International Union of Pure and Applied Chemistry Chemistry and Human Health Division Medicinal Chemistry Section Glossary of Terms Used in Medicinal Chemistry

The objective of the glossary is to provide in a single document a consistent terminology and concise definitions of terms covering the various aspects of medicinal chemistry. This was felt necessary with regard to the rapid changes occuring in medicinal chemistry and also by the need to establish international definition standards. Effectively the possibility exists that in different countries certain terms may not have the same meaning, in such a case the creation of an internationally accepted definition is particularly justified. A Working Party belonging to the IUPAC Section on Medicinal Chemistry has therefore been assembled which prepared the present glossary. Concise but sufficiently explanatory definitions have been formulated for about one hundred commonly employed terms which can be considered of particular interest to the medicinal chemistry community. The glossary has been compiled in part from definitions proposed by the Working Party in part from earlier IUPAC glossaries and in part from well-accepted definitions taken from the literature but which were sometimes published in journals or books that may not be readily accessible. ALPHABETICAL ORDERED ENTRIES The glossary has been compiled in part from definitions proposed by the Working Party and in part from well-accepted definitions taken from the literature. In most cases, definitions given here are for specific areas of medicinal chemistry. Some definitions taken from the Glossary for Chemists of Terms Used in Biotechnology (Pure Appl. Chem., 1992, 64, 143-168) were also included, eventually in a slightly modified form; they are identified by an asterisk*. Others, which appear in the Glossary on Computational Drug Design (Pure Appl. Chem., 1997, 69, 1137-1 152) and in Glossary for Chemists of terms used in Toxicology (Pure Appl. Chem. 1993,65,2003-2122), are identified by a double** and a triple*** asterisk respectively. Active transport* Active transport is the carriage of a solute across a biological membrane from low to high concentration that requires the expenditure of (metabolic) energy. Address-message concept Address-message concept refers to compounds in which part of the molecule is required for binding (address) and part for the biological action (message). ADME Abbreviation for Absorption, Distribution, Metabolism, Excretion. (See also Pharmacokinetics; Drug disposition). Affinity Affinity is the tendency of a molecule to associate with another. The affinity of a drug is its ability to bind to its biological target (receptor, enzyme, transport system, etc.) For pharmacological receptors it can be thought of as the frequency with which the drug, when brought into the proximity of a receptor by diffusion, will reside at a position of minimum free energy within the force field of that receptor. 1130