Measuring the χ1 torsion angle in protein by CH-CH cross-correlated relaxation: A new resolution-optimised experiment

T Carlomagno, W Bermel & C Griesinger

Journal Of Biomolecular NMR


Here we introduce an experiment with high sensitivity and resolution for the measurement of CH-CH dipolar-dipolar cross-correlated relaxation rates (CCRR) in protein side-chains. The new methodology aims to the determination of structural and dynamical parameters around the torsion angle χ1 by measuring CαHα-CβHβ cross-correlated relaxation rates. The method is validated on the protein ubiquitin: the χ1 angles determined from the CCRR data are compared with the χ1 angles of a previously determined NMR structure. The agreement between the two data sets is excellent for most residues. The few discrepancies that were found between the CCR-derived χ1 angles and the angles of the previously determined NMR structure could be explained by taking internal motion into account. The new methodology represents a very powerful tool to determine both structure and dynamics of protein side-chains in only one experiment.