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The Portal features a class of compounds we termed Unsuitables. These small molecules are typically non-selective or not sufficiently potent compared with other available chemical probes to merit the probe designation. We opted for the name "Unsuitables" to provide a category that allows us to distinguish them from chemical probes. The title recognizes that many of these compounds were once valuable, for example if they were the first compound available to study a protein target or target family. We also recognise that some scientists select non-specific compounds for experiments precisely because they are non-specific, as these compounds allow them to impact the activity of many proteins at the same time. Our goal with this category of compounds is not to indicate that they cannot be useful in research. Rather, we hope to discourage the misapplication of these reagents as if they were chemical probes (i.e., specific and selective tools for a particular target).

A table of all Unsuitables currently catalogued on the portal can be found here. To recommend an unsuitable that we do not yet feature - please use our probe submission form.

In the Portal, the Unsuitables can be readily distinguished from chemical probes: they are catalogued without much of the detailed validation information that accompanies a probe, they feature a generic warning image, and they are not rated by our SERP. To ensure there is no confusion, each of the Unsuitables is also designated by a generic and specific note to clarify the categorization. The generic note simply indicates that it is unsuitable for use as a chemical probe; the specific note provides some context for why it is considered so. For an example, please visit the staurosporine page.