Abstract: In one aspect, the present disclosure relates to methods for detecting an activity of an enzyme in a cell. In some embodiments, the methods include contacting a cell with a liposome containing at least one substrate thereby facilitating introduction of the substrate into the cell. The substrate is capable of producing a detectable light signal when acted on by the enzyme, and the signal is detected. The methods can be used in screening agents that can inhibit or activate an enzyme activity. The methods can also be used in various downstream assays such the detection of interactions between intracellular proteins, screening for variants of an enzyme, and detection of various diseases. Compositions and kits for carrying out the various methods are also provided.

Abstract: Disclosed are binding substrate compositions, methods and kits useful for, among other things, detecting and/or characterizing binding interactions between molecules of interest.