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To study the binding mechanisms of radionuclides to organic moieties in colloidal organic matter (COM), marine colloids (1 kDa–0.2 μm) were isolated by cross-flow ultrafiltration from seawater of the west Pacific Ocean and the northern Gulf of Mexico. For the same purpose, exopolymeric substances (EPS) produced by laboratory-cultured diatoms were collected as well. In our study areas, colloidal organic carbon (COC) concentrations ranged from 6.5 to 202 μg-C/L in the Pacific Ocean, and were 808 μg-C/L in the Gulf of Mexico. The COM compositions (organic carbon, organic nitrogen, proteins, total hydrolysable amino acids, total polysaccharides, uronic acids, hydroxamate siderophores, hydroquinone) were quantified to examine the relationships between partition coefficients (Kc) of five different radionuclides, 234Th, 233Pa, 210Pb, 210Po and 7Be, and concentration ratios to COC of individual chelating biomolecules that could potentially act as a chelating moiety. The range of partition coefficients (Kc, reported as logKc) of radionuclides between water and the different colloidal materials was 5.12 to 5.85 for 234Th, 5.19 to 6.01 for 233Pa, 4.21 to 4.85 for 210Pb, 4.87 to 5.68 for 210Po, and 4.49 to 4.92 for 7Be, similar to values previously reported for lab and field determinations under different particle concentrations. While any relationship obtained between Kc and abundance of specific moieties could not be taken as proving the existence of colloidal organic binding ligands for the different radionuclides, it could suggest possible organic moieties involved in the scavenging of these natural radionuclides. Together with results from isoelectric focusing of radiolabeled COM, we conclude that binding to different biomolecules is nuclide-specific, with colloidal hydroxamate siderophoric moieties being important for the binding of Th and Pa radionuclides. Hydroquinones/quinone (HQ/Q) facilitated redox and chelation reactions seem to be involved in the binding of Pa and Be. However, the actual mechanisms are not clear. Individual amino acids, proteins, total polysaccharides and uronic acids did not yield significant relationships with logKc values of the different radionuclides. Nonetheless, our results provide new insights into the relative importance of different potential ligand moieties in COM in the binding and possible scavenging of specific radionuclides in the ocean.

Lactobacillus kefiranofaciens M1 (M1) has been shown to possess many different beneficial health effects including anti-colitis activity. The purpose of this study was to develop a novel and easily scaled-up encapsulating technique that would improve the temperature tolerance of the bacterium and reduce the sensitivity of the organism to gastrointestinal fluid. A mixture of sodium alginate, gellan gum and skim milk powder was used as a coating material to entrap M1. The M1 gel was then directly freeze dried in order to dehydrate the covering and form microcapsules. The viable cell numbers of M1 present only dropped ten folds after the freeze-drying encapsulation process. The viable cell counts remained constant at 5 × 10(7) CFU/g after heating from 25 °C to 75 °C and holding at 75 °C for 1 min. The viable cell counts were reduced to 10(6) CFU/g and 10(5) CFU/g after 8-week storage at 4 °C and subsequent heat treatment with simulated gastrointestinal fluid test (SGFT) and bile salts, respectively. The effect of encapsulated M1 on the organism's anti-colitis activity was evaluated using the dextran sodium sulfate (DSS) induced colitis mouse model. An in vivo study indicated that administration of heat treated encapsulated M1 was able to ameliorate DSS-induced colitis producing a significant reduction in the bleeding score and an attenuation of inflammatory score. These findings clearly demonstrate that encapsulation of M1 using this novel technique is able to provide good protection from temperature changes and SGFT treatment and also does not affect the organism's anti-colitis activity.

