Isolation of a carbon disulfide utilizing Thiomonas sp. and its application in a biotrickling filter.

PubMed

Pol, Arjan; van der Drift, Chris; Op den Camp, Huub J M

2007-02-01

The carbon disulfide (CS2)-oxidizing bacterium Thiomonas sp. WZW was enriched and isolated using activated sewage sludge as inoculum. Growth of Thiomonas sp. WZW was observed on CS2, thiosulfate, dimethylsulfide (DMS), dimethyldisulfide (DMDS), and H2S. No growth occurred on dimethylsulfoxide, methanol, acetate, and on complex media with glucose, yeast extract, or tryptone. DMDS-grown cells respired CS2, DMS, and DMDS, while thiosulfate-grown cells did not respire CS2. Chemostat cultures growing on thiosulfate could be rapidly adapted to growth on CS2. Growth was observed between pH 6 and 8. The Ks values for CS2, thiosulfate, and sulfide of CS2-grown cells were between 5 and 10 microM. CS2 was inhibitory above 0.3 mM. A lab-scale biotrickling filter with lava stone as carrier material for treatment of CS2-polluted air was inoculated with Thiomonas sp. WZW. A rapid start up (95% removal in 1 week) was obtained at an inlet CS2 concentration of 2 cmol l(-1) and an initial space velocity (SV) of 54 h(-1). Subsequent thiosulfate addition for a week during start up increased the removal to 99%. The step-wise increase of SV to 130 h(-1) and a CS2 concentration to 3 micromol l(-1) resulted in a stable performance with a removal efficiency of 95%. Feeding mixtures of volatile sulfur compounds showed simultaneous conversion of H2S, CS2, dimethyldisulfide (DMDS), and DMS, with a preference in this order.

Sulfur speciation and sulfide oxidation in the water column of the Black Sea

NASA Astrophysics Data System (ADS)

Luther, George W., III; Church, Thomas M.; Powell, David

We have applied sulfur speciation techniques to understand the chemistry and cycling of sulfur in Black Sea waters. The only reduced dissolved inorganic sulfur species detected (above the low minimum detection limits of the voltammetric methods employed) in the water column was hydrogen sulfide. The maximum concentration of sulfide (423 μM) is similar to previous reports. Using a cathodic stripping square wave voltammetry (CSSWV) method for nanomolar levels of sulfide, we determined the precise boundary between the "free" hydrogen sulfide (sulfidic) zone and the upper (oxic/suboxic) water column at the two stations studied. This boundary has apparently moved up by about 50 m in the past 20 years. Our results help demonstrate three chemically distinct zones of water in the central basin of the Black Sea: (1) the oxic [0-65 m], (2) the anoxic/nonsulfidic [65-100 m] and (3) the sulfidic [>100 m]. Sulfide bound to metals ("complexed" sulfide) is observed in both the oxic and anoxic/nonsulfidic zones of the water column. This supports previous studies on metal sulfide forms. From the electrochemical data, it is possible to estimate the strength of the complexation of sulfide to metals (log K = 10 to 11). Thiosulfate and sulfite were below our minimum detectable limit (MDL) of 50 nM using CSSWV. Elemental sulfur (MDL 5 nM) was detected below the onset of the hydrogen sulfide zone (90-100 m) with a maximum of 30-60 nM near 120 m. The sulfur speciation results for the Black Sea are lower by one order of magnitude or more than other marine systems such as the Cariaco Trench and salt marshes. New HPLC techniques were applied to detect thiols at submicromolar levels. The presence of thiols (2-mercaptoethylamine, 2-mercaptoethanol, N-acetylcysteine and glutathione) is correlated with the remineralization of organic matter at the oxic and anoxic/nonsulfidic interface. Water samples collected from the upper 50 m of the sulfidic zone showed significant sulfide oxidation on storage onboard ship even though they were filtered (0.2 μm) and handled to exclude oxygen contamination. Chemical additives such as formaldehyde, glutaraldehyde, hydroxylamine and ascorbic acid prevented or retarded the sulfide loss. Thiosulfate and azide did not inhibit sulfide loss. These studies suggest an anaerobic chemical oxidation of sulfide rather than a biological oxidation on stored and filtered samples.

Thiosulfate Transfer Mediated by DsrE/TusA Homologs from Acidothermophilic Sulfur-oxidizing Archaeon Metallosphaera cuprina*

PubMed Central

Liu, Li-Jun; Stockdreher, Yvonne; Koch, Tobias; Sun, Shu-Tao; Fan, Zheng; Josten, Michaele; Sahl, Hans-Georg; Wang, Qian; Luo, Yuan-Ming; Liu, Shuang-Jiang; Dahl, Christiane; Jiang, Cheng-Ying

2014-01-01

Conserved clusters of genes encoding DsrE and TusA homologs occur in many archaeal and bacterial sulfur oxidizers. TusA has a well documented function as a sulfurtransferase in tRNA modification and molybdenum cofactor biosynthesis in Escherichia coli, and DsrE is an active site subunit of the DsrEFH complex that is essential for sulfur trafficking in the phototrophic sulfur-oxidizing Allochromatium vinosum. In the acidothermophilic sulfur (S0)- and tetrathionate (S4O62−)-oxidizing Metallosphaera cuprina Ar-4, a dsrE3A-dsrE2B-tusA arrangement is situated immediately between genes encoding dihydrolipoamide dehydrogenase and a heterodisulfide reductase-like complex. In this study, the biochemical features and sulfur transferring abilities of the DsrE2B, DsrE3A, and TusA proteins were investigated. DsrE3A and TusA proved to react with tetrathionate but not with NaSH, glutathione persulfide, polysulfide, thiosulfate, or sulfite. The products were identified as protein-Cys-S-thiosulfonates. DsrE3A was also able to cleave the thiosulfate group from TusA-Cys18-S-thiosulfonate. DsrE2B did not react with any of the sulfur compounds tested. DsrE3A and TusA interacted physically with each other and formed a heterocomplex. The cysteine residue (Cys18) of TusA is crucial for this interaction. The single cysteine mutants DsrE3A-C93S and DsrE3A-C101S retained the ability to transfer the thiosulfonate group to TusA. TusA-C18S neither reacted with tetrathionate nor was it loaded with thiosulfate with DsrE3A-Cys-S-thiosulfonate as the donor. The transfer of thiosulfate, mediated by a DsrE-like protein and TusA, is unprecedented not only in M. cuprina but also in other sulfur-oxidizing prokaryotes. The results of this study provide new knowledge on oxidative microbial sulfur metabolism. PMID:25122768

Improved fermentative L-cysteine overproduction by enhancing a newly identified thiosulfate assimilation pathway in Escherichia coli.

PubMed

Kawano, Yusuke; Onishi, Fumito; Shiroyama, Maeka; Miura, Masashi; Tanaka, Naoyuki; Oshiro, Satoshi; Nonaka, Gen; Nakanishi, Tsuyoshi; Ohtsu, Iwao

2017-09-01

Sulfate (SO 4 2- ) is an often-utilized and well-understood inorganic sulfur source in microorganism culture. Recently, another inorganic sulfur source, thiosulfate (S 2 O 3 2- ), was proposed to be more advantageous in microbial growth and biotechnological applications. Although its assimilation pathway is known to depend on O-acetyl-L-serine sulfhydrylase B (CysM in Escherichia coli), its metabolism has not been extensively investigated. Therefore, we aimed to explore another yet-unidentified CysM-independent thiosulfate assimilation pathway in E. coli. ΔcysM cells could accumulate essential L-cysteine from thiosulfate as the sole sulfur source and could grow, albeit slowly, demonstrating that a CysM-independent thiosulfate assimilation pathway is present in E. coli. This pathway is expected to consist of the initial part of the thiosulfate to sulfite (SO 3 2- ) conversion, and the latter part might be shared with the final part of the known sulfate assimilation pathway [sulfite → sulfide (S 2- ) → L-cysteine]. This is because thiosulfate-grown ΔcysM cells could accumulate a level of sulfite and sulfide equivalent to that of wild-type cells. The catalysis of thiosulfate to sulfite is at least partly mediated by thiosulfate sulfurtransferase (GlpE), because its overexpression could enhance cellular thiosulfate sulfurtransferase activity in vitro and complement the slow-growth phenotype of thiosulfate-grown ΔcysM cells in vivo. GlpE is therefore concluded to function in the novel CysM-independent thiosulfate assimilation pathway by catalyzing thiosulfate to sulfite. We applied this insight to L-cysteine overproduction in E. coli and succeeded in enhancing it by GlpE overexpression in media containing glucose or glycerol as the main carbon source, by up to ~1.7-fold (1207 mg/l) or ~1.5-fold (1529 mg/l), respectively.

21 CFR 582.6807 - Sodium thiosulfate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Sodium thiosulfate. 582.6807 Section 582.6807 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium thiosulfate. (a) Product. Sodium thiosulfate. (b) Tolerance. 0.1 percent. (c) Limitations...

21 CFR 582.6807 - Sodium thiosulfate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Sodium thiosulfate. 582.6807 Section 582.6807 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium thiosulfate. (a) Product. Sodium thiosulfate. (b) Tolerance. 0.1 percent. (c) Limitations...

21 CFR 582.6807 - Sodium thiosulfate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Sodium thiosulfate. 582.6807 Section 582.6807 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium thiosulfate. (a) Product. Sodium thiosulfate. (b) Tolerance. 0.1 percent. (c) Limitations...

21 CFR 582.6807 - Sodium thiosulfate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Sodium thiosulfate. 582.6807 Section 582.6807 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium thiosulfate. (a) Product. Sodium thiosulfate. (b) Tolerance. 0.1 percent. (c) Limitations...

21 CFR 582.6807 - Sodium thiosulfate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Sodium thiosulfate. 582.6807 Section 582.6807 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Sodium thiosulfate. (a) Product. Sodium thiosulfate. (b) Tolerance. 0.1 percent. (c) Limitations...

Microbial- and thiosulfate-mediated dissolution of mercury sulfide minerals and transformation to gaseous mercury

DOE PAGES

Vázquez-Rodríguez, Adiari I.; Hansel, Colleen M.; Zhang, Tong; ...

2015-06-23

Mercury (Hg) is a toxic heavy metal that poses significant environmental and human health risks. Soils and sediments, where Hg can exist as the Hg sulfide mineral metacinnabar (β-HgS), represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. In this study, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (a)biotic mechanismsmore » at play. We show that the abundant and widespread sulfur-oxidizing bacteria of the genus Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus thioparus cultures led to the release of metacinnabar-hosted Hg(II) and subsequent volatilization to Hg(0). This dissolution and volatilization was greatly enhanced in the presence of thiosulfate, which served a dual role by enhancing HgS dissolution through Hg complexation and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II) to Hg(0), while expanding the sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden sulfides. Lastly, they also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment.« less

Microbial- and thiosulfate-mediated dissolution of mercury sulfide minerals and transformation to gaseous mercury

PubMed Central

Vázquez-Rodríguez, Adiari I.; Hansel, Colleen M.; Zhang, Tong; Lamborg, Carl H.; Santelli, Cara M.; Webb, Samuel M.; Brooks, Scott C.

2015-01-01

Mercury (Hg) is a toxic heavy metal that poses significant environmental and human health risks. Soils and sediments, where Hg can exist as the Hg sulfide mineral metacinnabar (β-HgS), represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. Here, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (a)biotic mechanisms at play. We show that the abundant and widespread sulfur-oxidizing bacteria of the genus Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus thioparus cultures led to the release of metacinnabar-hosted Hg(II) and subsequent volatilization to Hg(0). This dissolution and volatilization was greatly enhanced in the presence of thiosulfate, which served a dual role by enhancing HgS dissolution through Hg complexation and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II) to Hg(0), while expanding the sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden sulfides. They also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment. PMID:26157421

21 CFR 184.1807 - Sodium thiosulfate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium thiosulfate. 184.1807 Section 184.1807 Food... Specific Substances Affirmed as GRAS § 184.1807 Sodium thiosulfate. (a) Sodium thiosulfate (Na2S2O3·5H2O, CAS Reg. No. 010102-0917-097) is also known as sodium hyposulfite. It is prepared synthetically by the...

21 CFR 184.1807 - Sodium thiosulfate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium thiosulfate. 184.1807 Section 184.1807 Food... Specific Substances Affirmed as GRAS § 184.1807 Sodium thiosulfate. (a) Sodium thiosulfate (Na2S2O3·5H2O, CAS Reg. No. 010102-0917-097) is also known as sodium hyposulfite. It is prepared synthetically by the...

21 CFR 184.1807 - Sodium thiosulfate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium thiosulfate. 184.1807 Section 184.1807 Food... Specific Substances Affirmed as GRAS § 184.1807 Sodium thiosulfate. (a) Sodium thiosulfate (Na2S2O3·5H2O, CAS Reg. No. 010102-0917-097) is also known as sodium hyposulfite. It is prepared synthetically by the...

21 CFR 184.1807 - Sodium thiosulfate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium thiosulfate. 184.1807 Section 184.1807 Food... Specific Substances Affirmed as GRAS § 184.1807 Sodium thiosulfate. (a) Sodium thiosulfate (Na2S2O3·5H2O, CAS Reg. No. 010102-0917-097) is also known as sodium hyposulfite. It is prepared synthetically by the...

21 CFR 184.1807 - Sodium thiosulfate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium thiosulfate. 184.1807 Section 184.1807 Food... GRAS § 184.1807 Sodium thiosulfate. (a) Sodium thiosulfate (Na2S2O3·5H2O, CAS Reg. No. 010102-0917-097) is also known as sodium hyposulfite. It is prepared synthetically by the reaction of sulfides and...

Microbial reduction of manganese oxides - Interactions with iron and sulfur

NASA Technical Reports Server (NTRS)

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.

Multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in Yellowstone National Park geothermal springs

PubMed Central

2014-01-01

Background The paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling. Results Water samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (<6 μmol L-1) in the pools with low pH due to fast disproportionation of thiosulfate. In the pools with higher pH, the concentration of thiosulfate varies, depending on different geochemical pathways of thiosulfate formation. The δ34S values of sulfate in four systems were close to those calculated using a mixing line of the model based on dilution and boiling of a deep hot parent water body. In two pools δ34S values of sulfate varied significantly from the values calculated from this model. Sulfur isotope fractionation between ZVS and hydrogen sulfide was close to zero at pH < 4. At higher pH zero-valent sulfur is slightly heavier than hydrogen sulfide due to equilibration in the rhombic sulfur–polysulfide – hydrogen sulfide system. Triple sulfur isotope (32S, 33S, 34S) fractionation patterns in waters of hydrothermal pools are more consistent with redox processes involving intermediate sulfur species than with bacterial sulfate reduction. Small but resolved differences in ∆33S among species and between pools are observed. Conclusions The variation of sulfate isotopic composition, the origin of differences in isotopic composition of sulfide and zero–valent sulfur, as well as differences in ∆33S of sulfide and sulfate are likely due to a complex network of abiotic redox reactions, including disproportionation pathways. PMID:24959098

Sequence analysis of the phs operon in Salmonella typhimurium and the contribution of thiosulfate reduction to anaerobic energy metabolism.

PubMed Central

Heinzinger, N K; Fujimoto, S Y; Clark, M A; Moreno, M S; Barrett, E L

1995-01-01

The phs chromosomal locus of Salmonella typhimurium is essential for the dissimilatory anaerobic reduction of thiosulfate to hydrogen sulfide. Sequence analysis of the phs region revealed a functional operon with three open reading frames, designated phsA, phsB, and phsC, which encode peptides of 82.7, 21.3, and 28.5 kDa, respectively. The predicted products of phsA and phsB exhibited significant homology with the catalytic and electron transfer subunits of several other anaerobic molybdoprotein oxidoreductases, including Escherichia coli dimethyl sulfoxide reductase, nitrate reductase, and formate dehydrogenase. Simultaneous comparison of PhsA to seven homologous molybdoproteins revealed numerous similarities among all eight throughout the entire frame, hence, significant amino acid conservation among molybdoprotein oxidoreductases. Comparison of PhsB to six other homologous sequences revealed four highly conserved iron-sulfur clusters. The predicted phsC product was highly hydrophobic and similar in size to the hydrophobic subunits of the molybdoprotein oxidoreductases containing subunits homologous to phsA and phsB. Thus, phsABC appears to encode thiosulfate reductase. Single-copy phs-lac translational fusions required both anaerobiosis and thiosulfate for full expression, whereas multicopy phs-lac translational fusions responded to either thiosulfate or anaerobiosis, suggesting that oxygen and thiosulfate control of phs involves negative regulation. A possible role for thiosulfate reduction in anaerobic respiration was examined. Thiosulfate did not significantly augment the final densities of anaerobic cultures grown on any of the 18 carbon sources tested. on the other hand, washed stationary-phase cells depleted of ATP were shown to synthesize small amounts of ATP on the addition of the formate and thiosulfate, suggesting that the thiosulfate reduction plays a unique role in anaerobic energy conservation by S typhimurium. PMID:7751291

Protection against cyanide-induced convulsions with alpha-ketoglutarate.

PubMed

Yamamoto, H

1990-04-30

Protection against convulsions induced by cyanide was observed after treatment with alpha-ketoglutarate, either alone or in combination with sodium thiosulfate, a classical antagonist for cyanide intoxication. However, sodium thiosulfate alone did not protect against cyanide (30 mg/kg)-induced convulsions. gamma-Aminobutyric acid (GABA) levels in brain were decreased by 31% in KCN-treated mice exhibiting convulsions. The combined administration of alpha-ketoglutarate and sodium thiosulfate completely abolished the decrease of GABA levels induced by cyanide. Furthermore, sodium thiosulfate alone also completely abolished the decrease of GABA levels. These results suggest that the depletion of brain GABA levels may not directly contribute to the development of convulsions induced by cyanide. On the other hand, cyanide increased calcium levels by 32% in brain crude mitochondrial fractions in mice with convulsions. The increased calcium levels were completely abolished by the combined administration of alpha-ketoglutarate and sodium thiosulfate, but not affected by sodium thiosulfate alone. These findings support the hypothesis proposed by Johnson et al. (Toxicol. Appl. Pharmacol., 84 (1986) 464) and Robinson et al. (Toxicology, 35 (1985) 59) that calcium may play an important role in mediating cyanide neurotoxicity.

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park: I. The origin of thiosulfate in hot spring waters

USGS Publications Warehouse

Xu, Y.; Schoonen, M.A.A.; Nordstrom, D. Kirk; Cunningham, K.M.; Ball, J.W.

1998-01-01

Thiosulfate (S2O2-3), polythionate (SxO2-6), dissolved sulfide (H2S), and sulfate (SO2-4) concentrations in thirty-nine alkaline and acidic springs in Yellowstone National Park (YNP) were determined. The analyses were conducted on site, using ion chromatography for thiosulfate, polythionate, and sulfate, and using colorimetry for dissolved sulfide. Thiosulfate was detected at concentrations typically less than 2 ??mol/L in neutral and alkaline chloride springs with low sulfate concentrations (C1-/SO2-4 > 25). The thiosulfate concentration levels are about one to two orders of magnitude lower than the concentration of dissolved sulfide in these springs. In most acid sulfate and acid sulfate-chloride springs (Cl-/SO2-4 < 10), thiosulfate concentrations were also typically lower than 2 ??mol/L. However, in some chloride springs enriched with sulfate (Cl-/SO2-4 between 10 to 25), thiosulfate was found at concentrations ranging from 9 to 95 ??mol/L, higher than the concentrations of dissolved sulfide in these waters. Polythionate was detected only in Cinder Pool, Norris Geyser basin, at concentrations up to 8 ??mol/L, with an average S-chain-length from 4.1 to 4.9 sulfur atoms. The results indicate that no thiosulfate occurs in the deeper parts of the hydrothermal system. Thiosulfate may form, however, from (1) hydrolysis of native sulfur by hydrothermal solutions in the shallower parts (<50 m) of the system, (2) oxidation of dissolved sulfide upon mixing of a deep hydrothermal water with aerated shallow groundwater, and (3) the oxidation of dissolved sulfide by dissolved oxygen upon discharge of the hot spring. Upon discharge of a sulfide-containing hydrothermal water, oxidation proceeds rapidly as atmospheric oxygen enters the water. The transfer of oxygen is particularly effective if the hydrothermal discharge is turbulent and has a large surface area.

Homologs from sulfur oxidation (Sox) and methanol dehydrogenation (Xox) enzyme systems collaborate to give rise to a novel pathway of chemolithotrophic tetrathionate oxidation.

PubMed

Pyne, Prosenjit; Alam, Masrure; Rameez, Moidu Jameela; Mandal, Subhrangshu; Sar, Abhijit; Mondal, Nibendu; Debnath, Utsab; Mathew, Boby; Misra, Anup Kumar; Mandal, Amit Kumar; Ghosh, Wriddhiman

2018-04-18

The SoxXAYZB(CD) 2 -mediated pathway of bacterial sulfur-chemolithotrophy explains the oxidation of thiosulfate, sulfide, sulfur and sulfite, but not tetrathionate. Advenella kashmirensis, which oxidizes tetrathionate to sulfate, besides forming it as an intermediate during thiosulfate-oxidation, possesses a soxCDYZAXOB operon. Knock-out-mutations proved that only SoxBCD is involved in A. kashmirensis tetrathionate-oxidation, whereas thiosulfate-to-tetrathionate-conversion is Sox-independent. Expression of two glutathione-metabolism-related proteins increased under chemolithotrophic conditions, as compared to the chemoorganotrophic one. Substrate-dependent oxygen-consumption pattern of whole-cells, and sulfur-oxidizing enzyme activities of cell-free-extracts, measured in the presence/absence of thiol-inhibitors/glutathione, corroborated glutathione-involvement in tetrathionate-oxidation. Furthermore, proteome analyses detected a sulfite:acceptor oxidoreductase (SorAB) exclusively under chemolithotrophic conditions, while expression of a methanol dehydrogenase (XoxF) homolog, subsequently named thiol dehydrotransferase (ThdT), was found to increase three- and ten-fold during thiosulfate-to-tetrathionate-conversion and tetrathionate-oxidation, respectively. A thdT-knocked-out mutant did not oxidize tetrathionate, but converted half of the supplied 40-mM-S thiosulfate to tetrathionate. Knock-out of another thiosulfate dehydrogenase (tsdA) gene proved that both ThdT and TsdA individually converted ∼20-mM-S thiosulfate to tetrathionate. The overexpressed and isolated ThdT protein exhibited PQQ-dependent thiosulfate dehydrogenation, whereas its PQQ-independent thiol-transfer activity involving tetrathionate and glutathione potentially produced a glutathione:sulfodisulfane adduct and sulfite. SoxBCD and SorAB were hypothesized to oxidize the aforesaid adduct and sulfite, respectively. This article is protected by copyright. All rights reserved. © 2018 John Wiley & Sons Ltd.

Anaerobic oxidation of methane coupled to thiosulfate reduction in a biotrickling filter.

PubMed

Cassarini, Chiara; Rene, Eldon R; Bhattarai, Susma; Esposito, Giovanni; Lens, Piet N L

2017-09-01

Microorganisms from an anaerobic methane oxidizing sediment were enriched with methane gas as the substrate in a biotrickling filter (BTF) using thiosulfate as electron acceptor for 213days. Thiosulfate disproportionation to sulfate and sulfide were the dominating sulfur conversion process in the BTF and the sulfide production rate was 0.5mmoll -1 day -1 . A specific group of sulfate reducing bacteria (SRB), belonging to the Desulforsarcina/Desulfococcus group, was enriched in the BTF. The BTF biomass showed maximum sulfate reduction rate (0.38mmoll -1 day -1 ) with methane as sole electron donor, measured in the absence of thiosulfate in the BTF. Therefore, a BTF fed with thiosulfate as electron acceptor can be used to enrich SRB of the DSS group and activate the inoculum for anaerobic oxidation of methane coupled to sulfate reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Metallization of Kevlar fibers with gold.

PubMed

Little, Brian K; Li, Yunfeng; Cammarata, V; Broughton, R; Mills, G

2011-06-01

Electrochemical gold plating processes were examined for the metallization of Kevlar yarn. Conventional Sn(2+)/Pd(2+) surface activation coupled with electroless Ni deposition rendered the fibers conductive enough to serve as cathodes for electrochemical plating. The resulting coatings were quantified gravimetrically and characterized via adhesion tests together with XRD, SEM, TEM; the coatings effect on fiber strength was also probed. XRD data showed that metallic Pd formed during surface activation whereas amorphous phases and trace amounts of pure Ni metal were plated via the electroless process. Electrodeposition in a thiosulfate bath was the most efficient Au coating process as compared with the analogous electroless procedure, and with electroplating using a commercial cyanide method. Strongly adhering coatings resulted upon metallization with three consecutive electrodepositions, which produced conductive fibers able to sustain power outputs in the range of 1 W. On the other hand, metallization affected the tensile strength of the fiber and defects present in the metal deposits make questionable the effectiveness of the coatings as protective barriers. © 2011 American Chemical Society

Thiosulfate oxidation by Thiomicrospira thermophila: metabolic flexibility in response to ambient geochemistry

PubMed Central

Houghton, J.L.; Foustoukos, D.; Flynn, T.M.; Vetriani, C.; Bradley, A.S.; Fike, D.A.

2017-01-01

Summary Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here we present reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise. At pH 8.0, thiosulfate is stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation are extracellular elemental sulfur and sulfate. We were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reports of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway (soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observe in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling. PMID:26914243

Thiosulfate oxidation by Thiomicrospira thermophila: Metabolic flexibility in response to ambient geochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Houghton, J. L.; Foustoukos, D. I.; Flynn, T. M.

Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here the reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise, is presented. At pH 8.0, thiosulfate was stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation were extracellular elemental sulfur and sulfate. Here, we were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reportsmore » of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway ( soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observed in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling.« less

Thiosulfate oxidation by Thiomicrospira thermophila: Metabolic flexibility in response to ambient geochemistry

DOE PAGES

Houghton, J. L.; Foustoukos, D. I.; Flynn, T. M.; ...

2016-03-21

Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here the reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise, is presented. At pH 8.0, thiosulfate was stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation were extracellular elemental sulfur and sulfate. Here, we were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reportsmore » of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway ( soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observed in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling.« less

Mixotrophic and autotrophic growth of Thiobacillus acidophilus on glucose and thiosulfate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pronk, J.T.; Meulenberg, R.; van den Berg, D.J.C.

1990-11-01

Mixotrophic growth of the facultatively autotrophic acidophile Thiobacillus acidophilus on mixtures of glucose and thiosulfate or tetrathionate was studied in substrate-limited chemostat cultures. Growth yields in mixotrophic cultures were higher than the sum of the heterotrophic and autographic growth yields. Pulse experiments with thiosulfate indicated that tetrathionate is an intermediate during thiosulfate oxidation by cell suspensions of T. acidophilus. From mixotrophic growth studied, the energetic value of thiosulfate and tetrathionate redox equivalents was estimated to be 50% of that of redox equivalents derived from glucose oxidation. Ribulose 1,5-bisphosphate carboxylase (RuBPCase) activities in cell extracts and rates of sulfur compound oxidationmore » by cell suspensions increased with increasing thiosulfate/glucose ratios in the influent medium of the mixotrophic cultures. Significant RuBPCase and sulfur compound-oxidizing activities were detected in heterotrophically grown T. acidophilus. Polyhedral inclusion bodies (carboxysomes) could be observed at low frequencies in thin sections of cells grown in heterotrophic, glucose-limited chemostat cultures. Highest RuBPCase activities and carboxysome abundancy were observed in cells from autotrophic, CO{sub 2}-limited chemostat cultures. The maximum growth rate at which thiosulfate was still completely oxidized was increased when glucose was utilized simultaneously. This, together with the fact that even during heterotrophic growth the organism exhibited significant activities of enzymes involved in autotrophic metabolism, indicates that T. acidophilus is well adapted to a mixotrophic lifestyle. In this respect, T. acidophilus may have a competitive advantage over autotrophic acidophiles with respect to the sulfur compound oxidation in environments in which organic compounds are present.« less

Genomic insights into metabolic versatility of a lithotrophic sulfur-oxidizing diazotrophic Alphaproteobacterium Azospirillum thiophilum.

PubMed

Orlova, Maria V; Tarlachkov, Sergey V; Dubinina, Galina A; Belousova, Elena V; Tutukina, Maria N; Grabovich, Margarita Y

2016-12-01

Diazotrophic Alphaproteobacteria of the genus Azospirillum are usually organotrophs, although some strains of Azospirillum lipoferum are capable of hydrogen-dependent autotrophic growth. Azospirillum thiophilum strain was isolated from a mineral sulfide spring, a biotope highly unusual for azospirilla. Here, the metabolic pathways utilized by A. thiophilum were revealed based on comprehensive analysis of its genomic organization, together with physiological and biochemical approaches. The A. thiophilum genome contained all the genes encoding the enzymes of carbon metabolism via glycolysis, tricarboxylic acid cycle and glyoxylate cycle. Genes for a complete set of enzymes responsible for autotrophic growth, with an active Calvin-Benson-Bassham cycle, were also revealed, and activity of the key enzymes was determined. Microaerobic chemolithoautotrophic growth of A. thiophilum was detected in the presence of thiosulfate and molecular hydrogen, being in line with the discovery of the genes encoding the two enzymes involved in dissimilatory thiosulfate oxidation, the Sox-complex and thiosulfate dehydrogenase and Ni-Fe hydrogenases. Azospirillum thiophilum utilizes methanol and formate, producing CO 2 that can further be metabolized via the Calvin cycle. Finally, it is capable of anaerobic respiration, using tetrathionate as a terminal electron acceptor. Such metabolic versatility is of great importance for adaptation of A. thiophilum to constantly changing physicochemical environment. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Derivatives of cysteine related to the thiosulfate metabolism of sulfur bacteria by the multi-enzyme complex "Sox"-studied by B3LYP-PCM and G3X(MP2) calculations.

PubMed

Steudel, Ralf; Steudel, Yana

2010-01-21

Certain sulfur bacteria oxidize thiosulfate enzymatically to sulfate, and derivatives of the amino acid cysteine play an important role as intermediates in this process. Since some of the proposed intermediates have so far been of hypothetical nature, we have investigated the structures and thermodynamic properties of more than 60 related derivatives of cysteine (CysH) by high-level quantum chemical calculations both in the gas phase and in a polarizable continuum using the PCM method to simulate an aqueous solution. Most of these molecules and anions were studied for the first time. Especially for the smaller species several conformational isomers of similar energy were identified; their relative stabilities are mainly determined by intramolecular hydrogen bonds. In contrast to the thiolate ion [Cys](-), the gaseous anions [CysS](-), [CysSO(2)](-), [CysSO(3)](-) and [CysSSO(3)](-) are most stable as zwitterions containing an NH(3) rather than an NH(2) group. This result also holds for the polarizable continuum. On the other hand, the related neutral molecules CysH, CysSH and CysSO(2)H are predicted to exist as NH(2) derivatives rather than zwitterions in the gas phase and this connectivity is predicted for CysH and CysSH also in the polarizable continuum. A model molecule of composition C(4)H(7)N(2)O(2)SH (abbreviated as RSH) simulating the structural environment of a cysteine residue within the peptide chain near the corresponding reaction center of the thiosulfate oxidizing enzyme complex "Sox" was used to elucidate the geometry of the proposed reaction intermediates as well as their thermodynamic properties. In the polarizable phase, the S-sulfonate ions [CysSO(3)](-) and [RSSO(3)](-) are predicted to react exothermically with water to the corresponding thiol and hydrogensulfate ions. These results support the proposed mechanism for enzymatic thiosulfate metabolism. Sulfur dioxide and hydrogensulfite anions are predicted to react exothermically and exergonically with thiolate and persulfide anions to give the corresponding S-sulfinate species [RSSO(2)](-) and [RSSSO(2)](-), respectively. The latter ions help to explain the inhibition of certain thiolate based enzymes by aqueous sulfite, disulfite and dithionite anions in sulfur oxidizing microorganisms.

Non-SRB sulfidogenic bacteria in oilfield production facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crolet, J.L.; Magot, M.F.

1996-03-01

The characterization of strictly anaerobic bacteria which can reduce thiosulfate into hydrogen sulfide is described. Although thiosulfate reduction is a common metabolism in the bacterial world, its implication regarding microbiologically influenced corrosion has never been investigated. Thiosulfate is in ecosystems where hydrogen sulfide and oxygen come in contact. An example is a sour oil-transporting pipeline in the Gulf of Guinea. In one year, this line corroded by pitting to a depth of about 1 cm.

Electrochemical Corrosion of Stainless Steel in Thiosulfate Solutions Relevant to Gold Leaching

NASA Astrophysics Data System (ADS)

Choudhary, Lokesh; Wang, Wei; Alfantazi, Akram

2016-01-01

This study aims to characterize the electrochemical corrosion behavior of stainless steel in the ammoniacal thiosulfate gold leaching solutions. Electrochemical corrosion response was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy, while the semi-conductive properties and the chemical composition of the surface film were characterized using Mott-Schottky analysis and X-ray photoelectron spectroscopy, respectively. The morphology of the corroded specimens was analyzed using scanning electron microscopy. The stainless steel 316L showed no signs of pitting in the ammoniacal thiosulfate solutions.

Potential Repercussions Associated with Halanaerobium Colonization of Hydraulically Fractured Shales

NASA Astrophysics Data System (ADS)

Booker, A. E.; Borton, M.; Daly, R. A.; Nicora, C.; Welch, S.; Dusane, D.; Johnston, M.; Sharma, S.; Mouser, P. J.; Cole, D. R.; Lipton, M. S.; Wrighton, K. C.; Wilkins, M.

2017-12-01

Hydraulic fracturing of black shale formations has greatly increased U.S. oil and natural gas recovery. Bacterial Halanaerobium strains become the dominant microbial community member in produced fluids from many fractured shales, regardless of their geographic location. Halanaerobium is not native to the subsurface, but is inadvertently introduced during the drilling and fracturing process. The accumulation of biomass in pipelines and reservoirs is detrimental due to possible well souring, microbially-induced corrosion, and pore clogging. Here, we used Halanaerobium strains isolated from a hydraulically fractured well in the Utica Shale, proteogenomics, isotopic and geochemical field observations, and laboratory growth experiments to identify detrimental effects associated with Halanaerobium growth. Analysis of Halanaerobium isolate genomes and reconstructed genomes from metagenomic datasets revealed the conserved presence of rhodanese-like proteins and anaerobic sulfite reductase complexes that can convert thiosulfate to sulfide. Furthermore, laboratory growth curves confirmed the capability of Halanaerobium to grow across a wide range of pressures (14-7000 PSI). Shotgun proteomic measurements were used to track the higher abundance of rhodanese and anaerobic sulfite reductase enzymes present when thiosulfate was available in the growth media. This technique also identified a higher abundance of proteins associated with the production of extracellular polymeric substances when Halanaerobium was grown under increasing pressures. Halanaerobium culture based assays identified thiosulfate-dependent sulfide production, while pressure incubations revealed higher cellular attachment to quartz surfaces. Increased production of sulfide and organic acids during stationary growth phase suggests that fermentative Halanaerobium use thiosulfate to remove excess reductant, aiding in NAD+ recovery. Additionally, the increased cellular attachment to surfaces under pressure indicates Halanaerobium has the capability of forming cellular clusters that could clog the shale fracture network and limit natural gas recovery. These findings bring awareness to the detrimental effects that could arise from Halanaerobium growth in hydraulically fractured shales throughout the U.S.

Sulfate but not thiosulfate reduces calculated and measured urinary ionized calcium and supersaturation: implications for the treatment of calcium renal stones.

PubMed

Rodgers, Allen; Gauvin, Daniel; Edeh, Samuel; Allie-Hamdulay, Shameez; Jackson, Graham; Lieske, John C

2014-01-01

Urinary sulfate (SO4(2-)) and thiosulfate (S2O3(2-)) can potentially bind with calcium and decrease kidney stone risk. We modeled the effects of these species on the concentration of ionized calcium (iCa) and on supersaturation (SS) of calcium oxalate (CaOx) and calcium phosphate (CaP), and measured their in vitro effects on iCa and the upper limit of stability (ULM) of these salts. Urine data from 4 different types of stone patients were obtained from the Mayo Nephrology Clinic (Model 1). A second data set was obtained from healthy controls and hypercalciuric stone formers in the literature who had been treated with sodium thiosulfate (STS) (Model 2). The Joint Expert Speciation System (JESS) was used to calculate iCa and SS. In Model 1, these parameters were calculated as a function of sulfate and thiosulfate concentrations. In Model 2, data from pre- and post STS urines were analyzed. ULM and iCa were determined in human urine as a function of sulfate and thiosulfate concentrations. Calculated iCa and SS values for all calcium salts decreased with increasing sulfate concentration. Thiosulfate had no effect on these parameters. In Model 2, calculated iCa and CaOx SS increased after STS treatment, but CaP SS decreased, perhaps due to a decrease in pH after STS treatment. In confirmatory in vitro experiments supplemental sulfate, but not thiosulfate, significantly increased the calcium needed to achieve the ULM of CaP and tended to increase the oxalate needed to reach the ULM of CaOx. Sulfate also significantly decreased iCa in human urine, while thiosulfate had no effect. Increasing urinary sulfate could theoretically reduce CaOx and CaP stone risk. Although STS may reduce CaP stone risk by decreasing urinary pH, it might also paradoxically increase iCa and CaOx SS. As such, STS may not be a viable treatment option for stone disease.

Production, crystallization and preliminary crystallographic analysis of Allochromatium vinosum thiosulfate dehydrogenase TsdA, an unusual acidophilic c-type cytochrome

PubMed Central

Brito, José A.; Gutierres, André; Denkmann, Kevin; Dahl, Christiane; Archer, Margarida

2014-01-01

The ability to perform the very simple oxidation of two molecules of thiosulfate to tetrathionate is widespread among prokaryotes. Despite the prevalent occurrence of tetrathionate formation and its well documented significance within the sulfur cycle, little is known about the enzymes that catalyze the oxidative condensation of two thiosulfate anions. To fill this gap, the thiosulfate dehydrogenase (TsdA) enzyme from the purple sulfur bacterium Allochromatium vinosum was recombinantly expressed in Escherichia coli, purified and crystallized, and a crystallographic data set was collected. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 79.2, b = 69.9, c = 57.9 Å, β = 129.3°, contained one monomer per asymmetric unit and diffracted to a resolution of 1.98 Å. PMID:25286955

Limnobacter thiooxidans gen. nov., sp. nov., a novel thiosulfate-oxidizing bacterium isolated from freshwater lake sediment.

PubMed

Spring, S; Kämpfer, P; Schleifer, K H

2001-07-01

Two novel thiosulfate-oxidizing strains were isolated from sediment of the littoral zone of a freshwater lake (Lake Chiemsee, Bavaria, Germany). The new isolates, designated CS-K1 and CS-K2T, were gram-negative, slightly curved rods with pointed ends that were motile by means of single polar flagella. Both strains were obligately aerobic and grew on a variety of organic substrates, but not autotrophically. The utilization of thiosulfate led to an increase in the growth yield, indicating that these strains were able to grow chemolithoheterotrophically by oxidation of thiosulfate to sulfate. The optimum thiosulfate concentrations for growth were determined to be 10 mM for strain CS-K1 and 20 mM for strain CS-K2T. Phylogenetically, both strains were affiliated to the beta-Proteobacteria. Their characterization by a polyphasic approach resulted in the placement of both strains into a single species that is related only distantly to any known type species. Thus, the creation of a novel taxon is proposed, with the name Limnobacter thiooxidans gen. nov., sp. nov., to include the novel strains. In addition, the phylogenetic position of the chemolithoheterotrophic strain 'Thiobacillus' Q was determined.

Wash efficiency tests. [silver sulfide as an index of the storability of photographic film

NASA Technical Reports Server (NTRS)

Maas, K. A.

1972-01-01

Processed film products were tested for residual thiosulfate by precipitation as colored silver sulfide. The quantity of thiosulfate was determined and correlated with the expected storage life of the film.

Engineering bacterial thiosulfate and tetrathionate sensors for detecting gut inflammation.

PubMed

Daeffler, Kristina N-M; Galley, Jeffrey D; Sheth, Ravi U; Ortiz-Velez, Laura C; Bibb, Christopher O; Shroyer, Noah F; Britton, Robert A; Tabor, Jeffrey J

2017-04-03

There is a groundswell of interest in using genetically engineered sensor bacteria to study gut microbiota pathways, and diagnose or treat associated diseases. Here, we computationally identify the first biological thiosulfate sensor and an improved tetrathionate sensor, both two-component systems from marine Shewanella species, and validate them in laboratory Escherichia coli Then, we port these sensors into a gut-adapted probiotic E. coli strain, and develop a method based upon oral gavage and flow cytometry of colon and fecal samples to demonstrate that colon inflammation (colitis) activates the thiosulfate sensor in mice harboring native gut microbiota. Our thiosulfate sensor may have applications in bacterial diagnostics or therapeutics. Finally, our approach can be replicated for a wide range of bacterial sensors and should thus enable a new class of minimally invasive studies of gut microbiota pathways. © 2017 The Authors. Published under the terms of the CC BY 4.0 license.

ISOLATION AND PROPERTIES OF AN IRON-OXIDIZING THIOBACILLUS

PubMed Central

Razzell, W. E.; Trussell, P. C.

1963-01-01

Razzell, W. E. (British Columbia Research Council, Vancouver, Canada) and P. C. Trussell. Isolation and properties of an iron-oxidizing Thiobacillus. J. Bacteriol. 85:595–603. 1963. — An organism isolated from acidic copper-leaching waters has been shown to oxidize ferrous ions, sulfur, and metallic sulfides but exhibit peculiar responses to thiosulfate. The name Thiobacillus ferrooxidans has been used to describe it. A pH of 2.5 is optimal for growth on iron, sulfur, and metallic sulfides, but cells free from iron can be obtained from growth at pH 1.6, and sulfur cultures adjusted to pH 5.5 readily attain a pH of 1.8. A stationary cultivation procedure appears superior to percolation techniques for studying the oxidation of finely divided metallic sulfides. Concentrations of soluble copper in excess of 1 g per liter were obtained from chalcopyrite in less than 4 weeks. Chalcocite oxidation proceeded in the absence of iron. Sodium chloride inhibits iron oxidation without preventing oxidation of metallic sulfides by the organism. PMID:14042937

Selective detection of thiosulfate-containing peptides using tandem mass spectrometry.

PubMed

Raftery, Mark J

2005-01-01

Incubation of proteins or peptides containing disulfide bonds (S-S) with sodium sulfite (Na(2)SO(3)) cleaves S-S bonds producing approximately equimolar amounts of free thiols (-SH) and thiosulfates (-S-SO(3)H), a process known as sulfitolysis. Proteins and peptides containing thiosulfates were separated by reverse-phase high-performance liquid chromatography (RP-HPLC) and characterized by mass spectrometry (MS) and peptide mapping. The mass of the thiosulfate-containing peptide formed from oxidized insulin B chain was 3478.02 Da, 80 Da greater than the reduced peptide and corresponding precisely to addition of sulfur trioxide (SO(3)). Disulfide bond cleavage was also observed using RP-HPLC and MS after incubation of the intramolecular homodimer of mouse S100A8 (mass 20614 Da). The mass of HPLC-separated A8-SH was 10308 Da, and 10388 Da for A8-S-SO(3)H. Loss of SO(3) from multiply charged precursor ions was generally observed at elevated declustering potentials in the source region or within q(2) at relatively low collision energies (approximately 20 V). The characteristic loss of SO(3) at low collision energies preceded peptide backbone fragmentations at higher collision energies. Accurate mass measurement and charge-state discrimination, using a hybrid quadrupole time-of-flight mass spectrometer, allowed specific detection of thiosulfate-containing peptides. An information-dependent acquisition method, where the switch criterion was loss of m/z 79.9568, specifically identified 11 thiosulfate-containing peptides using nano-LC/MS from a tryptic digest of bovine serum albumin (BSA).

Roles of thermophilic thiosulfate-reducing bacteria and methanogenic archaea in the biocorrosion of oil pipelines

PubMed Central

Liang, Renxing; Grizzle, Robert S.; Duncan, Kathleen E.; McInerney, Michael J.; Suflita, Joseph M.

2014-01-01

Thermophilic sulfide-producing microorganisms from an oil pipeline network were enumerated with different sulfur oxyanions as electron acceptors at 55°C. Most-probable number (MPN) analysis showed that thiosulfate-reducing bacteria were the most numerous sulfidogenic microorganisms in pipeline inspection gauge (PIG) scrapings. Thiosulfate-reducing and methanogenic enrichments were obtained from the MPN cultures that were able to use yeast extract as the electron donor. Molecular analysis revealed that both enrichments harbored the same dominant bacterium, which belonged to the genus Anaerobaculum. The dominant archaeon in the methanogenic enrichment was affiliated with the genus Methanothermobacter. With yeast extract as the electron donor, the general corrosion rate by the thiosulfate-reducing enrichment (8.43 ± 1.40 milli-inch per year, abbreviated as mpy) was about 5.5 times greater than the abiotic control (1.49 ± 0.15 mpy), while the comparable measures for the methanogenic culture were 2.03 ± 0.49 mpy and 0.62 ± 0.07 mpy, respectively. Total iron analysis in the cultures largely accounted for the mass loss of iron measured in the weight loss determinations. Profilometry analysis of polished steel coupons incubated in the presence of the thiosulfate-reducing enrichment revealed 59 pits over an area of 71.16 mm2, while only 6 pits were evident in the corresponding methanogenic incubations. The results show the importance of thiosulfate-utilizing, sulfide-producing fermentative bacteria such as Anaerobaculum sp. in the corrosion of carbon steel, but also suggest that Anaerobaculum sp. are of far less concern when growing syntrophically with methanogens. PMID:24639674

Roles of thermophilic thiosulfate-reducing bacteria and methanogenic archaea in the biocorrosion of oil pipelines.

PubMed

Liang, Renxing; Grizzle, Robert S; Duncan, Kathleen E; McInerney, Michael J; Suflita, Joseph M

2014-01-01

Thermophilic sulfide-producing microorganisms from an oil pipeline network were enumerated with different sulfur oxyanions as electron acceptors at 55°C. Most-probable number (MPN) analysis showed that thiosulfate-reducing bacteria were the most numerous sulfidogenic microorganisms in pipeline inspection gauge (PIG) scrapings. Thiosulfate-reducing and methanogenic enrichments were obtained from the MPN cultures that were able to use yeast extract as the electron donor. Molecular analysis revealed that both enrichments harbored the same dominant bacterium, which belonged to the genus Anaerobaculum. The dominant archaeon in the methanogenic enrichment was affiliated with the genus Methanothermobacter. With yeast extract as the electron donor, the general corrosion rate by the thiosulfate-reducing enrichment (8.43 ± 1.40 milli-inch per year, abbreviated as mpy) was about 5.5 times greater than the abiotic control (1.49 ± 0.15 mpy), while the comparable measures for the methanogenic culture were 2.03 ± 0.49 mpy and 0.62 ± 0.07 mpy, respectively. Total iron analysis in the cultures largely accounted for the mass loss of iron measured in the weight loss determinations. Profilometry analysis of polished steel coupons incubated in the presence of the thiosulfate-reducing enrichment revealed 59 pits over an area of 71.16 mm(2), while only 6 pits were evident in the corresponding methanogenic incubations. The results show the importance of thiosulfate-utilizing, sulfide-producing fermentative bacteria such as Anaerobaculum sp. in the corrosion of carbon steel, but also suggest that Anaerobaculum sp. are of far less concern when growing syntrophically with methanogens.

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. II. Formation and decomposition of thiosulfate and polythionate in Cinder Pool

NASA Astrophysics Data System (ADS)

Xu, Y.; Schoonen, M. A. A.; Nordstrom, D. K.; Cunningham, K. M.; Ball, J. W.

