saturation transfer difference nuclear magnetic resonance spectroscopy saturation transfer double difference nuclear magnetic resonance spectroscopy saturation-transfer double-difference nuclear magnetic resonance spectroscopy A type of NMR spectroscopy where radio frequency pulses are used to induce an equal population of upper and lower spin states in ('saturate') certain selected protons, removing their signal from the NMR spectrum. The signal from two different samples is obtained simultaneously and common signals are cancelled automatically. Saturation-transfer double-difference NMR is used to detect the transient binding of small molecule ligands to macromolecular receptors. STDD-NMR CHMO:0000898