Abstract: The present invention provides methods of screening for ligands of target molecules. The methods of the present invention include assays in which a target molecule is subjected to denaturing conditions, and compounds are screened for the ability to alter the susceptibility of the target to unfolding. The methods of the present invention use fluorescence detection to determine that degree of unfolding of a target molecule. In some aspects of the present invention, fluorescence resonance energy transfer (FRET) is detected. In other aspects of the invention, fluorescence polarization (FP) is detected. In preferred embodiments, a target molecule such as a target protein is heated to a temperature, called TATLAS, at which at least a portion of the target molecule unfolds, in the presence of a test compound.