Line narrowing in spectra of proteins dissolved in a dilute liquid crystalline phase by band-selective adiabatic decoupling: Application to ¹H(N)-¹⁵N residual dipolar coupling measurements

Residual heteronuclear dipolar couplings obtained from partially oriented protein samples can provide unique NMR constraints for protein structure determination. However, partial orientation of protein samples also causes severe ¹H line broadening resulting from residual ¹H-¹H dipolar couplings. In this communication we show that band-selective ¹H homonuclear decoupling during data acquisition is an efficient way to suppress residual ¹H-¹H dipolar couplings, resulting in spectra that are still amenable to solution NMR analysis, even with high degrees of alignment. As an example, we present a novel experiment with improved sensitivity for the measurement of one-bond ¹H(N)-¹⁵N residual dipolar couplings in a protein sample dissolved in magnetically aligned liquid crystalline bicelles.