INTEGRATION OF SPIN-STATE-SELECTIVE EXCITATION INTO 2D NMR CORRELATION EXPERIMENTS WITH HETERONUCLEAR ZQ 2Q PI-ROTATIONS FOR (1)J(XH)-RESOLVED E.COSY-TYPE MEASUREMENT OF HETERONUCLEAR COUPLING-CONSTANTS IN PROTEINS/

Spin-State-Selective Excitation ((SE)-E-3), which for example selectiv ely excites amide proton resonances corresponding to exclusively eithe r the alpha or the beta spin slate of the covalently bound N-15 atom i s employed for E.COSY-type extraction of heteronuclear J coupling cons tants. Instead of having one spectrum with two peaks (corresponding to the alpha or beta spin state of N-15), (SE)-E-3 generates two spectra , each with only one peak for each N-15 nucleus. These two spectra are generated from the same data set, so that there is no reduction in se nsitivity compared to conventional (1)J(NH)-resolved methods. Another interesting feature in comparison with conventional methods is that (1 )J(NH) can be suppressed during the evolution period, meaning that no heteronuclear multiplet structure is visible in the omega(1) frequency dimension. The (SE)-E-3 pulse sequence element is combined with NOESY for measurement of (3)J(N-H)beta and J(N-H)alpha coupling constants i n either a hetero- or a homonuclear correlated version. Experimental c onfirmation is obtained using the protein RAP 17-97 (N-terminal domain of alpha(2)-macroglobulin Receptor Associated Protein).