Side chain: backbone projections in aromatic and ASX residues from NMR cross-correlated relaxation
Vögeli, Beat ; Riek, Roland
In: Journal of Biomolecular NMR, 2010, vol. 46, no. 2, p. 135-147
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- The measurements of cross-correlated relaxation rates between HN-N and Cβ-Cγ intraresidual and sequential dipolar interactions is demonstrated in ASN, ASP and aromatic residues. The experiment can be used for deuterated samples and no additional knowledge such as Karplus parametrizations is required for the analysis. The data constitutes a new type of information since no other method relates the Cβ-Cγ bond to HN-N. Using this method the dominant populations of rotamer states of χ1 can be readily cross checked provided that φ or ψ are known. In addition, dynamics on all timescales can be probed. As opposed to standard dynamics analysis of isolated bonds, the presented observables depend on relative dynamics with an interesting prospect to analyze correlated fluctuations of the two torsion angles φ or ψ with χ1. Experimental rates are compared to single conformer and ensemble representations of GB3 and ubiquitin. In particular, it is found that the recently published ubiquitin ensemble 2k39 improves the agreement obtained for 1UBQ. In general, however, input data restricting ASX and aromatic side chains in structure calculation is sparse highlighting the need for new NMR observables