2000-04-01

Cinder Pool is an acid-sulfate-chloride boiling spring in Norris Geyser Basin, Yellowstone National Park. The pool is unique in that its surface is partially covered with mm-size, black, hollow sulfur spherules, while a layer of molten sulfur resides at the bottom of the pool (18 m depth). The sulfur speciation in the pool was determined on four different days over a period of two years. Samples were taken to evaluate changes with depth and to evaluate the importance of the sulfur spherules on sulfur redox chemistry. All analyses were conducted on site using a combination of ion chromatography and colorimetric techniques. Dissolved sulfide (H2S), thiosulfate (S2O32-), polythionates (SxO62-), and sulfate were detected. The polythionate concentration was highly variable in time and space. The highest concentrations were found in surficial samples taken from among the sulfur spherules. With depth, the polythionate concentrations dropped off. The maximum observed polythionate concentration was 8 μM. Thiosulfate was rather uniformly distributed throughout the pool and concentrations ranged from 35 to 45 μM. Total dissolved sulfide concentrations varied with time, concentrations ranged from 16 to 48 μM. Sulfate was relatively constant, with concentrations ranging from 1150 to 1300 μM. The sulfur speciation of Cinder Pool is unique in that the thiosulfate and polythionate concentrations are significantly higher than for any other acid-sulfate spring yet sampled in Yellowstone National Park. Complementary laboratory experiments show that thiosulfate is the intermediate sulfoxyanion formed from sulfur hydrolysis under conditions similar to those found in Cinder Pool and that polythionates are formed via the oxidation of thiosulfate by dissolved oxygen. This last reaction is catalyzed by pyrite that occurs as a minor constituent in the sulfur spherules floating on the pool's surface. Polythionate decomposition proceeds via two pathways: (1) a reaction with H2S, yielding thiosulfate and elemental sulfur; and (2) by disproportionation to sulfate and thiosulfate. This study demonstrates that the presence of a subaqueous molten sulfur pool and sulfur spherules in Cinder Pool is of importance in controlling the pathways of aqueous sulfur redox reactions. Some of the insights gained at Cinder Pool may be relevant to acid crater lakes where sulfur spherules are observed and variations in polythionate concentrations are used to monitor and predict volcanic activity.

The reaction of Grignard reagents with Bunte salts: a thiol-free synthesis of sulfides.

PubMed

Reeves, Jonathan T; Camara, Kaddy; Han, Zhengxu S; Xu, Yibo; Lee, Heewon; Busacca, Carl A; Senanayake, Chris H

2014-02-21

S-Alkyl, S-aryl, and S-vinyl thiosulfate sodium salts (Bunte salts) react with Grignard reagents to give sulfides in good yields. The S-alkyl Bunte salts are prepared from odorless sodium thiosulfate by an SN2 reaction with alkyl halides. A Cu-catalyzed coupling of sodium thiosulfate with aryl and vinyl halides was developed to access S-aryl and S-vinyl Bunte salts. The reaction is amenable to a broad structural array of Bunte salts and Grignard reagents. Importantly, this route to sulfides avoids the use of malodorous thiol starting materials or byproducts.

Mutagenicity and cytotoxicity of liquid waste, press water and pond water, produced in the cassava flour industry, and of antitoxic sodium thiosulfate.

PubMed

Viana, Lilian Ávila; Düsman, Elisângela; Vicentini, Veronica Elisa Pimenta

2014-02-01

Cassava (Manihot esculenta Crantz), a plant used as food and an ingredient in industry, contains cyanogenic glycosides. The cassava root contains wastewater, popularly known as manipueira, which is a toxic substance. Its ingestion by animals causes poisoning although they react positively to treatment with sodium thiosulfate. The present research evaluates the cytotoxicity and the mutagenicity of liquid waste produced in the process of industrialization of the bitter cassava, olho-junto variety. The liquid wastes are characterized as press water, which is obtained when the cassava roots are pressed; pond water, which is press water stored in impounded ponds; and a solution of sodium thiosulfate, pure and with other waste. The system tests comprised root meristematic cells of Allium cepa L. and bone marrow cells of Rattus norvegicus. Treatment with saline solution was cytotoxic for Allium cepa L. and significantly reduced cell division rate. Although no treatment was cytotoxic in any of the tests with rats, the thiosulfate solution was clastogenic for the chromosomal aberrations test. Since it is harmful to the genetic material submitted within the conditions of current research, sodium thiosulfate should only be used in emergency conditions in which the benefits exceed the risks. © 2013 Society of Chemical Industry.

Evidence of biogenic corrosion of titanium after exposure to a continuous culture of thiobacillus ferrooxidans grown in thiosulfate medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horn, J M; Martin, S I; Masterson, B

2000-12-07

Experiments were undertaken to evaluate extreme conditions under which candidate materials intended for use in a proposed nuclear waste repository might be susceptible to corrosion by endogenous microorganisms. Thiobucillus ferrooxidans, a sulfur-oxidizing bacterium, was grown in continuous culture using thiosulfate as an energy source; thiosulfate is oxidized to sulfate as a metabolic endproduct by this organism. Culture conditions were optimized to produce a high-density, metabolically active culture throughout a period of long term incubation in the presence of Alloy 22 (a high nickel-based alloy) and Titanium grade 7 (Tigr7) material coupons. After seven months incubation under these conditions, material couponsmore » were withdrawn and analyzed by high resolution microscopy and energy dispersive x-ray analyses. Alloy 22 coupons showed no detectable signs of corrosion. Tigr7, however, demonstrated distinct roughening of the coupon surface, and [presumably solubilized and precipitated] titanium was detected on Alloy 22 coupons incubated in the same T. ferrooxiduns culture vessel. Control coupons of these materials incubated in sterile thiosulfate medium did not demonstrate any signs of corrosion, thus showing that observed corrosive effects were due to the T. ferrooxidans metabolic activities. T. ferrooxidans intermediates of thiosulfate oxidation or sulfate may have caused the corrosive effects observed on Tigr7.« less

Thiosulfate leaching of gold from waste mobile phones.

PubMed

Ha, Vinh Hung; Lee, Jae-chun; Jeong, Jinki; Hai, Huynh Trung; Jha, Manis K

2010-06-15

The present communication deals with the leaching of gold from the printed circuit boards (PCBs) of waste mobile phones using an effective and less hazardous system, i.e., a copper-ammonia-thiosulfate solution, as an alternative to the conventional and toxic cyanide leaching of gold. The influence of thiosulfate, ammonia and copper sulfate concentrations on the leaching of gold from PCBs of waste mobile phones was investigated. Gold extraction was found to be enhanced with solutions containing 15-20 mM cupric, 0.1-0.14 M thiosulfate, and 0.2-0.3 M ammonia. Similar trends were obtained for the leaching of gold from two different types of scraps and PCBs of waste mobile phones. From the scrap samples, 98% of the gold was leached out using a solution containing 20 mM copper, 0.12 M thiosulfate and 0.2 M ammonia. Similarly, the leaching of gold from the PCBs samples was also found to be good, but it was lower than that of scrap samples in similar experimental conditions. In this case, only 90% of the gold was leached, even with a contact time of 10h. The obtained data will be useful for the development of processes for the recycling of gold from waste mobile phones. Copyright 2010 Elsevier B.V. All rights reserved.

Gamma-glutamylcysteine and thiosulfate are the major low-molecular-weight thiols in halobacteria

NASA Technical Reports Server (NTRS)

Newton, Gerald L.; Javor, Barbara

1985-01-01

Six representative species of extremely halophilic bacteria were found to contain approximately millimolar concentrations of gamma-glutamylcysteine in the absence of significant glutathione. Thiosulfate also accumulated in the halobacteria, apparently as a major product of cysteine oxidation.

The possible role of thiosulfate in the precipitation of 34S-rich barite in some Mississippi Valley-type deposits

USGS Publications Warehouse

Spirakis, C.S.

1991-01-01

The precipitation of extremely 34S-rich barite in the late stage of mineralization in the Mississippi Valleytype deposits of the Illinois-Kentucky district (U.S.A.) may be explained by reactions involving thiosulfate (S2O3=). Inorganic processes are known to concentrate 34S in the sulfonate site of thiosulfate and 32S in the sulfate site. In the mineralizing solution, these inorganic processes may have fractionated sulfur between the two sites by about 40 per mil. At the low temperatures of the late barite stage of mineralization, bacteria are known to metabolize thiosulfate by various reactions. In one of these, dissimilatory reduction, hydrogen sulfide and sulfite are produced. Isotopically light sulfite is preferentially reduced to sulfide by bacteria to leave a residual sulfite enriched in 34S. Part of the residual sulfite may be oxidized to form isotopically heavy sulfate; part may recombine with hydrogen sulfide to form thiosulfate. The recombination also enriches the sulfonate site in 34S and the sulfane site in 32S. Recycling the newly formed thiosulfate through the above steps further enriches sulfite and sulfate from oxidation of sulfite in 34S. During genesis of the ores, the aggregate effect of these reactions may have been the precipitation of extremely 34S-rich barite. The sequence of reactions suggested above requires the presence of organic matter. Previously proposed reactions to account for the precipitation of sulfide minerals and fluorite and for the carbonate paragenesis also require the presence of organic matter. Thus, organic matter in the host rocks may cause the various ore-zone reactions and account for the localization of the ores. ?? 1991 Springer-Verlag.

Importance of Hydrogen Sulfide, Thiosulfate, and Methylmercaptan for Growth of Thiobacilli during Simulation of Concrete Corrosion

PubMed Central

Sand, Wolfgang

1987-01-01

Biogenic sulfuric acid corrosion of concrete surfaces caused by thiobacilli was reproduced in simulation experiments. At 9 months after inoculation with thiobacilli, concrete blocks were severely corroded. The sulfur compounds hydrogen sulfide, thiosulfate, and methylmercaptan were tested for their corrosive action. With hydrogen sulfide, severe corrosion was noted. The flora was dominated by Thiobacillus thiooxidans. Thiosulfate led to medium corrosion and a dominance of Thiobacillus neapolitanus and Thiobacillus intermedius. Methylmercaptan resulted in negligible corrosion. A flora of heterotrophs and fungi grew on the blocks. This result implies that methylmercaptan cannot be degraded by thiobacilli. PMID:16347391

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. II. Formation and decomposition of thiosulfate and polythionate in Cinder Pool

USGS Publications Warehouse

Xu, Y.; Schoonen, M.A.A.; Nordstrom, D. Kirk; Cunningham, K.M.; Ball, J.W.

2000-01-01

Cinder Pool is an acid-sulfate-chloride boiling spring in Norris Geyser Basin, Yellowstone National Park. The pool is unique in that its surface is partially covered with mm-size, black, hollow sulfur spherules, while a layer of molten sulfur resides at the bottom of the pool (18 m depth). The sulfur speciation in the pool was determined on four different days over a period of two years. Samples were taken to evaluate changes with depth and to evaluate the importance of the sulfur spherules on sulfur redox chemistry. All analyses were conducted on site using a combination of ion chromatography and colorimetric techniques. Dissolved sulfide (H2S), thiosulfate (S2O32−), polythionates (SxO62−), and sulfate were detected. The polythionate concentration was highly variable in time and space. The highest concentrations were found in surficial samples taken from among the sulfur spherules. With depth, the polythionate concentrations dropped off. The maximum observed polythionate concentration was 8 μM. Thiosulfate was rather uniformly distributed throughout the pool and concentrations ranged from 35 to 45 μM. Total dissolved sulfide concentrations varied with time, concentrations ranged from 16 to 48 μM. Sulfate was relatively constant, with concentrations ranging from 1150 to 1300 μM. The sulfur speciation of Cinder Pool is unique in that the thiosulfate and polythionate concentrations are significantly higher than for any other acid-sulfate spring yet sampled in Yellowstone National Park. Complementary laboratory experiments show that thiosulfate is the intermediate sulfoxyanion formed from sulfur hydrolysis under conditions similar to those found in Cinder Pool and that polythionates are formed via the oxidation of thiosulfate by dissolved oxygen. This last reaction is catalyzed by pyrite that occurs as a minor constituent in the sulfur spherules floating on the pool's surface. Polythionate decomposition proceeds via two pathways: (1) a reaction with H2S, yielding thiosulfate and elemental sulfur; and (2) by disproportionation to sulfate and thiosulfate. This study demonstrates that the presence of a subaqueous molten sulfur pool and sulfur spherules in Cinder Pool is of importance in controlling the pathways of aqueous sulfur redox reactions. Some of the insights gained at Cinder Pool may be relevant to acid crater lakes where sulfur spherules are observed and variations in polythionate concentrations are used to monitor and predict volcanic activity.

Effect of surface application of ammonium thiosulfate on field-scale emissions of 1,3-dichloropropene

USDA-ARS?s Scientific Manuscript database

Soil fumigation is important for food production but has the potential to discharge toxic chemicals into the environment, which may adversely affect human and ecosystem health. A field experiment was conducted to evaluate the effect of applying ammonium thiosulfate fertilizer to the soil surface pr...

Synthesis and reversible hydration behavior of the thiosulfate intercalated layered double hydroxide of Zn and Al

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radha, S.; Milius, Wolfgang; Breu, Josef, E-mail: josef.breu@uni-bayreuth.de

2013-08-15

The thiosulfate-intercalated layered double hydroxide of Zn and Al undergoes reversible hydration with a variation in the relative humidity of the ambient. The hydrated and dehydrated phases, which represent the end members of the hydration cycle, both adopt the structure of the 3R{sub 1} polytype. In the intermediate range of relative humidity values (40–60%), the hydrated and dehydrated phases coexist. The end members of the hydration cycle adopt the structure of the same polytype, and vary only in their basal spacings. This points to the possibility that all the intermediate phases have a kinetic origin. - Graphical abstract: Basal spacingmore » evolution of the thiosulfate ion intercalated [Zn–Al] LDH during one complete hydration–dehydration cycle as a function of relative humidity. Display Omitted - Highlights: • Thiosulfate intercalated [Zn–Al] LDHs were synthesized by co-precipitation. • The LDH exhibits reversible hydration with variation in humidity. • Both the end members of the hydration cycle adopt the same polytype structure. • The interstratified intermediates observed are kinetic in origin.« less

Physiological characterization of strain DCB-1, a unique dehalogenating sulfidogenic bacterium.

PubMed Central

Stevens, T O; Linkfield, T G; Tiedje, J M

1988-01-01

Strain DCB-1 is an obligately anaerobic bacterium which carries out the reductive dehalogenation of halobenzoates and was previously known to grow only on pyruvate plus 20% ruminal fluid. When various electron acceptors were supplied, thiosulfate and sulfite were found to stimulate growth. Sulfide was produced from thiosulfate. Cytochrome c and desulfoviridin were detected. The mol% G+C was 49 (at the thermal denaturation temperature). Of 55 carbon sources tested, only pyruvate supported growth as the sole carbon source in mineral medium. Lactate, acetate, L- and D-malate, glycerol, and L- and D-arabinose stimulated growth when supplemented with 10% ruminal fluid and 20 mM thiosulfate. In mineral medium, pyruvate was converted to acetate and lactate, with small amounts of succinate and fumarate accumulating transiently. During growth with thiosulfate, all of these products accumulated transiently. Addition of excess hydrogen to pyruvate-grown cultures resulted in diversion of carbon to formate, lactate, and butyrate, which caused a decrease in cell yield. We conclude that strain DCB-1 is a new type of sulfidogenic bacterium. PMID:3223760

Protein changes in Lepidium sativum L. exposed to Hg during soil phytoremediation.

PubMed

Smolinska, Beata; Szczodrowska, Agnieszka; Leszczynska, Joanna

2017-08-03

Some investigations have been carried out in this study to find the best technique of soil reclamation in mercurypolluted soil. In this study, we examined Lepidium sativum L. as a plant useful for Hg phytoextraction. The simultaneous application of compost and thiosulfate was explored as a possible method of enhancing the process of phytoextraction. The results of the investigations of plant protein changes during assisted Hg phytoextraction were also provided. The results of the study show that combined use of compost and thiosulfate significantly increased both the total Hg accumulation and its translocation to aerial plant tissues. Plant protein analysis showed that L. sativum L. has the ability to respond to environmental stress condition by the activation of additional proteins. The additional proteins, like homocysteine methyltransferase, ribulose bisphosphate carboxylases (long and short chains), 14-3-3-like protein, and biosynthesis-related 40S ribosomal protein S15, were activated in plant shoots only in experiments carried out in Hg-polluted soil. There were no protein changes observed in plants exposed to compost and thiosulfate. It suggests that the combined use of compost and thiosulfate decreased Hg toxicity.

Growth of Acidithiobacillus Ferrooxidans ATCC 23270 in Thiosulfate Under Oxygen-Limiting Conditions Generates Extracellular Sulfur Globules by Means of a Secreted Tetrathionate Hydrolase

PubMed Central

Beard, Simón; Paradela, Alberto; Albar, Juan P.; Jerez, Carlos A.

2011-01-01

Production of sulfur globules during sulfide or thiosulfate oxidation is a characteristic feature of some sulfur bacteria. Although their generation has been reported in Acidithiobacillus ferrooxidans, its mechanism of formation and deposition, as well as the physiological significance of these globules during sulfur compounds oxidation, are currently unknown. Under oxygen-sufficient conditions (OSC), A. ferrooxidans oxidizes thiosulfate to tetrathionate, which accumulates in the culture medium. Tetrathionate is then oxidized by a tetrathionate hydrolase (TTH) generating thiosulfate, elemental sulfur, and sulfate as final products. We report here a massive production of extracellular conspicuous sulfur globules in thiosulfate-grown A. ferrooxidans cultures shifted to oxygen-limiting conditions (OLC). Concomitantly with sulfur globule deposition, the extracellular concentration of tetrathionate greatly diminished and sulfite accumulated in the culture supernatant. A. ferrooxidans cellular TTH activity was negligible in OLC-incubated cells, indicating that this enzymatic activity was not responsible for tetrathionate disappearance. On the other hand, supernatants from both OSC- and OLC-incubated cells showed extracellular TTH activity, which most likely accounted for tetrathionate consumption in the culture medium. The extracellular TTH activity described here: (i) gives experimental support to the TTH-driven model for hydrophilic sulfur globule generation, (ii) explains the extracellular location of A. ferrooxidans sulfur deposits, and (iii) strongly suggests that the generation of sulfur globules in A. ferrooxidans corresponds to an early step during its adaptation to an anaerobic lifestyle. PMID:21833324

Sulfur Species as Redox Partners and Electron Shuttles for Ferrihydrite Reduction by Sulfurospirillum deleyianum

PubMed Central

Lohmayer, Regina; Kappler, Andreas; Lösekann-Behrens, Tina

2014-01-01

Iron(III) (oxyhydr)oxides can represent the dominant microbial electron acceptors under anoxic conditions in many aquatic environments, which makes understanding the mechanisms and processes regulating their dissolution and transformation particularly important. In a previous laboratory-based study, it has been shown that 0.05 mM thiosulfate can reduce 6 mM ferrihydrite indirectly via enzymatic reduction of thiosulfate to sulfide by the sulfur-reducing bacterium Sulfurospirillum deleyianum, followed by abiotic reduction of ferrihydrite coupled to reoxidation of sulfide. Thiosulfate, elemental sulfur, and polysulfides were proposed as reoxidized sulfur species functioning as electron shuttles. However, the exact electron transfer pathway remained unknown. Here, we present a detailed analysis of the sulfur species involved. Apart from thiosulfate, substoichiometric amounts of sulfite, tetrathionate, sulfide, or polysulfides also initiated ferrihydrite reduction. The portion of thiosulfate produced during abiotic ferrihydrite-dependent reoxidation of sulfide was about 10% of the total sulfur at maximum. The main abiotic oxidation product was elemental sulfur attached to the iron mineral surface, which indicates that direct contact between microorganisms and ferrihydrite is necessary to maintain the iron reduction process. Polysulfides were not detected in the liquid phase. Minor amounts were found associated either with microorganisms or the mineral phase. The abiotic oxidation of sulfide in the reaction with ferrihydrite was identified as rate determining. Cysteine, added as a sulfur source and a reducing agent, also led to abiotic ferrihydrite reduction and therefore should be eliminated when sulfur redox reactions are investigated. Overall, we could demonstrate the large impact of intermediate sulfur species on biogeochemical iron transformations. PMID:24632263

Response of carnation (Dianthus caryophyllus) cultivars to different postharvest preservatives.

PubMed

Adugna, Biniam; Belew, Derbew; Kassa, Negussie

2013-10-01

Experiments were conducted to assess the effect of selected pulsing solutions on the days to flower bud shrinkage, leaf wilting and petal edge drying occurrence of carnation cultivars (Green-Go and Galy). The pulsing solutions used for this investigation were Silver Thiosulfate (STS) (0.2, 0.6, 1 mM) and also ethanol (6, 8, 10%), both received equal amount of sucrose (10%). Besides, to simulate the actual practice of the farm (0.4 mM Silver Thiosulfate (STS) plus 0.3 mM T.O.G) was used as a standard control. Senescence symptoms such as flower bud shrinkage, petal edge drying and leaf wilting were monitored. The results obtained showed that 1 mM STS plus 25 g sucrose achieved rapid petal edge drying for Green-Go cultivar. On the other hand, positive effects were also observed in days to flower bud shrinkage extended by 6 mM Silver Thiosulfate (STS) plus 25 g sucrose and being in par with 8% ethanol plus 25 g sucrose for Green-Go cultivar. Subsequently, the standard control, 0.6 mM Silver Thiosulfate (STS) plus 25 g sucrose and 8% ethanol plus 25 g sucrose attended comparable increment on the days to leaf wilting occurrences.

Isotope effects associated with the anaerobic oxidation of sulfite and thiosulfate by the photosynthetic bacterium, Chromatium vinosum

NASA Technical Reports Server (NTRS)

Fry, B.; Gest, H.; Hayes, J. M.

1985-01-01

The purple photosynthetic bacterium Chromatium vinosum, strain D, catalyzes several oxidations of reduced sulfur compounds under anaerobic conditions in the light: e.g., sulfide --> sulfur --> sulfate, sulfite --> sulfate, and thiosulfate --> sulfur + sulfate. Here it is shown that no sulfur isotope effect is associated with the last of these processes; isotopic compositions of the sulfur and sulfate produced can differ, however, if the sulfane and sulfonate positions within the thiosulfate have different isotopic compositions. In the second process, an observed change from an inverse to a normal isotope effect during oxidation of sulfite may indicate the operation of 2 enzymatic pathways. In contrast to heterotrophic anaerobic reduction of oxidized sulfur compounds, anaerobic oxidations of inorganic sulfur compounds by photosynthetic bacteria are characterized by relatively small isotope effects.

Observations of non SRB sulfidogenic bacteria from oilfield production facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crolet, J.L.; Magot, M.F.

1995-10-01

The first step is the failure of a major sealine transporting sour oil by a form of internal pitting apparently involving sulfate reducing bacteria(SRB). Then possible mechanisms were studied, where the theoretical roles of sulfate and thiosulfate were compared. Afterwards, the presence of thiosulfate was effectively identified in the produced water, and the growth of the local SRB was shown to be stronger on S{sub 2}O{sub 3}{sup {minus}} than on SO{sub 4}{sup {minus}}. Also non SRB fermentative strains, able to produce tremendous amount of H{sub 2}S and organic acids from thiosulfate and heavy nutrients (i.e. peptides) were collected. This mightmore » change the approach to microbially induced corrosion (MIC), in the oil and gas industry.« less

Engineering Bacterial Thiosulfate and Tetrathionate Sensors for Detecting Gut Inflammation

DTIC Science & Technology

2017-04-03

Article Engineering bacterial thiosulfate and tetrathionate sensors for detecting gut inflammation Kristina N-M Daeffler1 , Jeffrey D Galley2, Ravi U...interest in using genetically engineered sensor bacteria to study gut microbiota pathways, and diagnose or treat associated diseases. Here, we...understood. Genetically engineered sensor bacteria have untapped potential as tools for analyzing gut pathways. Bacteria have evolved sensors of a large

77 FR 71006 - Sodium Nitrite Injection and Sodium Thiosulfate Injection Drug Products Labeled for the Treatment...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-28

... 505(b) of the Federal Food, Drug, and Cosmetic Act (the FD&C Act) (21 U.S.C. 355(b)): Division of.... Methemoglobinemia can lead to neurological and cardiac symptoms due to lack of adequate oxygen in body tissues. The... discrepancies in dosing may lead to underdosing of sodium thiosulfate in children. III. Legal Status of Products...

Sodium Nitrite and Sodium Thiosulfate Are Effective Against Acute Cyanide Poisoning When Administered by Intramuscular Injection.

PubMed

Bebarta, Vikhyat S; Brittain, Matthew; Chan, Adriano; Garrett, Norma; Yoon, David; Burney, Tanya; Mukai, David; Babin, Michael; Pilz, Renate B; Mahon, Sari B; Brenner, Matthew; Boss, Gerry R

2017-06-01

The 2 antidotes for acute cyanide poisoning in the United States must be administered by intravenous injection. In the out-of-hospital setting, intravenous injection is not practical, particularly for mass casualties, and intramuscular injection would be preferred. The purpose of this study is to determine whether sodium nitrite and sodium thiosulfate are effective cyanide antidotes when administered by intramuscular injection. We used a randomized, nonblinded, parallel-group study design in 3 mammalian models: cyanide gas inhalation in mice, with treatment postexposure; intravenous sodium cyanide infusion in rabbits, with severe hypotension as the trigger for treatment; and intravenous potassium cyanide infusion in pigs, with apnea as the trigger for treatment. The drugs were administered by intramuscular injection, and all 3 models were lethal in the absence of therapy. We found that sodium nitrite and sodium thiosulfate individually rescued 100% of the mice, and that the combination of the 2 drugs rescued 73% of the rabbits and 80% of the pigs. In all 3 species, survival in treated animals was significantly better than in control animals (log rank test, P<.05). In the pigs, the drugs attenuated an increase in the plasma lactate concentration within 5 minutes postantidote injection (difference: plasma lactate, saline solution-treated versus nitrite- or thiosulfate-treated 1.76 [95% confidence interval 1.25 to 2.27]). We conclude that sodium nitrite and sodium thiosulfate administered by intramuscular injection are effective against severe cyanide poisoning in 3 clinically relevant animal models of out-of-hospital emergency care. Copyright © 2016 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.

Dimethyl trisulfide: A novel cyanide countermeasure.

PubMed

Rockwood, Gary A; Thompson, David E; Petrikovics, Ilona

2016-12-01

In the present studies, the in vitro and in vivo efficacies of a novel cyanide countermeasure, dimethyl trisulfide (DMTS), were evaluated. DMTS is a sulfur-based molecule found in garlic, onion, broccoli, and similar plants. DMTS was studied for effectiveness as a sulfur donor-type cyanide countermeasure. The sulfur donor reactivity of DMTS was determined by measuring the rate of the formation of the cyanide metabolite thiocyanate. In experiments carried out in vitro in the presence of the sulfurtransferase rhodanese (Rh) and at the experimental pH of 7.4, DMTS was observed to convert cyanide to thiocyanate with greater than 40 times higher efficacy than does thiosulfate, the sulfur donor component of the US Food and Drug Administration-approved cyanide countermeasure Nithiodote ® In the absence of Rh, DMTS was observed to be almost 80 times more efficient than sodium thiosulfate in vitro The fact that DMTS converts cyanide to thiocyanate more efficiently than does thiosulfate both with and without Rh makes it a promising sulfur donor-type cyanide antidote (scavenger) with reduced enzyme dependence in vitro The therapeutic cyanide antidotal efficacies for DMTS versus sodium thiosulfate were measured following intramuscular administration in a mouse model and expressed as antidotal potency ratios (APR = LD 50 of cyanide with antidote/LD 50 of cyanide without antidote). A dose of 100 mg/kg sodium thiosulfate given intramuscularly showed only slight therapeutic protection (APR = 1.1), whereas the antidotal protection from DMTS given intramuscularly at the same dose was substantial (APR = 3.3). Based on these data, DMTS will be studied further as a promising next-generation countermeasure for cyanide intoxication. © The Author(s) 2016.

A feasibility study on biological nitrogen removal (BNR) via integrated thiosulfate-driven denitratation with anammox.

PubMed

Qian, Jin; Zhang, Mingkuan; Wu, Yaoguo; Niu, Juntao; Chang, Xing; Yao, Hairui; Hu, Sihai; Pei, Xiangjun

2018-06-12

To exploit the advantages of less electron donor consumptions in partial-denitrification (denitratation, NO 3 - → NO 2 - ) as well as less sludge production in autotrophic denitrification (AD) and anammox, a novel biological nitrogen removal (BNR) process through combined anammox and thiosulfate-driven denitratation was proposed here. In this study, the ratio of S 2 O 3 2- -S/NO 3 - -N and pH are confirmed to be two key factors affecting the thiosulfate-driven denitratation activity and nitrite accumulation. Simultaneous high denitratation activity and substantial nitrite accumulation were observed at initial S 2 O 3 2- -S/NO 3 - -N ratio of 1.5:1 and pH of 8.0. The optimal pH for the anammox reaction is determined to be 8.0. A sequential batch reactor (SBR) and an up-flow anaerobic sludge blanket (UASB) reactor were established to proceed the anammox and the high-rate thiosulfate-driven denitratation, respectively. Under the ambient temperature of 35 °C, the total nitrogen removal efficiency and capacity are 73% and 0.35 kg N/day/m 3 in the anammox-SBR. At HRT of 30 min, the NO 3 - removal efficiency could achieve above 90% with the nitrate-to-nitrite transformation ratio of 0.8, implying the great potential to apply the thiosulfate-driven denitratation & anammox system for BNR with minimal sludge production. Without the occurrence of denitritation (NO 2 - → N 2 O → N 2 ), theoretically no N 2 O could be emitted from this BNR system. This study could shed light on how to operate a high rate BNR system targeting to electron donor and energy savings as well as biowastes minimization and greenhouse gas reductions. Copyright © 2018. Published by Elsevier Ltd.

Determination of Total Sulfur, Sulfate, Sulfite, Thiosulfate, and Sulfolipids in Plants.

PubMed

Kurmanbayeva, Assylay; Brychkova, Galina; Bekturova, Aizat; Khozin, Inna; Standing, Dominic; Yarmolinsky, Dmitry; Sagi, Moshe

2017-01-01

In response to oxidative stress the biosynthesis of the ROS scavenger, glutathione is induced. This requires the induction of the sulfate reduction pathway for an adequate supply of cysteine, the precursor for glutathione. Cysteine also acts as the sulfur donor for the sulfuration of the molybdenum cofactor, crucial for the last step of ABA biosynthesis. Sulfate and sulfite are, respectively, the precursor and intermediate for cysteine biosynthesis and there is evidence for stress-induced sulfate uptake and further downstream, enhanced sulfite generation by 5'-phosphosulfate (APS) reductase (APR, EC 1.8.99.2) activity. Sulfite reductase (SiR, E.C.1.8.7.1) protects the chloroplast against toxic levels of sulfite by reducing it to sulfide. In case of sulfite accumulation as a result of air pollution or stress-induced premature senescence, such as in extended darkness, sulfite can be oxidized to sulfate by sulfite oxidase. Additionally sulfite can be catalyzed to thiosulfate by sulfurtransferases or to UDP-sulfoquinovose by SQD1, being the first step toward sulfolipid biosynthesis.Determination of total sulfur in plants can be accomplished using many techniques such as ICP-AES, high-frequency induction furnace, high performance ion chromatography, sulfur combustion analysis, and colorimetric titration. Here we describe a total sulfur detection method in plants by elemental analyzer (EA). The used EA method is simple, sensitive, and accurate, and can be applied for the determination of total S content in plants.Sulfate anions in the soil are the main source of sulfur, required for normal growth and development, of plants. Plants take up sulfate ions from the soil, which are then reduced and incorporated into organic matter. Plant sulfate content can be determined by ion chromatography with carbonate eluents.Sulfite is an intermediate in the reductive assimilation of sulfate to the essential amino acids cysteine and methionine, and is cytotoxic above a certain threshold if not rapidly metabolized and can wreak havoc at the cellular and whole plant levels. Plant sulfite content affects carbon and nitrogen homeostasis Therefore, methods capable of determining sulfite levels in plants are of major importance. Here we present two robust laboratory protocols which can be used for sulfite detection in plants.Thiosulfate is an essential sulfur intermediate less toxic than sulfite which is accumulating in plants in response to sulfite accumulation. The complexity of thiosulfate detection is linked to its chemical properties. Here we present a rapid, sensitive, and accurate colorimetric method based on the enzymatic conversion of thiosulfate to thiocyanate.The plant sulfolipid sulfoquinovosyldiacylglycerol (SQDG) accounts for a large fraction of organic sulfur in the biosphere. Aside from sulfur amino acids, SQDG represents a considerable sink for sulfate in plants and is the only sulfur-containing anionic glycerolipid that is found in the photosynthetic membranes of plastids. We present the separation of sulfolipids from other fatty acids in two simple ways: by one- and two-dimensional thin-layer chromatography.

Method for aqueous gold thiosulfate extraction using copper-cyanide pretreated carbon adsorption

DOEpatents

Young, Courtney; Melashvili, Mariam; Gow, Nicholas V

2013-08-06

A gold thiosulfate leaching process uses carbon to remove gold from the leach liquor. The activated carbon is pretreated with copper cyanide. A copper (on the carbon) to gold (in solution) ratio of at least 1.5 optimizes gold recovery from solution. To recover the gold from the carbon, conventional elution technology works but is dependent on the copper to gold ratio on the carbon.

Acute, Sub-lethal Cyanide Poisoning in Mice is Ameliorated by Nitrite Alone: Complications Arising from Concomitant Administration of Nitrite and Thiosulfate as an Antidotal Combination

PubMed Central

Cambal, Leah K.; Swanson, Megan R.; Yuan, Quan; Weitz, Andrew C.; Li, Hui-Hua; Pitt, Bruce R.; Pearce, Linda L.; Peterson, Jim

2011-01-01

Sodium nitrite alone is shown to ameliorate sub-lethal cyanide toxicity in mice when given from ~1 hour before until 20 minutes after the toxic dose as demonstrated by the recovery of righting ability. An optimum dose (12 mg/kg) was determined to significantly relieve cyanide toxicity (5.0 mg/kg) when administered to mice intraperitoneally. Nitrite so administered was shown to rapidly produce NO in the bloodsteam as judged by the dose dependent appearance of EPR signals attributable to nitrosylhemoglobin and methemoglobin. It is argued that antagonism of cyanide inhibition of cytochrome c oxidase by NO is the crucial antidotal activity rather than the methemoglobin-forming action of nitrite. Concomitant addition of sodium thiosulfate to nitrite-treated blood resulted in the detection of sulfidomethemoblobin by EPR spectroscopy. Sulfide is a product of thiosulfate hydrolysis and, like cyanide, is known to be a potent inhibitor of cytochrome c oxidase; the effects of the two inhibitors being essentially additive under standard assay conditions, rather than dominated by either one. The findings afford a plausible explanation for an observed detrimental effect in mice associated with the use of the standard nitrite-thiosulfate combination therapy at sub-lethal levels of cyanide intoxication. PMID:21534623

The Role of Hydrogen for Sulfurimonas denitrificans’ Metabolism

PubMed Central

Han, Yuchen; Perner, Mirjam

2014-01-01

Sulfurimonas denitrificans was originally isolated from coastal marine sediments. It can grow with thiosulfate and nitrate or sulfide and oxygen. Recently sequencing of its genome revealed that it encodes periplasmic and cytoplasmic [NiFe]-hydrogenases but the role of hydrogen for its metabolism has remained unknown. We show the first experimental evidence that S. denitrificans can indeed express a functional hydrogen uptake active hydrogenase and can grow on hydrogen. In fact, under the provided conditions it grew faster and denser on hydrogen than on thiosulfate alone and even grew with hydrogen in the absence of reduced sulfur compounds. In our experiments, at the time points tested, the hydrogen uptake activity appeared to be related to the periplasmic hydrogenase and not to the cytoplasmic hydrogenase. Our data suggest that under the provided conditions S. denitrificans can grow more efficiently with hydrogen than with thiosulfate. PMID:25170905

Effect of variable hydrothermal conditions on sulfur speciation and isotopic compositions mediated by two Thiomicrospira strains

NASA Astrophysics Data System (ADS)

Houghton, J.; Wills, E.; Fike, D. A.

2012-12-01

Microbially mediated reactions involving elemental sulfur in low temperature hydrothermal environments are a critical component of the net hydrothermal flux of sulfur to the global oceans. We assess here the physiological impact on sulfur speciation and isotopic composition of two microbial strains at a range of pH conditions consistent with the sharp gradients found in seafloor hydrothermal environments. Thiomicrospira thermophila and T. crunogena, both isolated from hydrothermal vents at East Pacific Rise, were grown with thiosulfate as the electron donor under aerobic, closed system conditions at controlled pH and optimal temperature (35°C). T. thermophila at pH 8 produced sulfate at a 1:1 ratio with thiosulfate consumption during exponential growth, with the ratio decreasing as pH decreases. This stoichiometric ratio decreases more steeply as a function of pH during metabolism by T. crunogena. Sulfate:thiosulfate ratios less than one indicate the production of alternative oxidized sulfur compounds such as polythionates. The rate of sulfate production is comparable in both strains and is dependent on pH, decreasing from 0.8mM/hr at pH 8 to 0.2mM/hr at pH 5.6. Fractionation of 34S expressed as Δ34S between reactant and product range from 0‰ to 3‰ for both sulfate and elemental sulfur produced, with no difference between products in pH buffered experiments (pH 5.6 and 8.0). However, in unbuffered experiments during which growth causes pH to decrease from 7 to below 4.5, Δ34S(S2O3-SO4) is consistently larger than Δ34S(S2O3-S) in both strains by a factor of 2. The metabolic activity of these (and similar) strains indicate that complex and cryptic sulfur cycling may be occurring in the subsurface, associated with only minimal variation in the δ34S isotopic composition of sulfate and elemental sulfur.

Control of in vitro rooting and plant development in Corymbia maculata by silver nitrate, silver thiosulfate and thiosulfate ion.

PubMed

Steinitz, Benjamin; Barr, Nurit; Tabib, Yona; Vaknin, Yiftach; Bernstein, Nirit

2010-11-01

Plant regeneration and transformation in vitro is often improved by adding silver ion (Ag(+)) to the culture media as AgNO(3) or silver thiosulfate (STS). Ag(+) reacts with substances to form insoluble precipitates, while thiosulfate (S(2)O(3) (2-)) interferes with these reactions. We studied the implications of silver precipitation and S(2)O(3) (2-) in the medium for culture development by (1) examining formation of Ag(+) precipitates from AgNO(3) versus STS in agar gels and their possible dependence on agar type; (2) comparing Corymbia maculata culture responses to AgNO(3) and STS and determining which better suits control of culture development; (3) clarifying whether STS-dependent alterations in culture development are due to Ag(+) alone or also to a separate influence of S(2)O(3) (2-). Silver precipitates appeared in aqueous gels of four agar brands supplemented with AgNO(3), but not in Phytagel(™), which remained transparent. No precipitation was observed in gels with STS. Indole-3-butyric acid (IBA)-mediated adventitious root induction and shoot growth were higher in C. maculata shoot tips cultured on gels with STS versus AgNO(3) (6-25 μM Ag(+)). IBA-treated shoot tips exhibited enhanced adventitious root regeneration, accelerated root elongation, increased frequency of lateral root formation, and stimulated shoot growth mediated by 100-250 μM sodium thiosulfate (Na(2)S(2)O(3)) in medium without Ag(+). The potency of S(2)O(3) (2-) in facilitating culture development has never been recognized. It is inferred that superiority of STS in stimulating multiple responses of C. maculata culture results from sustained biological activity of Ag(+) through prevention of its precipitation, and from impact of S(2)O(3) (2-) on cell differentiation and growth.

[Ion chromatography of L-ascorbic acid, sulfite and thiosulfate using their postcolumn reactions with cerium (IV) and fluorescence detection of cerium (III)].

PubMed

Chen, Q; Hu, K; Miura, Y

1999-09-01

An ion chromatographic method was used to separate the species of L-ascorbic acid, sulfite and thiosulfate in their mixtures. This method is based on the separation of each anion in their mixtures by using a separation column, and then on the fluorimetric measurement of cerium (III) formed by a postcolumn reaction of cerium (IV) with the species of L-ascorbic acid, sulfite and thiosulfate in the effluent. The optimal conditions for separating and determining the above three species have been established. By using a 3 mmol/L carbonate eluent, the species of L-ascorbic acid, sulfite and thiosulfate could be eluted at the proper retention times of 1.7, 2.6 and 5.0 min, respectively, and these three anions could be separated completely. The effects of the concentrations of cerium (IV) and sulfuric acid in the postcolumn reaction solution on the chromatographic peak-height were tested in order to obtain the optimal peak-height. It was found that the peak-height at first increases rapidly with an increase in the concentration of cerium (IV) and sulfuric acid respectively up to a certain concertation, then increases slowly. These critical concentrations of cerium (IV) and sulfuric acid also depend on the amount of the analyte injected. Meanwhile the baseline signals of the sepectra increase with an increase in the concentration of cerium (IV). Some concentrations above the critical concentration of sulfuric acid could be selected as the optimal concentration of sulfuric acid, but the concentration of cerium (IV) should be optimized by establishing a compromise between the higher peak-height and the lower baseline signal. The detection limit of this method was found to be 1 mumol/L for thiosulfate when an amount of 100 microL analyte was injected.

From Mantle to Microbe to Mollusc: How Animal-Microbial Symbioses Influence Carbon and Sulfur Cycling in Hydrothermal Vent Flows.

NASA Astrophysics Data System (ADS)

Girguis, P. R.; Beinart, R.

2014-12-01

Symbioses between animals and chemoautotrophic bacteria dominate many hydrothermal vents. In these associations, symbiotic bacteria harness energy and "fix" carbon from the oxidation of reduced chemicals such as sulfide, methane, and hydrogen that are found in venting fluids. At vents along the Eastern Lau Spreading Center (ELSC) in the South Pacific, snails and mussels with chemoautotrophic symbionts have been shown to harness energy via the oxidation of sulfide. However, partially oxidized sulfur species such as thiosulfate and polysulfides have also been detected in abundance in their habitats. No studies to date have established whether thiosulfate or other partially oxidized sulfur compounds are used by these symbiotic associations, nor have studies constrained the potential role that symbioses might play in sulfur biogeochemical cycles at diffuse vent flows. To address these questions, we used high-pressure, flow through incubations to study three symbiotic molluscs from the ELSC - the snails Alviniconcha and Ifremeria nautilei and the mussel Bathymodiolus brevior - at conditions mimicking those in situ. Via the use of isotopically labeled inorganic carbon, shipboard mass spectrometry and voltammetric microelectrodes, we quantified the production and consumption of different sulfur compounds by each of these symbioses. We established that the uptake and oxidation of either sulfide or thiosulfate could -to varying degrees- support carbon fixation in all three species. Notably, we also observed that some symbioses excreted thiosulfate and polysulfides under sulfidic conditions, suggesting that these symbioses are a source of partially oxidized sulfur species in the environment. We further observed spatial disparity in the carbon fixation rates among the individuals in our incubations that have implications for the variability of productivity in situ.Collectively, these data reveal that thiosulfate can support net autotrophy, and may be an ecologically important energy source for vent symbioses. Furthermore, symbioses-mediated sulfur transformations may influence the ecology of the free-living community by governing the production and consumption of reduced sulfur species in this habitat.

Acute Cyanide Poisoning: Hydroxocobalamin and Sodium Thiosulfate Treatments with Two Outcomes following One Exposure Event.

PubMed

Meillier, Andrew; Heller, Cara

2015-01-01

Cyanide is rapidly reacting and causes arrest of aerobic metabolism. The symptoms are diffuse and lethal and require high clinical suspicion. Remediation of symptoms and mortality is highly dependent on quick treatment with a cyanide antidote. Presently, there are two widely accepted antidotes: sodium thiosulfate and hydroxocobalamin. These treatments act on different components of cyanide's metabolism. Here, we present two cases resulting from the same source of cyanide poisoning and the use of both antidotes separately used with differing outcomes.

Identification of the yeast mitochondrial transporter for oxaloacetate and sulfate.

PubMed

Palmieri, L; Vozza, A; Agrimi, G; De Marco, V; Runswick, M J; Palmieri, F; Walker, J E

1999-08-06

Saccharomyces cerevisiae encodes 35 members of the mitochondrial carrier family, including the OAC protein. The transport specificities of some family members are known, but most are not. The function of the OAC has been revealed by overproduction in Escherichia coli, reconstitution into liposomes, and demonstration that the proteoliposomes transport malonate, oxaloacetate, sulfate, and thiosulfate. Reconstituted OAC catalyzes both unidirectional transport and exchange of substrates. In S. cerevisiae, OAC is in inner mitochondrial membranes, and deletion of its gene greatly reduces transport of oxaloacetate sulfate, thiosulfate, and malonate. Mitochondria from wild-type cells swelled in isoosmotic solutions of ammonium salts of oxaloacetate, sulfate, thiosulfate, and malonate, indicating that these anions are cotransported with protons. Overexpression of OAC in the deletion strain increased greatly the [(35)S]sulfate/sulfate and [(35)S]sulfate/oxaloacetate exchanges in proteoliposomes reconstituted with digitonin extracts of mitochondria. The main physiological role of OAC appears to be to use the proton-motive force to take up into mitochondria oxaloacetate produced from pyruvate by cytoplasmic pyruvate carboxylase.

Morphological Survey of Microbial Mats Near Deep-Sea Thermal Vents †

PubMed Central

Jannasch, Holger W.; Wirsen, Carl O.

1981-01-01

A microscopic survey is presented of the most commonly observed and morphologically conspicuous microorganisms found attached to natural surfaces or to artificial materials deposited in the immediate vicinity of thermal submarine vents at the Galapagos Rift ocean spreading zone at a depth of 2,550 meters. Of special interest were the following findings: (i) all surfaces intermittently exposed to H2S-containing hydrothermal fluid were covered by layers, ca. 5 to 10 μm thick, of procaryotic, gram-negative cells interspaced with amorphous metal (Mn-Fe) deposits; (ii) although some of the cells were encased by dense metal deposits, there was little apparent correlation between metal deposition and the occurrence of microbial mats, (iii) highly differentiated forms appeared to be analogues of certain cyanobacteria, (iv) isolates from massive mats of a prosthecate bacterium could be identified as Hyphomicrobium spp., (v) intracellular membrane systems similar to those found in methylotrophic and nitrifying bacteria were observed in approximately 20% of the cells composing the mats, (vi) thiosulfate enrichments made from mat material resulted in isolations of different types of sulfur-oxidizing bacteria including the obligately chemolithotrophic genus Thiomicrospira. Images PMID:16345722

The colorimetric detection of Pb2+ by using sodium thiosulfate and hexadecyl trimethyl ammonium bromide modified gold nanoparticles.

PubMed

Zhang, Yujie; Leng, Yumin; Miao, Lijing; Xin, Junwei; Wu, Aiguo

2013-04-21

A simple, rapid colorimetric detection method for Pb(2+) in aqueous solution has been developed by using sodium thiosulfate (Na2S2O3) and hexadecyl trimethyl ammonium bromide (CTAB) modified gold nanoparticles (Au NPs). Na2S2O3 was added into the Au NP solution and thiosulfate ions (S2O3(2-)) were adsorbed on the surface of the Au NPs due to electrostatic interactions. Au atoms on the surface of the Au NPs were then oxidized to Au(i) by the O2 that existed in the solution in presence of thiosulfate. The addition of Pb(2+) (the final concentration was lower than 10 μM), accelerated the leaching of the Au NPs, and Pb-Au alloys also formed on the surface of the Au NPs. There was an obvious decrease in the surface plasmon resonance (SPR) absorption of the Au NPs. The lowest concentration for Pb(2+) that could be detected by the naked eye was 0.1 μM and using UV-vis spectroscopy was 40 nM. This is lower than the lead toxic level defined by the US Environmental Protection Agency (US EPA), which is 75 nM. In this method, CTAB, as a stabilizing agent for Au NPs, can accelerate the adsorption of S2O3(2-) on the surface of the Au NPs, which shortened the detection time to within 30 min. Moreover, this detection method is simple, cheap and environmentally friendly.

