Accurate measurement of 3 J HNHα couplings in small or disordered proteins from WATERGATE-optimized TROSY spectra
 

Accurate measurement of 3 J HNHα couplings in small or disordered proteins from WATERGATE-optimized TROSY spectra

Abstract

Provided that care is taken in adjusting the WATERGATE element of a 1Hâ??15N TROSY-HSQC experiment, such that neither the water magnetization nor the 1Hα protons are inverted by its final 180° pulse, 3JHNHα couplings can be measured directly from splittings in the 1H dimension of the spectrum. With band-selective 1H decoupling, very high 15N resolution can be achieved. A complete set of 3JHNHα values, ranging from 3.4 to 10.1Â*Hz was measured for the 56-residue third domain of IgG-binding protein G (GB3). Using the Hâ??Nâ??Cαâ??Hα dihedral angles extracted from a RDC-refined structure of GB3, 3JHNHα values predicted by a previously parameterized Karplus equation agree to within a root-mean-square deviation (rmsd) of 0.37Â*Hz with the experimental data. Values measured for the Alzheimerâ??s implicated Aβ1â??40 peptide fit to within an rmsd of 0.45Â*Hz to random coil 3JHNHα values.



Source: Journal of Biomolecular NMR