Diketopiperazine receptors: a novel class of highly selective receptors for binding small peptides.

A novel class of receptors consisting of a rigid diketopiperazine backbone and peptidic side chains has been developed with the use of combinatorial chemistry. These diketopiperazine receptors interact with peptidic substrates with high specificity as shown in combinatorial on-bead assays. The central diketopiperazine moiety can be easily obtained from natural 4-hydroxyproline and serves as a rigidifying template for the peptidic modules which allow for structural as well as functional variations. Screenings of several dye-marked receptor prototypes against an encoded tripeptide library demonstrated not only the high binding specificities of the diketopiperazine receptors towards peptides but also revealed that small structural changes induce significant changes in their binding properties.

Combinatorial chemistry: a tool for the discovery of new catalysts.

The discovery of new reactions and catalysts has always presented an intriguing challenge to scientists. With the rise of combinatorial chemistry, a new method has emerged that holds considerable promise to facilitate the task since it allows for the simultaneous generation and testing of a large number of compounds. The crucial difficulty lies in establishing general technologies for rapid and reliable screening of libraries to determine the catalytic activity of their members. Several recent publications have addressed this question by using infrared thermography, colorimetric assays and fluorescence spectroscopy. These techniques have not only been applied successfully to the high-throughput screening of parallel compound arrays but also to the screening of one-bead-one-compound libraries. This demonstrates that combinatorial chemistry possesses indeed the potential to establish itself as a powerful tool for the discovery of new catalysts. This review describes the methodologies used so far for the detection of catalytic events and will place particular emphasis on the on-bead screening of one-bead-one-compound libraries.