Abstract
Partial molecular alignment leads to an incomplete averaging of anisotropic magnetic interactions such as the magnetic dipoleβdipole interaction, the chemical shift anisotropy, or the electric quadrupole interaction. The resulting soβcalled βresidualβ anisotropic magnetic interactions currently become increasingly important in biomolecular NMR spectroscopy. In particular, residual dipolar couplings turn out to be extremely useful novel parameters for protein structure determination. The basic principles of this new methodology are discussed in the present review and recent applications are demonstrated. Different alignment mechanisms leading to partial orientation of protein molecules in solution are considered in detail. The influence of magnetic and electric fields applied to isotropic protein solutions is discussed. Various magnetically orienting media which can be admixed to protein solutions are described and compared. Experiments for the measurement of residual dipolar couplings in proteins and advantageous strategies for the use of residual dipolar couplings in structure calculations are reviewed.βΒ© 2001 John Wiley & Sons, Inc.βConcepts Magn Reson 13: 238β259, 2001