During the last few decades, considerable research efforts have been extended to identify more effective remediation treatment technologies to lower the (129)I concentrations to below federal drinking water standards at the Hanford Site (Richland, USA). Few studies have taken iodate into consideration, though recently iodate, instead of iodide, was identified as the major species in the groundwater of 200-West Area within the Hanford Site. The objective of this study was thus to quantify and understand aqueous radioiodine species transformations and uptake by three sediments collected from the semi-arid, carbonate-rich environment of the Hanford subsurface. All three sediments reduced iodate (IO3(-)) to iodide (I(-)), but the loamy-sand sediment reduced more IO3(-) (100% reduced within 7 days) than the two sand-textured sediments (∼20% reduced after 28 days). No dissolved organo-iodine species were observed in any of these studies. Iodate uptake Kd values ([Isolid]/[Iaq]; 0.8-7.6 L/kg) were consistently and appreciably greater than iodide Kd values (0-5.6 L/kg). Furthermore, desorption Kd values (11.9-29.8 L/kg) for both iodate and iodide were consistently and appreciably greater than uptake Kd values (0-7.6 L/kg). Major fractions of iodine associated with the sediments were unexpectedly strongly bound, such that only 0.4-6.6 % of the total sedimentary iodine could be exchanged from the surface with KCl solution, and 0-1.2% was associated with Fe or Mn oxides (weak NH2HCl/HNO3 extractable fraction). Iodine incorporated into calcite accounted for 2.9-39.4% of the total sedimentary iodine, whereas organic carbon (OC) is likely responsible for the residual iodine (57.1-90.6%) in sediments. The OC, even at low concentrations, appeared to be controlling iodine binding to the sediments, as it was found that the greater the OC concentrations in the sediments, the greater the values of uptake Kd, desorption Kd, and the greater residual iodine concentrations (non-exchangeable, non-calcite-incorporated and non-Mn, Fe-oxide associated). This finding is of particular interest because it suggests that even very low OC concentrations

Because iodine-129 has a half-life of nearly 16 million years, poses major health threats, and can be mobile in the environment, it is important to use the best estimates for kinetics of sorption in risk assessment models. Previous work estimating the iodine sorption has not allowed for samples to reach full equilibrium and field studies have reported significant fractions of up to three major species of iodine; therefore, further research into the kinetics of iodine sorption to sediments is warranted. The objective of this study is to investigate the kinetics of iodine sorption in the presence of subsurface upland sediments and wetland sediments from an area within an 129 I plume at the Savannah River Site in Aiken, SC. Batch sorption studies for these systems took longer than 8 weeks to reach equilibrium, which is significant as previous studies did not reach such timescales. In addition, experiments were conducted under oxic and anoxic conditions. Results confirm that there are three species present in these systems (iodide, iodate, and organo-iodine) with a majority as organo-iodine species at equilibrium for systems with high organic matter content. It is notable that the anoxic conditions exhibited reduced sorption for the iodate species to wetland sediment with high organic matter.

The release of radioactive iodine (i.e., iodine-129 and iodine-131) from nuclear reprocessing facilities is a potential threat to human health. The fate and transport of iodine are determined primarily by its redox status, but processes that affect iodine oxidation states in the environment are poorly characterized. Given the difficulty in removing electrons from iodide (I − ), naturally occurring iodide oxidation processes require strong oxidants, such as Mn oxides or microbial enzymes. In this study, we examine iodide oxidation by a marine bacterium, Roseobacter sp. AzwK-3b, which promotes Mn(II) oxidation by catalyzing the production of extracellular superoxide (O 2 − ). In the absence of Mn 2+ , Roseobacter sp. AzwK-3b cultures oxidized ∼90% of the provided iodide (10 μM) within 6 days, whereas in the presence of Mn(II), iodide oxidation occurred only after Mn(IV) formation ceased. Iodide oxidation was not observed during incubations in spent medium or with whole cells under anaerobic conditions or following heat treatment (boiling). Furthermore, iodide oxidation was significantly inhibited in the presence of superoxide dismutase and diphenylene iodonium (a general inhibitor of NADH oxidoreductases). In contrast, the addition of exogenous NADH enhanced iodide oxidation. Taken together, the results indicate that iodide oxidation was mediated primarily by extracellular superoxide generated by Roseobacter sp. AzwK-3b and not by the Mn oxides formed by this organism. Considering that extracellular superoxide formation is a widespread phenomenon among marine and terrestrial bacteria, this could represent an important pathway for iodide oxidation in some environments.

