5. Combinatorial chemistry
Another line of evidence is striking. Chemistry has acquired during the last few years a brand-new sub-discipline, known as “combinatorial chemistry.” It bridges the science and the industry, since most of the present applications are in the area of drug design for the pharmaceutical industry.
First, let me explain the concept. Let us assume, for simplicity’s sake, that we want to synthesize quadripartite molecules, consisting of the reunion of four modules A, B, C, D. Thus, the resulting product can be written A-B-C-D. To give a concrete example, if the component units A, B, C and D are aminoacid residues, A-B-C-D would be a tetrapeptide. This example points to the desirability of such a preparation, since numerous tetrapeptides are endowed with interesting and often beneficial biological activities, as hormones, neurotransmitters, etc.
Techniques are available for the automatized synthesis of all possible entities with the general formula A-B-C-D, separated from one another on small beads of polymer, from a variety of choices for each of the A-D modules. In the example of a tetrapeptide, and drawing from the store of the existing 20 natural aminoacids, one can thus synthesize (in a matter of a few days!) no less than 20x20x20x20 = 204= 160,000 tetrapeptides. This chemical library is then examined, using sensitive biological tests, for locating those (and only those) products that look promising, for future development as drugs.
This activity is not confined to the pharmaceutical industry, it can also be applied to many other goals, such as the systematic screening of novel types of materials, organic, inorganic or composite, for instance for discovery of new superconducting ceramics.
One can foresee quite a few other applications. This is a rather peculiar branch of science, unashamedly Edisonian, trial-and-error attempting to gain success (discoveries) through random chance rather than enlightened rational insight. The best analogy is the improbability of a monkey playing with the keyboard of a word processor and coming out with the text of Coleridge’s “Kubla Khan.”
Present-day chemistry includes explicitly a sub-discipline of “combinatorial chemistry.”