Photodynamic Action

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Photodynamic Action


injury to biological structures and disruption of their function upon the absorption of light by a pigment or dye in the presence of oxygen.

In photodynamic action, the unpigmented molecules, which do not directly absorb visible radiation, are damaged. A pigmented substance, which absorbs photons, serves as the photosensitizer, that is, the mediator in the photoreaction; it mediates the oxidation of the substrate and the formation of the product of photodynamic action. Molecules of the dye apparently participate in the photoprocess in the triplet excited state. Among the reactive dyes involved in photodynamic action are acridines, anthraquinones, a number of porphyrins, and riboflavin.

Various organic substances may serve as substrates of the reaction; many structures and functions on the organismic, cellular, and molecular levels are sensitive to photodynamic action. Thus, photodynamic action may produce erythema and photodermatitis when reactive dyes are applied to the skin; it may also produce intoxication when light is absorbed by the free porphyrins of the blood if there is disruption of porphyrin exchange. Poisonings have been known to occur in animals after they have eaten plants containing a photodynamically active pigment, for example, hypericin in Saint-John’s-wort. Photodynamic action may initiate carcinogenic processes in pigmented structures.

On the cellular level photodynamic action may stimulate or inhibit cell division, cause mutations, produce bactericidal action, and damage biomembranes. Photodynamic action is known to affect physiological and biochemical processes, such as respiration, oxidative phosphorylation, and photosynthesis. The basis of many of the effects of photodynamic action is the damage to the molecules of proteins, such as enzymes, caused by the oxidation of the amino acids in the molecules. The effect on the genetic apparatus, on bacteria, and on viruses is due to inactivation of the nucleic acids, which occurs as a result of the destruction of nitrogenous bases.


Konev, S. V., and I. D. Volotovskii. Fotobiologiia. Minsk, 1974.
Spikes, J. “Photodynamic action.” In Photophysiology, vol. 3. New York, 1968.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Although the large K value demonstrated high photosensitization activity, the EA autosensitized photooxidation reaction could compete against the preferred Type-I or type-II photosensitization process to cause adverse effect to photodynamic action. It has been reported that the K value of HA decreased when HA irradiated under long- wavelength (greater than 530 nm) light [17].
Photodynamic action of PpIX is mainly induced by the generation of singlet oxygen in a type II photodynamic reaction [4].
Chlorophyll, the green plant pigment, plays the main role in the production of this photodynamic action and, as well as some of its derivatives, it is used as a photosensitizer in PDT [8].
Our results confirmed that AQ internalization is essential for PDT-mediated by [0.sub.2.sup.1] photodynamic action in MCF-7C3 cells, due to the fact that soranjidiol and rubiadin have similar uptake (p >0.01), but soranjidiol.
Photodynamic action was soon reported to occur in most kinds of biological systems, including plants, animals, cells, viruses, and specifically to biomolecules such as enzymes, toxins and proteins (7).
(7.) Blum, H.F., 'Photodynamic Action and Diseases Caused by Light,' Reinhold, New York, NY, 1941.
coli cells were more resistant to photodynamic action of hypocrellin B than S.
aureus treated by photodynamic action of hypocrellin B [10].
Recently, growing data showed that photodynamic action could effectively kill pathogenic microorganisms, termed photodynamic inactivation (PDI) and photodynamic antimicrobial chemotherapy (PACT) [5-7, 9-11].
which displays several photodynamic actions (Diwu, 1995).