title: Flavins are source of visible-light-induced free radical formation in cells.
abstract: OBJECTIVE
  It has been hypothesized that reactive oxygen species (ROS) are created by an endogenous photosensitizer during low energy visible light illumination of tissue, and these ROS are responsible for reported biostimulative effects. This study aims to identify the endogenous photosensitizer responsible for ROS production by visible light.
  
  
  METHODS
  Electron paramagnetic resonance (EPR) spectroscopy was used to detect oxyradicals produced in cardiac and sperm cells during illumination by a halogen lamp. Oxyradical production was determined as a function of illumination wavelength, cell fraction, and molecular weight.
  
  
  RESULTS
  Oxyradicals were created solely by the 400-500 nm range of visible light. The endogenous photosensitizer is found predominantly in the cytosol and is smaller than 12 kD. Flavin mononucleotide produces the same signal at concentrations consistent with reported intracellular free flavin concentrations.
  
  
  CONCLUSIONS
  A small, water soluble photosensitizer active only at wavelengths shorter than 500 nm is consistent with a flavin, which reproduces cellular signals at physiological concentrations. Thus, flavins are responsible for the photosensitization of the observed oxyradicals in cells.
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel. scrabbler@walla.co.il
authors.forename: Maor
authors.initials: M
authors.lastname: Eichler
authors.forename: Ronit
authors.initials: R
authors.lastname: Lavi
authors.forename: Asher
authors.initials: A
authors.lastname: Shainberg
authors.forename: Rachel
authors.initials: R
authors.lastname: Lubart
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004578:Electron Spin Resonance Spectroscopy; D005415:Flavins / Q000378:metabolism*; D005609:Free Radicals / Q000378:metabolism*; D066298:In Vitro Techniques; D008027:Light; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012756:Sheep; D013094:Spermatozoa / Q000378:metabolism
chemical_list: D005415:Flavins; D005609:Free Radicals; D017382:Reactive Oxygen Species