Competition saturation transfer difference experiments improved with isotope editing and filtering schemes in NMR-based screening

6 páginas, 5 figuras, 1 esquema -- PAGS nros. 17148-17153Competition binding experiments are used in NMR-based screenings to match up to the binding site with that of a known ligand and to determine the strength of the interaction, thus providing a ranking of hits according to receptor affinity. These competition titration experiments must use a reference ligand for which the binding site on the receptor and the affinity of the interaction is known. These experiments rely on the observation of separate signals of the reference and hit compounds, which is very often hampered by signal overlap. Here, we present a combination of isotope editing and filtering schemes with saturation transfer difference (STD) experiments that allows the separation of the STD signals of the labeled reference ligand from that of the natural abundance hit compound even in the case of severe signal overlap. Thus, the measurement of well-defined titration curves in competition STD titration experiments is feasible and allows the quantitative determination of binding constants. Note that the method requires the availability of the reference ligand in an NMR-active, stable-isotope-labeled formWe thank Thomas Schallus for the expression vector of malectin and for sharing ideas prior to publication. K.E.K and G.B. acknowledge the support of the Hungarian Scientific Research Fund, OTKA NK-68578. C.M.-G. acknowledges the DFG Grant Mu1606/2-2. We also thank the scientific exchange program between CSIC (Spain) and Hungary for travel supportPeer reviewe