Nighttime atmospheric chemistry of iodine

Little attention has so far been paid to the nighttime atmospheric chemistry of iodine species. Current atmospheric models predict a buildup of HOI and I₂ during the night that leads to a spike of IO at sunrise, which is not observed by measurements. In this work, electronic structure calculations are used to survey possible reactions that HOI and I₂ could undergo at night in the lower troposphere, and hence reduce their nighttime accumulation. The new reaction NO₃+ HOI  →  IO + HNO₃ is proposed, with a rate coefficient calculated from statistical rate theory over the temperature range 260–300 K and at a pressure of 1000 hPa to be k(T)  =  2.7  ×  10¯¹² (300 K/T)²·⁶⁶ cm³ molecule¯¹ s¯¹. This reaction is included in two atmospheric models, along with the known reaction between I₂ and NO₃, to explore a new nocturnal iodine radical activation mechanism. The results show that this iodine scheme leads to a considerable reduction of nighttime HOI and I₂, which results in the enhancement of more than 25 % of nighttime ocean emissions of HOI +I₂ and the removal of the anomalous spike of IO at sunrise. We suggest that active nighttime iodine can also have a considerable, so far unrecognized, impact on the reduction of the NO₃ radical levels in the marine boundary layer (MBL) and hence upon the nocturnal oxidizing capacity of the marine atmosphere. The effect of this is exemplified by the indirect effect on dimethyl sulfide (DMS) oxidation

Modelling the Inorganic Bromine Partitioning in the Tropical Tropopause over the Pacific Ocean

The stratospheric inorganic bromine burden (Bry) arising from the degradation of brominated very short-lived organic substances (VSL org ), and its partitioning between reactive and reservoir species, is needed for a comprehensive assessment of the ozone depletion potential of brominated trace gases. Here we present modelled inorganic bromine abundances over the Pacific tropical tropopause based on aircraft observations of VSL org of two campaigns of the Airborne Tropical TRopopause EXperiment (ATTREX 2013 carried out over eastern Pacific and ATTREX 2014 carried out over the western Pacific) and chemistry-climate simulations (along ATTREX flight tracks) using the specific meteorology prevailing. Using the Community Atmosphere Model with Chemistry (CAM-Chem), we model that BrO and Br are the daytime dominant species. Integrated across all ATTREX flights BrO represents ~ 43 % and 48 % of daytime Bry abundance at 17 km over the Western and Eastern Pacific, respectively. The results also show zones where Br/BrO >1 depending on the solar zenith angle (SZA), ozone concentration and temperature. On the other hand, BrCl and BrONO 2 were found to be the dominant night-time species with ~ 61% and 56 % of abundance at 17 km over the Western and Eastern Pacific, respectively. The western-to-eastern differences in the partitioning of inorganic bromine are explained by different abundances of ozone (O3), nitrogen dioxide (NO2) , and total inorganic chlorine (Cly).Fil: Navarro, María A.. University of Miami; Estados UnidosFil: Saiz-lopez, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Cuevas, Carlos Alberto. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Fernandez, Rafael Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Universidad Tecnologica Nacional. Facultad Regional Mendoza. Secretaría de Ciencia, Tecnología y Postgrado; ArgentinaFil: Atlas, Elliot. University of Miami; Estados UnidosFil: Rodriguez Lloeveras, Xavier. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Kinnison, Douglas E.. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Lamarque, Jean Francois. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Tilmes, Simone. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Thornberry, Troy. State University of Colorado at Boulder; Estados Unidos. Earth System Research Laboratory; Estados UnidosFil: Rollins, Andrew. State University of Colorado at Boulder; Estados Unidos. Earth System Research Laboratory; Estados UnidosFil: Elkins, James W.. Earth System Research Laboratory; Estados UnidosFil: Hintsa, Eric J.. State University of Colorado at Boulder; Estados Unidos. Earth System Research Laboratory; Estados UnidosFil: Moore, Fred L.. State University of Colorado at Boulder; Estados Unidos. Earth System Research Laboratory; Estados Unido

A Molecular Platinum Cluster Junction: A Single-Molecule Switch

We present a theoretical study of the electronic transport through single-molecule junctions incorporating a Pt6 metal cluster bound within an organic framework. We show that the insertion of this molecule between a pair of electrodes leads to a fully atomically engineered nano-metallic device with high conductance at the Fermi level and two sequential high on/off switching states. The origin of this property can be traced back to the existence of a HOMO which consists of two degenerate and asymmetric orbitals, lying close in energy to the Fermi level of the metallic leads. Their degeneracy is broken when the molecule is contacted to the leads, giving rise to two resonances which become pinned close to the Fermi level and display destructive interference.Comment: 4 pages, 4 figures. Reprinted (adapted) with permission from J. Am. Chem. Soc., 2013, 135 (6), 2052. Copyright 2013 American Chemical Societ

