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Figure 1
Schematic view of the STD-NMR technique. (a) Top: direct excitation (saturation) of the protein protons leads to rapid spin diffusion and saturation transfer to a bound small ligand (light blue). After dissociation, the large, directly excited protein returns rapidly to the ground state (grey), while the ligand maintains the proton-specific excitation pattern that was transferred during the lifetime of the complex (light blue, with differentially excited protons). Bottom: schematic representation of the free-ligand spectrum with equally intense resonance signals (top, black) and the STD-NMR difference spectrum (bottom, blue) with relative peak intensities representing the location of each ligand proton in the binding pocket of the protein. (b) Proton resonance spectral windows of a 150 kDa protein (top) and a 970 Da tetrasaccharide (bottom). The HDO signal at 4.8 p.p.m. is truncated in both spectra. Spectra were recorded at 288 K and re-referenced to 298 K (Clore & Potts, 2012BB71). The relatively sharp signals in the protein spectrum at 2 p.p.m. and between 3.5 and 4 p.p.m. represent N-glycosylation chains with increased flexibility, hence their reduced linewidths.

ISSN: 2053-230X
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