Theories of chemical shift anisotropies in proteins and nucleic acids

This review examines our theoretical understanding of the origins of chemical shift anisotropy (CSA) in proteins and nucleic acids, based on theories for environmental and solvation effects and on quantum chemical calculations for peptides, sugars and bases that form the building blocks for biomolecules. Chemical shift tensors are influenced by 'through-bond' substituent or conformational effects, and by interactions with solvent or with chemically remote parts of the biomolecule. The latter arise from magnetic susceptibilities of remote groups, from electric fields that polarize bonds, and from van der Waals interactions. The strengths and geometric dependencies of these effects can be estimated from quantum chemistry calculations and from empirical fits of classical equations to observed shifts. Prospects for using CSA information for structural characterization of biomolecules will be discussed. (C) 1998 Elsevier Science B.V.