The table below summarises pictorially the most common correlations interrogated by NMR and the experiment classes associated with these investigations. Some further brief explanation of the techniques listed may be found on the NMR acronyms page. Full explanations of these methods may be found in the excellent text book: High-Resolution NMR techniques in Organic Chemistry by TDW Claridge. Correlation Principal technique(s) Comments 1H-1H COSY Proton J-coupling typically over 2 or 3 bonds. 1H-1H TOCSY Relayed proton J-couplings within a coupled spin system. Remote protons may be correlated provided there is a continuous coupling network in between them. 1H-X HSQC 1H-X HMQC One-bond heteronuclear couplings with proton observation. 1H-X HMBC Long-range (multiple-bond) heteronuclear couplings with proton observation. Typically over 2 or 3 bonds when X= 13C. X-X COSY X-X INADEQUATE H-X-X-H ADEQUATE COSY only used when X–spin natural abundance > 20 %. Sensitivity problems when X has low natural abundance; can be improved with proton detection methods. 1/2D NOESY 1/2D ROESY Through-space correlations. ROESY applicable to “mid-sized” molecules with masses of ca. 1-2 kDa. 2D HOESY Heteronuclear through-space correlations. Sensitivity limited by X-spin observation. 1D saturation or inversion transfer 2D EXSY Interchange of spins at chemically distinct locations. Exchange must be slow on NMR timescale for separate resonances to be observed. Intermediate to fast exchange may require lineshape analysis for deconvolution. Spin-echo or Stimulated-echo methods 2D DOSY Measurement of molecular self-diffusion using pulsed field gradient technology. Used often in studies of molecular associations. Relaxation editing STD Water-LOGSY Exchange transferred NOEs Chemical shift perturbation The qualitative detection of ligand binding to a macromolecular receptor, most often a protein, and the quantitative determination of binding affinities.