Fig. 6: NMR analysis of ¹⁵N-labeled α-syn interacting with SVD-1a (not isotope labeled).

A Overlay of two-dimensional ¹H-¹⁵N HSQC spectra of 25 µM ¹⁵N α-syn in the presence (red) and absence (black) of an equimolar amount of SVD-1a. B Enlargement of several resonances in the spectra shown under (A) that show small chemical changes for residues in the presence (red) relative to the absence (black) of SVD-1a (130E, 129S 126E, 122N, 119D, 65N); for comparison, resonance 77 V is shown that does not show any chemical shift change. C Residue-specific absolute NMR chemical shift changes in the spectra of ¹⁵N α-syn in the presence of SVD-1a relative to the absence of SVD-1a. The standard deviation, σ, as well as the 2-fold standard deviation, 2σ, of the distribution of observed chemical shift changes are indicated as dashed lines. D NMR PRE intensity ratios of ¹⁵N α-syn in the presence of the paramagnetically-labeled SVD-1a. Residue-specific intensity ratios, I_para/I_dia, of the cross-peak intensities in the two-dimensional ¹H–¹⁵N NMR spectra of the paramagnetic vs. diamagnetic sample are shown. The lower the intensity ratios, I_para/I_dia, the closer the proximity of the paramagnetically-labeled SVD-1a to the respective residue of α-syn. An intensity of one would indicate the absence of interactions. Data point to a bit more pronounced (transient) binding interaction of SVD-1a with residues in the C-terminal region of α-syn, as compared to the average effect on residues in the remaining N-terminal region.