MLP and Nature Chemical Biology Probes. The former has been outlined in the introduction. The latter was extracted from articles published in Nature Chemical Biology (although since 2018 this dedicated section of the Journal is no longer available) As legacy collections, probes from these two sources may lack the stringent characterisation of maintained collections. This is reflected in some cases by the a) lack of controls or orthogonal probes, b) unclear potency and selectivity criteria or c) no target annotation.