Acute Cyanide Poisoning: Hydroxocobalamin and Sodium Thiosulfate Treatments with Two Outcomes following One Exposure Event

PubMed Central

Meillier, Andrew; Heller, Cara

2015-01-01

Cyanide is rapidly reacting and causes arrest of aerobic metabolism. The symptoms are diffuse and lethal and require high clinical suspicion. Remediation of symptoms and mortality is highly dependent on quick treatment with a cyanide antidote. Presently, there are two widely accepted antidotes: sodium thiosulfate and hydroxocobalamin. These treatments act on different components of cyanide's metabolism. Here, we present two cases resulting from the same source of cyanide poisoning and the use of both antidotes separately used with differing outcomes. PMID:26543483

Analysis of Ecological Distribution and Genomic Content from a Clade of Bacteroidetes Endemic to Sulfidic Environments

NASA Astrophysics Data System (ADS)

Zhou, K.; Sylvan, J. B.; Hallam, S. J.

2017-12-01

The Bacteroidetes are a ubiquitous phylum of bacteria found in a wide variety of habitats. Marine Bacteroidetes are known to utilize complex carbohydrates and have a potentially important role in the global carbon cycle through processing these compounds, which are not digestible by many other microbes. Some members of the phylum are known to perform denitrification and are facultative anaerobes, but Bacteroidetes are not known to participate in sulfur redox cycling. Recently, it was shown that a clade of uncultured Bacteroidetes, including the VC2.1_Bac22 group, appears to be endemic to sulfidic environments, including hydrothermal vent sulfide chimneys, sediments and marine water column oxygen minimum zones (OMZs). This clade, dubbed the Sulfiphilic Bacteroidetes, is not detected in 16S rRNA amplicon studies from non-sulfidic environments. To test the hypothesis that the Sulphiphilic Bacteroidetes are involved in sulfur redox chemistry, we updated our meta-analysis of the clade using 16s rRNA sequences from public databases and employed single-cell genomics to survey their genomic potential using 19 single amplified genomes (SAGs) isolated from the seasonally anoxic Saanich Inlet, a seasonally hypoxic basin in British Columbia. Initial analysis of these SAGs indicates the Sulphiphilic Bacteroidetes may perform sulfur redox reactions using a three gene psrABC operon encoding the polysulfide reductase enzyme complex with a thiosulfate sulfurtransferase (rhodanese), which putatively uses cyanide to convert thiosulfate to sulfite, just upstream. Interestingly, this is the same configuration as discovered recently in some Marine Group A bacteria. Further aspects of the Sulphiphilic Bacteroidetes' genomic potential will be presented in light of their presence in sulfidic environments.

Terminal oxidase diversity and function in "Metallosphaera yellowstonensis": gene expression and protein modeling suggest mechanisms of Fe(II) oxidation in the sulfolobales.

PubMed

Kozubal, M A; Dlakic, M; Macur, R E; Inskeep, W P

2011-03-01

"Metallosphaera yellowstonensis" is a thermoacidophilic archaeon isolated from Yellowstone National Park that is capable of autotrophic growth using Fe(II), elemental S, or pyrite as electron donors. Analysis of the draft genome sequence from M. yellowstonensis strain MK1 revealed seven different copies of heme copper oxidases (subunit I) in a total of five different terminal oxidase complexes, including doxBCEF, foxABCDEFGHIJ, soxABC, and the soxM supercomplex, as well as a novel hypothetical two-protein doxB-like polyferredoxin complex. Other genes found in M. yellowstonensis with possible roles in S and or Fe cycling include a thiosulfate oxidase (tqoAB), a sulfite oxidase (som), a cbsA cytochrome b(558/566), several small blue copper proteins, and a novel gene sequence coding for a putative multicopper oxidase (Mco). Results from gene expression studies, including reverse transcriptase (RT) quantitative PCR (qPCR) of cultures grown autotrophically on either Fe(II), pyrite, or elemental S showed that the fox gene cluster and mco are highly expressed under conditions where Fe(II) is an electron donor. Metagenome sequence and gene expression studies of Fe-oxide mats confirmed the importance of fox genes (e.g., foxA and foxC) and mco under Fe(II)-oxidizing conditions. Protein modeling of FoxC suggests a novel lysine-lysine or lysine-arginine heme B binding domain, indicating that it is likely the cytochrome component of a heterodimer complex with foxG as a ferredoxin subunit. Analysis of mco shows that it encodes a novel multicopper blue protein with two plastocyanin type I copper domains that may play a role in the transfer of electrons within the Fox protein complex. An understanding of metabolic pathways involved in aerobic iron and sulfur oxidation in Sulfolobales has broad implications for understanding the evolution and niche diversification of these thermophiles as well as practical applications in fields such as bioleaching of trace metals from pyritic ores.

The Study and Application of Hydrometallurgical Gold Leaching in the Analysis of Refractory Precious Metals

NASA Astrophysics Data System (ADS)

Yang, M.; Geng, X.; Wang, Y. L.; Li, D. X.

2017-05-01

Three orthogonal tests are separately designed for each hydrometallurgical gold leaching process to finding the optimum reaction conditions of melting gold and palladium in each process. Under the optimum condition, the determination amount of gold and palladium in aqua regia—hydrofluoric acid, Sodium thiosulfate, and potassium iodide reaches 2.87g/kg and 8.34 g/kg, 2.39g/kg and 8.12 g/kg, 2.51g/kg and 7.84g/kg. From the result, the content of gold and palladium using the leaching process of combining Aqua regia, hydrofluoric acid and hydrogen peroxide is relatively higher than the other processes. In addition, the experiment procedure of aqua regia digestion operates easily, using less equipment, and its period is short.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vitvitsky, Victor; Yadav, Pramod K.; An, Sojin

Hydrogen sulfide is a cardioprotective signaling molecule but is toxic at elevated concentrations. Red blood cells can synthesize H2S but, lacking organelles, cannot dispose of H2S via the mitochondrial sulfide oxidation pathway. We have recently shown that at high sulfide concentrations, ferric hemoglobin oxidizes H2S to a mixture of thiosulfate and iron-bound polysulfides in which the latter species predominates. Here, we report the crystal structure of human hemoglobin containing low spin ferric sulfide, the first intermediate in heme-catalyzed sulfide oxidation. The structure provides molecular insights into why sulfide is susceptible to oxidation in human hemoglobin but is stabilized against itmore » in HbI, a specialized sulfide-carrying hemoglobin from a mollusk adapted to life in a sulfide-rich environment. We have also captured a second sulfide bound at a postulated ligand entry/exit site in the α-subunit of hemoglobin, which, to the best of our knowledge, represents the first direct evidence for this site being used to access the heme iron. Hydrodisulfide, a postulated intermediate at the junction between thiosulfate and polysulfide formation, coordinates ferric hemoglobin and, in the presence of air, generated thiosulfate. At low sulfide/heme iron ratios, the product distribution between thiosulfate and iron-bound polysulfides was approximately equal. The iron-bound polysulfides were unstable at physiological glutathione concentrations and were reduced with concomitant formation of glutathione persulfide, glutathione disulfide, and H2S. Hence, although polysulfides are unlikely to be stable in the reducing intracellular milieu, glutathione persulfide could serve as a persulfide donor for protein persulfidation, a posttranslational modification by which H2S is postulated to signal.« less

Clostridium thiosulfatireducens sp. nov., a proteolytic, thiosulfate- and sulfur-reducing bacterium isolated from an upflow anaerobic sludge blanket (UASB) reactor.

PubMed

Hernández-Eugenio, Guadalupe; Fardeau, Marie-Laure; Cayol, Jean-Luc; Patel, Bharat K C; Thomas, Pierre; Macarie, Hervé; Garcia, Jean-Louis; Ollivier, Bernard

2002-09-01

A strictly anaerobic, gram-positive, sporulating rod (0.5-0.6 x 2.0-4.0 microm), designated strain Lup 21T, was isolated from an upflow anaerobic sludge blanket (UASB) reactor treating cheese-factory wastewater. Strain Lup 21T was motile by means of peritrichous flagella, had a G+C content of 31.4 mol% and grew optimally at 37 degrees C, pH 7.4, in the absence of NaCl. It is a heterotrophic micro-organism, utilizing proteinaceous compounds (gelatin, peptides, Casamino acids and various single amino acids) but unable to use any of the carbohydrates tested as a carbon and energy source. It reduced thiosulfate and elemental sulfur to sulfide in the presence of Casamino acids as carbon and energy sources. Acetate, butyrate, isobutyrate, isovalerate, CO2 and sulfide were end products from oxidation of gelatin and Casamino acids in the presence of thiosulfate as an electron acceptor. In the absence of thiosulfate, serine, lysine, methionine and histidine were fermented. On the basis of 16S rRNA similarity, strain Lup 21T was related to members of the low-G+C Clostridiales group, Clostridium subterminale DSM 6970T being the closest relative (with a sequence similarity of 99.4%). DNA-DNA hybridization was 56% with this species. On the basis of phenotypic, genotypic and phylogenetic characteristics, the isolate was designated as a novel species of the genus Clostridium, Clostridium thiosulfatireducens sp. nov. The type strain is strain Lup 21T (= DSM 13105T = CIP 106908T).

Structure and water exchange of the hydrated thiosulfate ion in aqueous solution using QMCF MD simulation and large angle X-ray scattering.

PubMed

Eklund, Lars; Hofer, Tomas S; Weiss, Alexander K H; Tirler, Andreas O; Persson, Ingmar

2014-09-07

Theoretical ab initio quantum mechanical charge field molecular dynamics (QMCF MD) has been applied in conjunction with experimental large angle X-ray scattering (LAXS) to study the structure and dynamics of the hydrated thiosulfate ion, S2O3(2-), in aqueous solution. The S-O and SC-ST bond distances have been determined to be 1.479(5) and 2.020(6) Å by LAXS and to be 1.478 and 2.017 Å by QMCF MD simulations, which are slightly longer than the mean values found in the solid state, 1.467 and 2.002 Å, respectively. This is due to the hydrogen bonds formed at hydration. The water dynamics show that water molecules are exchanged at the hydrated oxygen and sulfur atoms, and that the water exchange is ca. 50% faster at the sulfur atom than at the oxygen atoms with mean residence times, τ0.5, of 2.4 and 3.6 ps, respectively. From this point of view the water exchange dynamics mechanism resembles the sulfate ion, while it is significantly different from the sulfite ion. This shows that the lone electron-pair in the sulfite ion has a much larger impact on the water exchange dynamics than a substitution of an oxygen atom for a sulfur one. The LAXS data did give mean SCOaq1 and SCOaq2 distances of 3.66(2) and 4.36(10) Å, respectively, and SC-Othio and OthioOaq1, SC-ST and STOaq2 distances of 1.479(5), 2.845(10), 2.020(6) and 3.24(5) Å, respectively, giving SC-OthioOaq1 and SC-STOaq2 angles close to 110°, strongly indicating a tetrahedral geometry around the terminal thiosulfate sulfur and the oxygens, and thereby, three water molecules are hydrogen bound to each of them. The hydrogen bonds between thiosulfate oxygens and the hydrating water molecules are stronger and with longer mean residence times than those between water molecules in the aqueous bulk, while the opposite is true for the hydrogen bonds between the terminal thiosulfate sulfur and the hydrating water molecules. The hydration of all oxo sulfur ions is discussed using the detailed observations for the sulfate, thiosulfate and sulfite ions, and the structure of the hydrated peroxodisulfate ion, S2O8(2-), in aqueous solution has been determined by means of LAXS to support the general observations. The mean S-O bond distances are 1.448(2) and 1.675(5) Å to the oxo and peroxo oxygens, respectively.

Effects of hydraulic retention time and [Formula: see text] ratio on thiosulfate-driven autotrophic denitrification for nitrate removal from micro-polluted surface water.

PubMed

Wang, Zheng; Fei, Xiang; He, Sheng-Bing; Huang, Jung-Chen; Zhou, Wei-Li

2017-11-01

This study was carried out to investigate the possibility of a thiosulfate-driven autotrophic denitrification for nitrate-N removal from micro-polluted surface water. The aim was to study the effects of [Formula: see text] ratio (S/N molar ratio) and hydraulic retention time (HRT) on the autotrophic denitrification performance. Besides, utilization efficiencies of [Formula: see text] along the biofilter and the restart-up of the bioreactor were also investigated. Autotrophic denitrification using thiosulfate as an electron donor for treating micro-polluted surface water without the addition of external alkalinity proved to be feasible and the biofilter could be readied in two weeks. Average nitrate-N removal efficiencies at HRTs of 0.5, 1 and 2 h were 78.7%, 87.8% and 97.4%, respectively, and corresponding removal rates were 186.24, 103.92 and 58.56 g [Formula: see text], respectively. When water temperature was in the range of 8-12°C and HRT was 1 h, average nitrate-N removal efficiencies of 41.9%, 97.1% and 97.0%, nitrite accumulation concentrations of 1.45, 0.46 and 0.22 mg/L and thiosulfate utilization efficiencies of 100%, 98.8% and 92.1% were obtained at S/N ratios of 1.0, 1.2 and 1.5, respectively. Besides, the autotrophic denitrification rate in the filtration media layer was the highest along the biofilter at an S/N ratio of 1.5. Finally, after a one-month period of starvation, the biofilter could be restarted successfully in three weeks without inoculation of seed sludge.

Analytical Method for the Detection of Residual Active Ingredients Found in Neutralized Suspensions of Antimicrobial Products.

PubMed

Kamel, Alaa; Tomasino, Stephen F

2017-03-01

An analytical method for determining the presence and levels of residual active ingredients found in neutralized suspensions of phenolic and quaternary ammonium salt-based antimicrobial products was developed using solid-phase extraction in combination with LC-tandem MS. A single-laboratory validation of the method was performed at three concentration levels for the quaternary ammonium compounds (also referred to as benzalkonium chlorides or BACs) and the phenols in the presence of letheen broth neutralizer at 2.5 and 2.75 μg/mL, respectively, as well as at dilutions of 1:10 and 1:100 in those concentrations. The method's lowest LODs were 0.005 μg/g for BACs and 0.006 μg/g for phenols. The average recovery of the fortified samples for both active ingredients ranged between 80 and 124%, and RSDs were generally <20%. In a related study, the effectiveness of letheen broth with and without sodium thiosulfate was evaluated as a neutralizer for sodium hypochlorite. The results showed that letheen broth without sodium thiosulfate neutralizes chlorine concentrations up to 60 ppm, and that 200 μg sodium thiosulfate are required to neutralize a 72 ppm concentrated chlorine solution in letheen broth.

Dealing with the sulfur part of cysteine: four enzymatic steps degrade l-cysteine to pyruvate and thiosulfate in Arabidopsis mitochondria.

PubMed

Höfler, Saskia; Lorenz, Christin; Busch, Tjorven; Brinkkötter, Mascha; Tohge, Takayuki; Fernie, Alisdair R; Braun, Hans-Peter; Hildebrandt, Tatjana M

2016-07-01

Amino acid catabolism is essential for adjusting pool sizes of free amino acids and takes part in energy production as well as nutrient remobilization. The carbon skeletons are generally converted to precursors or intermediates of the tricarboxylic acid cycle. In the case of cysteine, the reduced sulfur derived from the thiol group also has to be oxidized in order to prevent accumulation to toxic concentrations. Here we present a mitochondrial sulfur catabolic pathway catalyzing the complete oxidation of l-cysteine to pyruvate and thiosulfate. After transamination to 3-mercaptopyruvate, the sulfhydryl group from l-cysteine is transferred to glutathione by sulfurtransferase 1 and oxidized to sulfite by the sulfur dioxygenase ETHE1. Sulfite is then converted to thiosulfate by addition of a second persulfide group by sulfurtransferase 1. This pathway is most relevant during early embryo development and for vegetative growth under light-limiting conditions. Characterization of a double mutant produced from Arabidopsis thaliana T-DNA insertion lines for ETHE1 and sulfurtransferase 1 revealed that an intermediate of the ETHE1 dependent pathway, most likely a persulfide, interferes with amino acid catabolism and induces early senescence. © 2016 Scandinavian Plant Physiology Society.

Solution NMR structure and functional analysis of the integral membrane protein YgaP from Escherichia coli.

PubMed

Eichmann, Cédric; Tzitzilonis, Christos; Bordignon, Enrica; Maslennikov, Innokentiy; Choe, Senyon; Riek, Roland

2014-08-22

The solution NMR structure of the α-helical integral membrane protein YgaP from Escherichia coli in mixed 1,2-diheptanoyl-sn-glycerol-3-phosphocholine/1-myristoyl-2-hydroxy-sn-glycero-3-phospho-(1'-rac-glycerol) micelles is presented. In these micelles, YgaP forms a homodimer with the two transmembrane helices being the dimer interface, whereas the N-terminal cytoplasmic domain includes a rhodanese-fold in accordance to its sequence homology to the rhodanese family of sulfurtransferases. The enzymatic sulfur transfer activity of full-length YgaP as well as of the N-terminal rhodanese domain only was investigated performing a series of titrations with sodium thiosulfate and potassium cyanide monitored by NMR and EPR. The data indicate the thiosulfate concentration-dependent addition of several sulfur atoms to the catalytic Cys-63, which process can be reversed by the addition of potassium cyanide. The catalytic reaction induces thereby conformational changes within the rhodanese domain, as well as on the transmembrane α-helices of YgaP. These results provide insights into a potential mechanism of YgaP during the catalytic thiosulfate activity in vivo. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Aqueous pyrite oxidation by dissolved oxygen and by ferric iron

USGS Publications Warehouse

Moses, Carl O.; Nordstrom, D. Kirk; Herman, Janet S.; Mills, Aaron L.

1987-01-01

Rates of aqueous, abiotic pyrite oxidation were measured in oxygen-saturated and anaerobic Fe(III)-saturated solutions with initial pH from 2 to 9. These studies included analyses of sulfite, thiosulfate, polythionates and sulfate and procedures for cleaning oxidation products from pyrite surfaces were evaluated. Pyrite oxidation in oxygen-saturated solutions produced (1) rates that were only slightly dependent on initial pH, (2) linear increases in sulfoxy anions and (3) thiosulfate and polythionates at pH > 3.9. Intermediate sulfoxy anions were observed only at high stirring rates. In anaerobic Fe(III)-saturated solutions, no intermediates were observed except traces of sulfite at pH 9. The faster rate of oxidation in Fe(III)-saturated solutions supports a reaction mechanism in which Fe(III) is the direct oxidant of pyrite in both aerobic and anaerobic systems. The proposal of this mechanism is also supported by theoretical considerations regarding the low probability of a direct reaction between paramagnetic molecular oxygen and diamagnetic pyrite. Results from a study of sphalerite oxidation support the hypothesis that thiosulfate is a key intermediate in sulfate production, regardless of the bonding structure of the sulfide mineral.

Sulfur formation by steady-state continuous cultures of a sulfoxidizing consortium and Thiobacillus thioparus ATCC 23645.

PubMed

Alcántara, S; Velasco, A; Revah, S

2004-10-01

The elemental sulfur formation by the partial oxidation of thiosulfate by both a sulfoxidizing consortium and by Thiobacillus thioparus ATCC 23645 was studied under aerobic conditions in chemostat. Steady state was attained with essentially total conversion to sulfate when the dissolved oxygen concentration was 5 mgO2 l(-1) and below a dilution rate (D) of 3.0 d(-1)for the consortium and 0.9 d(-1) for T thioparus. The consortium formed elemental sulfur in steady state under oxygen limitation. Fifty percent of the theoretical elemental sulfur yield was obtained with a dissolved oxygen concentration of 0.2 mgO2 l(-1). Growth of T thioparus was negatively affected with a concentration below 1.9 mgO2 l(-1). Consortium yield from batch cultures was 2.1 g(-1) (protein) mol(-1) (thiosulfate), which was comparable with the values obtained in the chemostat at dilution rates of 0.4 d(-1) and 1.2 d(-1). The consortium showed a maximum degradation rate of 0.105 g(thiosulfate) g(-1) (protein) min(-1) and a saturation rate for S2O3(2-) of 1.9 mM.

Effect of thiosulfate on rapid start-up of sulfur-based reduction of high concentrated perchlorate: A study of kinetics, extracellular polymeric substances (EPS) and bacterial community structure.

PubMed

Guo, Jianbo; Zhang, Chao; Lian, Jing; Lu, Caicai; Chen, Zhi; Song, Yuanyuan; Guo, Yankai; Xing, Yajuan

2017-11-01

Perchlorate (ClO 4 - ) contamination is more and more concerned due to the hazards to humans. Based on the common primary bacterium (Helicobacteraceae) of both thiosulfate-acclimated sludge (T-Acc) and sulfur-acclimated sludge (S-Acc) for perchlorate reduction, the rapid start-up of sulfur-based perchlorate reduction reactor (SBPRR) was hypothesized by inoculating T-Acc. Furthermore, the performance of SBPRR, the SO 4 2- yield, kinetics of ClO 4 - reduction and the extracellular polymeric substances (EPS) of biofilm confirmed the hypothesis. The start-up time of R3 (reactor inoculating T-Acc) was 0.18 and 0.21 times that of R1 (control) and R2 (reactor with the influent containing thiosulfate), respectively. The SO 4 2- yield of R3 was lower than that of R2 and R1 with perchlorate removal rate 166.7mg/(Lh). The kinetic study and EPS demonstrated that inoculating T-Acc was beneficial for the development of biofilm. Consequently, the present study indicated that SBPRR can be rapidly and successfully started-up via inoculation of T-Acc. Copyright © 2017 Elsevier Ltd. All rights reserved.

Accelerated corrosion of stainless steel in thiocyanate-containing solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pistorius, P Chris; Li, Wen

2012-09-19

It is known that reduced sulfur compounds (such as thiocyanate and thiosulfate) can accelerate active corrosion of austenitic stainless steel in acid solutions, but before we started this project the mechanism of acceleration was largely unclear. This work combined electrochemical measurements and analysis using scanning electron microscopy (SEM) and X-ray photo-electron spectroscopy (XPS), which provided a comprehensive understanding of the catalytic effect of reduced sulfur species on the active corrosion of stainless steel. Both the behavior of the pure elements and the steel were studied and the work focused on the interaction between the pure elements of the steel, whichmore » is the least understood area. Upon completion of this work, several aspects are now much clearer. The main results from this work can be summarized as follows: The presence of low concentrations (around 0.1 mM) of thiocyanate or tetrathionate in dilute sulfuric acid greatly accelerates the anodic dissolution of chromium and nickel, but has an even stronger effect on stainless steels (iron-chromium-nickel alloys). Electrochemical measurements and surface analyses are in agreement with the suggestion that accelerated dissolution really results from suppressed passivation. Even well below the passivation potential, the electrochemical signature of passivation is evident in the electrode impedance; the electrode impedance shows clearly that this pre-passivation is suppressed in the presence of thiocyanate. For the stainless steels, remarkable changes in the morphology of the corroded metal surface and in the surface concentration of chromium support the suggestion that pre-passivation of stainless steels is suppressed because dissolution of chromium is accelerated. Surface analysis confirmed that adsorbed sulfur / sulfide forms on the metal surfaces upon exposure to solutions containing thiocyanate or thiosulfate. For pure nickel, and steels containing nickel (and residual copper), bulk sulfide (visible as a black corrosion product) forms during anodic dissolution. The sulfide is electronically conductive, and gives an increase of several orders of magnitude in the electrode capacitance; the sulfide also causes anodic activation to persist after the pure metals and steels were removed from the thiocyanate-containing electrolyte and transferred to a thiocyanate-free electrolyte. The main practical implications of this work are that low concentrations of reduced sulfur compounds strongly affect anodic dissolution of stainless steels, and that selecting steels with elevated concentrations of chromium, nickel or molybdenum would serve to limit the anodic dissolution rate in the presence of reduced sulfur compounds.« less

Metallurgical recovery of metals from electronic waste: a review.

PubMed

Cui, Jirang; Zhang, Lifeng

2008-10-30

Waste electric and electronic equipment, or electronic waste, has been taken into consideration not only by the government but also by the public due to their hazardous material contents. In the detailed literature survey, value distributions for different electronic waste samples were calculated. It is showed that the major economic driver for recycling of electronic waste is from the recovery of precious metals. The state of the art in recovery of precious metals from electronic waste by pyrometallurgical processing, hydrometallurgical processing, and biometallurgical processing are highlighted in the paper. Pyrometallurgical processing has been a traditional technology for recovery of precious metals from waste electronic equipment. However, state-of-the-art smelters are highly depended on investments. Recent research on recovery of energy from PC waste gives an example for using plastics in this waste stream. It indicates that thermal processing provides a feasible approach for recovery of energy from electronic waste if a comprehensive emission control system is installed. In the last decade, attentions have been removed from pyrometallurgical process to hydrometallurgical process for recovery of metals from electronic waste. In the paper, hydrometallurgical processing techniques including cyanide leaching, halide leaching, thiourea leaching, and thiosulfate leaching of precious metals are detailed. In order to develop an environmentally friendly technique for recovery of precious metals from electronic scrap, a critical comparison of main leaching methods is analyzed for both economic feasibility and environmental impact. It is believed that biotechnology has been one of the most promising technologies in metallurgical processing. Bioleaching has been used for recovery of precious metals and copper from ores for many years. However, limited research was carried out on the bioleaching of metals from electronic waste. In the review, initial researches on the topic are presented. In addition, mechanisms and models of biosorption of precious metal ions from solutions are discussed.

Control of copper resistance and inorganic sulfur metabolism by paralogous regulators in Staphylococcus aureus.

PubMed

Grossoehme, Nicholas; Kehl-Fie, Thomas E; Ma, Zhen; Adams, Keith W; Cowart, Darin M; Scott, Robert A; Skaar, Eric P; Giedroc, David P

2011-04-15

All strains of Staphylococcus aureus encode a putative copper-sensitive operon repressor (CsoR) and one other CsoR-like protein of unknown function. We show here that NWMN_1991 encodes a bona fide Cu(I)-inducible CsoR of a genetically unlinked copA-copZ copper resistance operon in S. aureus strain Newman. In contrast, an unannotated open reading frame found between NWMN_0027 and NWMN_0026 (denoted NWMN_0026.5) encodes a CsoR-like regulator that represses expression of adjacent genes by binding specifically to a pair of canonical operator sites positioned in the NWMN_0027-0026.5 intergenic region. Inspection of these regulated genes suggests a role in assimilation of inorganic sulfur from thiosulfate and vectorial sulfur transfer, and we designate NWMN_0026.5 as CstR (CsoR-like sulfur transferase repressor). Expression analysis demonstrates that CsoR and CstR control their respective regulons in response to distinct stimuli with no overlap in vivo. Unlike CsoR, CstR does not form a stable complex with Cu(I); operator binding is instead inhibited by oxidation of the intersubunit cysteine pair to a mixture of disulfide and trisulfide linkages by a likely metabolite of thiosulfate assimilation, sulfite. CsoR is unreactive toward sulfite under the same conditions. We conclude that CsoR and CstR are paralogs in S. aureus that function in the same cytoplasm to control distinct physiological processes.

Control of Copper Resistance and Inorganic Sulfur Metabolism by Paralogous Regulators in Staphylococcus aureus*

PubMed Central

Grossoehme, Nicholas; Kehl-Fie, Thomas E.; Ma, Zhen; Adams, Keith W.; Cowart, Darin M.; Scott, Robert A.; Skaar, Eric P.; Giedroc, David P.

2011-01-01

All strains of Staphylococcus aureus encode a putative copper-sensitive operon repressor (CsoR) and one other CsoR-like protein of unknown function. We show here that NWMN_1991 encodes a bona fide Cu(I)-inducible CsoR of a genetically unlinked copA-copZ copper resistance operon in S. aureus strain Newman. In contrast, an unannotated open reading frame found between NWMN_0027 and NWMN_0026 (denoted NWMN_0026.5) encodes a CsoR-like regulator that represses expression of adjacent genes by binding specifically to a pair of canonical operator sites positioned in the NWMN_0027–0026.5 intergenic region. Inspection of these regulated genes suggests a role in assimilation of inorganic sulfur from thiosulfate and vectorial sulfur transfer, and we designate NWMN_0026.5 as CstR (CsoR-like sulfur transferase repressor). Expression analysis demonstrates that CsoR and CstR control their respective regulons in response to distinct stimuli with no overlap in vivo. Unlike CsoR, CstR does not form a stable complex with Cu(I); operator binding is instead inhibited by oxidation of the intersubunit cysteine pair to a mixture of disulfide and trisulfide linkages by a likely metabolite of thiosulfate assimilation, sulfite. CsoR is unreactive toward sulfite under the same conditions. We conclude that CsoR and CstR are paralogs in S. aureus that function in the same cytoplasm to control distinct physiological processes. PMID:21339296

Syntheses and characterization of one-dimensional alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yohannan, Jinu P.; Vidyasagar, Kanamaluru, E-mail: kvsagar@iitm.ac.in

2015-01-15

Three new isostructural quaternary antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs) have been synthesized by using alkali metal thiosulfate flux and structurally characterized by X-ray diffraction. Their structures contain A{sup +} ions around the [Sb{sub 2}Sn{sub 3}S{sub 10}]{sup 2−} chains, which are built from SbS{sub 3} pyramids, SnS{sub 6} octahedra and SnS{sub 4} tetrahedra. Raman and Mössbauer spectroscopic measurements corroborate the oxidation states and coordination environments of Sb(III) and Sn(IV). All three compounds are wide band gap semiconductors. Potassium compound undergoes partial exchange with strontium, cadmium and lead ions. - Graphical abstract: Syntheses, crystal structure, spectroscopic andmore » partial ion-exchange studies of new one-dimensional alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs) are described. - Highlights: • Syntheses of new alkali metal antimony(III) thiostannates(IV), A{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} (A=K, Rb, Cs). • Wide band gap semiconductors with one-dimensional structure. • Topotactic partial exchange of K{sup +} ions of K{sub 2}Sb{sub 2}Sn{sub 3}S{sub 10} with Sr{sup 2+}, Cd{sup 2+} and Pb{sup 2+} ions.« less

Successfully Treated Calcific Uremic Arteriolopathy: Two Cases of a High Anion Gap Metabolic Acidosis with Intravenous Sodium Thiosulfate

PubMed Central

Rein, Joshua L.; Miyata, Kana N.; Dadzie, Kobena A.; Gruber, Steven J.; Sulica, Roxana; Winchester, James F.

2014-01-01

Calcific uremic arteriolopathy (CUA) is a rare and potentially fatal disorder of calcification involving subcutaneous small vessels and fat in patients with renal insufficiency. We describe the successful use of intravenous sodium thiosulfate (STS) for the treatment of CUA in two patients. The first case was complicated by the development of a severe anion gap metabolic acidosis, which was accompanied by a seizure. Both patients had complete wound healing within five months. Although STS should be considered in the treatment of CUA, little is known about pharmacokinetics and additional studies are required to determine dosing strategies to minimize severe potential side effects. PMID:25506005

Colorimetric assay for lead ions based on the leaching of gold nanoparticles.

PubMed

Chen, Yi-You; Chang, Huan-Tsung; Shiang, Yen-Chun; Hung, Yu-Lun; Chiang, Cheng-Kang; Huang, Chih-Ching

2009-11-15

A colorimetric, label-free, and nonaggregation-based gold nanoparticles (Au NPs) probe has been developed for the detection of Pb(2+) in aqueous solution, based on the fact that Pb(2+) ions accelerate the leaching rate of Au NPs by thiosulfate (S(2)O(3)(2-)) and 2-mercaptoethanol (2-ME). Au NPs reacted with S(2)O(3)(2-) ions in solution to form Au(S(2)O(3))(2)(3-) complexes on the Au NP surfaces, leading to slight decreases in their surface plasmon resonance (SPR) absorption. Surface-assisted laser desorption/ionization time-of-flight ionization mass spectrometry (SALDI-TOF MS) data reveals the formation of Pb-Au alloys on the surfaces of the Au NPs in the presence of Pb(2+) ions and 2-ME. The formation of Pb-Au alloys accelerated the Au NPs rapidly dissolved into solution, leading to dramatic decreases in the SPR absorption. The 2-ME/S(2)O(3)(2-)-Au NP probe is highly sensitive (LOD = 0.5 nM) and selective (by at least 1000-fold over other metal ions) toward Pb(2+) ions, with a linear detection range (2.5 nM-10 muM) over nearly 4 orders of magnitude. The cost-effective probe allows rapid and simple determination of the concentrations of Pb(2+) ions in environmental samples (Montana soil and river), with results showing its great practicality for the detection of lead in real samples.

Impact of reaction conditions on the laccase-catalyzed conversion of bisphenol A.

PubMed

Kim, Young-Jin; Nicell, James A

2006-08-01

The oxidative conversion of aqueous BPA catalyzed by laccase from Trametes versicolor was conducted in a closed, temperature-controlled system containing buffer for pH control. The effects of medium pH, buffer concentration, temperature and mediators and the impacts of dissolved wastewater constituents on BPA conversion were investigated. The optimal pH for BPA conversion was approximately 5, with greater than half maximal conversion and good enzyme stability in the range of 4-7. The stability of the enzyme was not impacted by buffer concentration, nor was BPA conversion. Despite the observation that the enzyme tended to be inactivated at elevated temperatures, enhanced conversion of BPA was observed up until a reaction temperature of 45 degrees C. Of the mediators studied, ABTS was most successful at enhancing the conversion of BPA. Dissolved wastewater constituents that were studied included various inorganic salts, organic compounds and heavy metal ions. BPA conversion was inhibited in the presence of anions such as sulfite, thiosulfate, sulfide, nitrite and cyanide. The metal ions Fe(III) and Cu(II) and the halogens chloride and fluoride substantially suppressed BPA conversion, but the presence of selected organic compounds did not significantly reduce the conversion of BPA.

Biological Nitrogen Removal through Nitritation Coupled with Thiosulfate-Driven Denitritation

PubMed Central

Qian, Jin; Zhou, Junmei; Zhang, Zhen; Liu, Rulong; Wang, Qilin

2016-01-01

A novel biological nitrogen removal system based on nitritation coupled with thiosulfate-driven denitritation (Nitritation-TDD) was developed to achieve a high nitrogen removal rate and low sludge production. A nitritation sequential batch reactor (nitritation SBR) and an anoxic up-flow sludge bed (AnUSB) reactor were applied for effective nitritation and denitritation, respectively. Above 75% nitrite was accumulated in the nitritation SBR with an influent ammonia loading rate of 0.43 kg N/d/m3. During Nitritation-TDD operation, particle sizes (d50) of the sludge decreased from 406 to 225 um in nitritation SBR and from 327–183 um in AnUSB reactor. Pyrosequencing tests revealed that ammonium-oxidizing bacteria (AOB) population was stabilized at approximately 7.0% (calculated as population of AOB-related genus divided by the total microbial population) in the nitritation SBR. In contrast, nitrite-oxidizing bacteria (NOB) population decreased from 6.5–0.6% over the same time, indicating the effective nitrite accumulation in the nitritation SBR. Thiobacillus, accounting for 34.2% in the AnUSB reactor, was mainly responsible for nitrogen removal via autotrophic denitritation, using an external source of thiosulfate as electron donor. Also, it was found that free nitrous acid could directly affect the denitritation activity. PMID:27272192

Respiration of arsenate and selenate by hyperthermophilic archaea.

PubMed

Huber, R; Sacher, M; Vollmann, A; Huber, H; Rose, D

2000-10-01

A novel, strictly anaerobic, hyperthermophilic, facultative organotrophic archaeon was isolated from a hot spring at Pisciarelli Solfatara, Naples, Italy. The rod-shaped cells grew chemolithoautotrophically with carbon dioxide as carbon source, hydrogen as electron donor and arsenate, thiosulfate or elemental sulfur as electron acceptor. H2S was formed from sulfur or thiosulfate, arsenite from arsenate. Organotrophically, the new isolate grew optimally in the presence of an inorganic electron acceptor like sulfur, selenate or arsenate. Cultures, grown on arsenate and thiosulfate or arsenate and L-cysteine, precipitated realgar (As2S2). During growth on selenate, elemental selenium was produced. The G+C content of the DNA was 58.3 mol%. Due to 16S rRNA gene sequence analysis combined with physiological and morphological criteria, the new isolate belongs to the Thermoproteales order. It represents a new species within the genus Pyrobaculum, the type species of which we name Pyrobaculum arsenaticum (type strain PZ6*, DSM 13514, ATCC 700994). Comparative studies with different Pyrobaculum-species showed, that Pyrobaculum aerophilum was also able to grow organotrophically under anaerobic culture conditions in the presence of arsenate, selenate and selenite. During growth on selenite, elemental selenium was formed as final product. In contrast to P. arsenaticum, P. aerophilum could use selenate or arsenate for lithoautotrophic growth with carbon dioxide and hydrogen.

Geobacter sulfurreducens sp. nov., a hydrogen- and acetate-oxidizing dissimilatory metal-reducing microorganism.

PubMed Central

Caccavo, F; Lonergan, D J; Lovley, D R; Davis, M; Stolz, J F; McInerney, M J

1994-01-01

A dissimilatory metal- and sulfur-reducing microorganism was isolated from surface sediments of a hydrocarbon-contaminated ditch in Norman, Okla. The isolate, which was designated strain PCA, was an obligately anaerobic, nonfermentative nonmotile, gram-negative rod. PCA grew in a defined medium with acetate as an electron donor and ferric PPi, ferric oxyhydroxide, ferric citrate, elemental sulfur, Co(III)-EDTA, fumarate, or malate as the sole electron acceptor. PCA also coupled the oxidation of hydrogen to the reduction of Fe(III) but did not reduce Fe(III) with sulfur, glucose, lactate, fumarate, propionate, butyrate, isobutyrate, isovalerate, succinate, yeast extract, phenol, benzoate, ethanol, propanol, or butanol as an electron donor. PCA did not reduce oxygen, Mn(IV), U(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PCA exhibited dithionite-reduced minus air-oxidized difference spectra which were characteristic of c-type cytochromes. Phylogenetic analysis of the 16S rRNA sequence placed PCA in the delta subgroup of the proteobacteria. Its closest known relative is Geobacter metallireducens. The ability to utilize either hydrogen or acetate as the sole electron donor for Fe(III) reduction makes strain PCA a unique addition to the relatively small group of respiratory metal-reducing microorganisms available in pure culture. A new species name, Geobacter sulfurreducens, is proposed. Images PMID:7527204

A hydrogen-oxidizing, Fe(III)-reducing microorganism from the Great Bay estuary, New Hampshire

USGS Publications Warehouse

Caccavo, F.; Blakemore, R.P.; Lovley, D.R.

1992-01-01

A dissimilatory Fe(III)- and Mn(IV)-reducing bacterium was isolated from bottom sediments of the Great Bay estuary, New Hampshire. The isolate was a facultatively anaerobic gram-negative rod which did not appear to fit into any previously described genus. It was temporarily designated strain BrY. BrY grew anaerobically in a defined medium with hydrogen or lactate as the electron donor and Fe(III) as the electron acceptor. BrY required citrate, fumarate, or malate as a carbon source for growth on H2 and Fe(III). With Fe(III) as the sole electron acceptor, BrY metabolized hydrogen to a minimum threshold at least 60-fold lower than the threshold reported for pure cultures of sulfate reducers. This finding supports the hypothesis that when Fe(III) is available, Fe(III) reducers can outcompete sulfate reducers for electron donors. Lactate was incompletely oxidized to acetate and carbon dioxide with Fe(III) as the electron acceptor. Lactate oxidation was also coupled to the reduction of Mn(IV), U(VI), fumarate, thiosulfate, or trimethylamine n-oxide under anaerobic conditions. BrY provides a model for how enzymatic metal reduction by respiratory metal-reducing microorganisms has the potential to contribute to the mobilization of iron and trace metals and to the immobilization of uranium in sediments of Great Bay Estuary.

Oxygen-Dependent Growth of the Sulfate-Reducing Bacterium Desulfovibrio oxyclinae in Coculture with Marinobacter sp. Strain MB in an Aerated Sulfate-Depleted Chemostat

PubMed Central

Sigalevich, Pavel; Cohen, Yehuda

2000-01-01

A chemostat coculture of the sulfate-reducing bacterium Desulfovibrio oxyclinae and the facultatively aerobic heterotroph Marinobacter sp. strain MB was grown for 1 week under anaerobic conditions at a dilution rate of 0.05 h−1. It was then exposed to an oxygen flux of 223 μmol min−1 by gassing the growth vessel with 5% O2. Sulfate reduction persisted under these conditions, though the amount of sulfate reduced decreased by 45% compared to the amount reduced during the initial anaerobic mode. After 1 week of growth under these conditions, sulfate was excluded from the incoming medium. The sulfate concentration in the growth vessel decreased exponentially from 4.1 mM to 2.5 μM. The coculture consumed oxygen effectively, and no residual oxygen was detected during either growth mode in which oxygen was supplied. The proportion of D. oxyclinae cells in the coculture as determined by in situ hybridization decreased from 86% under anaerobic conditions to 70% in the microaerobic sulfate-reducing mode and 34% in the microaerobic sulfate-depleted mode. As determined by the most-probable-number (MPN) method, the numbers of viable D. oxyclinae cells during the two microaerobic growth modes decreased compared to the numbers during the anaerobic growth mode. However, there was no significant difference between the MPN values for the two modes when oxygen was supplied. The patterns of consumption of electron donors and acceptors suggested that when oxygen was supplied in the absence of sulfate and thiosulfate, D. oxyclinae performed incomplete aerobic oxidation of lactate to acetate. This is the first observation of oxygen-dependent growth of a sulfate-reducing bacterium in the absence of either sulfate or thiosulfate. Cells harvested during the microaerobic sulfate-depleted stage and exposed to sulfate and thiosulfate in a respiration chamber were capable of anaerobic sulfate and thiosulfate reduction. PMID:11055958

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Neal X., E-mail: xuechen@iupui.edu; O’Neill, Kalisha; Akl, Nader Kassis

Highlights: • High phosphorus can induce calcification of adipocytes, even when fully differentiated. • Adipocytes can induce vascular calcification in an autocrine manner. • Sodium thiosulfate inhibits adipocyte calcification. - Abstract: Background: Calcification can occur in fat in multiple clinical conditions including in the dermis, breasts and in the abdomen in calciphylaxis. All of these are more common in patients with advanced kidney disease. Clinically, hyperphosphatemia and obesity are risk factors. Thus we tested the hypothesis that adipocytes can calcify in the presence of elevated phosphorus and/or that adipocytes exposed to phosphorus can induce vascular smooth muscle cell (VSMC) calcification.more » Methods: 3T3-L1 preadipocytes were induced into mature adipocytes and then treated with media containing high phosphorus. Calcification was assessed biochemically and PCR performed to determine the expression of genes for osteoblast and adipocyte differentiation. Adipocytes were also co-cultured with bovine VSMC to determine paracrine effects, and the efficacy of sodium thiosulfate was determined. Results: The results demonstrated that high phosphorus induced the calcification of differentiated adipocytes with increased expression of osteopontin, the osteoblast transcription factor Runx2 and decreased expression of adipocyte transcription factors peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT-enhancer-binding protein α (CEBPα), indicating that high phosphorus led to a phenotypic switch of adipocytes to an osteoblast like phenotype. Sodium thiosulfate, dose dependently decreased adipocyte calcification and inhibited adipocyte induced increase of VSMC calcification. Co-culture studies demonstrated that adipocytes facilitated VSMC calcification partially mediated by changes of secretion of leptin and vascular endothelial growth factor (VEGF) from adipocytes. Conclusion: High phosphorus induced calcification of mature adipocytes, and adipocytes exposed to elevated phosphorus can induce calcification of VSMC in a paracrine manner. Sodium thiosulfate inhibited this calcification and decreased the secretin of leptin and VEGF from adipocytes. These results suggest that adipocyte exposure to elevated phosphorus may be a pathogenic factor in calcification observed in the skin in calciphylaxis and other diseases.« less

Sodium thiosulfate protects brain in rat model of adenine induced vascular calcification.

PubMed

Subhash, N; Sriram, R; Kurian, Gino A

2015-11-01

Vascular bed calcification is a common feature of ends stage renal disease that may lead to a complication in cardiovascular and cerebrovascular beds, which is a promoting cause of myocardial infarction, stroke, dementia and aneurysms. Sodium thiosulfate (STS) due to its multiple properties such as antioxidant and calcium chelation has been reported to prevent vascular calcification in uremic rats, without mentioning its impact on cerebral function. Moreover, the previous studies have not explored the effect of STS on the mitochondrial dysfunction, one of the main pathophysiological features associated with the disease and the main site for STS metabolism. The present study addresses this limitation by using a rat model where 0.75% adenine was administered to induce vascular calcification and 400 mg/kg b wt. of STS was given as preventive and curative agent. The blood and urine chemistries along with histopathology of aorta confirms the renal protective effect of STS in two modes of administration. The brain oxidative stress assessment was made through TBARS level, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, found to be in the near normal level. STS administration not only reduced the mitochondrial oxidative stress (measured by TBARS, SOD, GPx and CAT) but also preserved the mitochondrial respiratory enzyme activities (NADH dehydrogenase, Succinate dehydrogenase and Malate dehydrogenase) and its physiology (measured by P/O ratio and RCR). In fact, the protective effect of STS was prominent, when it was administered as a curative agent, where low H2S and high thiosulfate level was observed along with low cystathionine β synthase activity, confirms thiosulfate mediated renal protection. In conclusion, STS when given after induction of calcification is protective to the brain by preserving its mitochondria, compared to the treatment given concomitantly. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sulfur-Mediated Electron Shuttling Sustains Microbial Long-Distance Extracellular Electron Transfer with the Aid of Metallic Iron Sulfides.

PubMed

Kondo, Katsuhito; Okamoto, Akihiro; Hashimoto, Kazuhito; Nakamura, Ryuhei

2015-07-07

In addition to serving as an energy source for microbial growth, iron sulfides are proposed to act as naturally occurring electrical wires that mediate long-distance extracellular electron transfer (EET) and bridge spatially discrete redox environments. These hypothetical EET reactions stand on the abilities of microbes to use the interfacial electrochemistry of metallic/semiconductive iron sulfides to maintain metabolisms; however, the mechanisms of these phenomena remain unexplored. To obtain insight into EET to iron sulfides, we monitored EET at the interface between Shewanella oneidensis MR-1 cells and biomineralized iron sulfides in an electrochemical cell. Respiratory current steeply increased with the concomitant formation of poorly crystalline mackinawite (FeS) minerals, indicating that S. oneidensis has the ability to exploit extracellularly formed metallic FeS for long-distance EET. Deletion of major proteins of the metal-reduction (Mtr) pathway (OmcA, MtrC, CymA, and PilD) caused only subtle effects on the EET efficiency, a finding that sharply contrasts the majority of studies that report that the Mtr pathway is indispensable for the reduction of metal oxides and electrodes. The gene expression analyses of polysulfide and thiosulfate reductase suggest the existence of a sulfur-mediated electron-shuttling mechanism by which HS(-) ions and water-soluble polysulfides (HS(n)(-), where n ≥ 2) generated in the periplasmic space deliver electrons from cellular metabolic processes to cell surface-associated FeS. The finding of this Mtr-independent pathway indicates that polysulfide reductases complement the function of outer-membrane cytochromes in EET reactions and, thus, significantly expand the number of microbial species potentially capable of long-distance EET in sulfur-rich anoxic environments.

Mitochondrial rhodanese: membrane-bound and complexed activity.

PubMed

Ogata, K; Volini, M

1990-05-15

We have proposed that phosphorylated and dephosphorylated forms of the mitochondrial sulfurtransferase, rhodanese, function as converter enzymes that interact with membrane-bound iron-sulfur centers of the electron transport chain to modulate the rate of mitochondrial respiration (Ogata, K., Dai, X., and Volini, M. (1989) J. Biol. Chem. 204, 2718-2725). In the present studies, we have explored some structural aspects of the mitochondrial rhodanese system. By sequential extraction of lysed mitochondria with phosphate buffer and phosphate buffer containing 20 mM cholate, we have shown that 30% of the rhodanese activity of bovine liver is membrane-bound. Resolution of cholate extracts on Sephadex G-100 indicates that part of the bound rhodanese is complexed with other mitochondrial proteins. Tests with the complex show that it forms iron-sulfur centers when incubated with the rhodanese sulfur-donor substrate thiosulfate, iron ions, and a reducing agent. Experiments on the rhodanese activity of rat liver mitochondria give similar results. Taken together, the findings indicate that liver rhodanese is in part bound to the mitochondrial membrane as a component of a multiprotein complex that forms iron-sulfur centers. The findings are consistent with the role we propose for rhodanese in the modulation of mitochondrial respiratory activity.