The concentrations of potential organic (e.g., proteins, polysaccharides, uronic acids, hydroquinones, hydroxamate- and catechol-type siderophores) and inorganic (Fe, Mn, Si, and CaCO 3 ) carrier phases for radionuclides ( 234 Th, 233 Pa, 210 Po, 210 Pb and 7 Be) and their particle–water partition coefficients (K d ) were determined for particles collected by sediment traps deployed at the Oceanic Flux Program (OFP) site off Bermuda (500, 1500 and 3200 m). The purpose was to better understand the mechanisms that control the chemical composition of sinking particles as well as the scavenging and fractionation behavior of those five radionuclides. Different components contributed differently to the scavenging of different radionuclides at the three depths. Chemical considerations (e.g., ionic potential, ionization energy, multifunctional group structures), as well as factor analysis (FA) and correlations of logK d values with chemical parameters, indicate that hydroxamate siderophores are major classes of biopolymers that have a role in binding Po and Pa. MnO 2 and FeO 2 , whose presence is closely related to that of hydroxamate siderophores (HS), are also involved in binding of Pa and Po. The carbonate and biogenic silica phases are identified to be important in predicting removal and fractionation of Th and Be in the ocean.

Major fractions of radioiodine ((129)I) are associated with natural organic matter (NOM) in the groundwater and surface soils of the Savannah River Site (SRS). Electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) was applied to elucidate the interactions between inorganic iodine species (iodide and iodate) and a fulvic acid (FA) extracted from a SRS surface soil. Iodate is likely reduced to reactive iodine species by the lignin- and tannin-like compounds or the carboxylic-rich alicyclic molecules (CRAM), during which condensed aromatics and lignin-like compounds were generated. Iodide is catalytically oxidized into reactive iodine species by peroxides, while FA is oxidized by peroxides into more aliphatic and less aromatic compounds. Only 9% of the total identified organo-iodine compounds derived from molecules originally present in the FA, whereas most were iodine binding to newly-produced compounds. The resulting iodinated molecules were distributed in three regions in the van Krevelen diagrams, denoting unsaturated hydrocarbons, lignin and protein. Moreover, characteristics of these organo-iodine compounds, such as their relatively low O/C ratios (0.2 or0.4) and yet some degree of un-saturation close to that of lignin, have multiple important environmental implications concerning possibly less sterically-hindered aromatic ring system for iodine to get access to and a lower hydrophilicity of the molecules thus to retard their migration in the natural aquatic systems. Lastly, ~69% of the identified organo-iodine species contains nitrogen, which is presumably present as NH2 or HNCOR groups and a ring-activating functionality to favor the electrophilic substitution. The ESI-FTICR-MS technique provides novel evidence to better understand the reactivity and scavenging properties of NOM towards radioiodine and possible influence of NOM on (129)I migration.

