The conformation of the Congo-red ligand bound to amyloid fibrils HET-s(218â??289): a solid-state NMR study
Abstract
We have previously shown that Congo red (CR) binds site specifically to amyloid fibrils formed by HET-s(218â??289) with the long axis of the CR molecule almost parallel to the fibril axis. HADDOCK docking studies indicated that CR adopts a roughly planar conformation with the torsion angle
Ï? characterizing the relative orientation of the two phenyl rings being a few degrees. In this study, we experimentally determine the torsion angle
Ï? at the center of the CR molecule when bound to HET-s(218â??289) amyloid fibrils using solid-state NMR tensor-correlation experiments. The method described here relies on the site-specific 13C labeling of CR and on the analysis of the two-dimensional magic-angle spinning tensor-correlation spectrum of 13C2-CR. We determined the torsion angle
Ï? to be 19°.
Source: Journal of Biomolecular NMR