Analysis of gold(I/III)-complexes by HPLC-ICP-MS demonstrates gold(III) stability in surface waters.

PubMed

Ta, Christine; Reith, Frank; Brugger, Joël; Pring, Allan; Lenehan, Claire E

2014-05-20

Understanding the form in which gold is transported in surface- and groundwaters underpins our understanding of gold dispersion and (bio)geochemical cycling. Yet, to date, there are no direct techniques capable of identifying the oxidation state and complexation of gold in natural waters. We present a reversed phase ion-pairing HPLC-ICP-MS method for the separation and determination of aqueous gold(III)-chloro-hydroxyl, gold(III)-bromo-hydroxyl, gold(I)-thiosulfate, and gold(I)-cyanide complexes. Detection limits for the gold species range from 0.05 to 0.30 μg L(-1). The [Au(CN)2](-) gold cyanide complex was detected in five of six waters from tailings and adjacent monitoring bores of working gold mines. Contrary to thermodynamic predictions, evidence was obtained for the existence of Au(III)-complexes in circumneutral, hypersaline waters of a natural lake overlying a gold deposit in Western Australia. This first direct evidence for the existence and stability of Au(III)-complexes in natural surface waters suggests that Au(III)-complexes may be important for the transport and biogeochemical cycling of gold in surface environments. Overall, these results show that near-μg L(-1) enrichments of Au in environmental waters result from metastable ligands (e.g., CN(-)) as well as kinetically controlled redox processes leading to the stability of highly soluble Au(III)-complexes.

Pyrobaculum igneiluti sp. nov., a novel anaerobic hyperthermophilic archaeon that reduces thiosulfate and ferric iron.

PubMed

Lee, Jerry Y; Iglesias, Brenda; Chu, Caleb E; Lawrence, Daniel J P; Crane, Edward Jerome

2017-06-01

A novel anaerobic, hyperthermophilic archaeon was isolated from a mud volcano in the Salton Sea geothermal system in southern California, USA. The isolate, named strain 521T, grew optimally at 90 °C, at pH 5.5-7.3 and with 0-2.0 % (w/v) NaCl, with a generation time of 10 h under optimal conditions. Cells were rod-shaped and non-motile, ranging from 2 to 7 µm in length. Strain 521T grew only in the presence of thiosulfate and/or Fe(III) (ferrihydrite) as terminal electron acceptors under strictly anaerobic conditions, and preferred protein-rich compounds as energy sources, although the isolate was capable of chemolithoautotrophic growth. 16S rRNA gene sequence analysis places this isolate within the crenarchaeal genus Pyrobaculum. To our knowledge, this is the first Pyrobaculum strain to be isolated from an anaerobic mud volcano and to reduce only either thiosulfate or ferric iron. An in silico genome-to-genome distance calculator reported <25 % DNA-DNA hybridization between strain 521T and eight other Pyrobaculum species. Due to its genotypic and phenotypic differences, we conclude that strain 521T represents a novel species, for which the name Pyrobaculum igneiluti sp. nov. is proposed. The type strain is 521T (=DSM 103086T=ATCC TSD-56T).

Metagenomic analysis of denitrifying wastewater enrichment cultures able to transform the explosive, 3-nitro-1,2,4-triazol-5-one (NTO).

PubMed

Eberly, Jed O; Indest, Karl J; Hancock, Dawn E; Jung, Carina M; Crocker, Fiona H

2016-06-01

Removal of 3-nitro-1,2,4-triazol-5-one (NTO) was investigated in conjunction with heterotrophic and autotrophic denitrifying growth conditions by a microbial consortium from a wastewater treatment plant. Microcosms were supplemented with molasses, methanol, or thiosulfate. Cultures were passaged twice by transferring 10 % of the culture volume to fresh media on days 11 and 21. Rates of NTO removal were 18.71 ± 0.65, 9.04 ± 2.61, and 4.34 ± 2.72 mg/L/day while rates of nitrate removal were 20.08 ± 1.13, 21.58 ± 1.20, and 24.84 ± 1.26 mg/L/day, respectively, for molasses, methanol, or thiosulfate. Metagenomic analysis showed that Proteobacteria and Firmicutes were the major phyla in the microbial communities. In molasses supplemented cultures, the community profile at the family level changed over time with Pseudomonadaceae the most abundant (67.4 %) at day 11, Clostridiaceae (65.7 %) at day 21, and Sporolactobacillaceae (35.4 %) and Clostridiaceae (41.0 %) at day 29. Pseudomonadaceae was the dominant family in methanol and thiosulfate supplemented cultures from day 21 to 29 with 76.6 and 81.6 % relative abundance, respectively.

Cytochromes and iron sulfur proteins in sulfur metabolism of phototrophic bacteria

NASA Technical Reports Server (NTRS)

Fischer, U.

1985-01-01

Dissimilatory sulfur metabolism in phototrophic sulfur bacteria provides the bacteria with electrons for photosynthetic electron transport chain and, with energy. Assimilatory sulfate reduction is necessary for the biosynthesis of sulfur-containing cell components. Sulfide, thiosulfate, and elemental sulfur are the sulfur compounds most commonly used by phototrophic bacteria as electron donors for anoxygenic photosynthesis. Cytochromes or other electron transfer proteins, like high-potential-iron-sulfur protein (HIPIP) function as electron acceptors or donors for most enzymatic steps during the oxidation pathways of sulfide or thiosulfate. Yet, heme- or siroheme-containing proteins themselves undergo enzymatic activities in sulfur metabolism. Sirohemes comprise a porphyrin-like prosthetic group of sulfate reductase. eenzymatic reactions involve electron transfer. Electron donors or acceptors are necessary for each reaction. Cytochromes and iron sulfur problems, are able to transfer electrons.

Microbial colonization and growth on metal sulfides and other mineral surfaces

NASA Technical Reports Server (NTRS)

Caldwell, D.; Sundquist, A. R.; Lawrence, J.; Doyle, A. P.

1985-01-01

To determine whether a bacterial film forms on sulfur minerals in situ, various sulfur containing and other minerals were incubated in Penitencia Creek. The rate of cell growth and attachment within the surface microenvironment of mineral surfaces was also determined. To determine whether surfaces enriched with soluble sulfur substrates (cysteine, glutathione, thioglycolate, sulfite, and thiosulfate) increased the rate of growth or attachment of natural communities, membrane enrichments were incubated. These rates were determined as described by Caldwell et al. (1981, 1983). The growth of Pseudomonas fluorescens, a heterotrophic sulfur oxidizer, was studied in batch cell suspensions and in continuous culture. In batch culture the cells were oxygen limited (growth rate 0.33 per hour under oxygen limitations and 0.52 per hour when vigorously aerated). Growth within the film was glucose limited. Several behavioral phenomena were observed for cells growing within the hydrodynamic boundary layer. Despite a flow of 10 cm per second in the environment, the bacteria were able to move freely in both directions within the hydrodynamic boundary layer.

Simultaneous production of bio-ethanol and bleached pulp from red algae.

PubMed

Yoon, Min Ho; Lee, Yoon Woo; Lee, Chun Han; Seo, Yung Bum

2012-12-01

The red algae, Gelidium corneum, was used to produce bleached pulp for papermaking and ethanol. Aqueous extracts obtained at 100-140 °C were subjected to saccharification, purification, fermentation, and distillation to produce ethanol. The solid remnants were bleached with chlorine dioxide and peroxide to make pulp. In the extraction process, sulfuric acid and sodium thiosulfate were added to increase the extract yield and to improve de-polymerization of the extracts, as well as to generate high-quality pulp. An extraction process incorporating 5% sodium thiosulfate by dry weight of the algae provided optimal production conditions for the production of both strong pulp and a high ethanol yield. These results suggest that it might be possible to utilize algae instead of trees and starch for pulp and ethanol production, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Primary hepatocytes from mice lacking cysteine dioxygenase show increased cysteine concentrations and higher rates of metabolism of cysteine to hydrogen sulfide and thiosulfate

PubMed Central

Jurkowska, Halina; Roman, Heather B.; Hirschberger, Lawrence L.; Sasakura, Kiyoshi; Nagano, Tetsuo; Hanaoka, Kenjiro; Krijt, Jakub

2016-01-01

The oxidation of cysteine in mammalian cells occurs by two routes: a highly regulated direct oxidation pathway in which the first step is catalyzed by cysteine dioxygenase (CDO) and by desulfhydration-oxidation pathways in which the sulfur is released in a reduced oxidation state. To assess the effect of a lack of CDO on production of hydrogen sulfide (H2S) and thiosulfate (an intermediate in the oxidation of H2S to sulfate) and to explore the roles of both cystathionine γ-lyase (CTH) and cystathionine β-synthase (CBS) in cysteine desulfhydration by liver, we investigated the metabolism of cysteine in hepatocytes isolated from Cdo1-null and wild-type mice. Hepatocytes from Cdo1-null mice produced more H2S and thiosulfate than did hepatocytes from wild-type mice. The greater flux of cysteine through the cysteine desulfhydration reactions catalyzed by CTH and CBS in hepatocytes from Cdo1-null mice appeared to be the consequence of their higher cysteine levels, which were due to the lack of CDO and hence lack of catabolism of cysteine by the cysteinesulfinate-dependent pathways. Both CBS and CTH appeared to contribute substantially to cysteine desulfhydration, with estimates of 56 % by CBS and 44 % by CTH in hepatocytes from wild-type mice, and 63 % by CBS and 37 % by CTH in hepatocytes from Cdo1-null mice. PMID:24609271

Influence of sulfur oxyanions on reductive dehalogenation activities in Desulfomonile tiedjei.

PubMed Central

Townsend, G T; Suflita, J M

1997-01-01

The inhibition of aryl reductive dehalogenation reactions by sulfur oxyanions has been demonstrated in environmental samples, dehalogenating enrichments, and the sulfate-reducing bacterium Desulfomonile tiedjei; however, this phenomenon is not well understood. We examined the effects of sulfate, sulfite, and thiosulfate on reductive dehalogenation in the model microorganism D. tiedjei and found separate mechanisms of inhibition due to these oxyanions under growth versus nongrowth conditions. Dehalogenation activity was greatly reduced in extracts of cells grown in the presence of both 3-chlorobenzoate, the substrate or inducer for the aryl dehalogenation activity, and either sulfate, sulfite, or thiosulfate, indicating that sulfur oxyanions repress the requisite enzymes. In extracts of fully induced cells, thiosulfate and sulfite, but not sulfate, were potent inhibitors of aryl dehalogenation activity even in membrane fractions lacking the cytoplasmically located sulfur oxyanion reductase. These results suggest that under growth conditions, sulfur oxyanions serve as preferred electron acceptors and negatively influence dehalogenation activity in D. tiedjei by regulating the amount of active aryl dehalogenase in cells. Additionally, in vitro inhibition by sulfur oxyanions is due to the interaction of the reactive species with enzymes involved in dehalogenation and need not involve competition between two respiratory processes for reducing equivalents. Sulfur oxyanions also inhibited tetrachloroethylene dehalogenation by the same mechanisms, further indicating that chloroethylenes are fortuitously dehalogenated by the aryl dehalogenase. The commonly observed inhibition of reductive dehalogenation reactions under sulfate-reducing conditions may be due to similar regulation mechanisms in other dehalogenating microorganisms that contain multiple respiratory activities. PMID:9293011

Elemental sulfur and thiosulfate disproportionation by Desulfocapsa sulfoexigens sp. nov., a new anaerobic bacterium isolated from marine surface sediment.

PubMed

Finster, K; Liesack, W; Thamdrup, B

1998-01-01

A mesophilic, anaerobic, gram-negative bacterium, strain SB164P1, was enriched and isolated from oxidized marine surface sediment with elemental sulfur as the sole energy substrate in the presence of ferrihydrite. Elemental sulfur was disproportionated to hydrogen sulfide and sulfate. Growth was observed exclusively in the presence of a hydrogen sulfide scavenger, e.g., ferrihydrite. In the absence of a scavenger, sulfide and sulfate production were observed but no growth occurred. Strain SB164P1 grew also by disproportionation of thiosulfate and sulfite. With thiosulfate, the growth efficiency was higher in ferrihydrite-supplemented media than in media without ferrihydrite. Growth coupled to sulfate reduction was not observed. However, a slight sulfide production occurred in cultures incubated with formate and sulfate. Strain SB164P1 is the first bacterium described that grows chemolithoautotrophically exclusively by the disproportionation of inorganic sulfur compounds. Comparative 16S rDNA sequencing analysis placed strain SB164P1 into the delta subclass of the class Proteobacteria. Its closest relative is Desulfocapsa thiozymogenes, and slightly more distantly related are Desulfofustis glycolicus and Desulforhopalus vacuolatus. This phylogenetic cluster of organisms, together with members of the genus Desulfobulbus, forms one of the main lines of descent within the delta subclass of the Proteobacteria. Due to the common phenotypic characteristics and the phylogenetic relatedness to Desulfocapsa thiozymogenes, we propose that strain SB164P1 be designated the type strain of Desulfocapsa sulfoexigens sp. nov.

Elemental Sulfur and Thiosulfate Disproportionation by Desulfocapsa sulfoexigens sp. nov., a New Anaerobic Bacterium Isolated from Marine Surface Sediment

PubMed Central

Finster, Kai; Liesack, Werner; Thamdrup, Bo

1998-01-01

A mesophilic, anaerobic, gram-negative bacterium, strain SB164P1, was enriched and isolated from oxidized marine surface sediment with elemental sulfur as the sole energy substrate in the presence of ferrihydrite. Elemental sulfur was disproportionated to hydrogen sulfide and sulfate. Growth was observed exclusively in the presence of a hydrogen sulfide scavenger, e.g., ferrihydrite. In the absence of a scavenger, sulfide and sulfate production were observed but no growth occurred. Strain SB164P1 grew also by disproportionation of thiosulfate and sulfite. With thiosulfate, the growth efficiency was higher in ferrihydrite-supplemented media than in media without ferrihydrite. Growth coupled to sulfate reduction was not observed. However, a slight sulfide production occurred in cultures incubated with formate and sulfate. Strain SB164P1 is the first bacterium described that grows chemolithoautotrophically exclusively by the disproportionation of inorganic sulfur compounds. Comparative 16S rDNA sequencing analysis placed strain SB164P1 into the delta subclass of the class Proteobacteria. Its closest relative is Desulfocapsa thiozymogenes, and slightly more distantly related are Desulfofustis glycolicus and Desulforhopalus vacuolatus. This phylogenetic cluster of organisms, together with members of the genus Desulfobulbus, forms one of the main lines of descent within the delta subclass of the Proteobacteria. Due to the common phenotypic characteristics and the phylogenetic relatedness to Desulfocapsa thiozymogenes, we propose that strain SB164P1 be designated the type strain of Desulfocapsa sulfoexigens sp. nov. PMID:9435068

Structural and biochemical analyses indicate that a bacterial persulfide dioxygenase–rhodanese fusion protein functions in sulfur assimilation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Motl, Nicole; Skiba, Meredith A.; Kabil, Omer

Hydrogen sulfide (H2S) is a signaling molecule that is toxic at elevated concentrations. In eukaryotes, it is cleared via a mitochondrial sulfide oxidation pathway, which comprises sulfide quinone oxidoreductase, persulfide dioxygenase (PDO), rhodanese, and sulfite oxidase and converts H2S to thiosulfate and sulfate. Natural fusions between the non-heme iron containing PDO and rhodanese, a thiol sulfurtransferase, exist in some bacteria. However, little is known about the role of the PDO–rhodanese fusion (PRF) proteins in sulfur metabolism. Herein, we report the kinetic properties and the crystal structure of a PRF from the Gram-negative endophytic bacterium Burkholderia phytofirmans. The crystal structures ofmore » wild-type PRF and a sulfurtransferase-inactivated C314S mutant with and without glutathione were determined at 1.8, 2.4, and 2.7 Å resolution, respectively. We found that the two active sites are distant and do not show evidence of direct communication. The B. phytofirmans PRF exhibited robust PDO activity and preferentially catalyzed sulfur transfer in the direction of thiosulfate to sulfite and glutathione persulfide; sulfur transfer in the reverse direction was detectable only under limited turnover conditions. Together with the kinetic data, our bioinformatics analysis reveals that B. phytofirmans PRF is poised to metabolize thiosulfate to sulfite in a sulfur assimilation pathway rather than in sulfide stress response as seen, for example, with the Staphylococcus aureus PRF or sulfide oxidation and disposal as observed with the homologous mammalian proteins.« less

Computer-assisted Crystallization.

ERIC Educational Resources Information Center

Semeister, Joseph J., Jr.; Dowden, Edward

1989-01-01

To avoid a tedious task for recording temperature, a computer was used for calculating the heat of crystallization for the compound sodium thiosulfate. Described are the computer-interfacing procedures. Provides pictures of laboratory equipment and typical graphs from experiments. (YP)

Synthesis of a thiol-β-cyclodextrin, a potential agent for controlling enzymatic browning in fruits and vegetables.

PubMed

Manta, Carmen; Peralta-Altier, Gabriela; Gioia, Larissa; Méndez, María F; Seoane, Gustavo; Ovsejevi, Karen

2013-11-27

A thiol-β-cyclodextrin was synthesized by a simple and environmentally friendly three-step method comprising epoxy activation of β-cyclodextrin, thiosulfate-mediated oxirane opening, and further reduction of the S-alkyl thiosulfate to a thiol group. The final step was optimized by using thiopropyl-agarose, a solid phase reducing agent with many advantages over soluble ones. β-Cyclodextrin thiolation was confirmed by titration with a thiol-reactive reagent, NMR studies, and MALDI-TOF/TOF. Thiolated cyclodextrin had an average value of one thiol group per molecule. Thiol-β-cyclodextrin proved to be an excellent agent for controlling polyphenol oxidase activity. This copper-containing enzyme is responsible for browning in fruits and vegetables. Under the same conditions, thiol-β-cyclodextrin generated a reductive microenvironment that increased the antibrowning effect on Red Delicious apples compared to unmodified β-cyclodextrin.

Insight into the molecular mechanism of the sulfur oxidation process by reverse sulfite reductase (rSiR) from sulfur oxidizer Allochromatium vinosum.

PubMed

Ghosh, Semanti; Bagchi, Angshuman

2018-04-26

Sulfur metabolism is one of the oldest known biochemical processes. Chemotrophic or phototrophic proteobacteria, through the dissimilatory pathway, use sulfate, sulfide, sulfite, thiosulfate or elementary sulfur by either reductive or oxidative mechanisms. During anoxygenic photosynthesis, anaerobic sulfur oxidizer Allochromatium vinosum forms sulfur globules that are further oxidized by dsr operon. One of the key redox enzymes in reductive or oxidative sulfur metabolic pathways is the DsrAB protein complex. However, there are practically no reports to elucidate the molecular mechanism of the sulfur oxidation process by the DsrAB protein complex from sulfur oxidizer Allochromatium vinosum. In the present context, we tried to analyze the structural details of the DsrAB protein complex from sulfur oxidizer Allochromatium vinosum by molecular dynamics simulations. The molecular dynamics simulation results revealed the various types of molecular interactions between DsrA and DsrB proteins during the formation of DsrAB protein complex. We, for the first time, predicted the mode of binding interactions between the co-factor and DsrAB protein complex from Allochromatium vinosum. We also compared the binding interfaces of DsrAB from sulfur oxidizer Allochromatium vinosum and sulfate reducer Desulfovibrio vulgaris. This study is the first to provide a comparative aspect of binding modes of sulfur oxidizer Allochromatium vinosum and sulfate reducer Desulfovibrio vulgaris.

Electrodeposition and characterization of ZnO thin films using sodium thiosulfate as an additive for photovoltaic solar cells

NASA Astrophysics Data System (ADS)

Rahal, Hassiba; Kihal, Rafiaa; Affoune, Abed Mohamed; Ghers, Mokhtar; Djazi, Faycal

2017-06-01

Zinc oxide thin films have been grown by electrodeposition technique onto Cu and ITO-coated glass substrates from an aqueous zinc nitrate solution with addition of sodium thiosulfate at 90 °C. The effects of sodium thiosulfate on the electrochemical deposition of ZnO were investigated by cyclic voltammetry and chronoamperometry techniques. Deposited films were obtained at -0.60 V vs. SCE and characterized by XRD, SEM, FTIR, optical, photoelectrochemical and electrical measurements. Thickness of the deposited film was measured to be 357 nm. X-ray diffraction results indicated that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along (002) plane. FTIR results confirmed the presence of ZnO films at peak 558 cm-1. SEM images showed uniform, compact morphology without any cracks and films composed of large flower-like ZnO agglomerates with star-shape. Optical properties of ZnO reveal a high optical transmission (> 80 % ) and high absorption coefficient (α > {10}5 {{cm}}-1) in visible region. The optical energy band gap was found to be 3.28 eV. Photoelectrochemical measurements indicated that the ZnO films had n-type semiconductor conduction. Electrical properties of ZnO films showed a low electrical resistivity of 6.54 {{Ω }}\\cdot {cm}, carrier concentration of -1.3× {10}17 {{cm}}-3 and mobility of 7.35 cm2 V-1 s-1. Project supported by the Algerian Ministry of Higher Education and Scientific Research, Algeria (No. J0101520090018).

A distal ligand mutes the interaction of hydrogen sulfide with human neuroglobin

PubMed Central

Ruetz, Markus; Kumutima, Jacques; Lewis, Brianne E.; Filipovic, Milos R.; Lehnert, Nicolai; Stemmler, Timothy L.; Banerjee, Ruma

2017-01-01

Hydrogen sulfide is a critical signaling molecule, but high concentrations cause cellular toxicity. A four-enzyme pathway in the mitochondrion detoxifies H2S by converting it to thiosulfate and sulfate. Recent studies have shown that globins like hemoglobin and myoglobin can also oxidize H2S to thiosulfate and hydropolysulfides. Neuroglobin, a globin enriched in the brain, was reported to bind H2S tightly and was postulated to play a role in modulating neuronal sensitivity to H2S in conditions such as stroke. However, the H2S reactivity of the coordinately saturated heme in neuroglobin is expected a priori to be substantially lower than that of the 5-coordinate hemes present in myoglobin and hemoglobin. To resolve this discrepancy, we explored the role of the distal histidine residue in muting the reactivity of human neuroglobin toward H2S. Ferric neuroglobin is slowly reduced by H2S and catalyzes its inefficient oxidative conversion to thiosulfate. Mutation of the distal His64 residue to alanine promotes rapid binding of H2S and its efficient conversion to oxidized products. X-ray absorption, EPR, and resonance Raman spectroscopy highlight the chemically different reaction options influenced by the distal histidine ligand. This study provides mechanistic insights into how the distal heme ligand in neuroglobin caps its reactivity toward H2S and identifies by cryo-mass spectrometry a range of sulfide oxidation products with 2–6 catenated sulfur atoms with or without oxygen insertion, which accumulate in the absence of the His64 ligand. PMID:28246171

Characterization and mediation of microbial deterioration of concrete bridge structures.

DOT National Transportation Integrated Search

2013-04-01

Samples obtained from deteriorated bridge structures in Texas were cultured in growth medium containing thiosulfate as an energy source and investigated for acid production, type of acid produced by microbes and the bio-deterioration of concrete cyli...

Decomposition of water-soluble mononitrosyl iron complexes with dithiocarbamates and of dinitrosyl iron complexes with thiol ligands in animal organisms.

PubMed

Serezhenkov, Vladimir A; Timoshin, Alexander A; Orlova, Tsvetina R; Mikoyan, Vasak D; Kubrina, Lioudmila N; Poltorakov, Alexander P; Ruuge, Enno K; Sanina, Natalia A; Vanin, Anatoly F

2008-05-01

EPR studies have shown that water-soluble mononitrosyl iron complexes with N-methyl-d-glucamine dithiocarbamate (MNIC-MGD) (3 micromol) injected to intact mice were decomposed virtually completely within 1h. The total content of MNIC-MGD in animal urine did not exceed 30 nmol/ml. In the liver, a small amount of MNIC-MGD were converted into dinitrosyl iron complexes (30 nmol/g of liver tissue). The same was observed in intact rabbits in which MNIC-MGD formation was induced by endogenous or exogenous NO binding to NO traps, viz., iron complexes with MGD. In mice, the content of MNIC-MGD in urine samples did not change after bacterial lipopolysaccharide-induced expression of iNOS. It was supposed that MNIC-MGD decomposition in intact animals was largely due to the release of NO from the complexes and its further transfer to other specific acceptors. In mice with iNOS expression, the main contribution to MNIC-MGD decomposition was made by superoxide ions whose destructive effect is mediated by an oxidative mechanism. This effect could fully compensate the augmented synthesis of MNIC-MGD involving endogenous NO whose production was supported by iNOS. Water-soluble dinitrosyl iron complexes (DNIC) with various thiol-containing ligands and thiosulfate injected to intact mice were also decomposed; however, in this case the effect was less pronounced than in the case of MNIC-MGD. It was concluded that DNIC decomposition was largely due to the oxidative effect of superoxide ions on these complexes.

Information Management Systems in the Undergraduate Instrumental Analysis Laboratory.

ERIC Educational Resources Information Center

Merrer, Robert J.

1985-01-01

Discusses two applications of Laboratory Information Management Systems (LIMS) in the undergraduate laboratory. They are the coulometric titration of thiosulfate with electrogenerated triiodide ion and the atomic absorption determination of calcium using both analytical calibration curve and standard addition methods. (JN)

Enrichment of Desulfitobacterium spp. from forest and grassland soil using the O-demethylation of phenyl methyl ethers as a growth-selective process.

PubMed

Mingo, Felix Sebastian; Diekert, Gabriele; Studenik, Sandra

2016-02-01

The O-demethylation of phenyl methyl ethers under anaerobic conditions is a metabolic feature of acetogens and Desulfitobacterium spp. Desulfitobacteria as well as most acetogens are Gram-positive bacteria with a low GC content and belong to the phylum Firmicutes. The consumption of the phenyl methyl ether syringate was studied in enrichment cultures originating from five different topsoils. Desulfitobacterium spp. were detected in all topsoils via quantitative PCR. Desulfitobacteria could be enriched using the O-demethylation of syringate as a growth-selective process. The enrichment was significantly favoured by an external electron acceptor such as 3-chloro-4-hydroxyphenylacetate or thiosulfate. Upon cultivation in the presence of syringate and thiosulfate, which naturally occur in soil, a maximum number of 16S rRNA gene copies of Desulfitobacterium spp. was reached within the first three subcultivation steps and accounted for 3-10% of the total microbial community depending on the soil type. Afterwards, a loss of Desulfitobacterium gene copies was observed. Community analyses revealed that Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes were the main phyla in the initial soil samples. Upon addition of syringate and thiosulfate as growth substrates, these phyla were rapidly outcompeted by Firmicutes, which were under-represented in soil. The main Firmicutes genera identified were Alkalibaculum, Clostridium, Sporobacterium, Sporomusa and Tissierella, which might be responsible for outcompeting the desulfitobacteria. Most of these organisms belong to the acetogens, which have previously been described to demethylate phenyl methyl ethers. The shift of the native community structure to almost exclusively Firmicutes supports the participation of members of this phylum in environmental demethylation processes.

Pseudodesulfovibrio hydrargyri sp. nov., a mercury-methylating bacterium isolated from a brackish sediment.

PubMed

Ranchou-Peyruse, Magali; Goñi-Urriza, Marisol; Guignard, Marion; Goas, Marjorie; Ranchou-Peyruse, Anthony; Guyoneaud, Rémy

2018-05-01

The strain BerOc1 T was isolated from brackish sediments contaminated with hydrocarbons and heavy metals. This strain has been used as a model strain of sulfate-reducer to study the biomethylation of mercury. The cells are vibrio-shaped, motile and not sporulated. Phylogeny and physiological traits placed this strain within the genus Pseudodesulfovibrio. Optimal growth was obtained at 30 °C, 1.5 % NaCl and pH 6.0-7.4. The estimated G+C content of the genomic DNA was 62.6 mol%. BerOc1 T used lactate, pyruvate, fumarate, ethanol and hydrogen. Terminal electron acceptors used were sulfate, sulfite, thiosulfate and DMSO. Only pyruvate could be used without a terminal electron acceptor. The major fatty acids were C18 : 0, anteiso-C15 : 0, C16 : 0 and C18 : 1ω7. The name Pseudodesulfovibrio hydrargyri sp. nov. is proposed for the type strain BerOc1 T (DSM 10384 T =JCM 31820 T ).

Clock Reaction: Outreach Attraction

ERIC Educational Resources Information Center

Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

2010-01-01

Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

[Effect of cultivation conditions on the growth and activities of sulfur metabolism enzymes and carboxylases of Sulfobacillus thermosulfidooxidans subsp. asporogenes strain 41].

PubMed

Egorova, M A; Tsaplina, I A; Zakharchuk, L M; Bogdanova, T I; Krasil'nikova, E N

2004-01-01

The moderately thermophilic acidophilic bacterium Sulfobacillus thermosulfidooxidans subsp. asporogenes strain 41 is capable of utilizing sulfides of gold-arsenic concentrate and elemental sulfur as a source of energy. The growth in the presence of S0 under auto- or mixotrophic conditions was less stable compared with the media containing iron monoxide. The enzymes involved in oxidation of sulfur inorganic compounds--thiosulfate-oxidizing enzyme, tetrathionate hydrolase, rhodonase, adenylyl sulfate reductase, sulfite oxidase, and sulfur oxygenase--were discovered in the cells of Sulfobacillus grown in the mineral medium containing 0.02% yeast extract and either sulfur or iron monoxide and thiosulfate. Cell-free extracts of the cultures grown in the medium with sulfur under auto- or mixotrophic conditions displayed activity of the key enzyme of the Calvin cycle--ribulose bisphosphate carboxylase--and several other enzymes involved in heterotrophic fixation of carbonic acid. Activities of carboxylases depended on the composition of cultivation media.

Pattern formation in the iodate-sulfite-thiosulfate reaction-diffusion system.

PubMed

Liu, Haimiao; Pojman, John A; Zhao, Yuemin; Pan, Changwei; Zheng, Juhua; Yuan, Ling; Horváth, Attila K; Gao, Qingyu

2012-01-07

Sodium polyacrylate-induced pH pattern formation and starch-induced iodine pattern formation were investigated in the iodate-sulfite-thiosulfate (IST) reaction in a one-side fed disc gel reactor (OSFR). As binding agents of the autocatalyst of hydrogen ions or iodide ions, different content of sodium polyacrylate or starch has induced various types of pattern formation. We observed pH pulses, striped patterns, mixed spots and stripes, and hexagonal spots upon increasing the content of sodium polyacrylate and observed iodine pulses, branched patterns, and labyrinthine patterns upon increasing the starch content in the system. Coexistence of a pH front and an iodine front was also studied in a batch IST reaction-diffusion system. Both pH and iodine front instabilities were observed in the presence of sodium polyacrylate, i.e., cellular fronts and transient Turing structures resulting from the decrease in diffusion coefficients of activators. The mechanism of multiple feedback may explain the different patterns in the IST reaction-diffusion system.

Pitting Corrosion of alloy 690 in thiosulfate-containing chloride solutions

NASA Astrophysics Data System (ADS)

Tsai, Wen-Ta; Wu, Tsung-Feng

2000-01-01

The effects of thiosulfate ion and solution pH on pitting corrosion of Alloy 690 in chloride solution were explored. Potentiodynamic polarization measurements were conducted to evaluate pitting corrosion susceptibility of Alloy 690 in these environments. The results showed that pitting corrosion occurred in the mill-annealed (1050°C/5min) Alloy 690 in 1 wt% NaCl solution but not in 0.1 M Na 2S 2O 3 solution. The value of pitting nucleation potential ( Enp) determined in 1 wt% NaCl solution (without Na 2S 2O 3 ) increased with increasing solution pH value in the range of 2-10. The addition of Na 2S 2O 3 to 1 wt% NaCl solution greatly affected the pitting corrosion behavior, which was dependent on concentration. The preformed nickel sulfide surface film due to the presence of Na 2S 2O 3 caused Alloy 690 to become more susceptible to pitting corrosion in 1 wt% NaCl solution.

Draft genome sequence of Bosea sp. WAO an arsenite and sulfide oxidizer isolated from a pyrite rock outcrop in New Jersey.

PubMed

Walczak, Alexandra B; Yee, Nathan; Young, Lily Y

2018-01-01

This genome report describes the draft genome and physiological characteristics of Bosea sp. WAO (=DSM 102914), a novel strain of the genus Bosea in the family Bradyrhizobiaceae . Bosea sp. WAO was isolated from pulverized pyritic shale containing elevated levels of arsenic. This aerobic, gram negative microorganism is capable of facultative chemolithoautotrophic growth under aerobic conditions by oxidizing the electron donors arsenite, elemental sulfur, thiosulfate, polysulfide, and amorphous sulfur. The draft genome is of a single circular chromosome 6,125,776 bp long consisting of 21 scaffolds with a G + C content of 66.84%. A total 5727 genes were predicted of which 5665 or 98.92% are protein-coding genes and 62 RNA genes. We identified the genes aioA and aioB , which encode the large and small subunits of the arsenic oxidase respectively. We also identified the genes for the complete sulfur oxidation pathway sox which is used to oxidize thiosulfate to sulfate.

Sulfur-based autotrophic denitrification from the micro-polluted water.

PubMed

Zhou, Weili; Liu, Xu; Dong, Xiaojing; Wang, Zheng; Yuan, Ying; Wang, Hui; He, Shengbing

2016-06-01

Eutrophication caused by high concentrations of nutrients is a huge problem for many natural lakes and reservoirs. Removing the nitrogen contamination from the low C/N water body has become an urgent need. Autotrophic denitrification with the sulfur compound as electron donor was investigated in the biofilter reactors. Through the lab-scale experiment, it was found that different sulfur compounds and different carriers caused very different treatment performances. Thiosulfate was selected to be the best electron donor and ceramsite was chosen as the suitable carrier due to the good denitrification efficiency, low cost and the good resistibility against the high hydraulic loads. Later the optimum running parameters of the process were determined. Then the pilot-scale experiment was carried out with the real micro-polluted water from the West Lake, China. The results indicated that the autotrophic denitrification with thiosulfate as electron donor was feasible and applicable for the micro-polluted lake water. Copyright © 2016. Published by Elsevier B.V.

Nitrocobinamide, a New Cyanide Antidote That Can Be Administered by Intramuscular Injection

PubMed Central

Chan, Adriano; Jiang, Jingjing; Fridman, Alla; Guo, Ling T.; Shelton, G. Diane; Liu, Ming-Tao; Green, Carol; Haushalter, Kristofer J.; Patel, Hemal H.; Lee, Jangwoen; Yoon, David; Burney, Tanya; Mukai, David; Mahon, Sari B.; Brenner, Matthew; Pilz, Renate B.; Boss, Gerry R.

2015-01-01

Currently available cyanide antidotes must be given by intravenous injection over 5–10 min, making them illsuited for treating many people in the field, as could occur in a major fire, an industrial accident, or a terrorist attack. These scenarios call for a drug that can be given quickly, e.g., by intramuscular injection. We have shown that aquohydroxocobinamide is a potent cyanide antidote in animal models of cyanide poisoning, but it is unstable in solution and poorly absorbed after intramuscular injection. Here we show that adding sodium nitrite to cobinamide yields a stable derivative (referred to as nitrocobinamide) that rescues cyanide-poisoned mice and rabbits when given by intramuscular injection. We also show that the efficacy of nitrocobinamide is markedly enhanced by coadministering sodium thiosulfate (reducing the total injected volume), and we calculate that ∼1.4 mL each of nitrocobinamide and sodium thiosulfate should rescue a human from a lethal cyanide exposure. PMID:25650735

Application of a 2-step process for the biological treatment of sulfidic spent caustics.

PubMed

de Graaff, Marco; Klok, Johannes B M; Bijmans, Martijn F M; Muyzer, Gerard; Janssen, Albert J H

2012-03-01

This research demonstrates the feasibility and advantages of a 2-step process for the biological treatment of sulfidic spent caustics under halo-alkaline conditions (i.e. pH 9.5; Na(+) = 0.8 M). Experiments with synthetically prepared solutions were performed in a continuously fed system consisting of two gas-lift reactors in series operated at aerobic conditions at 35 °C. The detoxification of sulfide to thiosulfate in the first step allowed the successful biological treatment of total-S loading rates up to 33 mmol L(-1) day(-1). In the second, biological step, the remaining sulfide and thiosulfate was completely converted to sulfate by haloalkaliphilic sulfide oxidizing bacteria. Mathematical modeling of the 2-step process shows that under the prevailing conditions an optimal reactor configuration consists of 40% 'abiotic' and 60% 'biological' volume, whilst the total reactor volume is 22% smaller than for the 1-step process. Copyright © 2011 Elsevier Ltd. All rights reserved.

Genetic identification of thiosulfate sulfurtransferase as an adipocyte-expressed anti-diabetic target in mice selected for leanness

PubMed Central

Morton, Nicholas M.; Beltram, Jasmina; Carter, Roderick N.; Michailidou, Zoi; Gorjanc, Gregor; Fadden, Clare Mc; Barrios-Llerena, Martin E.; Rodriguez-Cuenca, Sergio; Gibbins, Matthew T. G.; Aird, Rhona E.; Moreno-Navarrete, José Maria; Munger, Steven C.; Svenson, Karen L.; Gastaldello, Annalisa; Ramage, Lynne; Naredo, Gregorio; Zeyda, Maximilian; Wang, Zhao V.; Howie, Alexander F.; Saari, Aila; Sipilä, Petra; Stulnig, Thomas M.; Gudnason, Vilmundur; Kenyon, Christopher J.; Seckl, Jonathan R.; Walker, Brian R.; Webster, Scott P.; Dunbar, Donald R.; Churchill, Gary A.; Vidal-Puig, Antonio; Fernandez-Real, José Manuel; Emilsson, Valur; Horvat, Simon

2017-01-01

Discovery of genetic mechanisms for resistance to obesity and diabetes may illuminate new therapeutic strategies for the treatment of this global health challenge. We used the polygenic Lean mouse model, selected for low adiposity over 60 generations, to identify thiosulfate sulfurtransferase (Tst, Rhodanese) as a candidate obesity-resistance gene with selectively increased adipocyte expression. Elevated adipose Tst expression correlated with indices of metabolic health across diverse mouse strains. Transgenic overexpression of Tst in adipocytes protected mice from diet-induced obesity and insulin-resistant diabetes. Tst gene deficiency markedly exacerbated diabetes whereas pharmacological TST activation ameliorated diabetes in mice in vivo. Mechanistically, TST selectively augmented mitochondrial function combined with degradation of reactive oxygen species and sulfide. In humans, adipose TST mRNA correlated positively with adipose insulin sensitivity and negatively with fat mass. Genetic identification of Tst as a beneficial regulator of adipocyte mitochondrial function may have therapeutic significance for type 2 diabetes. PMID:27270587

RENAL TUBULAR TRANSPORT OF INORGANIC DIVALENT IONS BY THE AGLOMERULAR MARINE TELEOST, LOPHIUS AMERICANUS

PubMed Central

Berglund, Fredrik; Forster, Roy P.

1958-01-01

A characterization was attempted of the mechanisms involved in the tubular transport of inorganic divalent ions by the aglomerular kidney of Lophius, attention being paid particularly to the possible existence of transport maxima (Tm) and to competition for transport among related substances undergoing tubular excretion. Excretory rates of divalent ions in non-treated fish during standard laboratory conditions paralleled spontaneous changes in urine flow. Tm rates of excretion were reached for magnesium, sulfate, and thiosulfate with corresponding plasma levels of 2 to 5, 5 to 17, and 4 to 12 µM/ml. respectively. Elevation of magnesium chloride levels in plasma markedly depressed calcium excretion; sodium thiosulfate similarly depressed sulfate excretion. Experimental observations suggest the existence of a transport system for divalent cations separate from another for divalent anions. Within each transport system the ion with the higher excretion rate depressed competitively transfer of the other ion. Neither system was influenced by probenecid (benemid) in doses which markedly depressed the simultaneous excretion rate of p-aminohippuric acid. PMID:13491814

Reduction of Cr(VI) to Cr(III) in Artificially-Contaminated Soil using Chemical Reagents

NASA Astrophysics Data System (ADS)

Kostarelos, Konstantinos; Rao, Ennio; Reale, Daniela

2010-05-01

The presence of hexavalent chromium (CrVI) in soil is an environmental concern due to its effect on human health. The concern arises from the leaching and the seepage of Cr(VI) from soil to groundwater. A remediation approach that has been studied in the literature is that of reducing the hexavalent chromium to its trivalent form using a chemical reagent, namely ferrous sulfate heptahydrate (FeSO4.7H20). In this study, we compared performance of ferrous sulfate heptahydrate to sodium thiosulfate (Na2S2O3), a less costly reductant. The means of measuring the performance of the reductants is the US EPA's Toxicity Characteristic Leaching Procedure (TCLP), which states that the total chromium release from the soil must be less than 5 ppm. Because this treatment approach is pH sensitive and thus, susceptible to acid rain effects, it was studied with the intention that it be coupled with a stabilization/fixation approach so as to provide a second level of treatment; i.e., it is not intended to be the stand-alone treatment approach. In this study, the reductants were initially used to treat a contaminated, artificial soil and allowed to cure for varying time periods to determine the minimum curing time. Contaminated artificial soil were then prepared using the same percentage of white sand, kaolinite clay and potassium chromate and varying amount of water as a function of the humidity of the specimens in order to illucidate the effect of moisture on the reductant performance. Finally, the reductant (either ferrous sulfate heptahydrate or sodium thiosulfate) was added in varying doses to determine the best ratio Cr/reagent dose. Chromium release from the soil was evaluated with a modified Toxicity Characteristic Leaching Procedure (TCLP) test after allowing the samples to cure. Results indicated that chromium(VI) released from the specimens was less than 5 ppm for the samples treated with either ferrous sulfate heptahydrate (99.9% of reduction) and sodium thiosulfate (98.7% of reduction) with ratio Cr/reagent equal to 18.7 in both cases. In addition, samples treated with ferrous sulfate also exhibited a binding effect. In summary, reduction to a lower valence state can be an effective treatment option when coupled with a stabilization/solidification treatment, so that any chromium subsequently leached from the treated soil into groundwater is the less toxic and less mobile trivalent form of chromium. An alternative to ferrous sulfate heptahydrate, the less-expensive sodium thiosulfate, performed well as a reductant and is suggested for further study.

Evaluation of Physical Strength of Wheat Straw Under Different Fertilizer Treatments and Rates

USDA-ARS?s Scientific Manuscript database

Application of nitrogen (N) fertilizer as urea ammonium nitrate and N plus sulfur fertilizer as ammonium thiosulfate as a mist on crop residue to stimulate microbial activity and subsequent decomposition of the residue is often debated, particularly for its potential to solve stand establishment iss...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganji, Rakesh; Murugapiran, Senthil K.; Ong, John C.

The draft genome of Thermocrinis jamiesonii GBS1 T is 1,315,625 bp in 10 contigs and encodes 1,463 predicted genes. The presence of sox genes and various glycoside hydrolases and the absence of uptake NiFe hydrogenases ( hyaB) are consistent with a requirement for thiosulfate and suggest the ability to use carbohydrate polymers.

Evaluation of thiosulfate as a substitute for hydrogen sulfide in sour corrosion fatigue studies

NASA Astrophysics Data System (ADS)

Kappes, Mariano Alberto

This work evaluates the possibility of replacing hydrogen sulfide (H 2S) with thiosulfate anion (S2O32- ) in sour corrosion fatigue studies. H2S increases the corrosion fatigue crack growth rate (FCGR) and can be present in carbon steel risers and flowlines used in off-shore oil production. Corrosion tests with gaseous H2S require special facilities with safety features, because H2S is a toxic and flammable gas. The possibility of replacing H2S with S2O32-, a non-toxic anion, for studying stress corrosion cracking of stainless and carbon steels in H2S solutions was first proposed by Tsujikawa et al. ( Tsujikawa et al., Corrosion, 1993. 49(5): p. 409-419). In this dissertation, Tsujikawa work will be extended to sour corrosion fatigue of carbon steels. H2S testing is often conducted in deareated condition to avoid oxygen reaction with sulfide that yields sulfur and to mimic oil production conditions. Nitrogen deareation was also adopted in S2O3 2- testing, and gas exiting the cell was forced through a sodium hydroxide trap. Measurements of the sulfide content of this trap were used to estimate the partial pressure of H2S in nitrogen, and Henry's law was used to estimate the content of H2S in the solution in the cell. H2S was produced by a redox reaction of S2O 32-, which required electrons from carbon steel corrosion. This reaction is spontaneous at the open circuit potential of steel. Therefore, H2S concentration was expected to be maximum at the steel surface, and this concentration was estimated by a mass balance analysis. Carbon steel specimens exposed to S2O32- containing solutions developed a film on their surface, composed by iron sulfide and cementite. The film was not passivating and a good conductor of electrons. Hydrogen permeation experiments proved that this film controls the rate of hydrogen absorption of steels exposed to thiosulfate containing solutions. The absorption of hydrogen in S2O3 2- solutions was compared with the absorption of hydrogen in solutions saturated with different H2S partial pressures. The partial pressure was selected so that the concentration of H2S in the solution saturated with the gas would be the same as that reached in the surface of steel freely corroding in the thiosulfate solution. For solutions obtained by bubbling H2S, the rate of hydrogen absorption increased with the partial pressure of the gas, but the rate of hydrogen absorption reached a maximum at 10-3 M S2O3 2-, despite the surface concentration of H2S increased with the concentration of S2O32-. This effect was associated with the formation of thicker films, which inhibited the absorption of hydrogen. FCGR were evaluated at constant stress intensity factor range. Crack length was monitored in-situ by the direct current potential drop (DCPD) method. FCGR increased with the partial pressure of H2S in nitrogen. FCGR was controlled not only by the amount of hydrogen present in the steel, but also by inhibiting contributions like crack closure and crack tip blunting. FCGR in dilute thiosulfate solutions was near that measured in a solution saturated with a partial pressure of H2S equal to 0.56 kPa, in accord with hydrogen permeation results.

Method and apparatus for dissociating metals from metal compounds extracted into supercritical fluids

DOEpatents

Wai, Chien M.; Hunt, Fred H.; Smart, Neil G.; Lin, Yuehe

2000-01-01

A method for dissociating metal-ligand complexes in a supercritical fluid by treating the metal-ligand complex with heat and/or reducing or oxidizing agents is described. Once the metal-ligand complex is dissociated, the resulting metal and/or metal oxide form fine particles of substantially uniform size. In preferred embodiments, the solvent is supercritical carbon dioxide and the ligand is a .beta.-diketone such as hexafluoroacetylacetone or dibutyldiacetate. In other preferred embodiments, the metals in the metal-ligand complex are copper, silver, gold, tungsten, titanium, tantalum, tin, or mixtures thereof. In preferred embodiments, the reducing agent is hydrogen. The method provides an efficient process for dissociating metal-ligand complexes and produces easily-collected metal particles free from hydrocarbon solvent impurities. The ligand and the supercritical fluid can be regenerated to provide an economic, efficient process.

40 CFR 721.4596 - Diazo substituted carbomonocyclic metal complex.

Code of Federal Regulations, 2010 CFR

2010-07-01

... metal complex. 721.4596 Section 721.4596 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4596 Diazo substituted carbomonocyclic metal complex. (a) Chemical... as a diazo substituted carbomonocyclic metal complex (PMN P-94-1039) is subject to reporting under...

40 CFR 721.4596 - Diazo substituted carbomonocyclic metal complex.

Code of Federal Regulations, 2011 CFR

2011-07-01

... metal complex. 721.4596 Section 721.4596 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4596 Diazo substituted carbomonocyclic metal complex. (a) Chemical... as a diazo substituted carbomonocyclic metal complex (PMN P-94-1039) is subject to reporting under...

