Hyperfine interaction investigations of the internal dynamics of biomolecules

Three different types of low frequency internal motions in biomolecules are illustrated by representative modern applications of hyperfine spectroscopic techniques: (1) the rotation of aromatic amino acid residues is studied by¹H nuclear magnetic resonance via chemical shift averaging; (2) confined diffusion is studied by⁵⁷Fe Mössbauer-spectroscopy via the variation of the recoilfree fraction and via the appearance of very broad resonance absorption lines; (3) large-scale intramolecular reorientational motion is studied by perturbed angular correlation of γ-rays emitted from radioactive 199mHg labels via the loss of anisotropy.