HACACO revisited: Residual dipolar coupling measurements and resonance assignments in proteins

Abstract The revisited version of the HACACO experiment here presented, is more robust and straightforward to implement and continues to be, to a greater extent, a convenient tool for protein backbone resonance assignment. Additionally, it turns out to be a sensitive and accurate method to measure C α –H α residual dipolar couplings (RDCs). The performance of our new pulse scheme for measurement of RDCs was tested on two proteins with different secondary structures: one characterized by a high β-sheet content, the second dominated by the presence of α-helices. In both examples the new method provided significantly more accurate data, compared to all previously published 3D techniques.