129 I is a major by-product of nuclear fission and had become one of the major radiation risk drivers at Department of Energy (DOE) sites. 129 I is present at elevated levels in the surface soils of the Savannah River Site (SRS) F-Area and was found to be bound predominantly to soil organic matter (SOM). Naturally bound 127 I and 129 I to sequentially extracted humic acids (HAs), fulvic acids (FAs) and a water extractable colloid (WEC) were measured in a 129 I-contaminated wetland surface soil located on the SRS. WEC is a predominantly colloidal organic fraction obtained from soil re-suspension experiments to mimic the fraction that may be released during groundwater exfiltration, storm water or surface runoff events. For the first time, NMR techniques were applied to infer the molecular environment of naturally occurring stable iodine and radioiodine binding to SOM. Iodine uptake partitioning coefficients ( K d ) by these SOM samples at ambient iodine concentrations were also measured and related to quantitative structural analyses by 13 C DPMAS NMR and solution state 1 H NMR on the eight humic acid fractions. By assessing the molecular environment of iodine, it was found that it was closely associated with the aromatic regions containing esterified products of phenolic and formic acids or other aliphatic carboxylic acids, amide functionalities, quinone-like structures activated by electron-donating groups (e.g., NH 2 ), or a hemicellulose–lignin-like complex with phenyl-glycosidic linkages. However, FAs and WEC contained much greater concentrations of 127 I or 129 I than HAs. The contrasting radioiodine contents among the three different types of SOM (HAs, FAs and WEC) suggest that the iodine binding environment cannot be explained solely by the difference in the amount of their reactive binding sites. Instead, indirect evidence indicates that the macro-molecular conformation, such as the hydrophobic aliphatic periphery hindering the active aromatic cores and the hydrophilic polysaccharides favoring the access by hydrophilic iodine species, also influences iodine–SOM interactions.

In order to quantify changes in iodine speciation and to assess factors controlling the distribution and mobility of iodine at an iodine-129 ((129)I) contaminated site located at the U.S. Department of Energy's Savannah River Site (SRS), spatial distributions and transformation of (129)I and stable iodine ((127)I) species in groundwater were investigated along a gradient in redox potential (654 to 360 mV), organic carbon concentration (5 to 60 μmol L(-1)), and pH (pH 3.2 to 6.8). Total (129)I concentration in groundwater was 8.6±2.8 Bq L(-1) immediately downstream of a former waste seepage basin (well FSB-95DR), and decreased with distance from the seepage basin. (127)I concentration decreased similarly to that of (129)I. Elevated concentrations of (127)I or (129)I were not detected in groundwater collected from wells located outside of the mixed waste plume of this area. At FSB-95DR, the majority (55-86%) of iodine existed as iodide for both (127)I and (129)I. Then, as the iodide move down gradient, some of it transformed into iodate and organo-iodine. Considering that iodate has a higher K(d) value than iodide, we hypothesize that the production of iodate in groundwater resulted in the removal of iodine from the groundwater and consequently decreased concentrations of (127)I and (129)I in downstream areas. Significant amounts of organo-iodine species (30-82% of the total iodine) were also observed at upstream wells, including those outside the mixed waste plume. Concentrations of groundwater iodide decreased at a faster rate than organo-iodine along the transect from the seepage basin. We concluded that removal of iodine from the groundwater through the formation of high molecular weight organo-iodine species is complicated by the release of other more mobile organo-iodine species in the groundwater.

Lipase from Pseudomonas fluorescens efficiently catalyzed the alcoholysis of various TG in dry alcohols. For TG with short-chain FA, more MG were accumulated. The yields of MG were affected by the alcohols used. The maximum yields of MG were as follows: 85% for monoacetin in n-butanol, 96% for monobutyrin in ethanol or n-butanol, 50% for monocaprylin in n-butanol, 48% for monolaurin in isopropanol, and 45% for monopalmitin in isopropanol. The MG produced were judged to be 2-MG by TLC analysis. The presence of organic cosolvent affected the reaction rate of the lipase-catalyzed alcoholysis of TG. For the alcoholysis of various TG in ethanol and cosolvent (1∶1, vol/vol), the rates had the following orders: (i) for tributyrin, hexane > toluene > acetone > ethyl acetate > chloroform > acetonitrile > pyridine; (ii) for tricaprylin, hexane > acetone > toluene > acetonitrile > ethyl acetate > pyridine > chloroform; and (iii) for trialurin, hexane > acetonitrile=acetone > ethyl acetate > pyridine=chloroform > toluene.

