Prediction of Sterically Induced Alignment in a Dilute Liquid Crystalline Phase: Aid to Protein Structure Determination by NMR

A tunable, weak degree of macromolecular alignment with respect to a static magnetic field can be obtained in a dilute, lyotropic liquid crystalline phase. 1 Provided the degree of solute alignment is sufficiently weak, its NMR spectrum retains the simplicity of the regular solution spectrum, but nevertheless permits measurement of dipole -dipole interactions. 1,2 So far, most dipolar coupling measurements have focused on the largest, one-bond heteronuclear dipolar couplings, DNH andDCH. These residual dipolar couplings report on the average orientation of the bond vector with respect to the magnetic field, that is, with respect to the molecular alignment tensor. Alignment of biological macromolecules in such a dilute nematic liquid crystalline phase can result from steric or electrostatic interactions with the nematogen, or both. Tjandra et al.3 have recently demonstrated that in a bicelle medium, 4