The invention involves obtaining signatures of species (including chemical, biological, or biochemical molecules) and/or signatures of interactions between species and using them to characterize species, characterize interactions, and/or identify species that could be useful in a variety of settings. Signatures can be obtained using aqueous multi-phase partitioning and can be used to predict molecular interactions for applications such as drug discovery. A plurality of aqueous multi-phase partitioning arrangements can define an overall system providing an information-intensive signature, maximizing precision and sensitivity.