Patent ID: 8188011

Claim:
A method for identifying at least one ligand having an affinity for an RNA target molecule that is equal to or greater than a baseline affinity comprising: mixing an amount of ammonium with an excess amount of the RNA target molecule such that unbound RNA target molecule is present in the mixture; introducing the mixture of ammonium and RNA target molecule into a mass spectrometer; adjusting the mass spectrometer desolvation conditions such that the signal strength of the ammonium bound to the RNA target molecule is from 1% to about 30% of the signal strength of unbound RNA target molecule; introducing at least one ligand into a test mixture of the RNA target molecule and the ammonium; introducing the test mixture into the mass spectrometer; and identifying any complexes of the ligand and the RNA target wherein the ligand has greater than the baseline affinity for the RNA target molecule by discerning those signals that have a signal strength greater than the background noise of the mass spectrometer.