title: Iodide accumulation provides kelp with an inorganic antioxidant impacting atmospheric chemistry.
abstract: Brown algae of the Laminariales (kelps) are the strongest accumulators of iodine among living organisms. They represent a major pump in the global biogeochemical cycle of iodine and, in particular, the major source of iodocarbons in the coastal atmosphere. Nevertheless, the chemical state and biological significance of accumulated iodine have remained unknown to this date. Using x-ray absorption spectroscopy, we show that the accumulated form is iodide, which readily scavenges a variety of reactive oxygen species (ROS). We propose here that its biological role is that of an inorganic antioxidant, the first to be described in a living system. Upon oxidative stress, iodide is effluxed. On the thallus surface and in the apoplast, iodide detoxifies both aqueous oxidants and ozone, the latter resulting in the release of high levels of molecular iodine and the consequent formation of hygroscopic iodine oxides leading to particles, which are precursors to cloud condensation nuclei. In a complementary set of experiments using a heterologous system, iodide was found to effectively scavenge ROS in human blood cells.
authors.affiliation: Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll PA37 1QA, Scotland, United Kingdom. fck@sams.ac.uk
authors.forename: Frithjof C
authors.initials: FC
authors.lastname: Küpper
authors.forename: Lucy J
authors.initials: LJ
authors.lastname: Carpenter
authors.forename: Gordon B
authors.initials: GB
authors.lastname: McFiggans
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Palmer
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Waite
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Boneberg
authors.forename: Sonja
authors.initials: S
authors.lastname: Woitsch
authors.forename: Markus
authors.initials: M
authors.lastname: Weiller
authors.forename: Rafael
authors.initials: R
authors.lastname: Abela
authors.forename: Daniel
authors.initials: D
authors.lastname: Grolimund
authors.forename: Philippe
authors.initials: P
authors.lastname: Potin
authors.forename: Alison
authors.initials: A
authors.lastname: Butler
authors.forename: George W
authors.initials: GW
authors.lastname: Luther
authors.forename: Peter M H
authors.initials: PM
authors.lastname: Kroneck
authors.forename: Wolfram
authors.initials: W
authors.lastname: Meyer-Klaucke
authors.forename: Martin C
authors.initials: MC
authors.lastname: Feiters
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D001272:Atmosphere / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000378:metabolism; D006603:Hexuronic Acids / Q000494:pharmacology; D007454:Iodides / Q000378:metabolism*; D044423:Kelp / Q000378:metabolism*; D007795:Laminaria / Q000378:metabolism; D008954:Models, Biological; D010126:Ozone; D016897:Respiratory Burst; D013057:Spectrum Analysis; D013997:Time Factors
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D006603:Hexuronic Acids; D007454:Iodides; C007896:guluronic acid; D010126:Ozone