Relax, a flexible program for the back calculation of NOESY spectra based on complete-relaxation-matrix formalism.

RELAX is a flexible program for the quantitative analysis of NOESY spectra. It allows the simultaneous application of different models describing the internal and overall motion of the molecule under investigation for individual spin pairs or groups of spins. A correction for anisotropy effects due to the deviation of the molecule from a spherical shape is calculated automatically from the trial structure. The program can deal with completely relaxed spectra as well as spectra recorded with a short relaxation delay. An execution-time-controlled splitting of the relaxation matrix reduces the computation time significantly without any loss of accuracy. This is especially important for large molecules or medium distance cutoffs.