Frustration across the periodic table: heterolytic cleavage of dihydrogen by metal complexes.

PubMed

Bullock, R Morris; Chambers, Geoffrey M

2017-08-28

This perspective examines frustrated Lewis pairs (FLPs) in the context of heterolytic cleavage of H 2 by transition metal complexes, with an emphasis on molecular complexes bearing an intramolecular Lewis base. FLPs have traditionally been associated with main group compounds, yet many reactions of transition metal complexes support a broader classification of FLPs that includes certain types of transition metal complexes with reactivity resembling main group-based FLPs. This article surveys transition metal complexes that heterolytically cleave H 2 , which vary in the degree that the Lewis pairs within these systems interact. Many of the examples include complexes bearing a pendant amine functioning as the base with the metal functioning as the hydride acceptor. Consideration of transition metal compounds in the context of FLPs can inspire new innovations and improvements in transition metal catalysis.This article is part of the themed issue 'Frustrated Lewis pair chemistry'. © 2017 The Author(s).

Chemical Kinetics, Heat Transfer, and Sensor Dynamics Revisited in a Simple Experiment

ERIC Educational Resources Information Center

Sad, Maria E.; Sad, Mario R.; Castro, Alberto A.; Garetto, Teresita F.

2008-01-01

A simple experiment about thermal effects in chemical reactors is described, which can be used to illustrate chemical reactor models, the determination and validation of their parameters, and some simple principles of heat transfer and sensor dynamics. It is based in the exothermic reaction between aqueous solutions of sodium thiosulfate and…

Destruction of methyl bromide sorbed to activated carbon by thiosulfate and electrolysis

USDA-ARS?s Scientific Manuscript database

Methyl bromide is widely used as a fumigant for post-harvest and quarantine uses at port facilities due to the low treatment times required, but it is vented to the atmosphere after its use. Due to the potential contributions of methyl bromide to stratospheric ozone depletion, technologies for the c...

Disulfides as Cyanide Antidotes: Evidence for a New In Vivo Oxidative Pathway for Cyanide Detoxification

DTIC Science & Technology

2009-01-01

the quantum mechanical calculations in this paper. M.A.Z. further thanks Drs. Clarence Broomfield and Alan Brimfield for their assistance on this... fluorescence . Eur. J. Biochem. 28, 89–93. (8) Leininger, K. R., and Westley, J. (1968) The mechanism of the rhodanese-catalyzed thiosulfate-cyanide

40 CFR 63.457 - Test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 parts per million by volume methane or n-hexane. (e) Negative pressure procedures. To demonstrate negative pressure... between 6.95 and 7.05. (4) To prepare the 0.1 normality (N) sodium thiosulfate solution, dissolve 25 g of...

40 CFR 180.910 - Inert ingredients used pre- and post-harvest; exemptions from the requirement of a tolerance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... formulation Surfactant α-Alkyl(C6-C15)-ω-hydroxypoly(oxyethylene)sulfate, and its ammonium, calcium, magnesium..., related adjuvants of surfactants Alkyl (C8-C18) sulfate and its ammonium, calcium, isopropylamine... stearate Surfactant Ammonium sulfate Solid diluent, carrier Ammonium thiosulfate Intensifier when used with...

Dose and time-dependent effects of cyanide on thiosulfate sulfurtransferase, 3-mercaptopyruvate sulfurtransferase, and cystathionine λ-lyase activities.

PubMed

Singh, Poonam; Rao, Pooja; Bhattacharya, Rahul

2013-12-01

We assessed the dose-dependent effect of potassium cyanide (KCN) on thiosulfate sulfurtransferase (TST), 3-mercaptopyruvate sulfurtransferase (3-MPST), and cystathionine λ-lyase (CST) activities in mice. The time-dependent effect of 0.5 LD50 KCN on cyanide level and cytochrome c oxidase (CCO), TST, 3-MPST, and CST activities was also examined. Furthermore, TST, 3-MPST, and CST activities were measured in stored mice cadavers. Hepatic and renal TST activity increased by 0.5 LD50 KCN but diminished by ≥2.0 LD50. After 0.5 LD50 KCN, the elevated hepatic cyanide level was accompanied by increased TST, 3-MPST, and CST activities, and CCO inhibition. Elevated renal cyanide level was only accompanied by increased 3-MPST activity. No appreciable change in enzyme activities was observed in mice cadavers. The study concludes that high doses of cyanide exert saturating effects on its detoxification enzymes, indicating their exogenous use during cyanide poisoning. Also, these enzymes are not reliable markers of cyanide poisoning in autopsied samples. © 2013 Wiley Periodicals, Inc.

Investigation of transient forms of sulfur during biological treatment of spent caustic.

PubMed

Kalantari, Hamed; Nosrati, Mohsen; Shojaosadati, Seyed Abbas; Shavandi, Mahmoud

2018-06-01

In the present study, the production of various transient forms of sulfur during biological oxidation of sulfidic spent caustics under haloalkaline conditions in a stirred tank bioreactor is investigated. Also, the effects of abiotic aeration (chemical oxidation), dissolved oxygen (DO) concentration and sodium concentration on forms of sulfur during biological treatment are demonstrated. Thioalkalivibrio versutus strain was used for sulfide oxidation in spent caustic (SC). The aeration had an important effect on sulfide oxidation and its final products. At DO concentrations above 2 mg l -1 , majority of sulfide was oxidized to sulfate. Maximum sulfide removal efficiency (%R) and yield of sulfate production [Formula: see text] was obtained in Na + concentration ranging from 0.6 to 2 M. Abiotic aeration, which is the most important factor of production of thiosulfate, resulted in the formation of an undesired product-polysulfide. However, abiotic aeration can be used as a pretreatment to biological treatment. In the bioreactor the removal efficiency was obtained as 82.7% and various forms of sulfur such as polysulfide, biosulfur, thiosulfate and sulfate was observed during biological treatment of SC.

Characteristics of electron transport chain and affecting factors for thiosulfate-driven perchlorate reduction.

PubMed

Zhang, Chao; Guo, Jianbo; Lian, Jing; Lu, Caicai; Ngo, Huu Hao; Guo, Wenshan; Song, Yuanyuan; Guo, Yankai

2017-10-01

The mechanism for perchlorate reduction was investigated using thiosulfate-driven (T-driven) perchlorate reduction bacteria. The influences of various environmental conditions on perchlorate reduction, including pH, temperature and electron acceptors were examined. The maximum perchlorate removal rate was observed at pH 7.5 and 40 °C. Perchlorate reduction was delayed due to the coexistence of perchlorate-chlorate and perchlorate-nitrate. The mechanism of the T-driven perchlorate reduction electron transport chain (ETC) was also investigated by utilizing different inhibitors. The results were as follows: firstly, the NADH dehydrogenase was not involved in the ETC; secondly, the FAD dehydrogenase and quinone loop participated in the ETC; and thirdly, cytochrome oxidase was the main pathway in the ETC. Meanwhile, microbial consortium structure analysis indicated that Sulfurovum which can oxidize sulfur compounds coupled to the reduction of nitrate or perchlorate was the primary bacterium in the T-driven and sulfur-driven consortium. This study generates a better understanding of the mechanism of T-driven perchlorate reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Vestiges of Submarine Serpentinization Recorded in the Microbiology of Continental Ophiolite Complexes

NASA Astrophysics Data System (ADS)

Schrenk, M. O.; Sabuda, M.; Brazelton, W. J.; Twing, K. I.

2017-12-01

The study of serpentinization-influenced microbial ecosystems at and below the seafloor has accelerated in recent years with multidisciplinary drilling expeditions to the Atlantis Massif (X357), Southwest Indian Ridge (X360) and Mariana Forearc (X366). In parallel, a number of studies have surveyed serpentinizing systems in ophiolite complexes which host a range of geologic histories, geochemical characteristics, fluid pathways, and consequently microbiology. As ophiolite complexes originate as seafloor materials, it is likely that a microbiological record of seafloor serpentinization processes is maintained through the emplacement and weathering of continental serpentinites. This hypothesis was evaluated through a global comparison of continental serpentinite springs and groundwater, ranging from highly brackish (saline) to freshwater. One of the most saline sites, known as the Coast Range Ophiolite Microbial Observatory (CROMO), was used as a point-of-comparison to marine serpentinizing systems, such as the Lost City Hydrothermal Field. Although there was little taxonomic overlap between microbial populations in marine and terrestrial systems, both communities harbored an abundance of genes involved in sulfur metabolism, including sulfide oxidation, thiosulfate disproportionation, and sulfate reduction. The phylogeny of key genes involved in these metabolic processes was evaluated relative to published studies and compared between sites. Together, these data provide insights into both the functioning of microbial communities in modern-day serpentinizing systems, and the transport processes that disperse microorganisms between marine and terrestrial serpentinites.

Metal Complexation in Xylem Fluid 1

PubMed Central

White, Michael C.; Chaney, Rufus L.; Decker, A. Morris

1981-01-01

The capacity of ligands in xylem fluid to form metal complexes was tested with a series of in vitro experiments using paper electrophoresis and radiographs. The xylem fluid was collected hourly for 8 hours from soybean (Glycine max L. Merr.) and tomato (Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. Metal complexation was assayed by anodic or reduced cathodic movement of radionuclides (63Ni, 65Zn, 109Cd, 54Mn) that were presumed to have formed negatively charged complexes. Electrophoretic migration of Ni, Zn, Cd, and Mn added to xylem exudate and spotted on KCl- or KNO3-wetted paper showed that stable Ni, Zn, and Cd metal complexes were formed by exudate ligands. No anodic Mn complexes were observed in this test system. Solution pH, plant species, exudate collection time, and Zn phytotoxicity all affected the amount of metal complex formed in exudate. As the pH increased, there was increased anodic metal movement. Soybean exudate generally bound more of each metal than did tomato exudate. Metal binding usually decreased with increasing exudate collection time, and less metal was bound by the high-Zn exudate. Ni, Zn, Cd, and Mn in exudate added to exudate-wetted paper demonstrated the effect of ligand concentration on stable metal complex formation. Complexes for each metal were demonstratable with this method. Cathodic metal movement increased with time of exudate collection, and it was greater in the high-Zn exudate than in the normal-Zn exudate. A model study illustrated the effect of ligand concentration on metal complex stability in the electrophoretic field. Higher ligand (citric acid) concentrations increased the stability for all metals tested. Images PMID:16661666

Preparation and properties of chitosan-metal complex: Some factors influencing the adsorption capacity for dyes in aqueous solution.

PubMed

Rashid, Sadia; Shen, Chensi; Yang, Jing; Liu, Jianshe; Li, Jing

2018-04-01

Chitosan-metal complexes have been widely studied in wastewater treatment, but there are still various factors in complex preparation which are collectively responsible for improving the adsorption capacity need to be further studied. Thus, this study investigates the factors affecting the adsorption ability of chitosan-metal complex adsorbents, including various kinds of metal centers, different metal salts and crosslinking degree. The results show that the chitosan-Fe(III) complex prepared by sulfate salts exhibited the best adsorption efficiency (100%) for various dyes in very short time duration (10min), and its maximum adsorption capacity achieved 349.22mg/g. The anion of the metal salt which was used in preparation played an important role to enhance the adsorption ability of chitosan-metal complex. SO 4 2- ions not only had the effect of crosslinking through electrostatic interaction with amine group of chitosan polymer, but also could facilitate the chelation of metal ions with chitosan polymer during the synthesis process. Additionally, the pH sensitivity and the sensitivity of ionic environment for chitosan-metal complex were analyzed. We hope that these factors affecting the adsorption of the chitosan-metal complex can help not only in optimizing its use but also in designing new chitosan-metal based complexes. Copyright © 2017. Published by Elsevier B.V.

40 CFR 721.10104 - Halophosphate mixed metal complex (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halophosphate mixed metal complex... Specific Chemical Substances § 721.10104 Halophosphate mixed metal complex (generic). (a) Chemical... as halophosphate mixed metal complex (PMN P-04-254) is subject to reporting under this section for...

40 CFR 721.10104 - Halophosphate mixed metal complex (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halophosphate mixed metal complex... Specific Chemical Substances § 721.10104 Halophosphate mixed metal complex (generic). (a) Chemical... as halophosphate mixed metal complex (PMN P-04-254) is subject to reporting under this section for...

40 CFR 721.10104 - Halophosphate mixed metal complex (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Halophosphate mixed metal complex... Specific Chemical Substances § 721.10104 Halophosphate mixed metal complex (generic). (a) Chemical... as halophosphate mixed metal complex (PMN P-04-254) is subject to reporting under this section for...

40 CFR 721.10104 - Halophosphate mixed metal complex (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Halophosphate mixed metal complex... Specific Chemical Substances § 721.10104 Halophosphate mixed metal complex (generic). (a) Chemical... as halophosphate mixed metal complex (PMN P-04-254) is subject to reporting under this section for...

40 CFR 721.10104 - Halophosphate mixed metal complex (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Halophosphate mixed metal complex... Specific Chemical Substances § 721.10104 Halophosphate mixed metal complex (generic). (a) Chemical... as halophosphate mixed metal complex (PMN P-04-254) is subject to reporting under this section for...

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. III. An anion-exchange resin technique for sampling and preservation of sulfoxyanions in natural waters

USGS Publications Warehouse

Druschel, G.K.; Schoonen, M.A.A.; Nordstorm, D.K.; Ball, J.W.; Xu, Y.; Cohn, C.A.

2003-01-01

A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad??? AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site IC analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad??? AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns. ?? The Royal Society of Chemistry and the Division of Geochemistry of the American Chemical Society 2003.

40 CFR 721.4594 - Substituted azo metal complex dye.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted azo metal complex dye. 721... Substances § 721.4594 Substituted azo metal complex dye. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a substituted azo metal complex...

40 CFR 721.4594 - Substituted azo metal complex dye.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted azo metal complex dye. 721... Substances § 721.4594 Substituted azo metal complex dye. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a substituted azo metal complex...

Process for the enhanced capture of heavy metal emissions

DOEpatents

Biswas, Pratim; Wu, Chang-Yu

2001-01-01

This invention is directed to a process for forming a sorbent-metal complex. The process includes oxidizing a sorbent precursor and contacting the sorbent precursor with a metallic species. The process further includes chemically reacting the sorbent precursor and the metallic species, thereby forming a sorbent-metal complex. In one particular aspect of the invention, at least a portion of the sorbent precursor is transformed into sorbent particles during the oxidation step. These sorbent particles then are contacted with the metallic species and chemically reacted with the metallic species, thereby forming a sorbent-metal complex. Another aspect of the invention is directed to a process for forming a sorbent metal complex in a combustion system. The process includes introducing a sorbent precursor into a combustion system and subjecting the sorbent precursor to an elevated temperature sufficient to oxidize the sorbent precursor and transform the sorbent precursor into sorbent particles. The process further includes contacting the sorbent particles with a metallic species and exposing the sorbent particles and the metallic species to a complex-forming temperature whereby the metallic species reacts with the sorbent particles thereby forming a sorbent-metal complex under UV irradiation.

Electricity generation by Rhodopseudomonas palustris DX-1.

PubMed

Xing, Defeng; Zuo, Yi; Cheng, Shaoan; Regan, John M; Logan, Bruce E

2008-06-01

Bacteria able to generate electricity in microbial fuel cells (MFCs) are of great interest, but there are few strains capable of high power production in these systems. Here we report that the phototrophic purple nonsulfur bacterium Rhodopseudomonas palustris DX-1, isolated from an MFC, produced electricity at higher power densities (2720 +/- 60 mW/m2) than mixed cultures in the same device. While Rhodopseudomonas species are known for their ability to generate hydrogen, they have not previously been shown to generate power in an MFC, and current was generated without the need for light or hydrogen production. Strain DX-1 utilizes a wide variety of substrates (volatile acids, yeast extract, and thiosulfate) for power production in different metabolic modes, making it highly useful for studying power generation in MFCs and generating power from a range of simple and complex sources of organic matter. These results demonstrate that a phototrophic purple nonsulfur bacterium can efficiently generate electricity by direct electron transfer in MFCs, providing another model microorganism for MFC investigations.

40 CFR 721.4680 - Metal salts of complex inorganic oxyacids (generic name).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Metal salts of complex inorganic... New Uses for Specific Chemical Substances § 721.4680 Metal salts of complex inorganic oxyacids... substances identified generically as metal salts of complex inorganic oxyacids (PMNs P-89-576 and P-89-577...

Environmental and Body Concentrations of Heavy Metals at Sites Near and Distant from Industrial Complexes in Ulsan, Korea.

PubMed

Sung, Joo Hyun; Oh, Inbo; Kim, Ahra; Lee, Jiho; Sim, Chang Sun; Yoo, Cheolin; Park, Sang Jin; Kim, Geun Bae; Kim, Yangho

2018-01-29

Industrial pollution may affect the heavy metal body burden of people living near industrial complexes. We determined the average concentrations of atmospheric heavy metals in areas close to and distant from industrial complexes in Korea, and the body concentrations of these heavy metals in residents living near and distant from these facilities. The atmospheric data of heavy metals (lead and cadmium) were from the Regional Air Monitoring Network in Ulsan. We recruited 1,148 participants, 872 who lived near an industrial complex ("exposed" group) and 276 who lived distant from industrial complexes ("non-exposed" group), and measured their concentrations of blood lead, urinary cadmium, and urinary total mercury. The results showed that atmospheric and human concentrations of heavy metals were higher in areas near industrial complexes. In addition, residents living near industrial complexes had higher individual and combined concentrations (cadmium + lead + mercury) of heavy metals. We conclude that residents living near industrial complexes are exposed to high concentrations of heavy metals, and should be carefully monitored. © 2018 The Korean Academy of Medical Sciences.

Environmental and Body Concentrations of Heavy Metals at Sites Near and Distant from Industrial Complexes in Ulsan, Korea

PubMed Central

2017-01-01

Background Industrial pollution may affect the heavy metal body burden of people living near industrial complexes. We determined the average concentrations of atmospheric heavy metals in areas close to and distant from industrial complexes in Korea, and the body concentrations of these heavy metals in residents living near and distant from these facilities. Methods The atmospheric data of heavy metals (lead and cadmium) were from the Regional Air Monitoring Network in Ulsan. We recruited 1,148 participants, 872 who lived near an industrial complex (“exposed” group) and 276 who lived distant from industrial complexes (“non-exposed” group), and measured their concentrations of blood lead, urinary cadmium, and urinary total mercury. Results The results showed that atmospheric and human concentrations of heavy metals were higher in areas near industrial complexes. In addition, residents living near industrial complexes had higher individual and combined concentrations (cadmium + lead + mercury) of heavy metals. Conclusion We conclude that residents living near industrial complexes are exposed to high concentrations of heavy metals, and should be carefully monitored. PMID:29349943

Insights into aquatic toxicities of the antibiotics oxytetracycline and ciprofloxacin in the presence of metal: complexation versus mixture.

PubMed

Zhang, Yu; Cai, Xiyun; Lang, Xianming; Qiao, Xianliang; Li, Xuehua; Chen, Jingwen

2012-07-01

Co-contamination of ligand-like antibiotics (e.g., tetracyclines and quinolones) and heavy metals prevails in the environment, and thus the complexation between them is involved in environmental risks of antibiotics. To understand toxicological significance of the complex, effects of metal coordination on antibiotics' toxicity were investigated. The complexation of two antibiotics, oxytetracycline and ciprofloxacin, with three heavy metals, copper, zinc, and cadmium, was verified by spectroscopic techniques. The antibiotics bound metals via multiple coordination sites and rendered a mixture of various complexation speciations. Toxicity analysis indicated that metal coordination did modify the toxicity of the antibiotics and that antibiotic, metal, and their complex acted primarily as concentration addition. Comparison of EC(50) values revealed that the complex commonly was highest toxic and predominately correlated in toxicity to the mixture. Finally, environmental scenario analysis demonstrated that ignoring complexation would improperly classify environmental risks of the antibiotics. Copyright © 2012 Elsevier Ltd. All rights reserved.

Metal complexes of quinolone antibiotics and their applications: an update.

PubMed

Uivarosi, Valentina

2013-09-11

Quinolones are synthetic broad-spectrum antibiotics with good oral absorption and excellent bioavailability. Due to the chemical functions found on their nucleus (a carboxylic acid function at the 3-position, and in most cases a basic piperazinyl ring (or another N-heterocycle) at the 7-position, and a carbonyl oxygen atom at the 4-position) quinolones bind metal ions forming complexes in which they can act as bidentate, as unidentate and as bridging ligand, respectively. In the polymeric complexes in solid state, multiple modes of coordination are simultaneously possible. In strongly acidic conditions, quinolone molecules possessing a basic side nucleus are protonated and appear as cations in the ionic complexes. Interaction with metal ions has some important consequences for the solubility, pharmacokinetics and bioavailability of quinolones, and is also involved in the mechanism of action of these bactericidal agents. Many metal complexes with equal or enhanced antimicrobial activity compared to the parent quinolones were obtained. New strategies in the design of metal complexes of quinolones have led to compounds with anticancer activity. Analytical applications of complexation with metal ions were oriented toward two main directions: determination of quinolones based on complexation with metal ions or, reversely, determination of metal ions based on complexation with quinolones.

40 CFR 63.457 - Test methods and procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... volume of hydrocarbon in air); and (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 parts per million by volume methane or n-hexane. (e) Negative pressure... between 6.95 and 7.05. (4) To prepare the 0.1 normality (N) sodium thiosulfate solution, dissolve 25 g of...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogawa, E.; Suzuki, S.; Fukuda, R.

Pharmacological means to accelerate the elimination of Cs-137 introduced into the living organism are studied. Male dd mice and male Wistar rats are individually housed in metal metabolism cages, and provided with commercial solid diet and water. Radioactivity is determined in urine, and feces for 24 hours and 4 days after subcutaneous injection of a tracer dose of Cs/sup 137/Cl, and in various organs after sacrifices at the ends of these periods. Effects of various chemicals on these results are compared. Twenty five chemicals were investigated. They include inorganic Na salts such as Na bicarbonate, Na carbonate, Na suliate, Namore » thiosulfate, primary and secondary Na phosphates, and organic Na salts such as Na lactate, lactated Ringer, Na acetate, Na glucuronate, Na salt of thioctic acid, ATP Na, and Na pentobarbiturate. Na bicarbonate, Na phosphates, Na sulfate, and Na thiosulfate are found as eifective, especially Na bicarbonate, K bicarbonate shows scarcely any effect, nor do other K salts. It is therefore assumed that Cs will exchange with Na ion in the tubular cells. LiCl is found to accelerate the excretion of Cs-137 from mice and rats. This result is of interest with respect to the periodic law, since it is known that for the elimination of Sr-90, Ca salts are ineffective or slightly effective, whereas Mg salts are effective. Of the diuretics, chlorothiazide, which is considered to increase the excretion of K, does nor increase the elimination of Cs-137 in any dose. This result is different from that of Diamox, a diuretic of the same nature. Cardiac glycosides and xanthine derivatives are effective. Out of digitalis preparations, Digitamin (Shionogi), Digilanogen C (Fujisawa), Digosin (Chugai) are effective. Digitoxin and strospeside are ineffective, and after their application, retention of Cs-137 is observed in the heart muscle. G- strophanthin is ineffective in a smaller dose, but increases the elimination of Cs-137 in a larger dose. Caffeine and sodium benzoate are also effective, but theophylline and theobromine are not so effective. Out of osmotic diuretics, Na ferrocyanate alone increases fecal excretion of Cs-137, and decreases the retention in the body. NaI and KI have scarcely any effect. Phosphomolybdic acid inhibits the elimination of Cs-137 and increases its retention. The above mentioned effective chemicals are also investigated for effects on the elimination of Sr-90. (JAIF)« less

Dissolution of Fe(III) (hydr) oxides by metal-EDTA complexes

NASA Astrophysics Data System (ADS)

Ngwack, Bernd; Sigg, Laura

1997-03-01

The dissolution of Fe(III)(hydr)oxides (goethite and hydrous ferric oxide) by metal-EDTA complexes occurs by ligand-promoted dissolution. The process is initiated by the adsorption of metal-EDTA complexes to the surface and is followed by the dissociation of the complex at the surface and the release of Fe(III)EDTA into solution. The dissolution rate is decreased to a great extent if EDTA is complexed by metals in comparison to the uncomplexed EDTA. The rate decreases in the order EDTA CaEDTA ≫ PbEDTA > ZnEDTA > CuEDTA > Co(II)EDTA > NiEDTA. Two different rate-limiting steps determine the dissolution process: (1) detachment of Fe(III) from the oxide-structure and (2) dissociation of the metal-EDTA complexes. In the case of goethite, step 1 is slower than step 2 and the dissolution rates by various metals are similar. In the case of hydrous ferric oxide, step 2 is rate-limiting and the effect of the complexed metal is very pronounced.

Studies on DNA binding behaviour of biologically active transition metal complexes of new tetradentate N2O2 donor Schiff bases: inhibitory activity against bacteria.

PubMed

Sobha, S; Mahalakshmi, R; Raman, N

2012-06-15

A series of Cu(II), Ni(II) and Zn(II) complexes of the type ML have been synthesized with Schiff bases derived from o-acetoacetotoluidide, 2-hydroxybenzaldehyde and o-phenylenediamine/1,4-diaminobutane. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the six metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped to elucidate the structure of the metal complexes. The Schiff bases are found to act as tetradentate ligands using N(2)O(2) donor set of atoms leading to a square-planar geometry for the complexes around all the metal ions. The binding properties of metal complexes with DNA were investigated by absorption spectra, viscosity measurements and cyclic voltammetry. Detailed analysis reveals that the metal complexes intercalate into the DNA base stack as intercalators. All the metal complexes cleave the pUC19 DNA in presence of H(2)O(2.) The Schiff bases and their complexes have been screened for their antibacterial activity against five bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae) by disk diffusion method. All the metal complexes have potent biocidal activity than the free ligands. Copyright © 2012 Elsevier B.V. All rights reserved.

Microbial oxidative sulfur metabolism: biochemical evidence of the membrane-bound heterodisulfide reductase-like complex of the bacterium Aquifex aeolicus.

PubMed

Boughanemi, Souhela; Lyonnet, Jordan; Infossi, Pascale; Bauzan, Marielle; Kosta, Artémis; Lignon, Sabrina; Giudici-Orticoni, Marie-Thérèse; Guiral, Marianne

2016-08-01

The Hdr (heterodisulfide reductase)-like enzyme is predicted, from gene transcript profiling experiments previously published, to be essential in oxidative sulfur metabolism in a number of bacteria and archaea. Nevertheless, no biochemical and physicochemical data are available so far about this enzyme. Genes coding for it were identified in Aquifex aeolicus, a Gram-negative, hyperthermophilic, chemolithoautotrophic and microaerophilic bacterium that uses inorganic sulfur compounds as electron donor to grow. We provide biochemical evidence that this Hdr-like enzyme is present in this sulfur-oxidizing prokaryote (cultivated with thiosulfate or elemental sulfur). We demonstrate, by immunolocalization and cell fractionation, that Hdr-like enzyme is associated, presumably monotopically, with the membrane fraction. We show by co-immunoprecipitation assay or partial purification, that the Hdr proteins form a stable complex composed of at least five subunits, HdrA, HdrB1, HdrB2, HdrC1 and HdrC2, present in two forms of high molecular mass on native gel (∼240 and 450 kDa). These studies allow us to propose a revised model for dissimilatory sulfur oxidation pathways in A. aeolicus, with Hdr predicted to generate sulfite. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Frustration across the periodic table: heterolytic cleavage of dihydrogen by metal complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bullock, R. Morris; Chambers, Geoffrey M.

2017-07-24

This Perspective examines the field of Frustrated Lewis Pairs (FLPs) in the context of transition metal mediated heterolytic cleavage of H2, with a particular emphasis on molecular complexes bearing an intramolecular Lewis base. FLPs have traditionally been associated with group compounds, yet many transition metal reactions support a broader classification of FLPs to include certain types of transition metal complexes with reactivity resembling main group based FLPs. This article surveys transition metal complexes that heterolytically cleave H2, which vary in the degree that the Lewis pairs within these systems interact. Particular attention is focused on complexes bearing a pendant aminemore » function as the base. Consideration of transition metal compounds in the context of FLPs can inspire new innovations and improvements in transition metal catalysis.« less

Process for the displacement of cyanide ions from metal-cyanide complexes

DOEpatents

Smith, Barbara F.; Robinson, Thomas W.

1997-01-01

The present invention relates to water-soluble polymers and the use of such water-soluble polymers in a process for the displacement of the cyanide ions from the metal ions within metal-cyanide complexes. The process waste streams can include metal-cyanide containing electroplating waste streams, mining leach waste streams, mineral processing waste streams, and related metal-cyanide containing waste streams. The metal ions of interest are metals that give very strong complexes with cyanide, mostly iron, nickel, and copper. The physical separation of the water-soluble polymer-metal complex from the cyanide ions can be accomplished through the use of ultrafiltration. Once the metal-cyanide complex is disrupted, the freed cyanide ions can be recovered for reuse or destroyed using available oxidative processes rendering the cyanide nonhazardous. The metal ions are released from the polymer, using dilute acid, metal ion oxidation state adjustment, or competing chelating agents, and collected and recovered or disposed of by appropriate waste management techniques. The water-soluble polymer can then be recycled. Preferred water-soluble polymers include polyethyleneimine and polyethyleneimine having a catechol or hydroxamate group.

Gas phase reactions of doubly charged alkaline earth and transition metal(II)-ligand complexes generated by electrospray ionization

NASA Astrophysics Data System (ADS)

Kohler, Martin; Leary, Julie A.

1997-03-01

Doubly charged metal(II)-complexes of [alpha] 1-3, [alpha] 1-6 mannotriose and the conserved trimannosyl core pentasaccharide as well as doubly charged complexes of Co(II), Mn(II), Ca(II) and Sr(II) with acetonitrile generated by electrospray ionization were studied by low energy collision induced dissociation (CID). Two main fragmentation pathways were observed for the metal(II)-oligosaccharide complexes. Regardless of the coordinating metal, loss of a neutral dehydrohexose residue (162 Da) from the doubly charged precursor ion is observed, forming a doubly charged product ion. However, if the oligosaccharide is coordinated to Co(II) or Mn(II), loss of a dehydroxyhexose cation is also observed. Investigation of the low mass region of the mass spectra of the metal coordinated oligosaccharides revealed intense signals corresponding to [metal(II) + (CH3CN)n2+ (where n = 1-6) species which were being formed by the metal(II) ions and the acetonitrile present in the sample. Analysis of these metal(II)-acetonitrile complexes provided further insight into the processes occurring upon low energy CID of doubly charged metal complexes. The metal(II)-acetonitrile system showed neutral loss and ligand cleavage as observed with the oligosaccharide complexes, as well as a series of six different dissociation mechanisms, most notable among them reduction from [metal(II) + (CH3CN)n2+ to the bare [metal(I)]+ species by electron transfer. Depending on the metal and collision gas chosen, one observes electron transfer from the ligand to the metal, electron transfer from the collision gas to the metal, proton transfer between ligands, heterolytic cleavage of the ligands, reactive collisions and loss of neutral ligands.

The molecular structure and vibrational spectra of corrolazine metal complexes (CzM) by density functional theory

NASA Astrophysics Data System (ADS)

Wang, Hongming; Yang, Chuanlu; Zhang, Zhihong; Wang, Meishan; Han, Keli

2006-06-01

The ground-state geometries, electronic structures and vibrational frequencies of metal corrolazine complexes, CzM (M = Mn, Co, Ni and Fe) have been studied using B3LYP/6-311g(d) method. The molecular geometries are sensitive to the species of the metal, and the bond length of the M sbnd N is increase with the metal atom radii. The ground-state electronic structures indicate that there are strong interactions between d of the metal fragments and the corrolazine fragments. The calculations also indicate that the CzNi is the stabilest among the four metal corrolazine complexes. Vibrational frequencies of these metal corrolazine complexes were also calculated and were assigned to the local coordinates of the corrolazine ring, which reveals the some common feature of the molecular vibrations of the metal corrolazine complexes as four-coordination metallocorrolazines.

Extracting metal ions with diphosphonic acid, or derivative thereof

DOEpatents

Horwitz, Earl P.; Gatrone, Ralph C.; Nash, Kenneth L.

1994-01-01

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described.

Extracting metal ions with diphosphonic acid, or derivative thereof

DOEpatents

Horwitz, E.P.; Gatrone, R.C.; Nash, K.L.

1994-07-26

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulfur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described. 1 fig.

Preparation and characterization compatible pellets for immobilization of colloidal sulphur nanoparticles

NASA Astrophysics Data System (ADS)

Adlim, M.; Zarlaida, F.; Khaldun, I.; Dewi, R.; Jamilah, M.

2018-03-01

Mercury pollution in atmosphere is dominated by mercury vapour release from coal burning and gold-amalgam separation in gold mining. The initial steps in formulating a compatible mercury absorbent for mercury stabilization was fabrication of pellet supported colloidal sulphur. Sulphur is used to stabilize mercury vapour by formation of metacinnabar that has much lower toxicity. The sulphur reactivity toward mercury vapour can be enhanced by using colloidal sulphur nanoparticles immobilized on compatible pellets. Clay pellets would have heat resistance but in fact, they were less stable in aqueous solution although their stability increased with inclusion of rice husk ash and sawdust or pineapple leaf fibre in the composite. Pellets made of rice husk ash and polyvinyl acetate were stable in water at least for 24 hours. Sulphur from thiosulfate precursor that immobilized onto surface of pellet using chitosan as the stabilizer and the binding agent gave lower sulphur content compared to sulphur from other precursors (sulphur powder and sulphur-CS2). Sulphur from thiosulfate precursor was in form of colloid, has nanosize, and disperse particles on the surface of rice husk ash pellets. Sulphur immobilization methods affect on sulphur particles exposure on the pellet surface.

Sulfur Oxygenase Reductase (Sor) in the Moderately Thermoacidophilic Leaching Bacteria: Studies in Sulfobacillus thermosulfidooxidans and Acidithiobacillus caldus.

PubMed

Janosch, Claudia; Remonsellez, Francisco; Sand, Wolfgang; Vera, Mario

2015-10-21

The sulfur oxygenase reductase (Sor) catalyzes the oxygen dependent disproportionation of elemental sulfur, producing sulfite, thiosulfate and sulfide. Being considered an "archaeal like" enzyme, it is also encoded in the genomes of some acidophilic leaching bacteria such as Acidithiobacillus caldus, Acidithiobacillus thiooxidans, Acidithiobacillus ferrivorans and Sulfobacillus thermosulfidooxidans, among others. We measured Sor activity in crude extracts from Sb. thermosulfidooxidans DSM 9293(T). The optimum temperature for its oxygenase activity was achieved at 75 °C, confirming the "thermophilic" nature of this enzyme. Additionally, a search for genes probably involved in sulfur metabolism in the genome sequence of Sb. thermosulfidooxidans DSM 9293(T) was done. Interestingly, no sox genes were found. Two sor genes, a complete heterodisulfidereductase (hdr) gene cluster, three tetrathionate hydrolase (tth) genes, three sulfide quinonereductase (sqr), as well as the doxD component of a thiosulfate quinonereductase (tqo) were found. Seven At. caldus strains were tested for Sor activity, which was not detected in any of them. We provide evidence that an earlier reported Sor activity from At. caldus S1 and S2 strains most likely was due to the presence of a Sulfobacillus contaminant.

Connection between the membrane electron transport system and Hyn hydrogenase in the purple sulfur bacterium, Thiocapsa roseopersicina BBS.

PubMed

Tengölics, Roland; Mészáros, Lívia; Győri, E; Doffkay, Zsolt; Kovács, Kornél L; Rákhely, Gábor

2014-10-01

Thiocapsa. roseopersicina BBS has four active [NiFe] hydrogenases, providing an excellent opportunity to examine their metabolic linkages to the cellular redox processes. Hyn is a periplasmic membrane-associated hydrogenase harboring two additional electron transfer subunits: Isp1 is a transmembrane protein, while Isp2 is located on the cytoplasmic side of the membrane. In this work, the connection of HynSL to various electron transport pathways is studied. During photoautotrophic growth, electrons, generated from the oxidation of thiosulfate and sulfur, are donated to the photosynthetic electron transport chain via cytochromes. Electrons formed from thiosulfate and sulfur oxidation might also be also used for Hyn-dependent hydrogen evolution which was shown to be light and proton motive force driven. Hyn-linked hydrogen uptake can be promoted by both sulfur and nitrate. The electron flow from/to HynSL requires the presence of Isp2 in both directions. Hydrogenase-linked sulfur reduction could be inhibited by a QB site competitive inhibitor, terbutryne, suggesting a redox coupling between the Hyn hydrogenase and the photosynthetic electron transport chain. Based on these findings, redox linkages of Hyn hydrogenase are modeled. Copyright © 2014 Elsevier B.V. All rights reserved.

Sulfur Oxygenase Reductase (Sor) in the Moderately Thermoacidophilic Leaching Bacteria: Studies in Sulfobacillus thermosulfidooxidans and Acidithiobacillus caldus

PubMed Central

Janosch, Claudia; Remonsellez, Francisco; Sand, Wolfgang; Vera, Mario

2015-01-01

The sulfur oxygenase reductase (Sor) catalyzes the oxygen dependent disproportionation of elemental sulfur, producing sulfite, thiosulfate and sulfide. Being considered an “archaeal like” enzyme, it is also encoded in the genomes of some acidophilic leaching bacteria such as Acidithiobacillus caldus, Acidithiobacillus thiooxidans, Acidithiobacillus ferrivorans and Sulfobacillus thermosulfidooxidans, among others. We measured Sor activity in crude extracts from Sb. thermosulfidooxidans DSM 9293T. The optimum temperature for its oxygenase activity was achieved at 75 °C, confirming the “thermophilic” nature of this enzyme. Additionally, a search for genes probably involved in sulfur metabolism in the genome sequence of Sb. thermosulfidooxidans DSM 9293T was done. Interestingly, no sox genes were found. Two sor genes, a complete heterodisulfidereductase (hdr) gene cluster, three tetrathionate hydrolase (tth) genes, three sulfide quinonereductase (sqr), as well as the doxD component of a thiosulfate quinonereductase (tqo) were found. Seven At. caldus strains were tested for Sor activity, which was not detected in any of them. We provide evidence that an earlier reported Sor activity from At. caldus S1 and S2 strains most likely was due to the presence of a Sulfobacillus contaminant. PMID:27682113

Garciella nitratireducens gen. nov., sp. nov., an anaerobic, thermophilic, nitrate- and thiosulfate-reducing bacterium isolated from an oilfield separator in the Gulf of Mexico.

PubMed

Miranda-Tello, Elizabeth; Fardeau, Marie-Laure; Sepúlveda, José; Fernández, Luis; Cayol, Jean-Luc; Thomas, Pierre; Ollivier, Bernard

2003-09-01

A novel Gram-positive, anaerobic and thermophilic bacterium, strain MET79(T), was isolated from an oil well located in the Gulf of Mexico. Cells were straight rods, motile by a subpolar flagellum. Spores were formed in old cultures. Inner gas vacuoles swelled the cells when exposed to air. The optimum growth conditions were 55 degrees C, pH 7.5 and 1 % NaCl. Yeast extract was required for growth. Strain MET79(T) fermented several sugars, some organic acids and Casamino acids. Glucose was fermented into lactate, acetate, butyrate, H(2) and CO(2). Strain MET79(T) reduced thiosulfate to hydrogen sulfide and nitrate to ammonium. The DNA G+C content was 30.9 mol%. The closest phylogenetic relative of strain MET79(T) was Caloranaerobacter azorensis (88.7 % 16S rDNA sequence similarity). As strain MET79(T) (=DSM 15102(T)=CIP 107615(T)) was physiologically and phylogenetically different from its closest relatives, it is assigned as the type strain of a novel species of a new genus, Garciella nitratireducens gen. nov., sp. nov.

Gold--a controversial sensitizer. European Environmental and Contact Dermatitis Research Group.

PubMed

Bruze, M; Andersen, K E

1999-06-01

Until recently, gold allergy was considered to be extremely rare. Gold has been used and worshipped for thousands of years without any obvious complaints of skin problems, either in those participating in mining and other ways of prospecting, or in those wearing jewellery. When studies on contact allergy to gold sodium thiosulfate were published at the beginning of the 1990s, the allergic nature of the reported positive patch test reactions to gold was questioned. The major argument for such questioning was the lack of demonstrable clinical relevance in most positive reactors. A major reason for the questioning may have been confusion in differentiating between contact allergy and allergic contact dermatitis. To arrive at a diagnosis of allergic contact dermatitis, 3 steps have, in principle, to be fulfilled: (i) establishment of contact allergy; (ii) demonstration of present exposure; (iii) assessment of clinical relevance, i.e., causing or aggravating a contact dermatitis. In this paper, these steps are discussed with regard to gold. With our present knowledge of contact allergy-allergic contact dermatitis, we do not recommend including gold sodium thiosulfate in the standard series. It should be applied for scientific purposes and when allergic contact dermatitis from gold is suspected.

Reactions of Metal-Metal Multiple Bonds. 14. Synthesis and Characterization of Triangulo-W3 and Mo2W-oxo Capped Alkoxide Clusters. Comproportionation of M-M Triple Bonds, sigma(2)pi(4) and d(o) Metal-oxo Groups: M Triple Bond M + M Triple Bond O Yields M3(micron 3-O).

DTIC Science & Technology

1984-05-02

the syntheses of dinuclear and trinuclear complexes employing metal -alkylidyne or -alkylidene fragments.8 Reaction 1 also has a parallel with the...1 0 which was previously examined. The mixed metal complex is undoubtedly disordered with respect to the disposition of molybdenum and tungsten atoms...than for the analogous Mo3 complex suggests greater metal - metal overlap and possibly stronger bonding interactions in the W3 complex which would not

Reclamation with Recovery of Radionuclides and Toxic Metals from Contaminated Materials, Soils, and Wastes

NASA Technical Reports Server (NTRS)

Francis, A. J.; Dodge, C. J.

1993-01-01

A process has been developed at Brookhaven National Laboratory (BNL) for the removal of metals and radionuclides from contaminated materials, soils, and waste sites. In this process, citric acid, a naturally occurring organic complexing agent, is used to extract metals such as Ba, Cd, Cr, Ni, Zn, and radionuclides Co, Sr, Th, and U from solid wastes by formation of water soluble, metal-citrate complexes. Citric acid forms different types of complexes with the transition metals and actinides, and may involve formation of a bidentate, tridentate, binuclear, or polynuclear complex species. The extract containing radionuclide/metal complex is then subjected to microbiological degradation followed by photochemical degradation under aerobic conditions. Several metal citrate complexes are biodegraded, and the metals are recovered in a concentrated form with the bacterial biomass. Uranium forms binuclear complex with citric acid and is not biodegraded. The supernatant containing uranium citrate complex is separated and upon exposure to light, undergoes rapid degradation resulting in the formation of an insoluble, stable polymeric form of uranium. Uranium is recovered as a precipitate (polyuranate) in a concentrated form for recycling or for appropriate disposal. This treatment process, unlike others which use caustic reagents, does not create additional hazardous wastes for disposal and causes little damage to soil which can then be returned to normal use.

Synthesis, characterization and molecular modeling of some transition metal complexes of Schiff base derived from 5-aminouracil and 2-benzoyl pyridine

NASA Astrophysics Data System (ADS)

Abdel-Monem, Yasser K.; Abouel-Enein, Saeyda A.; El-Seady, Safa M.

2018-01-01

Multidentate Schiff base (H2L) ligand results from condensation of 5-aminouracil and 2-benzoyl pyridine and its metal chloride (Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Fe(III), Cr(III), Ru(III), Zr(IV) and Hf(IV)) complexes were prepared. The structural features of the ligand and its metal complexes were confirmed by elemental analyses, spectroscopic methods (IR, UV-Vis, 1H NMR, mass), magnetic moment measurements and thermal studies. The data refer to the ligand coordinates with metal ions in a neutral form and shows different modes of chelation toward the metal atom. All complexes have octahedral skeleton structure, tetrahedrally Mn(II), Ni(II), trigonalbipyramidal Co(II) and square planner Pd(II). Thermal decomposition of complexes as well as the interaction of different types of solvent of crystallization are assigned by thermogravimetric analysis. Molecular modeling of prepared complexes were investigated to study the expected anticancer activities of the prepared complexes. All metal complexes have no interaction except the complexes of Pd(II), Fe(III) and Mn(II).

Study of distorted octahedral structure in 3d transition metal complexes using XAFS

NASA Astrophysics Data System (ADS)

Gaur, A.; Nitin Nair, N.; Shrivastava, B. D.; Das, B. K.; Chakrabortty, Monideepa; Jha, S. N.; Bhattacharyya, D.

2018-01-01

Distortion in octahedral structure of 3d transition metal complexes (Mn, Fe, Co, Ni, Cu, Zn) has been studied using XAFS showing divergent nature of Cu complex. EXAFS analysis showed elongated metal-oxygen bonds for Cu complex leading to more distorted structure. Derivative XANES spectrum at Cu K-edge exhibits splitting of main edge which is correlated to elongated Cu-O bond length. Using these coordination geometry around metal centers, theoretical XANES spectra have been generated and features observed have been correlated to the corresponding metals p-DOS. It has been shown that distorted octahedral field in Cu complex is responsible for splitting of p-DOS.

Self-assembly of discrete metal complexes in aqueous solution via block copolypeptide amphiphiles.

PubMed

Kuroiwa, Keita; Masaki, Yoshitaka; Koga, Yuko; Deming, Timothy J

2013-01-21

The integration of discrete metal complexes has been attracting significant interest due to the potential of these materials for soft metal-metal interactions and supramolecular assembly. Additionally, block copolypeptide amphiphiles have been investigated concerning their capacity for self-assembly into structures such as nanoparticles, nanosheets and nanofibers. In this study, we combined these two concepts by investigating the self-assembly of discrete metal complexes in aqueous solution using block copolypeptides. Normally, discrete metal complexes such as [Au(CN)(2)]-, when molecularly dispersed in water, cannot interact with one another. Our results demonstrated, however, that the addition of block copolypeptide amphiphiles such as K(183)L(19) to [Au(CN)(2)]- solutions induced one-dimensional integration of the discrete metal complex, resulting in photoluminescence originating from multinuclear complexes with metal-metal interactions. Transmission electron microscopy (TEM) showed a fibrous nanostructure with lengths and widths of approximately 100 and 20 nm, respectively, which grew to form advanced nanoarchitectures, including those resembling the weave patterns of Waraji (traditional Japanese straw sandals). This concept of combining block copolypeptide amphiphiles with discrete coordination compounds allows the design of flexible and functional supramolecular coordination systems in water.

Evaluation of the tratment of metal-EDTA complexes using Ti0{sub 2} photocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madden, T.; Datyte, A.K.; Prairie, M.R.

1996-03-01

This study has demonstrated the feasibility of TiO{sub 2} photocatalysis to treat EDTA and several metal-EDTA complexes that can be found in industrial wastewaters. For the EDTA complexes of metals capable of photodeposition, such as Cu and Pb, certain reaction conditions were shown to facilitate the simultaneous complex degradation and photodeposition of these metals onto the catalyst. With metals that do not easily photodeposit, such as Ni and Cd, it is shown that the complex degradation is still facilitated, and can enhance other metals removal processes after photocatalytic treatment. Because the treatment of these metal-EDTA complexes typically requires special measures,more » there may exist situations where TiO{sub 2} photocatalysis could actually be the preferred method of treatment. However, its use should be compared economically to other more established advanced oxidation technologies. This necessity is demonstrated in the economic comparison to ozone treatment for EDTA degradation alone, where ozone treatment appears to be the clear choice in this application.« less

Determination of stability constants of aminoglycoside antibiotics with their metal complexes

NASA Astrophysics Data System (ADS)

Tiwow, Vanny M. A.

