Combinatorial Chemistry

A library of a billion or more different molecules is only useful if the molecules can be quickly and economically screened for the desired function. "High-throughput" techniques have been developed that automate most of the steps required to combine the molecules with their targets and evaluate the extent of any reaction.

Typically, the molecules are arrayed on a solid surface and the target is added. Unbound target is washed away. Fluorescent tags are often added to the target, to allow easy (and automated) visualization of the results. Robotic systems controlled by computers can react and evaluate billions of separate compounds in the time it would take a human to screen a dozen. One such approach is used in DNA microarrays, in which thousands of genes from a DNA library are attached to a solid base. These are reacted with messenger RNAs from a cell, and the results are visualized fluorescently.

A high-throughput screening assay can quickly assess the target-binding ability of millions of compounds.