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Molecular Libraries Small Molecule Repository (MLSMR)

The Molecular Libraries Small Molecule Repository (MLSMR) is designed to identify, acquire, maintain, and distribute to the Molecular Libraries Screening Centers Network (MLSCN)an eventual collection of approximately 500,000 chemically diverse compounds with known or unknown biological activities for use in high-throughput screening (HTS) of a diverse set of biological assays submitted by the research community and implemented within the centers. It is anticipated that a subset of the screening “hits” that are generated will be further developed by the MLSCN into optimized chemical analogs that can be used by the scientific community as bioactive Probe Guidelines to study molecular targets and cellular pathways, and potentially as starting points for therapeutics development outside of the MLSCN. The chemical structures of the compounds in the repository, along with the associated screening data obtained from the MLSCN, will be shared with the public through PubChem.


Established through a contract to Discovery Partners International in September 2004 as a component of the National Institutes of Health (NIH) Roadmap: New Pathways to Discovery: Molecular Libraries Initiative, the Molecular Libraries Small Molecule Repository (MLSMR) serves several critical roles in:

  1. Identifying and acquiring, in coordination with the NIH and external scientific advisory groups, compounds from government, academic, industry, and commercial sources and assembling a collection of compounds which meet specified criteria;
  2. Storing, maintaining, and tracking the compound collection inventory, and monitoring the stability of compounds in the library;
  3. Arraying all compounds in sets suitable for high-throughput screening (HTS) and distributing the compound arrays to the Molecular Libraries Screening Centers;
  4. Monitoring the compound inventory to ensure that sufficient quantities of all compounds are available to support screening needs and acquiring sufficient quantities of depleted compounds to replenish the inventory.

An initial set of nearly 100,000 compounds was acquired in November 2005, and acquisition of the second 100,000 compounds began in the Fall of 2006. The first two acquisitions similarly targeted four main compound categories.

  1. Specialty sets of known bioactive compounds;
  2. Targeted libraries for protease, kinase, GPCR, ion channel, and nuclear receptor targets;
  3. Diversity sets;
  4. Natural products.

The MLSMR compound collection will be expanded with acquisitions from a variety of sources including:

  1. Commercial chemical suppliers;
  2. NIH P41 grantees awarded through the “Pilot-Scale Libraries for High-Throughput Screening” initiative; and
  3. The international chemistry research community. (see left menu: Compound Submission to the SMR)