title: Red light-induced redox reactions in cells observed with TEMPO.
abstract: OBJECTIVE
  The aim of this study was to determine the wavelength dependence of light-induced redox reactions in cells, particularly whether there is any contribution by red wavelengths. An additional aim was to assess the potential of 2,2,6,6-tetramethyl piperidine-N-oxyl (TEMPO) as a tool for measuring these redox reactions.
  
  
  BACKGROUND
  Visible light has been shown to affect cells, and redox reactions, which have been detected previously using spin traps, have been proposed as a mechanism. However, there is little evidence that red light, which is used in most such experiments, is redox active in cells.
  
  
  METHODS
  Redox activity was observed by measuring the decay of the electron paramagnetic resonance signal of TEMPO that occurs in the presence of illuminated cells. Color filters were used to generate blue, green, and red light, and the decay resulting from these wavelengths was compared to the decay caused by white light.
  
  
  RESULTS
  Shorter wavelengths have a considerably stronger effect than longer wavelengths, although red light has some effect. Creation of reactive oxygen species by red light was confirmed with the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO).
  
  
  CONCLUSIONS
  Red light can induce redox reactions in illuminated cells. However, shorter wavelengths are more efficient in this regard. In addition, TEMPO was found to be a more sensitive probe than DMPO for detecting light-induced cellular redox reactions.
authors.affiliation: Department of Chemistry, Bar-Ilan University, Ramat Gan, Israel.
authors.forename: Maor
authors.initials: M
authors.lastname: Eichler
authors.forename: Ronit
authors.initials: R
authors.lastname: Lavi
authors.forename: Harry
authors.initials: H
authors.lastname: Friedmann
authors.forename: Asher
authors.initials: A
authors.lastname: Shainberg
authors.forename: Rachel
authors.initials: R
authors.lastname: Lubart
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D003116:Color; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D008027:Light; D032383:Myocytes, Cardiac / Q000528:radiation effects*; D010084:Oxidation-Reduction; D051381:Rats; D017382:Reactive Oxygen Species / Q000032:analysis; D013113:Spin Labels; D019097:Spin Trapping
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D017382:Reactive Oxygen Species; D013113:Spin Labels; C017245:5,5-dimethyl-1-pyrroline-1-oxide; C003959:TEMPO