Residual dipolar couplings in protein NMR

Partial molecular alignment leads to an incomplete averaging of anisotropic magnetic interactions such as the magnetic dipole-dipole interaction, the chemical shift anisotropy. or the electric quadrupole interaction The resul ting so-called "residual" anisotropic magnetic interactions currently becom e increasingly important in biomolecular NMR spectroscopy in particular, re sidual dipolar couplings turn out to be extremely useful novel parameters f or protein structure determination The basic principles of this new methodo logy are discussed in the present review and recent applications are demons trated. Different alignment mechanisms leading to partial orientation of pr otein molecules in solution are considered in detail. The influence of magn etic and electric fields applied to isotropic protein solutions is discusse d. Various magnetically orienting media which can be admired to protein sol utions are described and compared. Experiments for the measurement of resid ual dipolar couplings in proteins and advantageous strategies for the use o f residual dipolar couplings in structure calculations are reviewed. (C) 20 01 John Wiley & Sons. Inc.