oligodynamic action[¦äl·ə·gō·dī′nam·ik ′ak·shən]
the action of very small concentrations of positive ions (mainly of metals, such as copper, silver, and gold) on living organisms. Oligodynamic action was discovered by K. von Nägeli (findings published in 1893), who observed the retardation of growth of algae upon immersion of pieces of copper or silver in the vessels in which the algae were being cultivated. In oligodynamic action, metal ions concentrate on the surface of the living object (bacteria, algae, and so on), which causes blocking of the free carbonyl and sulfhydryl groups of the surface structures. Oligodynamic action extends to enzyme systems and even to the activity of inorganic catalysts. The toxic effect of negative ions—which are capable of inactivating enzyme systems, whose activity depends on the presence of metal atoms—is sometimes also included among the oligodynamic actions. An indispensable condition for the oligodynamic action of metals is their ability to pass into the ionized state. The oligodynamic action of silver is used to prevent spoilage of water—for example, during long space flights.