The protein of interest is suspended at high concentration. The electron shielding of any given atom is altered by neighboring atoms. Given sufficient spectra and spin-labeled derivatives, the spacial relationship between the atoms in a protein may be determined. Only works on small proteins that tumble quickly in solution. Requires lots of protein.
Spectrum collection can take months.
Very computationally intensive. Given an atomic structure determined by x-ray or NMR, the shape changes of the protein can be calculated by computationally surrounding the protein in a water shell, and stochastically determining its internal motions from first principles. One can also refine and estimate solution structures from crystal structures, or determine small unknown structues from known structures of similar amino-acid sequence. Not a true structure, but a prediction.