Protein structure in anisotropic environments: Development of orientational constraints

Solid state nuclear magnetic resonance has the potential to characterize me mbrane protein structures at very high resolution. This paper focuses on th e use of orientational constraints for this purpose, These constraints are based on observing the orientation dependence of nuclear spin interactions. The interpretation of these observations is based on accurate knowledge of the spin interaction tensors - the tensor element magnitudes and their ori entation to the molecular frame. Numerous possibilities exist for developin g these orientational constraints, each with their own strengths and weakne sses. This first of two papers focuses on the observation of these constrai nts and their inherent error, while the second paper demonstrates the utili ty, advantages, and disadvantages of these constraints for solving protein backbone structure. (C) 2000 John Wiley & Sons, Inc.