MetastamiRs: Non-Coding MicroRNAs Driving Cancer Invasion and Metastasis

MicroRNAs (miRNAs) are small non-coding RNAs of ~22 nucleotides that function as negative regulators of gene expression by either inhibiting translation or inducing deadenylation-dependent degradation of target transcripts. Notably, deregulation of miRNAs expression is associated with the initiation and progression of human cancers where they act as oncogenes or tumor suppressors contributing to tumorigenesis. Abnormal miRNA expression may provide potential diagnostic and prognostic tumor biomarkers and new therapeutic targets in cancer. Recently, several miRNAs have been shown to initiate invasion and metastasis by targeting multiple proteins that are major players in these cellular events, thus they have been denominated as metastamiRs. Here, we present a review of the current knowledge of miRNAs in cancer with a special focus on metastamiRs. In addition we discuss their potential use as novel specific markers for cancer progression

On the concentration and size distribution of sub-micron aerosol in the Galápagos Islands

During the CHARLEX campaign in the Galápagos Islands, a Scanning Particle Mobility Sizer was deployed on San Cristobal Island in July-August 2011 to carry out size-resolved measurements of the concentration of submicron aerosols. To our knowledge these are the first measurements of aerosol concentrations in this unique environment. The particles with marine origin displayed a tri-modal number size distribution with peak diameters of 0.016 μm, 0.050 μm and 0.174 μm and a cloud-processed intermodal minimum at 0.093 μm. The mean total aerosol number concentration for the marine contribution was 470 ± 160 cm. A low particle concentration of 70 ± 50 cm for the nucleation size range was measured, but no evidence of new particle production in the atmospheric marine boundary layer (MBL) was observed. The concentration of the Aitken size mode was found to be related to aerosol entrainment from the free troposphere off the coast of Chile followed by transport within the MBL to the Galápagos Islands. Cloud processing may activate the particles in the Aitken size range, growing through 'in-cloud' sulphate production and increasing the particle concentration in the accumulation size range. The 0.093 μm cloud processed minima suggests that the critical supersaturation at which the particle is activated to a cloud droplet is in the 0.14-0.21% range. The daytime marine particle background concentration was influenced by human activity around the sampling site, as well as by new particle formation triggered by biogenic emissions from the vegetation cover of the island's semiarid lowlands. Effective CCN formation may play a role in the formation and properties of the stratus clouds, which permanently cover the top of the windward side of the islands and establish one of their characteristic climatic bands.Peer Reviewe

Iodine oxide in the global marine boundary layer

Prados-Roman, C. ... et. al.-- 11 pages, 7 figures, 2 tables, The Supplement related to this article is available online at https://doi.org/10.5194/acp-15-583-2015-supplementEmitted mainly by the oceans, iodine is a halogen compound important for atmospheric chemistry due to its high ozone depletion potential and effect on the oxidizing capacity of the atmosphere. Here we present a comprehensive data set of iodine oxide (IO) measurements in the open marine boundary layer (MBL) made during the Malaspina 2010 circumnavigation. Results show IO mixing ratios ranging from 0.4 to 1 pmol mol-1 (30% uncertainty) and, complemented with additional field campaigns, this data set confirms through observations the ubiquitous presence of reactive iodine chemistry in the global marine environment. We use a global model with organic (CH3I, CH2ICl, CH2I2 and CH2IBr) and inorganic (HOI and I2) iodine ocean emissions to investigate the contribution of the different iodine source gases to the budget of IO in the global MBL. In agreement with previous estimates, our results indicate that, globally averaged, the abiotic precursors contribute about 75 % to the IO budget. However, this work reveals a strong geographical pattern in the contribution of organic vs. inorganic precursors to reactive iodine in the global MBL. © Author(s) 2015The Indian Institute of Tropical Meteorology is supported by the Ministry of Earth Sciences, Government of India. R. P. Fernandez would like to thank ANPCyT (PICT-PRH 2009-0063) for financial supportPeer Reviewe

Total and high molecular weight adiponectin have similar utility for the identification of insulin resistance

