Skip to main content
  • Poster presentation
  • Open access
  • Published:

Sublinear ligand-based virtual screening using bitmap indices

The contemporary standard approach for ligand-based virtual screening is based on a sequential screening pipeline which means that every compound of a given compound library has to be screened against a reference molecule. For tools based on small molecule alignments, this requires calculating superpositions between a reference ligand and each compound of the library to obtain a list of hit compounds.

As calculating molecular superpositions is computationally expensive, our new tool for ligand-based virtual screening named TrixS BMI tries to avoid the sequential screening pipeline of other ligand-based virtual screening tools by reducing the number of compounds to superimpose in a computationally much faster pre-processing step. This allows for sublinear runtimes with respect to the library size while still providing comparable enrichment and hit rates. TrixS BMI is an adaptation of the structure-based virtual screening tool TrixX BMI [1] and uses an approach based on descriptors containing pharmacophoric and shape information, as well as an indexed database. In addition, TrixS BMI allows user-defined pharmacophoric constraints and has a novel approach to handle partial shape similarity directly upon the indexed search process.

An outline of the workflow can be described as follows: as TrixS BMI does not decompose the compounds into smaller fragments, flexibility is handled by using a conformer generator, which calculates conformational ensembles for each compound of a given library. The ensembles are used to calculate descriptors, which are then stored in an indexed database. This is a one time effort. The same database is queried by descriptors calculated from a target molecule, which results in a preselection of compounds for the process of superpositioning.

Screening experiments on literature data show that TrixS BMI obtains comparable hit rates and enrichment values to standard alignment-based virtual screening tools like ROCS [2] and FlexS [3]. Computing times are in the range of 7 to 8 compounds per second in case of searching with drug-like target molecules.


  1. Schlosser J, Rarey M: From screening to searching: an index-driven approach to structure-based lead identification. 2008

    Google Scholar 

  2. Rush TS, Grant JA, Mosyak L, Nicholls A: A shape-based 3-D scaffold hopping method and its application to a bacterial protein-protein interaction. J Med Chem. 2005, 48 (5): 1489-1495. 10.1021/jm040163o.

    Article  CAS  Google Scholar 

  3. Lemmen C, Lengauer T, Klebe G: FLEXS: a method for fast flexible ligand superposition. J Med Chem. 1998, 41 (23): 4502-4520. 10.1021/jm981037l.

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and permissions

About this article

Cite this article

Schärfer, C., Schlosser, J. & Rarey, M. Sublinear ligand-based virtual screening using bitmap indices. Chemistry Central Journal 3 (Suppl 1), P27 (2009).

Download citation

  • Published:

  • DOI: