Tracking down new active agents for cancer or malaria treatment could soon become easier - thanks to a computer program with which researchers from the Max Planck Institute of Molecular Physiology in Dortmund aim to facilitate the search for suitable pharmaceutical substances. The program, which is called Scaffold Hunter, acts as a tool for navigating chemical space. It generates maps of chemically-related structures and links them to biological activity, that is, to their potential to bind to proteins, in particular medically relevant proteins. With the help of this new tool, the Max Planck scientists, together with colleagues from the universities of Frankfurt, Eindhoven and New Mexico, have identified substances that could provide possible candidates for the development of active agents for use in cancer treatment and malaria. Cartridge Filters The dimensions of the chemical space, which contains the total number of all conceivable chemical structures, are unimaginable: it is estimated to contain up to 10160 different molecules. Written out in full, this figure would fill two lines of closely-spaced numbers on a typed page. However, only some of these - 1060 molecules according to the estimates - are potential active agents. Identifying these islands of biological activity in the ocean of all potential compounds is not an easy task. "Organic synthesis cannot gauge the chemical space in its entirety," explains Stefan Wetzel, a researcher from Herbert Waldmann's group at the Max Planck Institute of Molecular Physiology in Dortmund. Chemists cannot cook up all possible compounds to test them. Therefore, the researchers have developed this navigation system to help them steer their way through this sea of possibilities.