<p>Abstract</p> <p>Background</p> <p>Insulin resistance (IR) and related metabolic disturbances are characterized by low levels of adiponectin. High molecular weight adiponectin (HMWA) is considered the active form of adiponectin and a better marker of IR than total adiponectin. The objective of this study is to compare the utility of total adiponectin, HMWA and the HMWA/total adiponectin index (S_Aindex) for the identification of IR and related metabolic conditions.</p> <p>Methods</p> <p>A cross-sectional analysis was performed in a group of ambulatory subjects, aged 20 to 70 years, in Mexico City. Areas under the receiver operator characteristic (ROC) curve for total, HMWA and the S_Aindex were plotted for the identification of metabolic disturbances. Sensitivity and specificity, positive and negative predictive values, and accuracy for the identification of IR were calculated.</p> <p>Results</p> <p>The study included 101 men and 168 women. The areas under the ROC curve for total and HMWA for the identification of IR (0.664 <it>vs</it>. 0.669, <it>P </it>= 0.74), obesity (0.592 <it>vs</it>. 0.610, <it>P </it>= 0.32), hypertriglyceridemia (0.661 <it>vs</it>. 0.671, <it>P </it>= 0.50) and hypoalphalipoproteinemia (0.624 <it>vs</it>. 0.633, <it>P </it>= 0.58) were similar. A total adiponectin level of 8.03 μg/ml was associated with a sensitivity of 57.6%, a specificity of 65.9%, a positive predictive value of 50.0%, a negative predictive value of 72.4%, and an accuracy of 62.7% for the diagnosis of IR. The corresponding figures for a HMWA value of 4.25 μg/dl were 59.6%, 67.1%, 51.8%, 73.7% and 64.2%.</p> <p>The area under the ROC curve of the S_Aindex for the identification of IR was 0.622 [95% CI 0.554-0.691], obesity 0.613 [95% CI 0.536-0.689], hypertriglyceridemia 0.616 [95% CI 0.549-0.683], and hypoalphalipoproteinemia 0.606 [95% CI 0.535-0.677].</p> <p>Conclusions</p> <p>Total adiponectin, HMWA and the S_Aindex had similar utility for the identification of IR and metabolic disturbances.</p

Iodine monoxide in the north subtropical free troposphere

Iodine monoxide (IO) differential slant column densities (DSCD) have been retrieved from a new multi-axis differential optical absorption spectroscopy (MAX-DOAS) instrument deployed at the Iza˜na subtropical observatory as part of the Network for the Detection of Atmospheric Composition Change (NDACC) programme.We acknowledge the support of the European Commission through the GEOmon (Global Earth Observation and Monitoring) Integrated Project under the 6th Framework Program (contract number FP6-2005-Global-4-036677) and NORS (Demonstration Network Of ground-based Remote Sensing Observations in support of the GMES Atmospheric Service) Integrated Project under the 7th Framework Program (contract number FP7-SPACE- 2011-284421)

Iodine chemistry after dark

Little attention has so far been paid to the nighttime atmospheric chemistry of iodine species. Current atmospheric models predict a buildup of HOI and I₂ during the night that leads to a spike of IO at sunrise, which is not observed by measurements. In this work, electronic structure calculations are used to survey possible reactions that HOI and I₂ could undergo at night in the lower troposphere, and hence reduce their nighttime accumulation. The new reaction NO₃ + HOI → IO + HNO₃ is proposed, with a rate coefficient calculated from statistical rate theory over the temperature range 260 - 300 K and at a pressure of 1000 hPa to be k(T) = 2.7 x 10-¹² (300 K / T ) ².⁶⁶ cm³ molecule-¹ s-¹ . This reaction is included in two atmospheric models, along with the known reaction between I₂ and NO₃, to explore a new nocturnal iodine radical activation mechanism. The results show that this iodine scheme leads to a considerable reduction of nighttime HOI and I₂, which results in the enhancement of more than 25% of nighttime ocean emissions of HOI + I₂ and the removal of the anomalous spike of IO at sunrise. We suggest that active nighttime iodine can also have a considerable, so far unrecognized, impact on the reduction of the NO₃ radical levels in the MBL and hence upon the nocturnal oxidizing capacity of the marine atmosphere. The effect of this is exemplified by the indirect effect on dimethyl sulfide (DMS) oxidation

Concerted Transport and Phosphorylation of Diacylglycerol at ER-PM Contacts Sites Regulates Phospholipid Dynamics During Stress

A universal response of plants to environmental stresses is the activation of plasma membrane (PM) phospholipase C (PLC) that hydrolyzes phosphatidylinositol phosphate (PIP) to produce soluble inositol phosphate (IP) and diacylglycerol (DAG). DAG produced in this way can be either phosphorylated by PM diacylglycerol kinases (DGKs) to produce the second messenger phosphatidic acid (PA) or transferred to the endoplasmic reticulum (ER) by the Synaptotagmin 1 (SYT1) protein at ER-PM Contact Sites (CS). In Arabidopsis, the clearance of DAG at the PM (avoiding deleterious accumulation) by the transfer activity of SYT is essential to maintain PM stability after stress. In this study we identify that DGK1 and DGK2 form a module with SYT1 at ER-PM CS through interaction of their C1 and C2 domains respectively. Global transcriptomic and metabolomic analyses confirms that SYT1 and DGK1/DGK2 are functionally related and lipidomic analysis supports the hypothesis that DGK1 and DGK2 function at the ER by phosphorylating DAG transferred by SYT1 from the PM. DGK1 and DGK2 show structural similarity to human DGKε, the DGK isoform that function at ER-PM CS in the phosphoinositide (PI) cycle. Our data indicate that components of the PI cycle are conserved between animals and plants and provide a novel mechanism leading to an increase in the efficiency of the PI cycle by channeling the transport and hydrolysis of DAG at the ER-PM CS