  Reorientational dynamics-motion defined by changes in the direction of a
vector or tensor-determine relaxation behavior in nuclear magnetic resonance
(NMR). However, if multiple processes exist that result in reorientation, then
analyzing the net effects becomes a complex task, so that one ideally would
separate those motions to simplify analysis. The model-free and two-step
approaches have established the separability of the total correlation function
of reorientation motion into contributions from statistically independent
motions. Separability has been used to justify the analysis of experimental
relaxation rate constants by fitting data to a total correlation function
resulting from the product of two or three individual correlation functions,
each representing an independent motion. The resulting parameters are used to
describe motion in the molecule, but if multiple internal motions are present,
interpreting those parameters is not trivial. We suggest an alternative
approach: quantitative and timescale-specific comparison of experiment and
simulation, as previously established using the detector analysis. This is
followed by separation of simulated correlation functions into independent
motions, and timescale-specific parameterization of the results, such that one
may determine how each motion contributes to experimental parameters. We
establish protocols for the separation of the correlation function into
components using coordinates from molecular dynamics simulation. Separation is
achieved by defining a series of frames, where the frames iteratively split the
total motion into contributions from motion within each frame and of each
frame. Then timescale specific parameters (e.g. detector responses) describing
the total motion may be interpreted in terms of the timescale-specific
parameterization of the individual motions.
