Ligand-Orientation Based Fragment Selection in STD NMR Screening

While saturation transfer difference (STD) is a widely used NMR method for ligand screening, the selection of specific binders requires the validation of the hits through competition experiments or orthogonal biophysical techniques. We show here that the quantitative STD analysis is a reliable and robust approach to discriminate between specific and nonspecific ligands, allowing selection of fragments that bind proteins with a privileged binding mode, in the absence of any structural data for the protein.