The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Tobin J. Marks - One of the best experts on this subject based on the ideXlab platform.
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A resonance Raman/Iodine Moessbauer investigation of the starch-Iodine structure. Aqueous solution and Iodine vapor preparations
Journal of the American Chemical Society, 2016Co-Authors: Robert C. Teitelbaum, Stanley L. Ruby, Tobin J. MarksAbstract:Abstract : The structure of the blue-black Iodine complex of amylose (the linear, helical component of starch) prepared either from Iodine and iodide in aqueous solution or from crystalline amylose and Iodine vapor, has been studied by resonance Raman and Iodine -129 Mossbauer spectroscopy. In both cases it is concluded that the identity of the major chromophore is essentially the same: the pentaiodide (I(5-1)) anion. For the material prepared from Iodine vapor, the iodide required for (I(5-1)) formation is produced by hydrolysis or alcoholysis of Iodine. The other product of this reaction, a hypoiodite, has been assigned in the Iodine Mossbauer spectrum. (Author)
Lucy J. Carpenter - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Reactive Inorganic Iodine Fluxes in the Indian and Southern Ocean Marine Boundary Layer
2020Co-Authors: Swaleha Inamdar, Lucy J. Carpenter, Liselotte Tinel, Rosie Chance, Prabhakaran Sabu, Racheal Chacko, Sarat C. Tripathy, Anvita U. Kerkar, Alok K. Sinha, Parli Venkateswaran BhaskarAbstract:Abstract. Iodine chemistry has noteworthysignificant impacts on the oxidising capacity of the marine boundary layer (MBL) through the depletion of ozone (O3) and changes to HOx (OH/HO2) and NOx (NO/NO2) ratios. Hitherto, studies have shown that the reaction of atmospheric O3 with surface seawater iodide (I−) contributes to the flux of Iodine species into the MBL mainly as hypoiodous acid (HOI) and molecular Iodine (I2). Here, we present the first concomitant observations of Iodine oxide (IO), O3 in the gas phase, and sea surface iodide concentrations. The results from three field campaigns in the Indian Ocean and the Southern Ocean during 2014–2017 are used to compute reactive Iodine fluxes to the MBL. Observations of atmospheric IO by MAX-DOAS show active Iodine chemistry in this environment, with IO values up to 1 pptv (parts per trillion by volume) below latitudes of 40° S. In order to compute the sea-to-air Iodine flux supporting this chemistry, we compare previously established global sea surface iodide parameterisations with new, region-specific parameterisations based on the new iodide observations. This study shows that regional changes in salinity and sea surface temperature play a role in surface seawater iodide estimation. Sea-air fluxes of HOI and I2, calculated from the atmospheric ozone and seawater iodide concentrations (observed and predicted), failed to adequately explain the detected IO in this region. This discrepancy highlights the need to measure direct fluxes of inorganic and organic Iodine species in the marine environment. Amongst other potential drivers of reactive Iodine chemistry investigated, chlorophyll-a showed a significant correlation with atmospheric IO (R = 0.7 above the 99 % significance level) to the north of the polar front. This correlation might be indicative of a biogenic control on Iodine sources in this region.
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Atmospheric Iodine levels influenced by sea surface emissions of inorganic Iodine
Nature Geoscience, 2013Co-Authors: Lucy J. Carpenter, Samantha M. Macdonald, Marvin D. Shaw, Ravi Kumar, Russell W. Saunders, Rajendran Parthipan, Julie Wilson, John M. C. PlaneAbstract:Naturally occurring bromine- and Iodine-containing compounds substantially reduce regional, and possibly global, tropospheric ozone levels. Experimental and model results suggest that the reaction of ozone with iodide could account for around 75% of observed Iodine oxide levels over the tropical Atlantic Ocean. Naturally occurring bromine- and Iodine-containing compounds substantially reduce regional, and possibly even global, tropospheric ozone levels^ 1 , 2 , 3 , 4 . As such, these halogen gases reduce the global warming effects of ozone in the troposphere^ 5 , and its capacity to initiate the chemical removal of hydrocarbons such as methane. The majority of halogen-related surface ozone destruction is attributable to Iodine chemistry^ 2 . So far, organic Iodine compounds have been assumed to serve as the main source of oceanic Iodine emissions^ 1 , 6 , 7 , 8 , 9 . However, known organic sources of atmospheric Iodine cannot account for gas-phase Iodine oxide concentrations in the lower troposphere over the tropical oceans^ 3 , 4 . Here, we quantify gaseous emissions of inorganic Iodine following the reaction of iodide with ozone in a series of laboratory experiments. We show that the reaction of iodide with ozone leads to the formation of both molecular Iodine and hypoiodous acid. Using a kinetic box model of the sea surface layer and a one-dimensional model of the marine boundary layer, we show that the reaction of ozone with iodide on the sea surface could account for around 75% of observed Iodine oxide levels over the tropical Atlantic Ocean. According to the sea surface model, hypoiodous acid—not previously considered as an oceanic source of Iodine—is emitted at a rate ten-fold higher than that of molecular Iodine under ambient conditions.
