There are several different ways to measure coupling constants in proteins ( 95ANG1671 , B99KRI195 and B99KRI259):

• Direct measurement (J-resolved) from the in-phase or anti-phase splitting of a particular resonance in a 1D/2D/3D spectrum with optional use of lineshape analysis, spectral simulation and/or fitting procedures.
• From E.COSY-like experiments in which the coupling between two nuclei A and B is measured from the relative displacement of the two resolved components of an AC cross-peak, which are displaced in one-dimension of the nD spectrum by J(AB) and in the other dimension by J(BC).
• From the quantitative J correlation approach in which the strength of a long-range correlation in a nD spectrum is related in a simple manner to the intensity of the corresponding cross-peak.
• Spin-state selective approach in which two sets of spectra with each displaying only one component (alpha or beta) of the coupling multiplet are compared.
• The DQ/ZQ method which allows the measurement and the sign determination of coupling constants in large biomolecules amd greatly reduces the effects of differential relaxation.