Short-Lived Trace Gases in the Surface Ocean and the Atmosphere

The two-way exchange of trace gases between the ocean and the atmosphere is important for both the chemistry and physics of the atmosphere and the biogeochemistry of the oceans, including the global cycling of elements. Here we review these exchanges and their importance for a range of gases whose lifetimes are generally short compared to the main greenhouse gases and which are, in most cases, more reactive than them. Gases considered include sulphur and related compounds, organohalogens, non-methane hydrocarbons, ozone, ammonia and related compounds, hydrogen and carbon monoxide. Finally, we stress the interactivity of the system, the importance of process understanding for modeling, the need for more extensive field measurements and their better seasonal coverage, the importance of inter-calibration exercises and finally the need to show the importance of air-sea exchanges for global cycling and how the field fits into the broader context of Earth System Science

Behavior of iodine in the soil-plant system

In order to understand the behaviour of radioactive and stable iodine in the environment, we have carried out radiotracer experiments and chemical analyses in the soil-plant systems. Parameters important for the assessment of radioiodine movement from the environment to man, e.g. soil-plant transfer factors for various agricultural crops and soil-solution distribution coefficient for different soils, were obtained. Mechanisms of iodine sorption and desorption on soil were also studied. Microorganisms and/or their products (e.g. enzymes) were found to play an important role in the fixation of iodine on soil. Iodine was observed to be desorbed from the flooded soils due to the reducing conditions (low Eh) created by the microbial activities. From the soil-rice plant system biogenesis methyl iodide was found to be evaporated into the atmosphere. Through experiment using 125I tracer, we found that volatile organic iodine was produced due to microbial activities (including bacterial activities)

Direct photoaffinity labeling of Kir6.2 by [gamma-(32)P]ATP-[gamma]4-azidoanilide.

ATP-sensitive potassium (K(ATP)) channels are under complex regulation by intracellular ATP and ADP. The potentiatory effect of MgADP is conferred by the sulfonylurea receptor subunit of the channel, SUR, whereas the inhibitory effect of ATP appears to be mediated via the pore-forming subunit, Kir6.2. We have previously reported that Kir6.2 can be directly labeled by 8-azido-[gamma-(32)P]ATP. However, the binding affinity of 8-azido-ATP to Kir6.2 was low probably due to modification at 8' position of adenine. Here we demonstrate that Kir6.2 can be directly photoaffinity labeled with higher affinity by [gamma-(32)P]ATP-[gamma]4-azidoanilide ([gamma-(32)P]ATP-AA), containing an unmodified adenine ring. Photoaffinity labeling of Kir6.2 by [gamma-(32)P]ATP-AA is not affected by the presence of Mg(2+), consistent with Mg(2+)-independent ATP inhibition of K(ATP) channels. Interestingly, SUR1, which can be strongly and specifically photoaffinity labeled by 8-azido-ATP, was not photoaffinity labeled by ATP-AA. These results identify key differences in the structure of the nucleotide binding sites on SUR1 and Kir6.2

Direct photoaffinity labeling of the Kir6.2 subunit of the ATP-sensitive K+ channel by 8-azido-ATP.

ATP-sensitive potassium channels are under complex regulation by intracellular ATP and ADP. The potentiating effect of MgADP is conferred by the sulfonylurea receptor subunit of the channel, SUR, whereas the inhibitory effect of ATP appears to be mediated via the pore-forming subunit, Kir6.2. We determined whether ATP directly interacts with a binding site on the Kir6.2 subunit to mediate channel inhibition by analyzing binding of a photoaffinity analog of ATP (8-azido-[gamma-32P]ATP) to membranes from COS-7 cells transiently expressing Kir6.2. We demonstrate that Kir6.2 can be directly labeled by 8-azido-[gamma-32P]ATP but that the related subunit Kir4.1, which is not inhibited by ATP, is not labeled. Photoaffinity labeling of Kir6.2 is reduced by approximately 50% with 100 microM ATP. In addition, mutations in the NH2 terminus (R50G) and the COOH terminus (K185Q) of Kir6.2, which have both been shown to reduce the inhibitory effect of ATP upon Kir6.2 channel activity, reduced photoaffinity labeling by >50%. These results demonstrate that ATP binds directly to Kir6.2 and that both the NH2- and COOH-terminal intracellular domains may influence ATP binding

Functional analysis of a mutant sulfonylurea receptor, SUR1-R1420C, that is responsible for persistent hyperinsulinemic hypoglycemia of infancy.

The ATP-sensitive potassium (K(ATP)(+)) channel is crucial for the regulation of insulin secretion from the pancreatic beta-cell, and mutations in either the sulfonylurea receptor type 1 (SUR1) or Kir6. 2 subunit of this channel can cause persistent hyperinsulinemic hypoglycemia of infancy (PHHI). We analyzed the functional consequences of the PHHI missense mutation R1420C, which lies in the second nucleotide-binding fold (NBF2) of SUR1. Mild tryptic digestion of SUR1 after photoaffinity labeling allowed analysis of the nucleotide-binding properties of NBF1 and NBF2. Labeling of NBF1 with 8-azido-[alpha-(32)P]ATP was inhibited by MgATP and MgADP with similar K(i) for wild-type SUR1 and SUR1-R1420C. However, the MgATP and MgADP affinities of NBF2 of SUR1-R1420C were about 5-fold lower than those of wild-type SUR1. MgATP and MgADP stabilized 8-azido-ATP binding at NBF1 of wild-type SUR1 by interacting with NBF2, but this cooperative nucleotide binding was not observed for SUR1-R1420C. Studies on macroscopic currents recorded in inside-out membrane patches revealed that the SUR1-R1420C mutation exhibits reduced expression but does not affect inhibition by ATP or tolbutamide or activation by diazoxide. However, co-expression with Kir6.2-R50G, which renders the channel less sensitive to ATP inhibition, revealed that the SUR1-R1420C mutation increases the EC(50) for MgADP activation from 74 to 197 microm. We suggest that the lower expression of the mutant channel and the reduced affinity of NBF2 for MgADP may lead to a smaller K(ATP)(+) current in R1420C-PHHI beta-cells and thereby to the enhanced insulin secretion. We also propose a new model for nucleotide activation of K(ATP)(+) channels

Changing concentrations of CO, CH(4), C(5)H(8), CH(3)Br, CH(3)I, and dimethyl sulfide during the Southern Ocean Iron Enrichment Experiments

Oceanic iron (Fe) fertilization experiments have advanced the understanding of how Fe regulates biological productivity and air–sea carbon dioxide (CO(2)) exchange. However, little is known about the production and consumption of halocarbons and other gases as a result of Fe addition. Besides metabolizing inorganic carbon, marine microorganisms produce and consume many other trace gases. Several of these gases, which individually impact global climate, stratospheric ozone concentration, or local photochemistry, have not been previously quantified during an Fe-enrichment experiment. We describe results for selected dissolved trace gases including methane (CH(4)), isoprene (C(5)H(8)), methyl bromide (CH(3)Br), dimethyl sulfide, and oxygen (O(2)), which increased subsequent to Fe fertilization, and the associated decreases in concentrations of carbon monoxide (CO), methyl iodide (CH(3)I), and CO(2) observed during the Southern Ocean Iron Enrichment Experiments