ABSTRACT
The principles of NMR (Wutrich 1986) and their application to the unfolded/disordered state of proteins (Chatterjee et al. 2005; Dyson and Wright 2002a; 2004) are amply covered in excellent monographs and reviews; here, only basic aspects are surveyed briefly. NMR spectroscopy is based upon the existence of nuclear spins and the intrinsic magnetic moment of atomic nuclei such as that of 1H, 13C, and 15N. These nuclei have two possible spin states, which are split in an external magnetic field (B0). Transitions between the two states can be induced by the resonant absorption of electromagnetic radiation at a frequency that matches the energy difference between the states. Because the difference depends on the chemical environment, the NMR signal contains a wealth of information on the local covalent and spatial arrangement of atoms.