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iodide accumulation provides kelp with an inorganic antioxidant impacting atmospheric chemistry
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Frithjof C Kupper, Lucy J. Carpenter, Gordon Mcfiggans, Carl J Palmer, Tim J Waite, Evamaria Boneberg, Sonja Woitsch, Markus Weiller, R Abela, Daniel GrolimundAbstract: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.
Robert C. Teitelbaum - One of the best experts on this subject based on the ideXlab platform.
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A resonance Raman/Iodine Moessbauer investigation of the starch-Iodine structure. Aqueous solution and Iodine vapor preparations
Journal of the American Chemical Society, 2016Co-Authors: Robert C. Teitelbaum, Stanley L. Ruby, Tobin J. MarksAbstract:Abstract : The structure of the blue-black Iodine complex of amylose (the linear, helical component of starch) prepared either from Iodine and iodide in aqueous solution or from crystalline amylose and Iodine vapor, has been studied by resonance Raman and Iodine -129 Mossbauer spectroscopy. In both cases it is concluded that the identity of the major chromophore is essentially the same: the pentaiodide (I(5-1)) anion. For the material prepared from Iodine vapor, the iodide required for (I(5-1)) formation is produced by hydrolysis or alcoholysis of Iodine. The other product of this reaction, a hypoiodite, has been assigned in the Iodine Mossbauer spectrum. (Author)
Koichi Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Iodine excess as an environmental risk factor for autoimmune thyroid disease
International Journal of Molecular Sciences, 2014Co-Authors: Yuqian Luo, Akira Kawashima, Yuko Ishido, Aya Yoshihara, Kenzaburo Oda, Naoki Hiroi, Tetsuhide Ito, Norihisa Ishii, Koichi SuzukiAbstract:The global effort to prevent Iodine deficiency disorders through Iodine supplementation, such as universal salt iodization, has achieved impressive progress during the last few decades. However, Iodine excess, due to extensive environmental Iodine exposure in addition to poor monitoring, is currently a more frequent occurrence than Iodine deficiency. Iodine excess is a precipitating environmental factor in the development of autoimmune thyroid disease. Excessive amounts of iodide have been linked to the development of autoimmune thyroiditis in humans and animals, while intrathyroidal depletion of Iodine prevents disease in animal strains susceptible to severe thyroiditis. Although the mechanisms by which iodide induces thyroiditis are still unclear, several mechanisms have been proposed: (1) excess Iodine induces the production of cytokines and chemokines that can recruit immunocompetent cells to the thyroid; (2) processing excess Iodine in thyroid epithelial cells may result in elevated levels of oxidative stress, leading to harmful lipid oxidation and thyroid tissue injuries; and (3) Iodine incorporation in the protein chain of thyroglobulin may augment the antigenicity of this molecule. This review will summarize the current knowledge regarding excess iodide as an environmental toxicant and relate it to the development of autoimmune thyroid disease.
Clemens Walther - One of the best experts on this subject based on the ideXlab platform.
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Sorption of Iodine in soils: insight from selective sequential extractions and X-ray absorption spectroscopy
Environmental Science and Pollution Research, 2019Co-Authors: Fabian Köhler, Beate Riebe, Andreas C. Scheinost, Claudia König, Alex Hölzer, Clemens WaltherAbstract:The environmental fate of Iodine is of general geochemical interest as well as of substantial concern in the context of nuclear waste repositories and reprocessing plants. Soils, and in particular soil organic matter (SOM), are known to play a major role in retaining and storing Iodine. Therefore, we investigated iodide and iodate sorption by four different reference soils for contact times up to 30 days. Selective sequential extractions and X-ray absorption spectroscopy (XAS) were used to characterize binding behavior to different soil components, and the oxidation state and local structure of Iodine. For iodide, sorption was fast with 73 to 96% being sorbed within the first 24 h, whereas iodate sorption increased from 11–41% to 62–85% after 30 days. The organic fraction contained most of the adsorbed iodide and iodate. XAS revealed a rapid change of iodide into organically bound Iodine when exposed to soil, while iodate did not change its speciation. Migration behavior of both Iodine species has to be considered as iodide appears to be the less mobile species due to fast binding to SOM, but with the potential risk of mobilization when oxidized to iodate.
