MLSMR identifies compounds appropriate for the NIH Molecular Libraries Probe Production Center Network collection by evaluating and selecting from commercial, academic, and government suppliers. We group compounds into four classes:

• Specialty Sets (SS) comprising known bioactives such as drugs, toxins, metabolites, and others
• Natural Products (NP) and derivatives from known and documented natural sources
• Targeted Libraries (TL) subcategorized into protease, kinase, GPCR, ion channel, and nuclear receptor sets
• Diversity Compounds (DC) all other compounds available for purchase or acquisition

MLSMR selects compounds for acquisition based on the following criteria.

• Samples are at least 90% pure; each sample is tested for identity and purity.
• At least 10 mg of each sample is available from the supplier.
• Compounds have an acceptable range of physicochemical properties, including calculated water solubility, to allow good performance in HTS assays
• Compounds exclude reactive functional groups or moieties known to interfere with HTS. View the MLSMR Excluded Functionality filters.
• Compounds contribute to the diversity of their class. MLSMR clusters as many as four close analogs around each diverse compound to provide instant Structure Activity Relationship (SAR) data for screening hits.