_N-Hβ and J_N-Hα coupling constants in either a hetero- or a homonuclear correlated version. Experimental confirmation is obtained using the protein RAP 17-97(N-terminal domain of α2-macroglobulin ReceptorAssociated Protein).