2014-03-01

One group of aminoglycoside antibiotics contains aminosugars. The aminosugar neomycin B with its derivate product neamine (2-Deoxy-4-0-(2,6-diamino-2,6-dideoxy-α-D-glucopyranosyl)-D-Streptamine) was identified as a free ligands and metal complexes. In particular, the stability constants of metal complexes by potentiometric titration techniques were investigated. Our previous study had determined the acid dissociation constants of these aminosugars with few metal complexes in fair depth. In this work, the complexation of two pyridine-containing amino alcohols and an amino sugar (neamine) have been measured potentiometrically. For instance, the stability constant of copper(II) complexation were determine and the model system generated an excellent fit. Stability constants with several metals have been determined and will be reported.

Heterobimetallic Complexes Comprised of Nb and Fe: Isolation of a Coordinatively Unsaturated NbIII/Fe0 Bimetallic Complex Featuring a Nb≡Fe Triple Bond.

PubMed

Culcu, Gursu; Iovan, Diana A; Krogman, Jeremy P; Wilding, Matthew J T; Bezpalko, Mark W; Foxman, Bruce M; Thomas, Christine M

2017-07-19

Heterometallic multiple bonds between niobium and other transition metals have not been reported to date, likely owing to the highly reactive nature of low-valent niobium centers. Herein, a C 3 -symmetric tris(phosphinoamide) ligand framework is used to construct a Nb/Fe heterobimetallic complex Cl-Nb( i PrNPPh 2 ) 3 Fe-Br (2), which features a Fe→Nb dative bond with a metal-metal distance of 2.4269(4) Å. Reduction of 2 in the presence of PMe 3 affords Nb( i PrNPPh 2 ) 3 Fe-PMe 3 (6), a compound with an unusual trigonal pyramidal geometry at a Nb III center, a Nb≡Fe triple bond, and the shortest bond distance (2.1446(8) Å) ever reported between Nb and any other transition metal. Complex 6 is thermally unstable and degrades via P-N bond cleavage to form a Nb V ═NR imide complex, i PrN═Nb( i PrNPPh 2 ) 3 Fe-PMe 3 (9). The heterobimetallic complexes i PrN═Nb( i PrNPPh 2 ) 3 Fe-Br (8) and 9 are independently synthesized, revealing that the strongly π-bonding imido functionality prevents significant metal-metal interactions. The 57 Fe Mössbauer spectra of 2, 6, 8, and 9 show a clear trend in isomer shift (δ), with a decrease in δ as metal-metal interactions become stronger and the Fe center is reduced. The electronic structure and metal-metal bonding of 2, 6, 8, and 9 are explored through computational studies, and cyclic voltammetry is used to better understand the effect of metal-metal interaction in early/late heterobimetallic complexes on the redox properties of the two metals involved.

Identification of metal species by ESI-MS/MS through release of free metals from the corresponding metal-ligand complexes

PubMed Central

Tsednee, Munkhtsetseg; Huang, Yu-Chen; Chen, Yet-Ran; Yeh, Kuo-Chen

2016-01-01

Electrospray ionization-mass spectrometry (ESI-MS) is used to analyze metal species in a variety of samples. Here, we describe an application for identifying metal species by tandem mass spectrometry (ESI-MS/MS) with the release of free metals from the corresponding metal–ligand complexes. The MS/MS data were used to elucidate the possible fragmentation pathways of different metal–deoxymugineic acid (–DMA) and metal–nicotianamine (–NA) complexes and select the product ions with highest abundance that may be useful for quantitative multiple reaction monitoring. This method can be used for identifying different metal–ligand complexes, especially for metal species whose mass spectra peaks are clustered close together. Different metal–DMA/NA complexes were simultaneously identified under different physiological pH conditions with this method. We further demonstrated the application of the technique for different plant samples and with different MS instruments. PMID:27240899

Quantitative Interpretation of Multifrequency Multimode EPR Spectra of Metal Containing Proteins, Enzymes, and Biomimetic Complexes.

PubMed

Petasis, Doros T; Hendrich, Michael P

2015-01-01

Electron paramagnetic resonance (EPR) spectroscopy has long been a primary method for characterization of paramagnetic centers in materials and biological complexes. Transition metals in biological complexes have valence d-orbitals that largely define the chemistry of the metal centers. EPR spectra are distinctive for metal type, oxidation state, protein environment, substrates, and inhibitors. The study of many metal centers in proteins, enzymes, and biomimetic complexes has led to the development of a systematic methodology for quantitative interpretation of EPR spectra from a wide array of metal containing complexes. The methodology is now contained in the computer program SpinCount. SpinCount allows simulation of EPR spectra from any sample containing multiple species composed of one or two metals in any spin state. The simulations are quantitative, thus allowing determination of all species concentrations in a sample directly from spectra. This chapter will focus on applications to transition metals in biological systems using EPR spectra from multiple microwave frequencies and modes. © 2015 Elsevier Inc. All rights reserved.

A Study on Spectro-Analytical Aspects, DNA - Interaction, Photo-Cleavage, Radical Scavenging, Cytotoxic Activities, Antibacterial and Docking Properties of 3 - (1 - (6 - methoxybenzo [d] thiazol - 2 - ylimino) ethyl) - 6 - methyl - 3H - pyran - 2, 4 - dione and its Metal Complexes.

PubMed

Ravi, Mudavath; Chennam, Kishan Prasad; Ushaiah, B; Eslavath, Ravi Kumar; Perugu, Shyam; Ajumeera, Rajanna; Devi, Ch Sarala

2015-09-01

The focus of the present work is on the design, synthesis, characterization, DNA-interaction, photo-cleavage, radical scavenging, in-vitro cytotoxicity, antimicrobial, docking and kinetic studies of Cu (II), Cd (II), Ce (IV) and Zr (IV) metal complexes of an imine derivative, 3 - (1 - (6 - methoxybenzo [d] thiazol - 2 - ylimino) ethyl) - 6 - methyl - 3H - pyran - 2, 4 - dione. The investigation of metal ligand interactions for the determination of composition of metal complexes, corresponding kinetic studies and antioxidant activity in solution was carried out by spectrophotometric methods. The synthesized metal complexes were characterized by EDX analysis, Mass, IR, (1)H-NMR, (13)C-NMR and UV-Visible spectra. DNA binding studies of metal complexes with Calf thymus (CT) DNA were carried out at room temperature by employing UV-Vis electron absorption, fluorescence emission and viscosity measurement techniques. The results revealed that these complexes interact with DNA through intercalation. The results of in vitro antibacterial studies showed the enhanced activity of chelating agent in metal chelated form and thus inferring scope for further development of new therapeutic drugs. Cell viability experiments indicated that all complexes showed significant dose dependent cytotoxicity in selected cell lines. The molecular modeling and docking studies were carried out with energy minimized structures of metal complexes to identify the receptor to metal interactions.

Report: complexation of β-sitosterol with tris (dibenzylideneacetone) dipalladium and its anti-microbial activity.

PubMed

Mahmood, Talat; Bibi, Yasmeen; Zafar, Raana; Wahab, Aneela; Mahmood, Iffat; Arshad, Nuzhat; Sherwani, Sikandar Khan

2015-03-01

β-sitosterol is a naturally occurring plant sterol (phytosterol) present in many fruits and vegetables. Scientific research has proven that β-sitosterol is helpful in maintaining the proper functioning of our body. Previously we described the complexation of β-sitosterol with trace metals (Mahmood et al., 2013). Trace metals after the formation of complex unable to absorb in the body and hence eliminated out from the body thus reducing metal toxicity (Marsha, 1996). The present article describes the complexation of μ-sitosterol with Palladium (Pd) metal. Palladium is a toxic metal and due to polluted and hazardous environment traces of this metal can be transferred into the body, which is harmful for human health. Our aim is to make Pd-sterol complex so that this toxic metal (Pd) does not absorb in the body and hence excreted out from the body in the complex form. In order to form this complex μ-sitosterol (Ib) is reacted with Tris (dibenzylideneacetone) dipalladium or [Pd(2) (DBA)(3)] (Ia) in 2:1 ratio in an inert atmosphere and dimethylformamid (DMF) added as a solvent. The resulting complex [Pd(2) (DBA)(3).(β-sitosterol) (Ic) was identified by various spectroscopic techniques such as IR, Mass and (1)H-NMR. This new organo metallic complex (Ic) also showed significant antibacterial and antifungal activity. The present work revealed that Pd-sterol complex does not only reduce metal toxicity but also helpful in minimizing bacterial and fungal infections present in the body. Our research also concluded that we must take plenty of fruits and vegetables in our diet so that natural plant sterol such as β-sitosterol can enhance our defense mechanism and maintain other functions of our body.

Design, synthesis, spectral characterization, DNA interaction and biological activity studies of copper(II), cobalt(II) and nickel(II) complexes of 6-amino benzothiazole derivatives

NASA Astrophysics Data System (ADS)

Daravath, Sreenu; Kumar, Marri Pradeep; Rambabu, Aveli; Vamsikrishna, Narendrula; Ganji, Nirmala; Shivaraj

2017-09-01

Two novel Schiff bases, L1 = (2-benzo[d]thiazol-6-ylimino)methyl)-4,6-dichlorophenol), L2 = (1-benzo[d]thiazol-6-ylimino)methyl)-6-bromo-4-chlorophenol) and their bivalent transition metal complexes [M(L1)2] and [M(L2)2], where M = Cu(II), Co(II) and Ni(II) were synthesized and characterized by elemental analysis, NMR, IR, UV-visible, mass, magnetic moments, ESR, TGA, SEM, EDX and powder XRD. Based on the experimental data a square planar geometry around the metal ion is assigned to all the complexes (1a-2c). The interaction of synthesized metal complexes with calf thymus DNA was explored using UV-visible absorption spectra, fluorescence and viscosity measurements. The experimental evidence indicated that all the metal complexes strongly bound to CT-DNA through an intercalation mode. DNA cleavage experiments of metal(II) complexes with supercoiled pBR322 DNA have also been explored by gel electrophoresis in the presence of H2O2 as well as UV light, and it is found that the Cu(II) complexes cleaved DNA more effectively compared to Co(II), Ni(II) complexes. In addition, the ligands and their metal complexes were screened for antimicrobial activity and it is found that all the metal complexes were more potent than free ligands.

Reactions catalyzed by haloporphyrins

DOEpatents

Ellis, P.E. Jr.; Lyons, J.E.

1996-02-06

The invention provides novel methods for the oxidation of hydrocarbons with oxygen-containing gas to form hydroxy-group containing compounds and for the decomposition of hydroperoxides to form hydroxy-group containing compounds. The catalysts used in the methods of the invention comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The catalyst compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of alkanes is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of alkanes and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of alkanes and decomposition of alkyl hydroperoxides.

Haloporphyrins and their preparation and use as catalysts

DOEpatents

Ellis, Jr., Paul E.; Lyons, James E.

1997-01-01

The invention provides novel catalyst compositions, useful in the oxidation of hydrocarbons with air or oxygen to form hydroxy-group containing compounds and in the decomposition of hydroperoxides to form hydroxy-group containing compounds. The catalysts comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of hydrocarbons is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of hydrocarbons and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of hydrocarbons and decomposition of alkyl hydroperoxides.

Reactions catalyzed by haloporphyrins

DOEpatents

Ellis, Jr., Paul E.; Lyons, James E.

1996-01-01

The invention provides novel methods for the oxidation of hydrocarbons with oxygen-containing gas to form hydroxy-group containing compounds and for the decomposition of hydroperoxides to form hydroxygroup containing compounds. The catalysts used in the methods of the invention comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The catalyst compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of alkanes is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of alkanes and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of alkanes and decomposition of alkyl hydroperoxides.

Haloporphyrins and their preparation and use as catalysts

DOEpatents

Ellis, P.E. Jr.; Lyons, J.E.

1997-09-02

The invention provides novel catalyst compositions, useful in the oxidation of hydrocarbons with air or oxygen to form hydroxy-group containing compounds and in the decomposition of hydroperoxides to form hydroxy-group containing compounds. The catalysts comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of hydrocarbons is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of hydrocarbons and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of hydrocarbons and decomposition of alkyl hydroperoxides.

Transition metal-chelating surfactant micelle templates for facile synthesis of mesoporous silica nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hye Sun; Department of Materials Science and Engineering, Yonsei University, Seoul 120-749; Kim, Won Hee

2012-01-15

Highly ordered mesoporous silica nanoparticles with tunable morphology and pore-size are prepared by the use of a transition metal-chelating surfactant micelle complex using Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}, and Zn{sup 2+} ions. These metal ions formed a metal-P123 micelle complex in an aqueous solution, while the metal ions are chelated to the hydrophilic domain such as the poly(ethylene oxide) group of a P123 surfactant. The different complexation abilities of the utilized transition metal ions play an important role in determining the formation of nano-sized ordered MSNs due to the different stabilization constant of the metal-P123 complex. Consequently, from amore » particle length of 1700 nm in the original mesoporous silica materials, the particle length of ordered MSNs through the metal-chelating P123 micelle templates can be reduced to a range of 180-800 nm. Furthermore, the variation of pore size shows a slight change from 8.8 to 6.6 nm. In particular, the Cu{sup 2+}-chelated MSNs show only decreased particle size to 180 nm. The stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism of MSNs by the metal-chelating P123 complex templates. In addition, solid-state {sup 29}Si, {sup 13}C-NMR and ICP-OES measurements are used for quantitative characterization reveal that the utilized metal ions affect only the formation of a metal-P123 complex in a micelle as a template. - Graphical abstract: Metal-chelating surfactant micelle templates support a simple and facile preparations of size-tunable ordered MSNs. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Facile preparation of mesoporous silica nanoparticles (MSNs) was achieved by metal-chelating surfactant micelle complex using Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}, and Zn{sup 2+} ions. Black-Right-Pointing-Pointer Different complexation of metal ions plays an important role in determining the formation of nano-sized ordered MSNs. Black-Right-Pointing-Pointer Systematic characterization of the synthesized materials was achieved by solid-state {sup 29}Si and {sup 13}C-NMR techniques, BET, FT-IR, and XPS. Black-Right-Pointing-Pointer Stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism.« less

[The role of essential metal ions in the human organism and their oral supplementation to the human body in deficiency states].

PubMed

Lakatos, Béla; Szentmihályi, Klára; Vinkler, Péter; Balla, József; Balla, György

2004-06-20

The role of essential nutrient metal ions (Mg, Fe, Cu, Zn, Mn and Co) often deficient in our foodstuffs, although vitally essential in the function of the human organism as well as the different reasons for these deficiencies both in foods and in the human body have been studied. The most frequent nutritional disease is iron deficient anaemia. Inorganic salts, artificial synthetic monomer organic metal complexes of high stability or organic polymer complexes of high molecular mass are unsatisfactory for supplementation to the human body, owing to poor absorption, low availability and/or harmful side effects. In contrast, we have recently found that mixed metal complexes of oligo/polygalacturonic acids with medium molecular weight prepared from natural pectin of plant origin are efficient for oral supplementation. Sufficient absorption of essential metal ions from metal oligo/polygalacturonate mixed complexes with polynuclear innersphere structure is due to the high ionselectivity and medium stability values. Metal oligo/polygalacturonate mixed complexes contain all deficient essential metal ions in adequate amounts and ratios for higher bioavailability of metal ions and optimal vital function. Therefore, by oral administration of these complexes, metal ion homeostasis and optimal interactions with vitamins and hormones can be ensured. Prelatent or latent macroelement Mg deficiency can often be observed among clinical or ambulance patients. Latent or manifest mesoelement iron deficiency is the most common, however, the occurrence of microelement copper, zinc, manganese and cobalt latent deficiencies is not seldom either. Supplementation studies utilizing essential metal oligo/polygalacturonate complexes led to satisfactory outcome without harmful side effects.

Synthesis, crystal structure, fluorescence and electrochemical studies of a new tridentate Schiff base ligand and its nickel(II) and palladium(II) complexes

NASA Astrophysics Data System (ADS)

Shafaatian, Bita; Soleymanpour, Ahmad; Kholghi Oskouei, Nasim; Notash, Behrouz; Rezvani, Seyyed Ahmad

2014-07-01

A new unsymmetrical tridentate Schiff base ligand was derived from the 1:1 M condensation of ortho-vanillin with 2-mercaptoethylamine. Nickel and palladium complexes were obtained by the reaction of the tridentate Schiff base ligand with nickel(II) acetate tetrahydrate and palladium(II) acetate in 2:1 M ratio. In nickel and palladium complexes the ligand was coordinated to metals via the imine N and enolic O atoms. The S groups of Schiff bases were not coordinated to the metals and S-S coupling was occured. The complexes have been found to possess 1:2 Metal:Ligand stoichiometry and the molar conductance data revealed that the metal complexes were non-electrolytes. The complexes exhibited octahedral coordination geometry. The emission spectra of the ligand and its complexes were studied in methanol. Electrochemical properties of the ligand and its metal complexes were investigated in the CH3CN solvent at the 100 mV s-1 scan rate. The ligand and metal complexes showed both reversible and quasi-reversible processes at this scan rate. The Schiff base and its complexes have been characterized by IR, 1H NMR, UV/Vis, elemental analyses and conductometry. The crystal structure of nickel complex has been determined by single crystal X-ray diffraction.

Novel Dialkylamino Derivatives of Phosphorus and Silicon.

DTIC Science & Technology

1987-10-19

Metal Carbonyl Complexes ," Inorg. Chem. 1985, 24, 3136-3139. (7) King, R. B., Fu, W.-K.; Holt, E. M. "The Synthesis of Heterobimetallic Complexes from...Carbonyl Complexes of Diisopropylaminohalophosphines and their Application for the Synthesis of Novel Bimetallic Complexes ," presented by W.-K. Fu at the...necessary and identify by block number) FIELD -GROUP SUB-GROUP Phosphorus /Metal Complexes Silicon Dialkylamino Metal Carbonyls Boron Cyclopolyphosphinesl

Metal-organic complexes in geochemical processes: temperature dependence of the standard thermodynamic properties of aqueous complexes between metal cations and dicarboxylate ligands

NASA Astrophysics Data System (ADS)

Prapaipong, Panjai; Shock, Everett L.; Koretsky, Carla M.

1999-10-01

By combining results from regression and correlation methods, standard state thermodynamic properties for aqueous complexes between metal cations and divalent organic acid ligands (oxalate, malonate, succinate, glutarate, and adipate) are evaluated and applied to geochemical processes. Regression of experimental standard-state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state yields standard partial molal entropies (S¯°) of aqueous metal-organic complexes, which allow determination of thermodynamic properties of the complexes at elevated temperatures. In cases where S¯° is not available from either regression or calorimetric measurement, the values of S¯° can be estimated from a linear correlation between standard partial molal entropies of association (ΔS¯°r) and standard partial molal entropies of aqueous cations (S¯°M). The correlation is independent of cation charge, which makes it possible to predict S¯° for complexes between divalent organic acids and numerous metal cations. Similarly, correlations between standard Gibbs free energies of association of metal-organic complexes (ΔḠ°r) and Gibbs free energies of formation (ΔḠ°f) for divalent metal cations allow estimates of standard-state equilibrium constants where experimental data are not available. These correlations are found to be a function of ligand structure and cation charge. Predicted equilibrium constants for dicarboxylate complexes of numerous cations were included with those for inorganic and other organic complexes to study the effects of dicarboxylate complexes on the speciation of metals and organic acids in oil-field brines. Relatively low concentrations of oxalic and malonic acids affect the speciation of cations more than similar concentrations of succinic, glutaric, and adipic acids. However, the extent to which metal-dicarboxylate complexes contribute to the speciation of dissolved metals depends on the type of dicarboxylic acid ligand; relative concentration of inorganic, mono-, and dicarboxylate ligands; and the type of metal cation. As an example, in the same solution, dicarboxylic acids have a greater influence on the speciation of Fe+2 and Mg+2 than on the speciation of Zn+2 and Mn+2.

Cyanide - Mechanism of Prophylaxis and Effect on Cytochrome Oxidase.

DTIC Science & Technology

1981-08-15

thiosulfate by chlorpromazine was studied alone and in various combinations with the classic cyanide antidotal combination of sodium nitrite and sodium...greater in the groups given oxygen over the respective groups given air, but the difference was signi- ficant only with groups receiving oxygen alone or...cyanide intoxication by chlorpromazine, parti- cularly when it is employed in combination with the classic cyanide antagonists, sodium nitrite and

High-Quality Draft Genomes from Thermus caliditerrae YIM 77777 and T. tengchongensis YIM 77401, Isolates from Tengchong, China

DOE PAGES

Mefferd, Chrisabelle C.; Zhou, En-Min; Yu, Tian-Tian; ...

2016-04-28

The draft genomes ofThermus  tengchongensisYIM 77401 andT. caliditerraeYIM 77777 are 2,562,314 and 2,218,114 bp and encode 2,726 and 2,305 predicted genes, respectively. Gene content and growth experiments demonstrate broad metabolic capacity, including starch hydrolysis, thiosulfate oxidation, arsenite oxidation, incomplete denitrification, and polysulfide reduction.

High-Quality Draft Genome Sequence of Thermocrinis jamiesonii GBS1 T Isolated from Great Boiling Spring, Nevada

DOE PAGES

Ganji, Rakesh; Murugapiran, Senthil K.; Ong, John C.; ...

2016-10-20

The draft genome of Thermocrinis jamiesonii GBS1 T is 1,315,625 bp in 10 contigs and encodes 1,463 predicted genes. The presence of sox genes and various glycoside hydrolases and the absence of uptake NiFe hydrogenases ( hyaB) are consistent with a requirement for thiosulfate and suggest the ability to use carbohydrate polymers.

Stress Corrosion Cracking of Aluminum Alloys

DTIC Science & Technology

2012-09-10

Hossain and B. J, O’Toole: Stress Corrosion Cracking of Martensitic Stainless Steel for Transmutation Application, Presented at 2003 International...SCC of marternsitic stainless steel by Roy,[12] and learn the annealing effect on SCC of carbon steel by Haruna.[13] The application of slow...observations. In his study on SCC of AISI 304 stainless steel , Roychowdhury[3] detected no apparent SCC in solutions containing 1 ppm thiosulfate and

Genomic Analysis of Caldithrix abyssi, the Thermophilic Anaerobic Bacterium of the Novel Bacterial Phylum Calditrichaeota

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kublanov, Ilya V.; Sigalova, Olga M.; Gavrilov, Sergey N.

The genome of Caldithrix abyssi, the first cultivated representative of a phylum-level bacterial lineage, was sequenced within the framework of Genomic Encyclopedia of Bacteria and Archaea (GEBA) project. The genomic analysis revealed mechanisms allowing this anaerobic bacterium to ferment peptides or to implement nitrate reduction with acetate or molecular hydrogen as electron donors. The genome encoded five different [NiFe]- and [FeFe]-hydrogenases, one of which, group 1 [NiFe]-hydrogenase, is presumably involved in lithoheterotrophic growth, three other produce H 2 during fermentation, and one is apparently bidirectional. The ability to reduce nitrate is determined by a nitrate reductase of the Nap family,more » while nitrite reduction to ammonia is presumably catalyzed by an octaheme cytochrome c nitrite reductase εHao. The genome contained genes of respiratory polysulfide/thiosulfate reductase, however, elemental sulfur and thiosulfate were not used as the electron acceptors for anaerobic respiration with acetate or H 2, probably due to the lack of the gene of the maturation protein. Nevertheless, elemental sulfur and thiosulfate stimulated growth on fermentable substrates (peptides), being reduced to sulfide, most probably through the action of the cytoplasmic sulfide dehydrogenase and/or NAD(P)-dependent [NiFe]-hydrogenase (sulfhydrogenase) encoded by the genome. Surprisingly, the genome of this anaerobic microorganism encoded all genes for cytochrome c oxidase, however, its maturation machinery seems to be non-operational due to genomic rearrangements of supplementary genes. Despite the fact that sugars were not among the substrates reported when C. abyssi was first described, our genomic analysis revealed multiple genes of glycoside hydrolases, and some of them were predicted to be secreted. This finding aided in bringing out four carbohydrates that supported the growth of C. abyssi: starch, cellobiose, glucomannan and xyloglucan. The genomic analysis demonstrated the ability of C. abyssi to synthesize nucleotides and most amino acids and vitamins. Finally, the genomic sequence allowed us to perform a phylogenomic analysis, based on 38 protein sequences, which confirmed the deep branching of this lineage and justified the proposal of a novel phylum Calditrichaeota.« less

Genomic Analysis of Caldithrix abyssi, the Thermophilic Anaerobic Bacterium of the Novel Bacterial Phylum Calditrichaeota

DOE PAGES

Kublanov, Ilya V.; Sigalova, Olga M.; Gavrilov, Sergey N.; ...

2017-02-20

The genome of Caldithrix abyssi, the first cultivated representative of a phylum-level bacterial lineage, was sequenced within the framework of Genomic Encyclopedia of Bacteria and Archaea (GEBA) project. The genomic analysis revealed mechanisms allowing this anaerobic bacterium to ferment peptides or to implement nitrate reduction with acetate or molecular hydrogen as electron donors. The genome encoded five different [NiFe]- and [FeFe]-hydrogenases, one of which, group 1 [NiFe]-hydrogenase, is presumably involved in lithoheterotrophic growth, three other produce H 2 during fermentation, and one is apparently bidirectional. The ability to reduce nitrate is determined by a nitrate reductase of the Nap family,more » while nitrite reduction to ammonia is presumably catalyzed by an octaheme cytochrome c nitrite reductase εHao. The genome contained genes of respiratory polysulfide/thiosulfate reductase, however, elemental sulfur and thiosulfate were not used as the electron acceptors for anaerobic respiration with acetate or H 2, probably due to the lack of the gene of the maturation protein. Nevertheless, elemental sulfur and thiosulfate stimulated growth on fermentable substrates (peptides), being reduced to sulfide, most probably through the action of the cytoplasmic sulfide dehydrogenase and/or NAD(P)-dependent [NiFe]-hydrogenase (sulfhydrogenase) encoded by the genome. Surprisingly, the genome of this anaerobic microorganism encoded all genes for cytochrome c oxidase, however, its maturation machinery seems to be non-operational due to genomic rearrangements of supplementary genes. Despite the fact that sugars were not among the substrates reported when C. abyssi was first described, our genomic analysis revealed multiple genes of glycoside hydrolases, and some of them were predicted to be secreted. This finding aided in bringing out four carbohydrates that supported the growth of C. abyssi: starch, cellobiose, glucomannan and xyloglucan. The genomic analysis demonstrated the ability of C. abyssi to synthesize nucleotides and most amino acids and vitamins. Finally, the genomic sequence allowed us to perform a phylogenomic analysis, based on 38 protein sequences, which confirmed the deep branching of this lineage and justified the proposal of a novel phylum Calditrichaeota.« less

Membrane extraction with thermodynamically unstable diphosphonic acid derivatives

DOEpatents

Horwitz, Earl Philip; Gatrone, Ralph Carl; Nash, Kenneth LaVerne

1997-01-01

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described.

Intercalation of Transition Metals into Stacked Benzene Rings: A Model Study of the Intercalation of Transition Metals into Bilayered Graphene.

PubMed

Youn, Il Seung; Kim, Dong Young; Singh, N Jiten; Park, Sung Woo; Youn, Jihee; Kim, Kwang S

2012-01-10

Structures of neutral metal-dibenzene complexes, M(C6H6)2 (M = Sc-Zn), are investigated by using Møller-Plesset second order perturbation theory (MP2). The benzene molecules change their conformation and shape upon complexation with the transition metals. We find two types of structures: (i) stacked forms for early transition metal complexes and (ii) distorted forms for late transition metal ones. The benzene molecules and the metal atom are bound together by δ bonds which originate from the interaction of π-MOs and d orbitals. The binding energy shows a maximum for Cr(C6H6)2, which obeys the 18-electron rule. It is noticeable that Mn(C6H6)2, a 19-electron complex, manages to have a stacked structure with an excess electron delocalized. For other late transition metal complexes having more than 19 electrons, the benzene molecules are bent or stray away from each other to reduce the electron density around a metal atom. For the early transition metals, the M(C6H6) complexes are found to be more weakly bound than M(C6H6)2. This is because the M(C6H6) complexes do not have enough electrons to satisfy the 18-electron rule, and so the M(C6H6)2 complexes generally tend to have tighter binding with a shorter benzene-metal length than the M(C6H6) complexes, which is quite unusual. The present results could provide a possible explanation of why on the Ni surface graphene tends to grow in a few layers, while on the Cu surface the weak interaction between the copper surface and graphene allows for the formation of a single layer of graphene, in agreement with chemical vapor deposition experiments.

Multiheteromacrocycles that Complex Metal Ions. Ninth Progress Report (includes results of last three years), 1 May 1980 -- 30 April 1983

DOE R&D Accomplishments Database

Cram, D. J.

1982-09-15

The overall objective of this research is to design, synthesize, and evaluate cyclic and polycyclic host organic compounds for the abilities to complex and lipophilize guest metal ions, their complexes, and their clusters. Host organic compounds consist of strategically placed solvating, coordinating, and ion-pairing sites tied together by covalent bonds through hydrocarbon units around cavities shaped to be occupied by guest metal ions, or by metal ions plus their ligands. Specificity in complexation is sought by matching the following properties of host and guest: cavity and metal ion sizes; geometric arrangements of binding sites; numbers of binding sites; characters of binding sites; and valences. The hope is to synthesize new classes of compounds useful in the separation of metal ions, their complexes, and their clusters.

Energetic lanthanide complexes: coordination chemistry and explosives applications

NASA Astrophysics Data System (ADS)

Manner, V. W.; Barker, B. J.; Sanders, V. E.; Laintz, K. E.; Scott, B. L.; Preston, D. N.; Sandstrom, M.; Reardon, B. L.

2014-05-01

Metals are generally added to organic molecular explosives in a heterogeneous composite to improve overall heat and energy release. In order to avoid creating a mixture that can vary in homogeneity, energetic organic molecules can be directly bonded to high molecular weight metals, forming a single metal complex with Angstrom-scale separation between the metal and the explosive. To probe the relationship between the structural properties of metal complexes and explosive performance, a new series of energetic lanthanide complexes has been prepared using energetic ligands such as NTO (5-nitro-2,4-dihydro-1,2,4-triazole-3-one). These are the first examples of lanthanide NTO complexes where no water is coordinated to the metal, demonstrating novel control of the coordination environment. The complexes have been characterized by X-ray crystallography, NMR and IR spectroscopies, photoluminescence, and sensitivity testing. The structural and energetic properties are discussed in the context of enhanced blast effects and detection. Cheetah calculations have been performed to fine-tune physical properties, creating a systematic method for producing explosives with 'tailor made' characteristics. These new complexes will be benchmarks for further study in the field of metalized high explosives.

Energetic Lanthanide Complexes: Coordination Chemistry and Explosives Applications

NASA Astrophysics Data System (ADS)

Manner, Virginia; Barker, Beau; Sanders, Eric; Laintz, Kenneth; Scott, Brian; Preston, Daniel; Sandstrom, Mary; Reardon, Bettina

2013-06-01

Metals are generally added to organic molecular explosives in a heterogeneous composite to improve overall heat and energy release. In order to avoid creating a mixture that can vary in homogeneity, energetic organic molecules can be directly bonded to high molecular weight metals, forming a single metal complex with Angstrom-scale separation between the metal and the explosive. To probe the relationship between the structural properties of metal complexes and explosive performance, a new series of energetic lanthanide complexes has been prepared using energetic ligands such as NTO (5-nitro-2,4-dihydro-1,2,4-triazole-3-one). These are the first examples of lanthanide NTO complexes where no water is coordinated to the metal, demonstrating novel control of the coordination environment. The complexes have been characterized by X-ray crystallography, NMR and IR spectroscopies, photoluminescence, and sensitivity testing. The structural and energetic properties are discussed in the context of enhanced blast effects and detection. Cheetah calculations have been performed to fine-tune physical properties, creating a systematic method for producing explosives with ``tailor made'' characteristics. These new complexes will be benchmarks for further study in the field of metalized high explosives.

Interaction between transition metals and phenylalanine: a combined experimental and computational study.

PubMed

Elius Hossain, Md; Mahmudul Hasan, Md; Halim, M E; Ehsan, M Q; Halim, Mohammad A

2015-03-05

Some transition metal complexes of phenylalanine of general formula [M(C9H10NO2)2]; where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) are prepared in aqueous medium and characterized by spectroscopic, thermo-gravimetric (TG) and magnetic susceptibility analysis. Density functional theory (DFT) has been employed calculating the equilibrium geometries and vibrational frequencies of those complexes at B3LYP level of theory using 6-31G(d) and SDD basis sets. In addition, frontier molecular orbital and time-dependent density functional theory (TD-DFT) calculations are performed with CAM-B3LYP/6-31+G(d,p) and B3LYP/SDD level of theories. Thermo-gravimetric analysis confirms the composition of the complexes by comparing the experimental and calculated data for C, H, N and metals. Experimental and computed IR results predict a significant change in vibrational frequencies of metal-phenylalanine complexes compared to free ligand. DFT calculation confirms that Mn, Co, Ni and Cu complexes form square planar structure whereas Zn adopts distorted tetrahedral geometry. The metal-oxygen bonds in the optimized geometry of all complexes are shorter compared to the metal-nitrogen bonds which is consistent with a previous study. Cation-binding energy, enthalpy and Gibbs free energy indicates that these complexes are thermodynamically stable. UV-vis and TD-DFT studies reveal that these complexes demonstrate representative metal-to-ligand charge transfer (MLCT) and d-d transitions bands. TG analysis and IR spectra of the metal complexes strongly support the absence of water in crystallization. Magnetic susceptibility data of the complexes exhibits that all except Zn(II) complex are high spin paramagnetic. Copyright © 2014 Elsevier B.V. All rights reserved.

The Effect of Complex Formation upon the Redox Potentials of Metallic Ions. Cyclic Voltammetry Experiments.

ERIC Educational Resources Information Center

Ibanez, Jorge G.; And Others

1988-01-01

Describes experiments in which students prepare in situ soluble complexes of metal ions with different ligands and observe and estimate the change in formal potential that the ion undergoes upon complexation. Discusses student formation and analysis of soluble complexes of two different metal ions with the same ligand. (CW)

Electronic Structure and Bonding in Transition Metal Inorganic and Organometallic Complexes: New Basis Sets, Linear Semibridging Carbonyls and Thiocarbonyls, and Oxidative Addition of Molecular Hydrogen to Square - Iridium Complexes.

NASA Astrophysics Data System (ADS)

Sargent, Andrew Landman

Approximate molecular orbital and ab initio quantum chemical techniques are used to investigate the electronic structure, bonding and reactivity of several transition metal inorganic and organometallic complexes. Modest-sized basis sets are developed for the second-row transition metal atoms and are designed for use in geometry optimizations of inorganic and organometallic complexes incorporating these atoms. The basis sets produce optimized equilibrium geometries which are slightly better than those produced with standard 3-21G basis sets, and which are significantly better than those produced with effective core potential basis sets. Linear semibridging carbonyl ligands in heterobimetallic complexes which contain a coordinatively unsaturated late transition metal center are found to accept electron density from, rather than donate electron density to, these centers. Only when the secondary metal center is a coordinatively unsaturated early transition metal center does the semibridging ligand donate electron density to this center. Large holes in the d shell around the metal center are more prominent and prevalent in early than in late transition metal centers, and the importance of filling in these holes outweighs the importance of mitigating the charge imbalance due to the dative metal-metal interaction. Semibridging thiocarbonyl ligands are more effective donors of electron density than the carbonyl ligands since the occupied donor orbitals of pi symmetry are higher in energy. The stereoselectivity of H_2 addition to d^8 square-planar transition metal complexes is controlled by the interactions between the ligands in the plane of addition and the concentrations of electronic charge around the metal center as the complex evolves from a four-coordinate to a six-coordinate species. Electron -withdrawing ligands help stabilize the five-coordinate species while strong electron donor ligands contribute only to the destabilizing repulsive interactions. The relative thermodynamic stabilities of the final complexes can be predicted based on the relative orientations of the strongest sigma-donor ligands.

Metal adsorption onto bacterial surfaces: development of a predictive approach

NASA Astrophysics Data System (ADS)

Fein, Jeremy B.; Martin, Aaron M.; Wightman, Peter G.

2001-12-01

Aqueous metal cation adsorption onto bacterial surfaces can be successfully modeled by means of a surface complexation approach. However, relatively few stability constants for metal-bacterial surface complexes have been measured. In order to determine the bacterial adsorption behavior of cations that have not been studied in the laboratory, predictive techniques are required that enable estimation of the stability constants of bacterial surface complexes. In this study, we use a linear free-energy approach to compare previously measured stability constants for Bacillus subtilis metal-carboxyl surface complexes with aqueous metal-organic acid anion stability constants. The organic acids that we consider are acetic, oxalic, citric, and tiron. We add to this limited data set by conducting metal adsorption experiments onto Bacillus subtilis, determining bacterial surface stability constants for Co, Nd, Ni, Sr, and Zn. The adsorption behavior of each of the metals studied here was described well by considering metal-carboxyl bacterial surface complexation only, except for the Zn adsorption behavior, which required carboxyl and phosphoryl complexation to obtain a suitable fit to the data. The best correlation between bacterial carboxyl surface complexes and aqueous organic acid anion stability constants was obtained by means of metal-acetate aqueous complexes, with a linear correlation coefficient of 0.97. This correlation applies only to unhydrolyzed aqueous cations and only to carboxyl binding of those cations, and it does not predict the binding behavior under conditions where metal binding to other bacterial surface site types occurs. However, the relationship derived in this study permits estimation of the carboxyl site adsorption behavior of a wide range of aqueous metal cations for which there is an absence of experimental data. This technique, coupled with the observation of similar adsorption behaviors across bacterial species (Yee and Fein, 2001), enables estimation of the effects of bacterial adsorption on metal mobilities for a large number of environmental and geologic applications.

Assigning Oxidation States to Some Metal Dioxygen Complexes of Biological Interest.

ERIC Educational Resources Information Center

Summerville, David A.; And Others

1979-01-01

The bonding of dioxygen in metal-dioxygen complexes is discussed, paying particular attention to the problems encountered in assigning conventional oxidation numbers to both the metal center and coordinated dioxygen. Complexes of iron, cobalt, chromium, and manganese are considered. (BB)

Metal complex-based electron-transfer mediators in dye-sensitized solar cells

DOEpatents

Elliott, C. Michael; Sapp, Shawn A.; Bignozzi, Carlo Alberto; Contado, Cristiano; Caramori, Stefano

2006-03-28

This present invention provides a metal-ligand complex and methods for using and preparing the same. In particular, the metal-ligand complex of the present invention is of the formula: L.sub.a-M-X.sub.b where L, M, X, a, and b are those define herein. The metal-ligand complexes of the present invention are useful in a variety of applications including as electron-transfer mediators in dye-sensitized solar cells and related photoelectrochromic devices.

Ursolic Acid Hydrazide Based Organometallic Complexes: Synthesis, Characterization, Antibacterial, Antioxidant and Docking Studies

NASA Astrophysics Data System (ADS)

Jabeen, Muafia; Ahmad, Sajjad; Shahid, Khadija; Sadiq, Abdul; Rashid, Umer

2018-03-01

In the current research work,eleven metal complexes were synthesized from the hydrazide derivative of ursolic acid. Metal complexes of tin, antimony and iron were synthesized and characterized by FT-IR and NMR spectroscopy. The antibacterial and antioxidant activities were performed for these complexes, which revealed that the metal complexes synthesized are more potent than their parent compounds. We observed that antioxidant activity showed by triphenyltin complex was significant and least activity have been shown by antimony trichloride complex.The synthesized metal complexes were then evaluated against two Gram-negative and two Gram-positive bacterial strains. Triphenyl tin complex emerged as potent antibacterial agent with MIC value of 8 μg/ml each against Shigellaspp, S. typhi and S. aureus. While, the MIC value againstS. pneumoniae is 4 μg/ml.Computational docking studies were carried out on molecular targets to interpret the results of antioxidant and antibacterial activities. Based on the results, it may be inferred that the metal complexes of ursolic acid are more active as compared to the parent drug and may be proved for some other pharmacological potential by further analysis.

Methods of selectively incorporating metals onto substrates

DOEpatents

Ernst; Richard D. , Eyring; Edward M. , Turpin; Gregory C. , Dunn; Brian C.

2008-09-30

A method for forming multi-metallic sites on a substrate is disclosed and described. A substrate including active groups such as hydroxyl can be reacted with a pretarget metal complex. The target metal attached to the active group can then be reacted with a secondary metal complex such that an oxidation-reduction (redox) reaction occurs to form a multi-metallic species. The substrate can be a highly porous material such as aerogels, xerogels, zeolites, and similar materials. Additional metal complexes can be reacted to increase catalyst loading or control co-catalyst content. The resulting compounds can be oxidized to form oxides or reduced to form metals in the ground state which are suitable for practical use.

Surface-enhanced Raman scattering and DFT investigation of 1,5-diphenylcarbazide and its metal complexes with Ca(II), Mn(II), Fe(III) and Cu(II)

NASA Astrophysics Data System (ADS)

Szabó, László; Herman, Krisztian; Mircescu, Nicoleta Elena; Tódor, István Szabolcs; Simon, Botond Lorand; Boitor, Radu Alex; Leopold, Nicolae; Chiş, Vasile

2014-09-01

In recent years, surface-enhanced Raman scattering (SERS) has become an increasingly viable method for the detection of metal ions, evidenced by the existing studies on metal complexes. In this study, 1,5-diphenylcarbazide (DPC) and its Ca(II), Mn(II), Fe(III) and Cu(II) complexes were investigated by FTIR/ATR, FT-Raman and surface-enhanced Raman spectroscopies. The hybrid B3LYP exchange-correlation functional was used for the molecular geometry optimizations, molecular electrostatic potential (MEP) distribution and vibrational frequencies calculations of the DPC molecule and its complexes. Based on experimental and theoretical data, we were able to accurately identify unique and representative features for each DPC-metal complex, features that enable the detection of said metal complexes in millimolar concentrations.

Application of Δ- and λ-isomerism of octahedral metal complexes for inducing chiral nematic phases.

PubMed

Sato, Hisako; Yamagishi, Akihiko

2009-11-20

The Delta- and Lambda-isomerism of octahedral metal complexes is employed as a source of chirality for inducing chiral nematic phases. By applying a wide range of chiral metal complexes as a dopant, it has been found that tris(beta-diketonato)metal(III) complexes exhibit an extremely high value of helical twisting power. The mechanism of induction of the chiral nematic phase is postulated on the basis of a surface chirality model. The strategy for designing an efficient dopant is described, together with the results using a number of examples of Co(III), Cr(III) and Ru(III) complexes with C(2) symmetry. The development of photo-responsive dopants to achieve the photo-induced structural change of liquid crystal by use of photo-isomerization of chiral metal complexes is also described.

Application of Δ- and Λ-Isomerism of Octahedral Metal Complexes for Inducing Chiral Nematic Phases

PubMed Central

Sato, Hisako; Yamagishi, Akihiko

2009-01-01

The Δ- and Λ-isomerism of octahedral metal complexes is employed as a source of chirality for inducing chiral nematic phases. By applying a wide range of chiral metal complexes as a dopant, it has been found that tris(β-diketonato)metal(III) complexes exhibit an extremely high value of helical twisting power. The mechanism of induction of the chiral nematic phase is postulated on the basis of a surface chirality model. The strategy for designing an efficient dopant is described, together with the results using a number of examples of Co(III), Cr(III) and Ru(III) complexes with C2 symmetry. The development of photo-responsive dopants to achieve the photo-induced structural change of liquid crystal by use of photo-isomerization of chiral metal complexes is also described. PMID:20057959

Synthesis, spectral studies and biological evaluation of 2-aminonicotinic acid metal complexes

NASA Astrophysics Data System (ADS)

Nawaz, Muhammad; Abbasi, Muhammad Waseem; Hisaindee, Soleiman; Zaki, Muhammad Javed; Abbas, Hira Fatima; Mengting, Hu; Ahmed, M. Arif

2016-05-01

We synthesized 2-aminonicotinic acid (2-ANA) complexes with metals such as Co(II), Fe(III), Ni(II), Mn(II), Zn(II), Ag(I),Cr(III), Cd(II) and Cu(II) in aqueous media. The complexes were characterized and elucidated using FT-IR, UV-Vis, a fluorescence spectrophotometer and thermo gravimetric analysis (TGA). TGA data showed that the stoichiometry of complexes was 1:2 metal/ligand except for Ag(I) and Mn(II) where the ratio was 1:1. The metal complexes showed varied antibacterial, fungicidal and nematicidal activities. The silver and zinc complexes showed highest activity against Bacillus subtilis and Bacillus licheniformis respectively. Fusarium oxysporum was highly susceptible to nickel and copper complexes whereas Macrophomina phaseolina was completely inert to the complexes. The silver and cadmium complexes were effective against the root-knot nematode Meloidogyne javanica.

Geovibrio ferrireducens, a phylogenetically distinct dissimilatory Fe(III)-reducing bacterium

USGS Publications Warehouse

Caccavo, F.; Coates, J.D.; Rossello-Mora, R. A.; Ludwig, W.; Schleifer, K.H.; Lovley, D.R.; McInerney, M.J.

1996-01-01

A new, phylogenetically distinct, dissimilatory, Fe(III)-reducing bacterium was isolated from surface sediment of a hydrocarbon-contaminated ditch. The isolate, designated strain PAL-1, was an obligately anaerobic, non-fermentative, motile, gram-negative vibrio. PAL-1 grew in a defined medium with acetate as electron donor and ferric pyrophosphate, ferric oxyhydroxide, ferric citrate, Co(III)-EDTA, or elemental sulfur as sole electron acceptor. PAL-1 also used proline, hydrogen, lactate, propionate, succinate, fumarate, pyruvate, or yeast extract as electron donors for Fe(III) reduction. It is the first bacterium known to couple the oxidation of an amino acid to Fe(III) reduction. PAI-1 did not reduce oxygen, Mn(IV), U(VI), Cr(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PAL-1 exhibited dithionite-reduced minus air-oxidized difference spectra that were characteristic of c-type cytochromes. Analysis of the 16S rRNA gene sequence of PAL-1 showed that the strain is not related to any of the described metal-reducing bacteria in the Proteobacteria and, together with Flexistipes sinusarabici, forms a separate line of descent within the Bacteria. Phenotypically and phylogenetically, strain PAI-1 differs from all other described bacteria, and represents the type strain of a new genus and species. Geovibrio ferrireducens.

Synthesis and Spectral Characterization of Antifungal Sensitive Schiff Base Transition Metal Complexes

PubMed Central

Sakthivel, A.; Rajasekaran, K.

2007-01-01

New N2O2 donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and 1H NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of 10~31 µg/ml. PMID:24015086

On the existence of free and metal complexed sulfide in the Arabian Sea and its oxygen minimum zone

NASA Astrophysics Data System (ADS)

Theberge, Stephen M.; Luther, George W.; Farrenkopf, Anna M.

Free hydrogen sulfide was not detected in the oxygen minimum zone (OMZ) of the Arabian Sea during legs D1 (September 1992) and D3 (October-November 1992) of the Netherlands Indian Ocean Programme (NIOP). However, sulfide complexed to metals was detected by cathodic stripping square wave voltammetry at 2 nM or less throughout the water column. A slight increase in sulfide was measured in the OMZ relative to the surface waters and may be related to sulfur release from organic matter during decomposition. Sulfide complexes are of two general types at low concentrations of metal and sulfide. First, metals such as Mn, Fe, Co and Ni form complexes with bisulfide ion (HS -) that are kinetically labile to dissociation and are reactive. Second, metals such as Cu and Zn form multinuclear complexes with sulfide (S 2-) that are kinetically inert to dissociation; thus, they are less reactive than free (bi)sulfide and the labile metal bisulfide complexes. Zinc and copper sulfide complexes are important in allowing hydrogen sulfide to persist in seawater which contains measurable oxygen.

Solubility enhancement of seven metal contaminants using carboxymethyl-β-cyclodextrin (CMCD)

NASA Astrophysics Data System (ADS)

Skold, Magnus E.; Thyne, Geoffrey D.; Drexler, John W.; McCray, John E.