(129)I derived from a former radionuclide disposal basin located on the Savannah River Site (SRS) has concentrated in a wetland 600 m downstream. To evaluate temporal environmental influences on iodine speciation and mobility in this subtropical wetland environment, groundwater was collected over a three-year period (2010-2012) from a single location. Total (127)I and (129)I showed significant temporal variations, ranging from 68-196 nM for (127)I and5-133 pCi/L for (129)I. These iodine isotopes were significantly correlated with groundwater acidity and nitrate, two parameters elevated within the contaminant plume. Additionally, (129)I levels were significantly correlated with those of (127)I, suggesting that biogeochemical controls on (127)I and (129)I are similar within the SRS aquifer/wetland system. Iodine speciation demonstrates temporal variations as well, reflecting effects from surface recharges followed by acidification of groundwater and subsequent formation of anaerobic conditions. Our results reveal a complex system where few single ancillary parameters changed in a systematic manner with iodine speciation. Instead, changes in groundwater chemistry and microbial activity, driven by surface hydrological events, interact to control iodine speciation and mobility. Future radiological risk models should consider the flux of (129)I in response to temporal changes in wetland hydrologic and chemical conditions.

Iodine occurs in multiple oxidation states in aquatic systems in the form of organic and inorganic species. This feature leads to complex biogeochemical cycling of stable iodine and its long-lived isotope, (129)I. In this study, we investigated the sorption, transport, and interconversion of iodine species by comparing their mobility in groundwaters at ambient concentrations of iodine species (10(-8) to 10(-7) M) to those at artificially elevated concentrations (78.7 μM), which often are used in laboratory analyses. Results demonstrate that the mobility of iodine species greatly depends on, in addition to the type of species, the iodine concentration used, presumably limited by the number of surface organic carbon binding sites to form covalent bonds. At ambient concentrations, iodide and iodate were significantly retarded (K(d) values as high as 49 mL g(-1)), whereas at concentrations of 78.7 μM, iodide traveled along with the water without retardation. Appreciable amounts of iodide during transport were retained in soils due to iodination of organic carbon, specifically retained by aromatic carbon. At high input concentration of iodate (78.7 μM), iodate was found to be reduced to iodide and subsequently followed the transport behavior of iodide. These experiments underscore the importance of studying iodine geochemistry at ambient concentrations and demonstrate the dynamic nature of their speciation during transport conditions.

Protein phosphorylation was studied in Xanthomonas campestris pv. oryzae in vivo and in vitro. In vitro labelling showed that the protein kinases in this bacterium used both ATP and GTP as nucleotide substrates at nearly the same efficiency. At least 6 proteins were phosphorylated in vitro, including abundant species of p81, p44, and p32 with Mr of 81000, 44000, and 32000, respectively. Three types of phosphate-protein linkage were found in this bacterium: O-phosphate, N-phosphate and probably acyl phosphate. The p81 and p32 were phosphorylated at histidine. The p44 had mainly phosphoserine and a small part of phosphohistidine. The phosphorylation profile was variable depending on the growth conditions. Furthermore, by a virulent phage Xp10 infection the quantity of phosphorylation increased: for phosphohistinine more than 10-fold, and for phosphoserine about 3-fold. Thus, in this bacterium phosphorylation may be linked with a physiological regulation system and with Xp10 phage development.

In his comment on our paper “Iodine-129 and Iodine-127 Speciation in Groundwater at Hanford Site, U.S.: Iodate Incorporation into Calcite”, Lu specified three concerns for Zhang et al’s study,1 including (1) precipitation mechanism (degassing vs freezing), (2) analytical methods, and (3) mass balance control. In response, comparative and comprehensive discussions on the precipitation mechanisms and iodine incorporation can be found in the paper, as well as below. This includes additional experiments of iodine distribution and speciation in calcite precipitates. In addition, the measurements of total iodine in soils/sediment were clarified below as well. The calculations on mass balance in this comment were clarified by using correct data sets. Lu proposed that freezing samples