PhotochromismPhotochromism is the reversible transformation of a chemical species between two forms by the absorption of electromagnetic radiation, where the two forms have different absorption spectra. Trivially, this can be described as a reversible change of color upon exposure to light. The phenomenon was discovered in the late 1880s, including work by Markwald, who studied the reversible change of color of 2,3,4,4-tetrachloronaphthalen-1(4H)-one in the solid state. He labeled this phenomenon "phototropy", and this name was used until the 1950s when Yehuda Hirshberg, of the Weizmann Institute of Science in Israel proposed the term "photochromism".Photochromism can take place in both organic and inorganic compounds, and also has its place...
Fischer Indole Synthesis
Fischer Indole SynthesisOverall ReactionThis oldest indole synthesis method transforms aryl hydrazones to indoles and requires elevated temperatures and the addition of Brønsted or Lewis acids. This reaction is good for preparing 2-, 3-, 5-and 7-substituted indoles but is poorer for the preparation of 4- and 6-substituted indoles, due to lack of regioselectivity.Mechanism of Fischer Indole Synthes...
Drug Screening
Screening and DesignThe process of finding a new drug against a chosen target for a particular disease usually involves high-throughput screening (HTS), wherein large libraries of chemicals are tested for their ability to modify the target. For example, if the target is a novel GPCR, compounds will be screened for their ability to inhibit or stimulate that receptor (see antagonist and agonist): if the target is a protein kinase, the chemicals will be tested for their ability to inhibit that kinase.Another important function of HTS is to show how selective the compounds are for the chosen target. The ideal is to find a molecule which will interfere with only the chosen target, but not other, related targets. To this end, other screening runs...