2009-07-01

Carboxymethyl-β-cyclodextrin (CMCD) has been suggested as a complexing agent for remediation of sites co-contaminated with metals and organic pollutants. As part of an attempt to construct a geochemical complexation model for metal-CMCD interactions, conditional formation constants for the complexes between CMCD and 7 metal ions (Ba, Ca, Cd, Ni, Pb, Sr, and Zn) are estimated from experimental data. Stable metal concentrations were reached after approximately 1 day and estimated logarithmic conditional formation constants range from - 3.2 to - 5.1 with confidence intervals within ± 0.08 log units. Experiments performed at 10 °C and 25 °C show that temperature affects the solubility of the metal salts but the strength of CMCD-metal complexes are not affected by this temperature variation. The conditional stability constants and complexation model presented in this work can be used to screen CMCD as a potential remediation agent for clean-up of contaminated soil and groundwater.

Nuclear reactor cooling system decontamination reagent regeneration. [PWR; BWR

DOEpatents

Anstine, L.D.; James, D.B.; Melaika, E.A.; Peterson, J.P. Jr.

1980-06-06

An improved method for decontaminating the coolant system of water-cooled nuclear power reactors and for regenerating the decontamination solution is described. A small amount of one or more weak-acid organic complexing agents is added to the reactor coolant, and the pH is adjusted to form a decontamination solution which is circulated throughout the coolant system to dissolve metal oxides from the interior surfaces and complex the resulting metal ions and radionuclide ions. The coolant containing the complexed metal ions and radionuclide ions is passed through a strong-base anion exchange resin bed which has been presaturated with a solution containing the complexing agents in the same ratio and having the same pH as the decontamination solution. As the decontamination solution passes through the resin bed, metal-complexed anions are exchanged for the metal-ion-free anions on the bed, while metal-ion-free anions in the solution pass through the bed, thus removing the metal ions and regenerating the decontamination solution.

Mass balance of metal species in supercritical fluid extraction using sodium diethyldithiocarbamate and dibutylammonium dibutyldithiocarbamate.

PubMed

Wang, Joanna Shaofen; Chiu, Kong-Hwa

2006-03-01

The objective of this work is to track the amount of metal complexes distributed in the extraction cell, collection vial, and tubing used in supercritical fluid extraction (SFE) systems after progressive removal of metal ions in supercritical carbon dioxide (SC-CO2). Sodium diethyldithiocarbamate (NaDDC) and dibutylammonium dibutyldithiocarbamate (DBDC) ligands were used to form complexes with Cd, Cu, Pb, and Zn and CO(2)/5% methanol as a supercritical fluid. The mass balance of metal complexes were obtained before and after extraction, and metals in different locations in the system were flushed out using an organic solvent and nitric acid (HNO3). These results infer that the stability constant (beta) of the metal-ligand complex has a strong correlation with SFE. Because of the composition of the stainless-steel cell, Fe, Cr, and Ni or other trace elements in the cell might interfere with the mass balance of metal complexes in SFE due to an exchange mechanism taking place between the cell and the sample.

Nuclear reactor cooling system decontamination reagent regeneration

DOEpatents

Anstine, Larry D.; James, Dean B.; Melaika, Edward A.; Peterson, Jr., John P.

1985-01-01

An improved method for decontaminating the coolant system of water-cooled nuclear power reactors and for regenerating the decontamination solution. A small amount of one or more weak-acid organic complexing agents is added to the reactor coolant, and the pH is adjusted to form a decontamination solution which is circulated throughout the coolant system to dissolve metal oxides from the interior surfaces and complex the resulting metal ions and radionuclide ions. The coolant containing the complexed metal ions and radionuclide ions is passed through a strong-base anion exchange resin bed which has been presaturated with a solution containing the complexing agents in the same ratio and having the same pH as the decontamination solution. As the decontamination solution passes through the resin bed, metal-complexed anions are exchanged for the metal-ion-free anions on the bed, while metal-ion-free anions in the solution pass through the bed, thus removing the metal ions and regenerating the decontamination solution.

Electrokinetic treatment of an agricultural soil contaminated with heavy metals.

PubMed

Figueroa, Arylein; Cameselle, Claudio; Gouveia, Susana; Hansen, Henrik K

2016-07-28

The high organic matter content in agricultural soils tends to complex and retain contaminants such as heavy metals. Electrokinetic remediation was tested in an agricultural soil contaminated with Co(+2), Zn(+2), Cd(+2), Cu(+2), Cr(VI), Pb(+2) and Hg(+2). The unenhanced electrokinetic treatment was not able to remove heavy metals from the soil due to the formation of precipitates in the alkaline environment in the soil section close to the cathode. Moreover, the interaction between metals and organic matter probably limited metal transportation under the effect of the electric field. Citric acid and ethylenediaminetetraacetic acid (EDTA) were used in the catholyte as complexing agents in order to enhance the extractability and removal of heavy metals from soil. These complexing agents formed negatively charged complexes that migrated towards the anode. The acid front electrogenerated at the anode favored the dissolution of heavy metals that were transported towards the cathode. The combined effect of the soil pH and the complexing agents resulted in the accumulation of heavy metals in the center of the soil specimen.

Method for the recovery of silver from waste photographic fixer solutions

DOEpatents

Posey, F.A.; Palko, A.A.

The method of the present invention is directed to the recovery of silver from spent photographic fixer solutions and for providing an effluent essentially silver-free that is suitable for discharge into commercial sewage systems. The present method involves the steps of introducing the spent photographic fixer solution into an alkaline hypochlorite solution. The oxidizing conditions of the alkaline hypochlorite solution are maintained during the addition of the fixer solution so that the silver ion complexing agents of thiosulfate and sulfite ions are effectively destroyed. Hydrazine monohydrate is then added to the oxidizing solution to form a reducing solution to effect the formation of a precipitate of silver which can be readily removed by filtration of decanting. Experimental tests indicate that greater than 99.99% of the original silver in the spent photographic fixer can be efficiently removed by practicing the present method. Also, the chemical and biological oxygen demand of the remaining effluent is significantly reduced so as to permit the discharge thereof into sewage systems at levels in compliance with federal and state environmental standards.

Method for the recovery of silver from waste photographic fixer solutions

DOEpatents

Posey, Franz A.; Palko, Aloysius A.

1984-01-01

The method of the present invention is directed to the recovery of silver from spent photographic fixer solutions and for providing an effluent essentially silver-free that is suitable for discharge into commercial sewage systems. The present method involves the steps of introducing the spent photographic fixer solution into an alkaline hypochlorite solution. The oxidizing conditions of the alkaline hypochlorite solution are maintained during the addition of the fixer solution so that the silver ion complexing agents of thiosulfate and sulfite ions are effectively destroyed. Hydrazine monohydrate is then added to the oxidizing solution to form a reducing solution to effect the formation of a precipitate of silver which can be readily removed by filtration or decanting. Experimental tests indicate that greater than 99.99% of the original silver in the spent photographic fixer can be efficiently removed by practicing the present method. Also, the chemical and biological oxygen demand of the remaining effluent is significantly reduced so as to permit the discharge thereof into sewage systems at levels in compliance with federal and state environmental standards.

METHODS FOR DETERMINING SMALL AMOUNTS OF NIOBIUM AND TANTALUM IN ORES (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bykova, V.S.; Skrizhinskaya, V.I.

1960-01-01

Several current colorimetric methods for determining Nb and Ta were evaluated by comparing the results obtained from analyzing artificial mixtures and minerals, such as loparite, tantalite-columbite, perovskite, pyrochlore, cassiterite-tantalite and Ti-bearing minerals such as sphene. A modification of the thiosulfate method had a sensitivity of 0.05% Nb and was found useful when the sample contained less than 1% Ti. The dimethyl fluorene method for Ta was sensitive to 0.002% and could be used only if most of the Ti was previously removed from the sample. The pyrogallol extraction method, based on the extraction of complex Ta fluoride wtth cyclohexane, presentedmore » a sensitivity of 0.01% of Ta, similar to the pyrogallol-tannin method used for both elements. If their concentration is smaller, the samples must be analyzed subsequently according to the first two methods. The absorption method allows a determination of the two elements without separating them, if their concentration is higher than 0.5%, although the individual sensitivity of the method is 0.05% for Ta and 0.005% for Nb. (TTT)« less

Ascorbic Acid as a Standard for Iodometric Titrations. An Analytical Experiment for General Chemistry

NASA Astrophysics Data System (ADS)

Silva, Cesar R.; Simoni, Jose A.; Collins, Carol H.; Volpe, Pedro L. O.

1999-10-01

Ascorbic acid is suggested as the weighable compound for the standardization of iodine solutions in an analytical experiment in general chemistry. The experiment involves an iodometric titration in which iodine reacts with ascorbic acid, oxidizing it to dehydroascorbic acid. The redox titration endpoint is determined by the first iodine excess that is complexed with starch, giving a deep blue-violet color. The results of the titration of iodine solution using ascorbic acid as a calibration standard were compared with the results acquired by the classic method using a standardized solution of sodium thiosulfate. The standardization of the iodine solution using ascorbic acid was accurate and precise, with the advantages of saving time and avoiding mistakes due to solution preparation. The colorless ascorbic acid solution gives a very clear and sharp titration end point with starch. It was shown by thermogravimetric analysis that ascorbic acid can be dried at 393 K for 2 h without decomposition. This experiment allows general chemistry students to perform an iodometric titration during a single laboratory period, determining with precision the content of vitamin C in pharmaceutical formulations.

Ultrafine particles derived from mineral processing: A case study of the Pb-Zn sulfide ore with emphasis on lead-bearing colloids.

PubMed

Mikhlin, Yuri; Vorobyev, Sergey; Romanchenko, Alexander; Karasev, Sergey; Karacharov, Anton; Zharkov, Sergey

2016-03-01

Although mining and mineral processing industry is a vast source of heavy metal pollutants, the formation and behavior of micrometer- and nanometer-sized particles and their aqueous colloids entered the environment from the technological media has received insufficient attention to date. Here, the yield and characteristics of ultrafine mineral entities produced by routine grinding of the Pb-Zn sulfide ore (Gorevskoe ore deposit, Russia) were studied using laser diffraction analysis (LDA), dynamic light scattering (DLS) and zeta potential measurement, microscopy, X-ray photoelectron spectroscopy, with most attention given to toxic lead species. It was revealed, in particular, that the fraction of particles less that 1 μm in the ground ore typical reaches 0.4 vol. %. The aquatic particles in supernatants were micrometer size aggregates with increased content of zinc, sulfur, calcium as compared with the bulk ore concentrations. The hydrodynamic diameter of the colloidal species decreased with time, with their zeta potentials remaining about -12 mV. The colloids produced from galena were composed of 20-50 nm PbS nanoparticles associated with lead sulfate and thiosulfate, while the surface oxidation products at precipitated galena were largely lead oxyhydroxides. The size and zeta potential of the lead-bearing colloids decreased with time down to about 100 nm and from -15 mV to -30 mV, respectively. And, conversely, lead sulfide nanoparticles were mobilized before the aggregates during redispersion of the precipitates in fresh portions of water. The potential environmental impact of the metal-bearing colloids, which is due to the large-scale production and relative stability, is discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Genome information of Methylobacterium oryzae, a plant-probiotic methylotroph in the phyllosphere.

PubMed

Kwak, Min-Jung; Jeong, Haeyoung; Madhaiyan, Munusamy; Lee, Yi; Sa, Tong-Min; Oh, Tae Kwang; Kim, Jihyun F

2014-01-01

Pink-pigmented facultative methylotrophs in the Rhizobiales are widespread in the environment, and many Methylobacterium species associated with plants produce plant growth-promoting substances. To gain insights into the life style at the phyllosphere and the genetic bases of plant growth promotion, we determined and analyzed the complete genome sequence of Methylobacterium oryzae CBMB20T, a strain isolated from rice stem. The genome consists of a 6.29-Mb chromosome and four plasmids, designated as pMOC1 to pMOC4. Among the 6,274 coding sequences in the chromosome, the bacterium has, besides most of the genes for the central metabolism, all of the essential genes for the assimilation and dissimilation of methanol that are either located in methylotrophy islands or dispersed. M. oryzae is equipped with several kinds of genes for adaptation to plant surfaces such as defense against UV radiation, oxidative stress, desiccation, or nutrient deficiency, as well as high proportion of genes related to motility and signaling. Moreover, it has an array of genes involved in metabolic pathways that may contribute to promotion of plant growth; they include auxin biosynthesis, cytokine biosynthesis, vitamin B12 biosynthesis, urea metabolism, biosorption of heavy metals or decrease of metal toxicity, pyrroloquinoline quinone biosynthesis, 1-aminocyclopropane-1-carboxylate deamination, phosphate solubilization, and thiosulfate oxidation. Through the genome analysis of M. oryzae, we provide information on the full gene complement of M. oryzae that resides in the aerial parts of plants and enhances plant growth. The plant-associated lifestyle of M. oryzae pertaining to methylotrophy and plant growth promotion, and its potential as a candidate for a bioinoculant targeted to the phyllosphere and focused on phytostimulation are illuminated.

Genome Information of Methylobacterium oryzae, a Plant-Probiotic Methylotroph in the Phyllosphere

PubMed Central

Madhaiyan, Munusamy; Lee, Yi; Sa, Tong-Min; Oh, Tae Kwang; Kim, Jihyun F.

2014-01-01

Pink-pigmented facultative methylotrophs in the Rhizobiales are widespread in the environment, and many Methylobacterium species associated with plants produce plant growth-promoting substances. To gain insights into the life style at the phyllosphere and the genetic bases of plant growth promotion, we determined and analyzed the complete genome sequence of Methylobacterium oryzae CBMB20T, a strain isolated from rice stem. The genome consists of a 6.29-Mb chromosome and four plasmids, designated as pMOC1 to pMOC4. Among the 6,274 coding sequences in the chromosome, the bacterium has, besides most of the genes for the central metabolism, all of the essential genes for the assimilation and dissimilation of methanol that are either located in methylotrophy islands or dispersed. M. oryzae is equipped with several kinds of genes for adaptation to plant surfaces such as defense against UV radiation, oxidative stress, desiccation, or nutrient deficiency, as well as high proportion of genes related to motility and signaling. Moreover, it has an array of genes involved in metabolic pathways that may contribute to promotion of plant growth; they include auxin biosynthesis, cytokine biosynthesis, vitamin B12 biosynthesis, urea metabolism, biosorption of heavy metals or decrease of metal toxicity, pyrroloquinoline quinone biosynthesis, 1-aminocyclopropane-1-carboxylate deamination, phosphate solubilization, and thiosulfate oxidation. Through the genome analysis of M. oryzae, we provide information on the full gene complement of M. oryzae that resides in the aerial parts of plants and enhances plant growth. The plant-associated lifestyle of M. oryzae pertaining to methylotrophy and plant growth promotion, and its potential as a candidate for a bioinoculant targeted to the phyllosphere and focused on phytostimulation are illuminated. PMID:25211235

Membrane extraction with thermodynamically unstable diphosphonic acid derivatives

DOEpatents

Horwitz, E.P.; Gatrone, R.C.; Nash, K.L.

1997-10-14

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described. 1 fig.

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

DOEpatents

Lilga, Michael A.; Hallen, Richard T.

1990-01-01

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately .pi.-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancilliary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H.sub.2 from mixed gas streams such as the produce gas from coal gasification processes.

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

DOEpatents

Lilga, M.A.; Hallen, R.T.

1991-10-15

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately [pi]-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancillary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H[sub 2] from mixed gas streams such as the product gas from coal gasification processes. 3 figures.

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

DOEpatents

Lilga, M.A.; Hallen, R.T.

1990-08-28

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately [pi]-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancillary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H[sub 2] from mixed gas streams such as the producer gas from coal gasification processes. 3 figs.

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation

DOEpatents

Lilga, Michael A.; Hallen, Richard T.

1991-01-01

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately .pi.-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancilliary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H.sub.2 from mixed gas streams such as the product gas from coal gasification processes.

Multiheteromacrocycles that Complex Metal Ions. Sixth Progress Report, 1 May 1979-30 April 1980

DOE R&D Accomplishments Database

Cram, D. J.

1980-01-15

Objective is to design synthesize, and evaluate cyclic and polycyclic host organic compounds for their abilities to complex and lipophilize guest metal ions, their complexes, and their clusters. Host organic compounds consist of strategically placed solvating, coordinating, and ion-pairing sites tied together by covalent bonds through hydrocarbon units around cavities shaped to be occupied by guest metal ions or by metal ions plus their ligands. Specificity in complexation is sought by matching the following properties of host and guest: cavity and metal ion sizes; geometric arrangements of binding sites; number of binding sites; character of binding sites; and valences. During this period, hemispherands based on an aryloxy or cyclic urea unit, spherands based on aryloxyl units only, and their complexes with alkali metals and alkaline earths were investigated. An attempt to separate {sup 6}Li and {sup 7}Li by gel permeation chromatography of lithiospherium chloride failed. (DLC)

Drug Delivery Systems For Anti-Cancer Active Complexes of Some Coinage Metals.

PubMed

Zhang, Ming; Saint-Germain, Camille; He, Guiling; Sun, Raymond Wai-Yin

2018-02-12

Although cisplatin and a number of platinum complexes have widely been used for the treatment of neoplasia, patients receiving these treatments have frequently suffered from their severe toxic side effects, the development of resistance with consequent relapse. In the recent decades, numerous complexes of coinage metals including that of gold, copper and silver have been reported to display promising in vitro and/or in vivo anti-cancer activities as well as potent activities towards cisplatin-resistant tumors. Nevertheless, the medical development of these metal complexes has been hampered by their instability in aqueous solutions and the nonspecific binding in biological systems. One of the approaches to overcome these problems is to design and develop adequate drug delivery systems (DDSs) for the transport of these complexes. By functionalization, encapsulation or formulation of the metal complexes, several types of DDSs have been reported to improve the desired pharmacological profile of the metal complexes, improving their overall stability, bioavailability, anti-cancer activity and reducing their toxicity towards normal cells. In this review, we summarized the recent findings for different DDSs for various anti- cancer active complexes of some coinage metals. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Spectral characterization, cyclic voltammetry, morphology, biological activities and DNA cleaving studies of amino acid Schiff base metal(II) complexes

NASA Astrophysics Data System (ADS)

Neelakantan, M. A.; Rusalraj, F.; Dharmaraja, J.; Johnsonraja, S.; Jeyakumar, T.; Sankaranarayana Pillai, M.

2008-12-01

Metal complexes are synthesized with Schiff bases derived from o-phthalaldehyde (opa) and amino acids viz., glycine (gly) L-alanine (ala), L-phenylalanine (pal). Metal ions coordinate in a tetradentate or hexadentate manner with these N 2O 2 donor ligands, which are characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic, 1H NMR and EPR spectral studies. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). Based on EPR studies, spin-Hamiltonian and bonding parameters have been calculated. The g-values calculated for copper complexes at 300 K and in frozen DMSO (77 K) indicate the presence of the unpaired electron in the d orbital. The evaluated metal-ligand bonding parameters showed strong in-plane σ- and π-bonding. X-ray diffraction (XRD) and scanning electron micrography (SEM) analysis provide the crystalline nature and the morphology of the metal complexes. The cyclic voltammograms of the Cu(II)/Mn(II)/VO(II) complexes investigated in DMSO solution exhibit metal centered electroactivity in the potential range -1.5 to +1.5 V. The electrochemical data obtained for Cu(II) complexes explains the change of structural arrangement of the ligand around Cu(II) ions. The biological activity of the complexes has been tested on eight bacteria and three fungi. Cu(II) and Ni(II) complexes show an increased activity in comparison to the controls. The metal complexes of opapal Schiff base were evaluated for their DNA cleaving activities with calf-thymus DNA (CT DNA) under aerobic conditions. Cu(II) and VO(II) complexes show more pronounced activity in presence of the oxidant.

Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

NASA Astrophysics Data System (ADS)

Lichtenberg, Dennis L.

During this period some important breakthroughs were accomplished in understanding the relationships between molecular ionization energies and bond energies in transition metal complexes, in understanding the electronic factors of carbon-hydrogen bond activation by transition metals, in characterizing small molecule bonding interactions with transition metals, and in investigating intermolecular interactions in thin films of transition metal complexes. The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies was developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. The relationship was used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. The ionization energies were also used to correlate the rates of carbonyl substitution reactions of (eta(sup 5)-C5H4X)Rh(CO)2 complexes, and to reveal the factors that control the stability of the transition state. The investigations of the fundamental interactions of C-H sigma and sigma* orbitals metals were continued with study of eta(sup 3)-1-methylallyl metal complexes. Direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal was obtained. The ability to observe the electronic effects of intermolecular interactions by comparing the ionizations of metal complexes in the gas phase with the ionizations of thin solid organometallic films prepared in ultra-high vacuum was established. Most significantly, the scanning tunneling microscope imaging of these thin films was accomplished.

Synthesis, characterization, single crystal X-ray determination, fluorescence and electrochemical studies of new dinuclear nickel(II) and oxovanadium(IV) complexes containing double Schiff base ligands

NASA Astrophysics Data System (ADS)

Shafaatian, Bita; Ozbakzaei, Zahra; Notash, Behrouz; Rezvani, S. Ahmad

2015-04-01

A series of new bimetallic complexes of nickel(II) and vanadium(IV) have been synthesized by the reaction of the new double bidentate Schiff base ligands with nickel acetate and vanadyl acetylacetonate in 1:1 M ratio. In nickel and also vanadyl complexes the ligands were coordinated to the metals via the imine N and enolic O atoms. The complexes have been found to possess 1:1 metals to ligands stoichiometry and the molar conductance data revealed that the metal complexes were non-electrolytes. The nickel and vanadyl complexes exhibited distorted square planar and square pyramidal coordination geometries, respectively. The emission spectra of the ligands and their complexes were studied in methanol. Electrochemical properties of the ligands and their metal complexes were also investigated in DMSO solvent at 150 mV s-1 scan rate. The ligands and metal complexes showed both quasi-reversible and irreversible processes at this scan rate. The Schiff bases and their complexes have been characterized by FT-IR, 1H NMR, UV/Vis spectroscopies, elemental analysis and conductometry. The crystal structure of the nickel complex has been determined by single crystal X-ray diffraction.

Influence of metal ions on flavonoid protection against asbestos-induced cell injury.

PubMed

Kostyuk, V A; Potapovich, A I; Vladykovskaya, E N; Korkina, L G; Afanas'ev, I B

2001-01-01

Influence of metal ions (Fe2+, Fe3+, Cu2+, Zn2+) on the protective effect of rutin, dihydroquercetin, and green tea epicatechins against in vitro asbestos-induced cell injury was studied. Metals have been found to increase the capacity of rutin and dihydroquercetin to protect peritoneal macrophages against chrysotile asbestos-induced injury. The data presented here show that this effect is due to the formation of flavonoid metal complexes, which turned out to be more effective radical scavengers than uncomplexed flavonoids. At the same time epicatechins and their metal complexes have similar antiradical properties and protective capacities against the asbestos induced injury of macrophages. Metal complexes of all flavonoids were found to be considerably more potent than parent flavonoids in protecting red blood cells against asbestos-induced injury. It was also found that the metal complexes of all flavonoids were absorbed by chrysotile asbestos fibers considerably better than uncomplexed compounds and probably for this reason flavonoid metal complexes have better protective properties against asbestos induced hemolysis. Thus, the results of the present study show that flavonoid metal complexes may be effective therapy for the inflammatory response associated with the inhalation of asbestos fiber. The advantage of their application could be the strong increase in ROS scavenging by flavonoids and finally a better cell protection under the conditions of cellular oxidative stress.

Chemical behavior of Cu, Zn, Cd, and Pb in a eutrophic reservoir: speciation and complexation capacity.

PubMed

Tonietto, Alessandra Emanuele; Lombardi, Ana Teresa; Choueri, Rodrigo Brasil; Vieira, Armando Augusto Henriques

2015-10-01

This research aimed at evaluating cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) speciation in water samples as well as determining water quality parameters (alkalinity, chlorophyll a, chloride, conductivity, dissolved organic carbon, dissolved oxygen, inorganic carbon, nitrate, pH, total suspended solids, and water temperature) in a eutrophic reservoir. This was performed through calculation of free metal ions using the chemical equilibrium software MINEQL+ 4.61, determination of labile, dissolved, and total metal concentrations via differential pulse anodic stripping voltammetry, and determination of complexed metal by the difference between the total concentration of dissolved and labile metal. Additionally, ligand complexation capacities (CC), such as the strength of the association of metals-ligands (logK'ML) and ligand concentrations (C L) were calculated via Ruzic's linearization method. Water samples were taken in winter and summer, and the results showed that for total and dissolved metals, Zn > Cu > Pb > Cd concentration. In general, higher concentrations of Cu and Zn remained complexed with the dissolved fraction, while Pb was mostly complexed with particulate materials. Chemical equilibrium modeling (MINEQL+) showed that Zn(2+) and Cd(2+) dominated the labile species, while Cu and Pb were complexed with carbonates. Zinc was a unique metal for which a direct relation between dissolved species with labile and complexed forms was obtained. The CC for ligands indicated a higher C L for Cu, followed by Pb, Zn, and Cd in decreasing amounts. Nevertheless, the strength of the association of all metals and their respective ligands was similar. Factor analysis with principal component analysis as the extraction procedure confirmed seasonal effects on water quality parameters and metal speciation. Total, dissolved, and complexed Cu and total, dissolved, complexed, and labile Pb species were all higher in winter, whereas in summer, Zn was mostly present in the complexed form. A high degree of deterioration of the reservoir was confirmed by the results of this study.

Metal–organic complexation in the marine environment

PubMed Central

Luther, George W; Rozan, Timothy F; Witter, Amy; Lewis, Brent

2001-01-01

We discuss the voltammetric methods that are used to assess metal–organic complexation in seawater. These consist of titration methods using anodic stripping voltammetry (ASV) and cathodic stripping voltammetry competitive ligand experiments (CSV-CLE). These approaches and a kinetic approach using CSV-CLE give similar information on the amount of excess ligand to metal in a sample and the conditional metal ligand stability constant for the excess ligand bound to the metal. CSV-CLE data using different ligands to measure Fe(III) organic complexes are similar. All these methods give conditional stability constants for which the side reaction coefficient for the metal can be corrected but not that for the ligand. Another approach, pseudovoltammetry, provides information on the actual metal–ligand complex(es) in a sample by doing ASV experiments where the deposition potential is varied more negatively in order to destroy the metal–ligand complex. This latter approach gives concentration information on each actual ligand bound to the metal as well as the thermodynamic stability constant of each complex in solution when compared to known metal–ligand complexes. In this case the side reaction coefficients for the metal and ligand are corrected. Thus, this method may not give identical information to the titration methods because the excess ligand in the sample may not be identical to some of the actual ligands binding the metal in the sample. PMID:16759421

Infrared Spectroscopic Analysis of Linkage Isomerism in Metal-Thiocyanate Complexes

ERIC Educational Resources Information Center

Baer, Carl; Pike, Jay

2010-01-01

We developed an experiment suitable for an advanced inorganic chemistry laboratory that utilizes a cooperative learning environment, which allows students to develop an empirical method of determining the bonding mode of a series of unknown metal-thiocyanate complexes. Students synthesize the metal-thiocyanate complexes and obtain the FT-IR…

Water-in-Supercritical CO2 Microemulsion Stabilized by a Metal Complex.

PubMed

Luo, Tian; Zhang, Jianling; Tan, Xiuniang; Liu, Chengcheng; Wu, Tianbin; Li, Wei; Sang, Xinxin; Han, Buxing; Li, Zhihong; Mo, Guang; Xing, Xueqing; Wu, Zhonghua

2016-10-17

Herein we propose for the first time the utilization of a metal complex for forming water-in-supercritical CO 2 (scCO 2 ) microemulsions. The water solubility in the metal-complex-stabilized microemulsion is significantly improved compared with the conventional water-in-scCO 2 microemulsions stabilized by hydrocarbons. Such a microemulsion provides a promising route for the in situ CO 2 reduction catalyzed by a metal complex at the water/scCO 2 interface. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of the toxicity of some metals and their tetracyanide complexes on the respiration of non acclimated activated sludges.

PubMed

Morozzi, G; Cenci, G

1978-12-01

The toxic effect of the metal ions of cadmium, zinc, nickel and mercury and their tetracyanide salt complexes, on the activated sludge not previously acclimated, has been studied. The evaluation of the effect was carried out using both the Warburg and TTC-method. The results obtained have shown that the toxicity of the cadmium and zinc complexes is higher than that of the corresponding metals, while the toxicity of Ni(CN)4(2-) is lower than that of the corresponding metals. No differences have been found between the effect of mercury and the corresponding tetracyanide complex. From the data obtained it appears that it is not possible to generalize about the biological effect of complexation with the CN- group, but it should be stated that, generally, there are substantial differences between metals and their cyanide complexes as far as toxicity for activated sludge is concerned.

Synthesis, spectral studies and biological evaluation of 2-aminonicotinic acid metal complexes.

PubMed

Nawaz, Muhammad; Abbasi, Muhammad Waseem; Hisaindee, Soleiman; Zaki, Muhammad Javed; Abbas, Hira Fatima; Mengting, Hu; Ahmed, M Arif

2016-05-15

We synthesized 2-aminonicotinic acid (2-ANA) complexes with metals such as Co(II), Fe(III), Ni(II), Mn(II), Zn(II), Ag(I),Cr(III), Cd(II) and Cu(II) in aqueous media. The complexes were characterized and elucidated using FT-IR, UV-Vis, a fluorescence spectrophotometer and thermo gravimetric analysis (TGA). TGA data showed that the stoichiometry of complexes was 1:2 metal/ligand except for Ag(I) and Mn(II) where the ratio was 1:1. The metal complexes showed varied antibacterial, fungicidal and nematicidal activities. The silver and zinc complexes showed highest activity against Bacillus subtilis and Bacillus licheniformis respectively. Fusarium oxysporum was highly susceptible to nickel and copper complexes whereas Macrophomina phaseolina was completely inert to the complexes. The silver and cadmium complexes were effective against the root-knot nematode Meloidogyne javanica. Copyright © 2016 Elsevier B.V. All rights reserved.

Antimalarial and antimicrobial activities of 8-Aminoquinoline-Uracils metal complexes

PubMed Central

Phopin, Kamonrat; Sinthupoom, Nujarin; Treeratanapiboon, Lertyot; Kunwittaya, Sarun; Prachayasittikul, Supaluk; Ruchirawat, Somsak; Prachayasittikul, Virapong

2016-01-01

8-Aminoquinoline (8AQ) derivatives have been reported to have antimalarial, anticancer, and antioxidant activities. This study investigated the potency of 8AQ-5-substituted (iodo and nitro) uracils metal (Mn, Cu, Ni) complexes (1-6) as antimalarial and antimicrobial agents. Interestingly, all of these metal complexes (1-6) showed fair antimalarial activities. Moreover, Cu complexes 2 (8AQ-Cu-5Iu) and 5 (8AQ-Cu-5Nu) exerted antimicrobial activities against Gram-negative bacteria including P. shigelloides and S. dysenteriae. The results reveal application of 8AQ and its metal complexes as potential compounds to be further developed as novel antimalarial and antibacterial agents. PMID:27103894

Antimalarial and antimicrobial activities of 8-Aminoquinoline-Uracils metal complexes.

PubMed

Phopin, Kamonrat; Sinthupoom, Nujarin; Treeratanapiboon, Lertyot; Kunwittaya, Sarun; Prachayasittikul, Supaluk; Ruchirawat, Somsak; Prachayasittikul, Virapong

2016-01-01

8-Aminoquinoline (8AQ) derivatives have been reported to have antimalarial, anticancer, and antioxidant activities. This study investigated the potency of 8AQ-5-substituted (iodo and nitro) uracils metal (Mn, Cu, Ni) complexes (1-6) as antimalarial and antimicrobial agents. Interestingly, all of these metal complexes (1-6) showed fair antimalarial activities. Moreover, Cu complexes 2 (8AQ-Cu-5Iu) and 5 (8AQ-Cu-5Nu) exerted antimicrobial activities against Gram-negative bacteria including P. shigelloides and S. dysenteriae. The results reveal application of 8AQ and its metal complexes as potential compounds to be further developed as novel antimalarial and antibacterial agents.

Decontamination of Casualties from Battlefield Under CW and BW Attack

DTIC Science & Technology

1984-11-15

anion present. Thus the films containing periodide, perbromide, chlorochromate , permanganate, dichromate, and pyridinium azide each had a detectable...38 4. Preparation of Azide Films 38 5. Preparation of Hydroxide Films 39 6. Preparation of Thiosulfate Film 39 7. Preparation of Chlorochromate Films...dichromate, hypochlorite, m-chioroperbenzoaite and related polymers of BD-5-Q film. 𔄁. Preparation of Chlorochromate Films Chromium trioxide (CrO 3 , 9.8 g

Acute cyanide toxicity caused by apricot kernel ingestion.

PubMed

Suchard, J R; Wallace, K L; Gerkin, R D

1998-12-01

A 41-year-old woman ingested apricot kernels purchased at a health food store and became weak and dyspneic within 20 minutes. The patient was comatose and hypothermic on presentation but responded promptly to antidotal therapy for cyanide poisoning. She was later treated with a continuous thiosulfate infusion for persistent metabolic acidosis. This is the first reported case of cyanide toxicity from apricot kernel ingestion in the United States since 1979.

Limnobacter litoralis sp. nov., a thiosulfate-oxidizing, heterotrophic bacterium isolated from a volcanic deposit, and emended description of the genus Limnobacter.

PubMed

Lu, Hongsheng; Sato, Yoshinori; Fujimura, Reiko; Nishizawa, Tomoyasu; Kamijo, Takashi; Ohta, Hiroyuki

2011-02-01

A Gram-negative, aerobic, heterotrophic bacterium, designated KP1-19(T), was isolated from a 22-year-old volcanic deposit at a site lacking vegetation on the island of Miyake, Japan. Strain KP1-19(T) was able to use thiosulfate (optimum concentration 10 mM) as an additional energy source. 16S rRNA gene sequence analysis indicated that strain KP1-19(T) was closely related to Limnobacter thiooxidans CS-K2(T) within the class Betaproteobacteria (97.7 % 16S rRNA gene sequence similarity). The cellular fatty acid profile was characteristic of the genus Limnobacter: the major fatty acids (>5 %) were C(16 : 0), C(16 : 1)ω7c and C(18 : 1)ω7c and minor amounts of C(10 : 0) 3-OH were also found. DNA-DNA relatedness between strain KP1-19(T) and L. thiooxidans LMG 19593(T) was 18 %. Therefore, strain KP1-19(T) represents a novel species, for which the name Limnobacter litoralis sp. nov. is proposed. The type strain is KP1-19(T) (=LMG 24869(T) =NBRC 105857(T) =CIP 109929(T)).

The role of silver nano-particles and silver thiosulfate on the longevity of cut carnation (Dianthus caryophyllus) flowers.

PubMed

Hashemabadi, Davood

2014-07-01

The purpose of this study was to evaluate the efficacy of silver nano-particles (SNP) and silver thiosulfate (STS) in extending the vase life of cut carnation (Dianthus caryophyllus L. cv. 'Tempo') flowers. Pulse treatments of SNP @ 0, 5, 10 and 15 mg l(-1) and STS @ 0, 0.1, 0.2 and 0.3 mM were administered to carnation flowers for 24 hr. The longest vase life (16.1 days) was observed in flowers treated with 15 mg l(-1) of SNP + 0.2 mM STS. The least chlorophyll was destroyed in flowers treated with 15 mg I(-1) of SNP + 0.3 mM STS. Our findings showed that the 15 mg l(-1) SNP treatment inhibited bacterial growth in the preservative solution. The control flowers bloomed faster than the treated flowers. The maximum peroxidase activity and the minimum lipid peroxidation were obtained in cut flowers that were treated with 15 mg l(-1) of SNP and 0.3 mM STS. Overall, results of the study revealed that SNP and STS treatment extended the longevity of cut carnation 'Tempo' flowers by reducing oxidative stress, improving anti-oxidant system, reducing bacterial populations and delaying flowering.

Thiosulfate and sulfite distributions in porewater of marine sediments related to manganese, iron, and sulfur geochemistry

NASA Astrophysics Data System (ADS)

Thamdrup, Bo; Finster, Kai; Fossing, Henrik; Hansen, Jens Würgler; Jørgensen, Bo Barker

1994-01-01

Depth distributions of thiosulfate (S 2O 32-) and sulfite (SO 32-) were measured in the porewaters of a Danish salt marsh and subtidal marine sediments by HPLC analysis after derivatization with DTNP [2,2'-dithiobis(5-nitropyridine)]. The distributions were compared to the redox zonation as indicated by Eh and Mn 2+, Fe 2+ and H 2S distributions. Concentrations of S 2O 32- varied from below detection (<50 nM) to 600 nM while SO 32- concentrations generally were 2-3 times higher, 100-1500 nM. Depth distributions of the two species were roughly similar. Lowest concentrations were found in the oxidized zone, including both the oxic surface layer and the suboxic zone of intense manganese and iron reduction, and concentrations tended to increase through the suboxic and into the reduced, sulfidic zone. The similarity of SO 32- and S 2O 32- profiles suggested a close coupling of the cycling of the two species. Rates of consumption were suggested as the main factor governing their distribution. Rapid turnover times for S 2O 32- and H 2S of 4 and 1.1 h, respectively, were estimated for the upper 0-1 cm of a subtidal sediment.

Atypical one-carbon metabolism of an acetogenic and hydrogenogenic Moorella thermoacetica strain.

PubMed

Jiang, Bo; Henstra, Anne-Meint; Paulo, Paula L; Balk, Melike; van Doesburg, Wim; Stams, Alfons J M

2009-02-01

A thermophilic spore-forming bacterium (strain AMP) was isolated from a thermophilic methanogenic bioreactor that was fed with cobalt-deprived synthetic medium containing methanol as substrate. 16S rRNA gene analysis revealed that strain AMP was closely related to the acetogenic bacterium Moorella thermoacetica DSM 521(T) (98.3% sequence similarity). DNA-DNA hybridization showed 75.2 +/- 4.7% similarity to M. thermoacetica DSM 521(T), suggesting that strain AMP is a M. thermoacetica strain. Strain AMP has a unique one-carbon metabolism compared to other Moorella species. In media without cobalt growth of strain AMP on methanol was only sustained in coculture with a hydrogen-consuming methanogen, while in media with cobalt it grew acetogenically in the absence of the methanogen. Addition of thiosulfate led to sulfide formation and less acetate formation. Growth of strain AMP with CO resulted in the formation of hydrogen as the main product, while other CO-utilizing Moorella strains produce acetate as product. Formate supported growth only in the presence of thiosulfate or in coculture with the methanogen. Strain AMP did not grow with H(2)/CO(2), unlike M. thermoacetica (DSM 521(T)). The lack of growth with H(2)/CO(2) likely is due to the absence of cytochrome b in strain AMP.

Successful Treatment of Lung Calciphylaxis With Sodium Thiosulfate in a Patient With Sickle Cell Disease

PubMed Central

Arrestier, Romain; Dudreuilh, Caroline; Remy, Philippe; Boulahia, Ghada; Bentaarit, Bouteina; Leibler, Claire; Adedjouma, Amir; Kofman, Tomek; Matignon, Marie; Sahali, Dil; Dufresne, Roger; Deux, Jean-Francois; Colin, Charlotte; Grimbert, Philippe; Lang, Philippe; Bartolucci, Pablo; Maitre, Bernard; Tran Van Nhieu, Jeanne; Audard, Vincent

2016-01-01

Abstract Calciphylaxis is a small vessel vasculopathy, characterized by medial wall calcification that develops in a few patients with chronic renal failure. The prognosis of skin calciphylaxis has improved considerably since the introduction of sodium thiosulfate (STS), but it remains unclear whether this therapy is effective against organ lesions related to calciphylaxis. Pulmonary calciphylaxis is a usually fatal medical condition that may occur in association with skin involvement in patients with end-stage renal disease. We report here the case of a 49-year-old woman homozygous sickle cell disease patient on chronic hemodialysis with biopsy-proven systemic calciphylaxis involving the lungs and skin. On admission, ulcerative skin lesions on the lower limbs and bilateral pulmonary infiltrates on chest computerized tomography scan were the main clinical and radiological findings. Skin and bronchial biopsies demonstrated calciphylaxis lesions. The intravenous administration of STS in association with cinacalcet for 8 consecutive months led to a clear improvement in skin lesions and thoracic lesions on chest computerized tomography scan. This case suggests for the first time that organ lesions related to calciphylaxis, and particularly lung injury, are potentially reversible. This improvement probably resulted from the combination of 3 interventions (more frequent dialysis, cinacalcet, and STS), rather than the administration of STS alone. PMID:26871829

The pressure tunning Raman and IR spectral studies on the multinuclear metal carbyne complexes

NASA Astrophysics Data System (ADS)

Xu, Zhenhua; Butler, Ian S.; Mayr, Andreas

2005-03-01

The Raman and infrared (IR) spectra of four tungsten metal carbyne complexes I, II, IV and V [Cl(CO) 2(L)W tbnd CC 6H 4sbnd (C tbnd CC 6H 4) nsbnd N tbnd C sbnd ] 2M (L = TMEDA, n = 0, M = PdI 2 or ReCl(CO) 3; L = DPPE, n = 1, M = PdI 2 or ReCl(CO) 3) were studied at high external pressure. Their pressure-induced phase transitions were observed near 20 kbar (complexes I), 15 kbar (complexes II), 25 kbar (complex IV) and 30 kbar (complex V). The pressure-induced phase transition likely is first order in complex I and the pressure-induced phase transitions of complexes II, IV and V are mostly second order. The pressure sensitivities d ν/d p of ν(W tbnd C) are high in the low-pressure phase area and very low in the high-pressure phase area due to the pressure strengthening π back-bonding from metal W to π * orbital of C tbnd O in fragment Cl(CO) 2(L)W tbnd C. The pressure strengthening metal π back-bonding from metal Re or Pd to π * orbital of C tbnd O or C tbnd N also happened to both of central metal centers of NCPd(I 2)CN in complex I and NCReCl(CO) 3CN in complex II.

Low frequency vibrational spectra and the nature of metal-oxygen bond of alkaline earth metal acetylacetonates

NASA Astrophysics Data System (ADS)

Fakheri, Hamideh; Tayyari, Sayyed Faramarz; Heravi, Mohammad Momen; Morsali, Ali

2017-12-01

Theoretical quantum chemistry calculations were used to assign the observed vibrational band frequencies of Be, Mg, Ca, Sr, and Ba acetylacetonates complexes. Density functional theory (DFT) calculations have been carried out at the B3LYP level, using LanL2DZ, def2SVP, and mixed, GenECP, (def2SVP for metal ions and 6-311++G** for all other atoms) basis sets. The B3LYP level, with mixed basis sets, was utilized for calculations of vibrational frequencies, IR intensity, and Raman activity. Analysis of the vibrational spectra indicates that there are several bands which could almost be assigned mainly to the metal-oxygen vibrations. The strongest Raman band in this region could be used as a measure of the stability of the complex. The effects of central metal on the bond orders and charge distributions in alkaline earth metal acetylacetonates were studied by the Natural Bond Orbital (NBO) method for fully optimized compounds. Optimization were performed at the B3LYP/6-311++G** level for the lighter alkaline earth metal complexes (Be, Mg, and Ca acetylacetonates) while the B3LYP level, using LanL2DZ (extrabasis, d and f on oxygen and metal atoms), def2SVP and mixed (def2SVP on metal ions and 6-311++G** for all other atoms) basis sets for all understudy complexes. Calculations indicate that the covalence nature of metal-oxygen bonds considerably decreases from Be to Ba complexes. The nature of metal-oxygen bond was further studied by using Atoms In Molecules (AIM) analysis. The topological parameters, Wiberg bond orders, natural charges of O and metal ions, and also some vibrational band frequencies were correlated with the stability constants of understudy complexes.

Luminescent Organometallic Nanomaterials with Aggregation-Induced Emission.

PubMed

Shu, Tong; Wang, Jianxing; Su, Lei; Zhang, Xueji

2018-07-04

Recent researches in metal nanoclusters (NCs) have prompted their promising practical applications in biomedical fields as novel inorganic luminophores. More recently, to further improve the photoluminescence (PL) performance of NCs, the aggregation-induced emission (AIE) effect has been introduced to develop highly luminescent metal NCs and metal complex materials. In this review, we start our discussion from recent progresses on AIE materials developments. Then, we address our understandings on the PL properties of thiolated metal NCs. Subsequently, we link thiolated metal NCs with AIE effect. We also highlight some recent advances in synthesizing the AIE-type metal complex nanomaterials. We finally discuss visions and directions for future development of AIE-type metal complex nanomaterials.

Allylic amination reactivity of Ni, Pd, and Pt heterobimetallic and monometallic complexes.

PubMed

Carlsen, Ryan W; Ess, Daniel H

2016-06-14

Transition metal heterobimetallic complexes with dative metal-metal interactions have the potential for novel fast reactivity. There are few studies that both compare the reactivity of different metal centers in heterobimetallic complexes and compare bimetallic reactivity to monometallic reactivity. Here we report density-functional calculations that show the reactivity of [Cl2Ti(N(t)BuPPh2)2M(II)(η(3)-methallyl)] heterobimetallic complexes for allylic amination follows M = Ni > Pd > Pt. This reactivity trend was not anticipated since the amine addition transition state involves M(II) to M(0) reduction and this could disadvantage Ni. Comparison of heterobimetallic complexes to the corresponding monometallic (CH2)2(N(t)BuPPh2)2M(II)(η(3)-methallyl) complexes reveals that this reactivity trend is due to the bimetallic interaction and that the bimetallic interaction significantly lowers the barrier height for amine addition by >10 kcal mol(-1). The impact of the early transition metal center on the amination addition barrier height depends on the late transition metal center. The lowest barrier heights for this reaction occur when late and early transition metal centers are from the same periodic table row.

Correlation between oxygen adsorption energy and electronic structure of transition metal macrocyclic complexes.

PubMed

Liu, Kexi; Lei, Yinkai; Wang, Guofeng

2013-11-28

Oxygen adsorption energy is directly relevant to the catalytic activity of electrocatalysts for oxygen reduction reaction (ORR). In this study, we established the correlation between the O2 adsorption energy and the electronic structure of transition metal macrocyclic complexes which exhibit activity for ORR. To this end, we have predicted the molecular and electronic structures of a series of transition metal macrocyclic complexes with planar N4 chelation, as well as the molecular and electronic structures for the O2 adsorption on these macrocyclic molecules, using the density functional theory calculation method. We found that the calculated adsorption energy of O2 on the transition metal macrocyclic complexes was linearly related to the average position (relative to the lowest unoccupied molecular orbital of the macrocyclic complexes) of the non-bonding d orbitals (d(z(2)), d(xy), d(xz), and d(yz)) which belong to the central transition metal atom. Importantly, our results suggest that varying the energy level of the non-bonding d orbitals through changing the central transition metal atom and/or peripheral ligand groups could be an effective way to tuning their O2 adsorption energy for enhancing the ORR activity of transition metal macrocyclic complex catalysts.

Biomedical Applications of Organometal-Peptide Conjugates

NASA Astrophysics Data System (ADS)

Metzler-Nolte, Nils

Peptides are well suited as targeting vectors for the directed delivery of metal-based drugs or probes for biomedical investigations. This chapter describes synthetic strategies for the preparation of conjugates of medically interesting peptides with covalently bound metal complexes. Peptides that were used include neuropeptides (enkephalin, neuropeptide Y, neurotensin), uptake peptides (TAT and poly-Arg), and intracellular localization sequences. To these peptides, a whole variety of transition metal complexes has been attached in recent years by solid-phase peptide synthesis (SPPS) techniques. The metal complex can be attached to the peptide on the resin as part of the SPPS scheme. Alternatively, the metal complex may be attached to the peptide as a postsynthetic modification. Advantages as well as disadvantages for either strategy are discussed. Biomedical applications include radiopharmaceutical applications, anticancer and antibacterial activity, metal-peptide conjugates as targeted CO-releasing molecules, and metal-peptide conjugates in biosensor applications.

Chemodynamics of aquatic metal complexes: from small ligands to colloids.

PubMed

Van Leeuwen, Herman P; Buffle, Jacques

2009-10-01

Recent progress in understanding the formation/dissociation kinetics of aquatic metal complexes with complexants in different size ranges is evaluated and put in perspective, with suggestions for further studies. The elementary steps in the Eigen mechanism, i.e., diffusion and dehydration of the metal ion, are reviewed and further developed. The (de)protonation of both the ligand and the coordinating metal ion is reconsidered in terms of the consequences for dehydration rates and stabilities of the various outer-sphere complexes. In the nanoparticulate size range, special attention is given to the case of fulvic ligands, for which the impact of electrostatic interactions is especially large. In complexation with colloidal ligands (hard, soft, and combination thereof) the diffusive transport of metal ions is generally a slower step than in the case of complexation with small ligands in a homogeneous solution. The ensuing consequences for the chemodynamics of colloidal complexes are discussed in detail and placed in a generic framework, encompassing the complete range of ligand sizes.

DFT study of the interaction between DOTA chelator and competitive alkali metal ions.

PubMed

Frimpong, E; Skelton, A A; Honarparvar, B

2017-09-01

1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetracetic acid (DOTA) is an important chelator for radiolabeling of pharmaceuticals. The ability of alkali metals found in the body to complex with DOTA and compete with radio metal ions can alter the radiolabeling process. Non-covalent interactions between DOTA complexed with alkali metals Li + , Na + , K + and Rb + , are investigated with density functional theory using B3LYP and ωB97XD functionals. Conformational possibilities of DOTA were explored with a varying number of carboxylic pendant arms of DOTA in close proximity to the ions. It is found that the case in which four arms of DOTA are interacting with ions is more stable than other conformations. The objective of this study is to explore the electronic structure properties upon complexation of alkali metals Li + Na + , K + and Rb + with a DOTA chelator. Interaction energies, relaxation energies, entropies, Gibbs free energies and enthalpies show that the stability of DOTA, complexed with alkali metals decreases down the group of the periodic table. Implicit water solvation affects the complexation of DOTA-ions leading to decreases in the stability of the complexes. NBO analysis through the natural population charges and the second order perturbation theory, revealed a charge transfer between DOTA and alkali metals. Conceptual DFT-based properties such as HOMO/LUMO energies, ΔE HOMO-LUMO and chemical hardness and softness indicated a decrease in the chemical stability of DOTA-alkali metal complexes down the alkali metal series. This study serves as a guide to researchers in the field of organometallic chelators, particularly, radiopharmaceuticals in finding the efficient optimal match between chelators and various metal ions. Copyright © 2017 Elsevier Inc. All rights reserved.

Spectroscopic, cyclic voltammetric and biological studies of transition metal complexes with mixed nitrogen-sulphur (NS) donor macrocyclic ligand derived from thiosemicarbazide

NASA Astrophysics Data System (ADS)

Chandra, Sulekh; Gupta, Lokesh Kumar; Sangeetika

2005-11-01

The complexation of new mixed thia-aza-oxa macrocycle viz., 2,12-dithio-5,9,14,18-tetraoxo-7,16-dithia-1,3,4,10,11,13-hexaazacyclooctadecane containing thiosemicarba-zone unit with a series of transition metals Co(II), Ni(II) and Cu(II) has been investigated, by different spectroscopic techniques. The structural features of the ligand have been studied by EI-mass, 1H NMR and IR spectral techniques. Elemental analyses, magnetic moment susceptibility, molar conductance, IR, electronic, and EPR spectral studies characterized the complexes. Electronic absorption and IR spectra of the complexes indicate octahedral geometry for chloro, nitrato, thiocyanato or acetato complexes. The dimeric and neutral nature of the sulphato complexes are confirmed from magnetic susceptibility and low conductance values. Electronic spectra suggests square-planar geometry for all sulphato complexes. The redox behaviour was studied by cyclic voltammetry, show metal-centered reduction processes for all complexes. The complexes of copper show both oxidation and reduction process. The redox potentials depend on the conformation of central atom in the macrocyclic complexes. Newly synthesized macrocyclic ligand and its transition metal complexes show markedly growth inhibitory activity against pathogenic bacterias and plant pathogenic fungi under study. Most of the complexes have higher activity than that of the metal free ligand.

Synthesis, spectroscopic, biological activity and thermal characterization of ceftazidime with transition metals

NASA Astrophysics Data System (ADS)

Masoud, Mamdouh S.; Ali, Alaa E.; Elasala, Gehan S.; Kolkaila, Sherif A.

2018-03-01

Synthesis, physicochemical characterization and thermal analysis of ceftazidime complexes with transition metals (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)) were discussed. It's obtained that ceftazidime act as bidentate ligand. From magnetic measurement and spectral data, octahedral structures were proposed for all complexes except for cobalt, nickel and mercury had tetrahedral structural. Hyper chemistry program confirmed binding sites of ceftazidime. Ceftazidime complexes show higher activity than ceftazidime for some strains. From TG and DTA curves the thermal decomposition mechanisms of ceftazidime and their metal complexes were suggested. The thermal decomposition of the complexes ended with the formation of metal oxides as a final product except in case of Hg complex.

Structural analysis of the coordination of dinitrogen to transition metal complexes.

PubMed

Peigné, Benjamin; Aullón, Gabriel

2015-06-01

Transition-metal complexes show a wide variety of coordination modes for the nitrogen molecule. A structural database study has been undertaken for dinitrogen complexes, and geometrical parameters around the L(n)M-N2 unit are retrieved from the Cambridge Structural Database. These data were classified in families of compounds, according to metal properties, to determine the degree of lengthening for the dinitrogen bonding. The importance of the nature of the metal center, such as coordination number and electronic configuration, is reported. Our study reveals poor activation by coordination of dinitrogen in mononuclear complexes, always having end-on coordination. However, partial weakening of nitrogen-nitrogen bonding is found for end-on binuclear complexes, whereas side-on complexes can be completely activated.

Functional microporous materials of metal carboxylate: Gas-occlusion properties and catalytic activities

NASA Astrophysics Data System (ADS)

Mori, Wasuke; Sato, Tomohiko; Ohmura, Tesushi; Nozaki Kato, Chika; Takei, Tohru

2005-08-01

Copper(II) terephthalate is the first transition metal complex found capable of adsorbing gases. This complex has opened the new field of adsorbent complex chemistry. It is recognized as the lead complex in the construction of microporous complexes. This specific system has been expanded to a systematic series of derivatives of other isomorphous transition metals, molybdenum(II), ruthenium(II, III), and rhodium(II). These complexes with open frameworks are widely recognized as very useful materials for applications to catalysis, separation at molecular level, and gas storage.

Trace Metal-Humic Complexes in Natural Waters: Insights From Speciation Experiments

NASA Astrophysics Data System (ADS)

Stern, J. C.; Salters, V.; Sonke, J.

2006-12-01

The DOM cycle is intimately linked to the cycling and bioavailability of trace metals in aqueous environments. The presence or absence of DOM in the water column can determined whether trace elements will be present in limited quantities as a nutrient, or in surplus quantities as a toxicant. Humic substances (HS), which represent the refractory products of DOM degradation, strongly affect the speciation of trace metals in natural waters. To simulate metal-HS interactions in nature, experiments must be carried out using trace metal concentrations. Sensitive detection systems such as ICP-MS make working with small (nanomolar) concentrations possible. Capillary electrophoresis coupled with ICP-MS (CE-ICP-MS) has recently been identified as a rapid and accurate method to separate metal species and calculate conditional binding constants (log K_c) of metal-humic complexes. CE-ICP-MS was used to measure partitioning of metals between humic substances and a competing ligand (EDTA) and calculate binding constants of rare earth element (REE) and Th, Hf, and Zr-humic complexes at pH 3.5-8 and ionic strength of 0.1. Equilibrium dialysis ligand exchange (EDLE) experiments to validate the CE-ICP-MS method were performed to separate the metal-HS and metal-EDTA species by partitioning due to size exclusion via diffusion through a 1000 Da membrane. CE-ICP-MS experiments were also conducted to compare binding constants of REE with humic substances of various origin, including soil, peat, and aquatic DOM. Results of our experiments show an increase in log K_c with decrease in ionic radius for REE-humic complexes (the lanthanide contraction effect). Conditional binding constants of tetravalent metal-humic complexes were found to be several orders of magnitude higher than REE-humic complexes, indicating that tetravalent metals have a very strong affinity for humic substances. Because thorium is often used as a proxy for the tetravalent actinides, Th-HS binding constants can allow us to assess the importance of tetravalent actinide-humic complexes in groundwater transport from nuclear repositories. Our results suggest that tetravalent actinide-humic complexes couild be more important to account for in predictive speciation models than previously thought.

Preservation of NOM-metal complexes in a modern hyperalkaline stalagmite: Implications for speleothem trace element geochemistry

NASA Astrophysics Data System (ADS)

Hartland, Adam; Fairchild, Ian J.; Müller, Wolfgang; Dominguez-Villar, David

2014-03-01

We report the first quantitative study of the capture of colloidal natural organic matter (NOM) and NOM-complexed trace metals (V, Co, Cu, Ni) in speleothems. This study combines published NOM-metal dripwater speciation measurements with high-resolution laser ablation ICPMS (LA-ICPMS) and sub-annual stable isotope ratio (δ18O and δ13C), fluorescence and total organic carbon (TOC) analyses of a fast-growing hyperalkaline stalagmite (pH ˜11) from Poole’s Cavern, Derbyshire UK, which formed between 1997 and 2008 AD. We suggest that the findings reported here elucidate trace element variations arising from colloidal transport and calcite precipitation rate changes observed in multiple, natural speleothems deposited at ca. pH 7-8. We find that NOM-metal(aq) complexes on the boundary between colloidal and dissolved (˜1 nm diameter) show an annual cyclicity which is inversely correlated with the alkaline earth metals and is explained by calcite precipitation rate changes (as recorded by kinetically-fractionated stable isotopes). This relates to the strength of the NOM-metal complexation reaction, resulting in very strongly bound metals (Co in this system) essentially recording NOM co-precipitation (ternary complexation). More specifically, empirical partition coefficient (Kd) values between surface-reactive metals (V, Co, Cu, Ni) [expressed as ratio of trace element to Ca ratios in calcite and in solution] arise from variations in the ‘free’ fraction of total metal in aqueous solution (fm). Hence, differences in the preservation of each metal in calcite can be explained quantitatively by their complexation behaviour with aqueous NOM. Differences between inorganic Kd values and field measurements for metal partitioning into calcite occur where [free metal] ≪ [total metal] due to complexation reactions between metals and organic ligands (and potentially inorganic colloids). It follows that where fm ≈ 0, apparent inorganic Kd app values are also ≈0, but the true partition coefficient (Kd actual) is significantly higher. Importantly, the Kd of NOM-metal complexes [organic carbon-metal ratio) approaches 1 for the most stable aqueous complexes, as is shown here for Co, but has values of 24-150 for V, Ni and Cu. This implies that ternary surface complexation (metal-ligand co-adsorption) can occur (as for NOM-Co), but is the exception rather than the rule. We also demonstrate the potential for trace metals to record information on NOM composition as expressed through changing NOM-metal complexation patterns in dripwaters. Therefore, a suite of trace metals in stalagmites show variations clearly attributable to changes in organic ligand concentration and composition, and which potentially reflect the state of overlying surface ecosystems. The heterogeneous speciation and size distribution of aqueous NOM and metals (Lead and Wilkinson, 2006; Aiken et al., 2011). The variability in NOM-metal transport in caves that arises from the interaction between infiltration, flow routing, and the hydrodynamic properties of the fine colloids and particulates (Hartland et al., 2012). Variable dissociation kinetics through time as a function of (a) (Hartland et al., 2011). The surface charge of calcite and the availability of CaCO3 lattice sites as well as increased incidence of crystallographic defects with implications for incorporation of a range of trace species (Fairchild and Treble, 2009; Fairchild and Hartland, 2010). Thus, incorporation in speleothem calcite with consistent surface site properties will be determined by: The size and composition (i.e. hydrophilicity/hydrophobicity) of the NOM ligand, affecting adsorption and stability at the calcite surface. The lability (i.e. exchangeability) of the complexed metal and its binding affinity for the calcite surface. The concentration of aqueous complexes. Given the complexities, a partitioning approach to the problem is appropriate as a first approximation rather than a precise description. This study seeks to make the first quantitative connection between the organic and inorganic compositions of speleothems and thus determine the potential for speleothems to encode fluctuations in colloid-facilitated trace metal transport in karst aquifers. Recent findings of direct relevance to the present studyThe conjugate dripwater (PE1) to the stalagmite studied here (PC-08-1) was characterised in June 2009 using an array of complementary techniques, in which the size, speciation and lability of NOM-metal complexes was characterised (Hartland et al., 2011), where lability is defined as the capacity for complexes to dissociate in the context of the on-going interfacial process at the stalagmite surface. In PE1 dripwater, the most stable aqueous complexes were formed between Co and the finest, low molecular weight component of the NOM spectrum (Hartland et al., 2011). Speciation experiments demonstrated that Co was essentially non-exchangeable (free metal (fm) = <0.05), being retained in aqueous complexes, whilst Cu, Ni and V were all predominantly bound by NOM (fm = 0.2-0.3).In contrast, Sr and Ba were freely exchangeable between the solution and solid phase (Hartland et al., 2011) and Mg was absent, presumably due to the poor solubility of Mg(OH)2 at hyperalkaline pH (Ksp = 1.5 × 10-11): Mg2+(aq)+2OH-(aq)↔Mg( On the other hand, the transition metals were not lost as insoluble hydroxides (Hartland et al., 2012), despite having lower solubility than Mg (e.g. Cu(OH)2Ksp = 2.2 × 10-20); and this is consistent with the dominant role of NOM in solubilising and transporting the transition metals in this system (Hartland et al., 2011).The transport of metals by complexes with NOM in PE1 dripwater through the hydrological year was studied by Hartland et al. (2012). This study had two findings of direct relevance to the study of trace metal variations in the conjugate PC-08-1 stalagmite: Complexes between metals and the smallest, low-molecular weight fraction of NOM showed an attenuated delivery in dripwaters consistent with the non-conservative behaviour of analogous tracers in fractured-rock studies due to diffusion into micro-fractures. This mode of transport was termed ‘low-flux’ and was the dominant mode of transport for Co and V. Complexes between metals and coarse colloids (>100 nm) and particulates (>1000 nm) showed a rapid responsiveness to infiltration events. This was termed the ‘high-flux’ mode of NOM-metal transport and was interpreted as being dominantly fracture-fed. This mode of transport was dominated by Cu, Zn and Ni. The ‘high-flux’ vs ‘low-flux’ interplay of trace metal transport is summarised in Fig. 1.The PC-08-1 stalagmite studied here was deposited following the removal of stalagmite PC-97-1 studied by Baker et al. (1999b) and which grew under the PE1 drip point between 1927 and 1997. Both the PC-97-1 stalagmite and its regrowth (PC-08-1) are characterised by annual lamina couplets consisting of a porous pale layer and a dense fluorescent layer. Fluorescence in the PC-97-1 stalagmite displayed a marked sinusoidal pattern with 10% of laminae exhibiting a double band structure (Baker et al., 1999b).

Antimicrobial, spectral, magnetic and thermal studies of Cu(II), Ni(II), Co(II), UO(2)(VI) and Fe(III) complexes of the Schiff base derived from oxalylhydrazide.

PubMed

Melha, Khlood Abou

2008-04-01

The Schiff base ligand, oxalyl [( 2 - hydroxybenzylidene) hydrazone] [corrected].H(2)L, and its Cu(II), Ni(II), Co(II), UO(2)(VI) and Fe(III) complexes were prepared and tested as antibacterial agents. The Schiff base acts as a dibasic tetra- or hexadentate ligand with metal cations in molar ratio 1:1 or 2:1 (M:L) to yield either mono- or binuclear complexes, respectively. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H NMR, Mass, and UV-Visible spectra and the magnetic moments and electrical conductance of the complexes were also determined. For binuclear complexes, the magnetic moments are quite low compared to the calculated value for two metal ions complexes and this shows antiferromagnetic interactions between the two adjacent metal ions. The ligand and its metal complexes were tested against a Gram + ve bacteria (Staphylococcus aureus), a Gram -ve bacteria (Escherichia coli), and a fungi (Candida albicans). The tested compounds exhibited high antibacterial activities.

Formation of metal-nicotianamine complexes as affected by pH, ligand exchange with citrate and metal exchange. A study by electrospray ionization time-of-flight mass spectrometry.

PubMed

Rellán-Alvarez, Rubén; Abadía, Javier; Alvarez-Fernández, Ana

2008-05-01

Nicotianamine (NA) is considered as a key element in plant metal homeostasis. This non-proteinogenic amino acid has an optimal structure for chelation of metal ions, with six functional groups that allow octahedral coordination. The ability to chelate metals by NA is largely dependent on the pK of the resulting complex and the pH of the solution, with most metals being chelated at neutral or basic pH values. In silico calculations using pKa and pK values have predicted the occurrence of metal-NA complexes in plant fluids, but the use of soft ionization techniques (e.g. electrospray), together with high-resolution mass spectrometers (e.g. time-of-flight mass detector), can offer direct and metal-specific information on the speciation of NA in solution. We have used direct infusion electrospray ionization mass spectrometry (time-of-flight) ESI-MS(TOF) to study the complexation of Mn, Fe(II), Fe(III), Ni, Cu by NA. The pH dependence of the metal-NA complexes in ESI-MS was compared to that predicted in silico. Possible exchange reactions that may occur between Fe-NA and other metal micronutrients as Zn and Cu, as well as between Fe-NA and citrate, another possible Fe ligand candidate in plants, were studied at pH 5.5 and 7.5, values typical of the plant xylem and phloem saps. Metal-NA complexes were generally observed in the ESI-MS experiments at a pH value approximately 1-2 units lower than that predicted in silico, and this difference could be only partially explained by the estimated error, approximately 0.3 pH units, associated with measuring pH in organic solvent-containing solutions. Iron-NA complexes are less likely to participate in ligand- and metal-exchange reactions at pH 7.5 than at pH 5.5. Results support that NA may be the ligand chelating Fe at pH values usually found in phloem sap, whereas in the xylem sap NA is not likely to be involved in Fe transport, conversely to what occurs with other metals such as Cu and Ni. Some considerations that need to be addressed when studying metal complexes in plant compartments by ESI-MS are also discussed.

Co(II) and Cd(II) Complexes Derived from Heterocyclic Schiff-Bases: Synthesis, Structural Characterisation, and Biological Activity

PubMed Central

Ahmed, Riyadh M.; Yousif, Enaam I.; Al-Jeboori, Mohamad J.

2013-01-01

New monomeric cobalt and cadmium complexes with Schiff-bases, namely, N′-[(E)-(3-hydroxy-4-methoxyphenyl)methylidene]furan-2-carbohydrazide (L1) and N′-[(E)-(3-hydroxy-4-methoxyphenyl)methylidene]thiophene-2-carbohydrazide (L2) are reported. Schiff-base ligands L1 and L2 were derived from condensation of 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with furan-2-carboxylic acid hydrazide and thiophene-2-carboxylic acid hydrazide, respectively. Complexes of the general formula [M(L)2]Cl2 (where M = Co(II) or Cd(II), L = L1 or L2) have been obtained from the reaction of the corresponding metal chloride with the ligands. The ligands and their metal complexes were characterised by spectroscopic methods (FTIR, UV-Vis, 1H, and 13C NMR spectra), elemental analysis, metal content, magnetic measurement, and conductance. These studies revealed the formation of four-coordinate complexes in which the geometry about metal ion is tetrahedral. Biological activity of the ligands and their metal complexes against gram positive bacterial strain Bacillus (G+) and gram negative bacteria Pseudomonas (G−) revealed that the metal complexes become less resistive to the microbial activities as compared to the free ligands. PMID:24027449

Influence of Humic Acid Complexation with Metal Ions on Extracellular Electron Transfer Activity.

PubMed

Zhou, Shungui; Chen, Shanshan; Yuan, Yong; Lu, Qin

2015-11-23

Humic acids (HAs) can act as electron shuttles and mediate biogeochemical cycles, thereby influencing the transformation of nutrients and environmental pollutants. HAs commonly complex with metals in the environment, but few studies have focused on how these metals affect the roles of HAs in extracellular electron transfer (EET). In this study, HA-metal (HA-M) complexes (HA-Fe, HA-Cu, and HA-Al) were prepared and characterized. The electron shuttle capacities of HA-M complexes were experimentally evaluated through microbial Fe(III) reduction, biocurrent generation, and microbial azoreduction. The results show that the electron shuttle capacities of HAs were enhanced after complexation with Fe but were weakened when using Cu or Al. Density functional theory calculations were performed to explore the structural geometry of the HA-M complexes and revealed the best binding sites of the HAs to metals and the varied charge transfer rate constants (k). The EET activity of the HA-M complexes were in the order HA-Fe > HA-Cu > HA-Al. These findings have important implications for biogeochemical redox processes given the ubiquitous nature of both HAs and various metals in the environment.

Parametrization of a force field for metals complexed to biomacromolecules: applications to Fe(II), Cu(II) and Pb(II)

NASA Astrophysics Data System (ADS)

David, Laurent; Amara, Patricia; Field, Martin J.; Major, François

2002-08-01

Although techniques for the simulation of biomolecules, such as proteins and RNAs, have greatly advanced in the last decade, modeling complexes of biomolecules with metal ions remains problematic. Precise calculations can be done with quantum mechanical methods but these are prohibitive for systems the size of macromolecules. More qualitative modeling can be done with molecular mechanical potentials but the parametrization of force fields for metals is often difficult, particularly if the bonding between the metal and the groups in its coordination shell has significant covalent character. In this paper we present a method for deriving bond and bond-angle parameters for metal complexes from experimental bond and bond-angle distributions obtained from the Cambridge Structural Database. In conjunction with this method, we also introduce a non-standard energy term of gaussian form that allows us to obtain a stable description of the coordination about a metal center during a simulation. The method was evaluated on Fe(II)-porphyrin complexes, on simple Cu(II) ion complexes and a number of complexes of the Pb(II) ion.

Schiff bases in medicinal chemistry: a patent review (2010-2015).

PubMed

Hameed, Abdul; Al-Rashida, Mariya; Uroos, Maliha; Abid Ali, Syed; Khan, Khalid Mohammed

2017-01-01

Schiff bases are synthetically accessible and structurally diverse compounds, typically obtained by facile condensation between an aldehyde, or a ketone with primary amines. Schiff bases contain an azomethine (-C = N-) linkage that stitches together two or more biologically active aromatic/heterocyclic scaffolds to form various molecular hybrids with interesting biological properties. Schiff bases are versatile metal complexing agents and have been known to coordinate all metals to form stable metal complexes with vast therapeutic applications. Areas covered: This review aims to provide a comprehensive overview of the various patented therapeutic applications of Schiff bases and their metal complexes from 2010 to 2015. Expert opinion: Schiff bases are a popular class of compounds with interesting biological properties. Schiff bases are also versatile metal complexing ligands and have been used to coordinate almost all d-block metals as well as lanthanides. Therapeutically, Schiff bases and their metal complexes have been reported to exhibit a wide range of biological activities such as antibacterial including antimycobacterial, antifungal, antiviral, antimalarial, antiinflammatory, antioxidant, pesticidal, cytotoxic, enzyme inhibitory, and anticancer including DNA damage.

Water-soluble polymers for recovery of metal ions from aqueous streams

DOEpatents

Smith, Barbara F.; Robison, Thomas W.

1998-01-01

A process of selectively separating a target metal contained in an aqueous solution by contacting the aqueous solution containing a target metal with an aqueous solution including a water-soluble polymer capable of binding with the target metal for sufficient time whereby a water-soluble polymer-target metal complex is formed, and, separating the solution including the water-soluble polymer-target metal complex from the solution is disclosed.

Highly versatile heteroditopic ligand scaffolds for accommodating group 8, 9 & 11 heterobimetallic complexes.

PubMed

Gatus, Mark R D; Bhadbhade, Mohan; Messerle, Barbara A

2017-10-24

Two highly versatile xanthene scaffolds containing pairs of heteroditopic ligands were found to be capable of accommodating a range of transition metal ions, including Au(i), Ir(i), Ir(iii), Rh(i), and Ru(ii) to generate an array of heterobimetallic complexes. The metal complexes were fully characterised and proved to be stable in the solid and solution state, with no observed metal-metal scrambling. Heterobimetallic complexes containing the Rh(i)/Ir(i) combinations were tested as catalysts for the two-step dihydroalkoxylation reaction of alkynediols and sequential hydroamination/hydrosilylation reaction of alkynamines.

Charge-separated and molecular heterobimetallic rare earth-rare earth and alkaline earth-rare earth aryloxo complexes featuring intramolecular metal-pi-arene interactions.

PubMed

Deacon, Glen B; Junk, Peter C; Moxey, Graeme J; Ruhlandt-Senge, Karin; St Prix, Courtney; Zuniga, Maria F

2009-01-01

Treatment of a rare earth metal (Ln) and a potential divalent rare earth metal (Ln') or an alkaline earth metal (Ae) with 2,6-diphenylphenol (HOdpp) at elevated temperatures (200-250 degrees C) afforded heterobimetallic aryloxo complexes, which were structurally characterised. A charge-separated species [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] was obtained for a range of metals, demonstrating the similarities between the chemistry of the divalent rare earth metals and the alkaline earth metals. The [(Ln'/Ae)(2)(Odpp)(3)](+) cation in the heterobimetallic structures is unusual in that it consists solely of bridging aryloxide ligands. A molecular heterobimetallic species [AeEu(Odpp)(4)] (Ae = Ca, Sr, Ba) was obtained by treating an alkaline earth metal and Eu metal with HOdpp at elevated temperatures. Similarly, [BaSr(Odpp)(4)] was prepared by treating Ba metal and Sr metal with HOdpp. Treatment of [Ba(2)(Odpp)(4)] with [Mg(Odpp)(2)(thf)(2)] in toluene afforded [Ba(2)(Odpp)(3)][Mg(Odpp)(3)(thf)]. Analogous solution-based syntheses were not possible for [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] complexes, for which the free-metal route was essential. As a result of the absence of additional donor ligands, the crystal structures of the heterobimetallic complexes feature extensive pi-Ph-metal interactions involving the pendant phenyl groups of the Odpp ligands, thus enabling the large electropositive metal atoms to attain coordination saturation. The charge-separated heterobimetallic species were purified by extraction with toluene/thf mixtures at ambient temperature (Ba-containing compounds) or by extraction with toluene under pressure above the boiling point of the solvent (other products). In donor solvents, heterobimetallic complexes other than those containing barium were found to fragment into homometallic species.

Synthesis, spectroscopic characterization, electrochemistry and biological evaluation of some binuclear transition metal complexes of bicompartmental ONO donor ligands containing benzo[b]thiophene moiety

NASA Astrophysics Data System (ADS)

Mahendra Raj, K.; Vivekanand, B.; Nagesh, G. Y.; Mruthyunjayaswamy, B. H. M.

2014-02-01

A series of new binucleating Cu(II), Co(II), Ni(II) and Zn(II) complexes of bicompartmental ligands with ONO donor were synthesized. The ligands were obtained by the condensation of 3-chloro-6-substituted benzo[b]thiophene-2-carbohydrazides and 4,6-diacetylresorcinol. The synthesized ligands and their complexes were characterized by elemental analysis and various spectroscopic techniques. Elemental analysis, IR, 1H NMR, ESI-mass, UV-Visible, TG-DTA, magnetic measurements, molar conductance and powder-XRD data has been used to elucidate their structures. The bonding sites are the oxygen atom of amide carbonyl, azomethine nitrogen and phenolic oxygen for ligands 1 and 2. The binuclear nature of the complexes was confirmed by ESR spectral data. TG-DTA studies for some complexes showed the presence of coordinated water molecules and the final product is the metal oxide. All the complexes were investigated for their electrochemical activity, only the Cu(II) complexes showed the redox property. Cu(II) complexes were square planar, whereas Co(II), Ni(II) and Zn(II) complexes were octahedral. Powder-XRD pattern have been studied in order to test the degree of crystallinity of the complexes and unit cell calculations were made. In order to evaluate the effect of antimicrobial activity of metal ions upon chelation, both the ligands and their metal complexes were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The results showed that the metal complexes were found to be more active than free ligands. The DNA cleaving capacities of all the complexes were analyzed by agarose gel electrophoresis method against supercoiled plasmid DNA. Among the compounds tested for antioxidant capacity, ligand 1 displayed excellent activity than its metal complexes.

Spectro Analytical, Computational and In Vitro Biological Studies of Novel Substituted Quinolone Hydrazone and it's Metal Complexes.

PubMed

Nagula, Narsimha; Kunche, Sudeepa; Jaheer, Mohmed; Mudavath, Ravi; Sivan, Sreekanth; Ch, Sarala Devi

2018-01-01

Some novel transition metal [Cu (II), Ni (II) and Co (II)] complexes of nalidixic acid hydrazone have been prepared and characterized by employing spectro-analytical techniques viz: elemental analysis, 1 H-NMR, Mass, UV-Vis, IR, TGA-DTA, SEM-EDX, ESR and Spectrophotometry studies. The HyperChem 7.5 software was used for geometry optimization of title compound in its molecular and ionic forms. Quantum mechanical parameters, contour maps of highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) and corresponding binding energy values were computed using semi empirical single point PM3 method. The stoichiometric equilibrium studies of metal complexes carried out spectrophotometrically using Job's continuous variation and mole ratio methods inferred formation of 1:2 (ML 2 ) metal complexes in respective systems. The title compound and its metal complexes screened for antibacterial and antifungal properties, exemplified improved activity in metal complexes. The studies of nuclease activity for the cleavage of CT- DNA and MTT assay for in vitro cytotoxic properties involving metal complexes exhibited high activity. In addition, the DNA binding properties of Cu (II), Ni (II) and Co (II) complexes investigated by electronic absorption and fluorescence measurements revealed their good binding ability and commended agreement of K b values obtained from both the techniques. Molecular docking studies were also performed to find the binding affinity of synthesized compounds with DNA (PDB ID: 1N37) and "Thymidine phosphorylase from E.coli" (PDB ID: 4EAF) protein targets.

Ammonia release method for depositing metal oxides

DOEpatents

Silver, Gary L.; Martin, Frank S.

1994-12-13

A method of depositing metal oxides on substrates which is indifferent to the electrochemical properties of the substrates and which comprises forming ammine complexes containing metal ions and thereafter effecting removal of ammonia from the ammine complexes so as to permit slow precipitation and deposition of metal oxide on the substrates.

Radical bonding: structure and stability of bis(phenalenyl) complexes of divalent metals from across the periodic table.

PubMed

Craciun, Smaranda; Donald, Kelling J

2009-07-06

We examine the bonding possibilities of the bis(phenalenyl) MP(2) sandwich complexes of the divalent metals M = Be, Mg, Ca, Sr, Ba, Zn, Cd, and Hg, at the B3LYP level of theory. The outcome is an extraordinarily diverse class of low symmetry bis(phenalenyl)metal complexes in which bonding preferences and binding enthalpies differ dramatically. The lowest energy group 2 metal MP(2) complexes include an intriguing eta(1),eta(3) BeP(2) structure, and bent eta(6),eta(6) systems for M = Ca, Sr, and Ba. The group 12 bis(phenalenyl) complexes are thermodynamically unstable eta(1),eta(1) slip-sandwich structures. To better understand changes in the structural preferences going from the (eta(6),eta(6)) group 2 to the (eta(1),eta(1)) group 12 complexes, we explored the bonding in the bis(phenalenyl) complexes of transition metals with stable +2 oxidations states between Ca and Zn in period 4. The computed binding enthalpies are large and negative for nearly all of the minimum energy bis(phenalenyl) complexes of the group 2 and the transition metals; they are tiny for MgP(2), and are quite positive for the group 12 systems. The structural preferences and stability of the complexes is a subtle negotiation of several influences: the (un)availability of (n - 1)d and np, orbitals for bonding, the cost of the rehybridization at carbon sites in the phenalenyl rings in preparation for bonding to the metals, and the (P---P) interaction between the phenalenyl radicals.

Utility of Lithium in Rare-Earth Metal Reduction Reactions to Form Nontraditional Ln2+ Complexes and Unusual [Li(2.2.2-cryptand)]1+ Cations.

PubMed

Huh, Daniel N; Darago, Lucy E; Ziller, Joseph W; Evans, William J

2018-02-19

The utility of lithium compared to other alkali metals in generating Ln 2+ rare-earth metal complexes via reduction of Ln 3+ precursors in reactions abbreviated as LnA 3 /M (Ln = rare-earth metal; A = anionic ligand; M = alkali metal) is described. Lithium reduction of Cp' 3 Ln (Cp' = C 5 H 4 SiMe 3 ; Ln = Y, Tb, Dy, Ho) under Ar in the presence of 2.2.2-cryptand (crypt) forms new examples of crystallographically characterizable Ln 2+ complexes of these metals, [Li(crypt)][Cp' 3 Ln]. In each complex, lithium is found in an N 2 O 4 donor atom coordination geometry that is unusual for the cryptand ligand. Magnetic susceptibility data on these new examples of nontraditional divalent lanthanide complexes are consistent with 4f n 5d 1 electronic configurations. The Dy and Ho complexes have exceptionally high single-ion magnetic moments, 11.35 and 11.67 μ B , respectively. Lithium reduction of Cp' 3 Y under N 2 at -35 °C forms the Y 2+ complex (Cp' 3 Y) 1- , which reduces dinitrogen upon warming to room temperature to generate the (N 2 ) 2- complex [Cp' 2 Y(THF)] 2 (μ-η 2 :η 2 -N 2 ). These results provide insight on the factors that lead to reduced dinitrogen complexes and/or stable divalent lanthanide complexes as a function of the specific reducing agent and conditions.

Supramolecular control of transition metal complexes in water by a hydrophobic cavity: a bio-inspired strategy.

PubMed

Bistri, Olivia; Reinaud, Olivia

2015-03-14

Supramolecular chemistry in water is a very challenging research area. In biology, water is the universal solvent where transition metal ions play major roles in molecular recognition and catalysis. In enzymes, it participates in substrate binding and/or activation in the heart of a pocket defined by the folded protein. The association of a hydrophobic cavity with a transition metal ion is thus a very appealing strategy for controlling the metal ion properties in the very competitive water solvent. Various systems based on intrinsically water-soluble macrocyclic structures such as cyclodextrins, cucurbituryls, and metallo-cages have been reported. Others use calixarenes and resorcinarenes functionalized with hydrophilic substituents. One approach for connecting a metal complex to these cavities is to graft a ligand for metal ion binding at their edge. Early work with cyclodextrins has shown Michaelis-Menten like catalysis displaying enhanced kinetics and substrate-selectivity. Remarkable examples of regio- and stereo-selective transformation of substrates have been reported as well. Dynamic two-phase systems for transition metal catalysis have also been developed. They rely on either water-transfer of the metal complex through ligand embedment or synergistic coordination of a metal ion and substrate hosting. Another strategy consists in using metallo-cages, which provide a well-defined hydrophobic space, to stabilize metal complexes in water. When the cages can host simultaneously a substrate and a reactive metal complex, size- and regio-selective catalysis was obtained. Finally, construction of a polydentate coordination site closely interlocked with a calixarene or resorcinarene macrocycle has been shown to be a very fruitful strategy for obtaining metal complexes with remarkable hosting properties. For each of these systems, the synergism resulting from the biomimetic association of a hydrophobic cavity and a metal ion is discussed within the objective of developing new tools for either selective molecular recognition (with analytical perspectives) or performant catalysis, in water.

Complex transition metal hydrides: linear correlation of countercation electronegativity versus T-D bond lengths.

PubMed

Humphries, T D; Sheppard, D A; Buckley, C E

2015-06-30

For homoleptic 18-electron complex hydrides, an inverse linear correlation has been established between the T-deuterium bond length (T = Fe, Co, Ni) and the average electronegativity of the metal countercations. This relationship can be further employed towards aiding structural solutions and predicting physical properties of novel complex transition metal hydrides.

Analysis of Supercritical-Extracted Chelated Metal Ions From Mixed Organic-Inorganic Samples

NASA Technical Reports Server (NTRS)

Sinha, Mahadeva P. (Inventor)

1996-01-01

Organic and inorganic contaminants of an environmental sample are analyzed by the same GC-MS instrument by adding an oxidizing agent to the sample to oxidize metal or metal compounds to form metal ions. The metal ions are converted to chelate complexes and the chelate complexes are extracted into a supercritical fluid such as CO2. The metal chelate extract after flowing through a restrictor tube is directly injected into the ionization chamber of a mass spectrometer, preferably containing a refractory metal filament such as rhenium to fragment the complex to release metal ions which are detected. This provides a fast, economical method for the analysis of metal contaminants in a sample and can be automated. An organic extract of the sample in conventional or supercritical fluid solvents can be detected in the same mass spectrometer, preferably after separation in a supercritical fluid chromatograph.

Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

NASA Technical Reports Server (NTRS)

Stern, Jennifer C.; Foustoukos, Dionysis I.; Sonke, Jeroen E.; Salters, Vincent J. M.

2014-01-01

The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values attained at very low metal loading conditions are compared to existing literature data. Overall, experimental data suggest that the tetravalent transition metal/-actinide-humic acid complexation is important over a wide range of pH values, including mildly acidic conditions, and thus, these complexes should be included in speciation models.

Different binding modes of Cu and Pb vs. Cd, Ni, and Zn with the trihydroxamate siderophore desferrioxamine B at seawater ionic strength

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schijf, Johan; Christenson, Emily A.; Potter, Kailee J.

2015-07-01

The solution speciation in seawater of divalent trace metals (Cd, Cu, Ni, Pb, Zn) is dominated by strong, ostensibly metal-specific organic ligands that may play important roles in microbial metal acquisition and/or detoxification processes. We compare the effective stabilities of these metal-organic complexes to the stabilities of their complexes with a model siderophore, desferrioxamine B (DFOB). While metal-DFOB complexation has been studied in various dilute but often moderately coordinating media, for the purpose of this investigation we measured the stability constants in a non-coordinating background electrolyte at seawater ionic strength (0.7 M NaClO4). Potentiometric titrations of single metals (M) weremore » performed in the presence of ligand (L) at different M:L molar ratios, whereupon the stability constants of multiple complexes were simultaneously determined by non-linear regression of the titration curves with FITEQL, using the optimal binding mode for each metal. Cadmium, Ni, and Zn, like trivalent Fe, sequentially form a bi-, tetra-, and hexadentate complex with DFOB as pH increases, consistent with their coordination number of 6 and regular octahedral geometry. Copper has a Jahn-Teller-distorted square-bipyramidal geometry whereas the geometry of Pb is cryptic, involving a range of bond lengths. Supported by a thermodynamic argument, our data suggest that this impedes binding of the third hydroxamate group and that the hexadentate Cu-DFOB and Pb-DFOB complex identified in earlier reports may instead be a deprotonated tetradentate complex. Absence of the hexadentate complex promotes the formation of a dinuclear (bidentate-tetradentate) complex, M2HL2+, albeit not for Pb in 0.7 M NaCl, evidently due to extensive complexation with chloride. Stabilities of the hexadentate Ni-DFOB, Zn-DFOB, and the tetradentate Pb-DFOB complex are nearly equal, yet about 2 orders of magnitude higher and 4 orders of magnitude lower than those of the hexadentate Cd-DFOB and tetradentate Cu-DFOB complex, respectively. Linear free-energy relations defined by the rare earth elements are able to predict stabilities of the Cd, Zn, and one of the Pb complexes, but underestimate those of the Ni and Cu complexes. The comparison with metal-specific organic ligands detected in seawater yields fair agreement for three of the five metals, implying that they could be siderophore-like. The Cd- and Ni-specific ligands are much stronger and may contain quite different functional groups. Calculations with MINEQL incorporating our new stability constants indicate that very high DFOB concentrations would be required to match the extent of metal-organic complexation observed in seawater, however DFOB may well represent a much broader class of structurally related ligands.« less

Metal Ion Binding at the Catalytic Site Induces Widely Distributed Changes in a Sequence Specific Protein–DNA Complex

PubMed Central

2016-01-01

Metal ion cofactors can alter the energetics and specificity of sequence specific protein–DNA interactions, but it is unknown if the underlying effects on structure and dynamics are local or dispersed throughout the protein–DNA complex. This work uses EcoRV endonuclease as a model, and catalytically inactive lanthanide ions, which replace the Mg2+ cofactor. Nuclear magnetic resonance (NMR) titrations indicate that four Lu3+ or two La3+ cations bind, and two new crystal structures confirm that Lu3+ binding is confined to the active sites. NMR spectra show that the metal-free EcoRV complex with cognate (GATATC) DNA is structurally distinct from the nonspecific complex, and that metal ion binding sites are not assembled in the nonspecific complex. NMR chemical shift perturbations were determined for 1H–15N amide resonances, for 1H–13C Ile-δ-CH3 resonances, and for stereospecifically assigned Leu-δ-CH3 and Val-γ-CH3 resonances. Many chemical shifts throughout the cognate complex are unperturbed, so metal binding does not induce major conformational changes. However, some large perturbations of amide and side chain methyl resonances occur as far as 34 Å from the metal ions. Concerted changes in specific residues imply that local effects of metal binding are propagated via a β-sheet and an α-helix. Both amide and methyl resonance perturbations indicate changes in the interface between subunits of the EcoRV homodimer. Bound metal ions also affect amide hydrogen exchange rates for distant residues, including a distant subdomain that contacts DNA phosphates and promotes DNA bending, showing that metal ions in the active sites, which relieve electrostatic repulsion between protein and DNA, cause changes in slow dynamics throughout the complex. PMID:27786446

Magnetic behavior control in niccolite structural metal formate frameworks [NH2(CH3)2][Fe(III)M(II)(HCOO)6] (M = Fe, Mn, and Co) by varying the divalent metal ions.

PubMed

Zhao, Jiong-Peng; Hu, Bo-Wen; Lloret, Francesc; Tao, Jun; Yang, Qian; Zhang, Xiao-Feng; Bu, Xian-He

2010-11-15

By changing template cation but introducing trivalent iron ions in the known niccolite structural metal formate frameworks, three complexes formulated [NH(2)(CH(3))(2)][Fe(III)M(II)(HCOO)(6)] (M = Fe for 1, Mn for 2, and Co for 3) were synthesized and magnetically characterized. The variation in the compositions of the complexes leads to three different complexes: mixed-valent complex 1, heterometallic but with the same spin state complex 2, and heterometallic heterospin complex 3. The magnetic behaviors are closely related to the divalent metal ions used. Complex 1 exhibits negative magnetization assigned as Néel N-Type ferrimagnet, with an asymmetric magnetization reversal in the hysteresis loop, and complex 2 is an antiferromagnet with small spin canting (α(canting) ≈ 0.06° and T(canting) = 35 K), while complex 3 is a ferrimagnet with T(N) = 32 K.

Syntheses, spectroscopic characterization, thermal study, molecular modeling, and biological evaluation of novel Schiff's base benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) with Ni(II), and Cu(II) metal complexes

NASA Astrophysics Data System (ADS)

Chandra, Sulekh; Gautam, Seema; Rajor, Hament Kumar; Bhatia, Rohit

2015-02-01

Novel Schiff's base ligand, benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) was synthesized by the condensation of benzil and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio. The structure of ligand was determined on the basis of elemental analyses, IR, 1H NMR, mass, and molecular modeling studies. Synthesized ligand behaved as tetradentate and coordinated to metal ion through sulfur atoms of thiol ring and nitrogen atoms of imine group. Ni(II), and Cu(II) complexes were synthesized with this nitrogen-sulfur donor (N2S2) ligand. Metal complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic spectra, EPR, thermal, and molecular modeling studies. All the complexes showed molar conductance corresponding to non-electrolytic nature, expect [Ni(L)](NO3)2 complex, which was 1:2 electrolyte in nature. [Cu(L)(SO4)] complex may possessed square pyramidal geometry, [Ni(L)](NO3)2 complex tetrahedral and rest of the complexes six coordinated octahedral/tetragonal geometry. Newly synthesized ligand and its metal complexes were examined against the opportunistic pathogens. Results suggested that metal complexes were more biological sensitive than free ligand.

N-heterocyclic carbene metal complexes as bio-organometallic antimicrobial and anticancer drugs.

PubMed

Patil, Siddappa A; Patil, Shivaputra A; Patil, Renukadevi; Keri, Rangappa S; Budagumpi, Srinivasa; Balakrishna, Geetha R; Tacke, Matthias

2015-01-01

Late transition metal complexes that bear N-heterocyclic carbene (NHC) ligands have seen a speedy growth in their use as both, metal-based drug candidates and potentially active homogeneous catalysts in a plethora of C-C and C-N bond forming reactions. This review article focuses on the recent developments and advances in preparation and characterization of NHC-metal complexes (metal: silver, gold, copper, palladium, nickel and ruthenium) and their biomedical applications. Their design, syntheses and characterization have been reviewed and correlated to their antimicrobial and anticancer efficacies. All these initial discoveries help validate the great potential of NHC-metal derivatives as a class of effective antimicrobial and anticancer agents.

Structural characterization of 1,8-naphthalimides and in vitro microbiological activity of their Cu(II) and Zn(II) complexes

NASA Astrophysics Data System (ADS)

Grabchev, Ivo; Yordanova, Stanislava; Bosch, Paula; Vasileva-Tonkova, Evgenia; Kukeva, Rositsa; Stoyanov, Stanimir; Stoyanova, Radostina

2017-02-01

Two new 1,8-naphthalimide derivatives (NI1 and NI2) have been synthesized and characterized. The photophysical properties of the new compounds have been investigated in organic solvents of different polarity. It has been shown that both compounds are solvent depended. Cu(II) and Zn(II) complexes of NI2 were obtained and characterized by IR-NMR, fluorescence and EPR spectroscopy. The influence of different metal cations on the fluorescence intensity has been investigated in acetonitrile solution. Antimicrobial composite PLA-metal complexes materials have been obtained for the first time. Microbiological activity of both metal complexes has been investigated in vitro against different Gram-positive and Gram-negative bacteria and two yeasts. The various antimicrobial activities and the minimum inhibitory concentrations (MICs) of both complexes have been determined. The microbiological activity of composite materials PLA-metal complexes in thin polymeric film has also been investigated. The results suggest that the new metal complexes could find application in designing new antimicrobial preparations to control the spread of infections.

Synthesis, characterization and solid state electrical properties of 1-D coordination polymer of the type [Cu{sub x}Ni{sub 1-x}(dadb){center_dot}yH{sub 2}O]{sub n}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prasad, R.L., E-mail: rlpjc@yahoo.co.in; Kushwaha, A.; Shrivastava, O.N.

2012-12-15

New heterobimetallic complexes [Cu{sub x}Ni{sub 1-x}(dadb){center_dot}yH{sub 2}O]{sub n} {l_brace}where dadb=2,5-Diamino-3,6-dichloro-1,4-benzoquinone (1); x=1 (2), 0.5 (4), 0.25 (5), 0.125 (6), 0.0625 (7) and 0 (3); y=2; n=degree of polymerization{r_brace} were synthesized and characterized. Heterobimetallic complexes show normal magnetic moments, whereas, monometallic complexes exhibit magnetic moments less than the value due to spin only. Thermo-gravimetric analysis shows that degradation of the ligand dadb moiety is being controlled by the electronic environment of the Cu(II) ions in preference over Ni(II) in heterobimetallic complexes. Existence of the mixed valency/non-integral oxidation states of copper and nickel metal ions in the complex 4 has been attributedmore » from magnetic moment and ESR spectral results. Solid state dc electrical conductivity of all the complexes was investigated. Monometallic complexes were found to be semiconductors, whereas heterobimetallic coordination polymer 4 was found to exhibit metallic behaviour. Existence of mixed valency/ non-integral oxidation state of metal ions seems to be responsible for the metallic behaviour. - Graphical abstract: Contrast to the semiconductor monometallic complexes 2 and 3, the heterobimetallic complex 4 exhibits metallic behaviour attributed to the mixed valency/non-integral oxidation state of the metal ions concluded from magnetic and ESR spectral studies. Highlights: Black-Right-Pointing-Pointer 1-D coordination compounds of the type Cu{sub x}Ni{sub 1-x}(dadb){center_dot}yH{sub 2}O were synthesized and characterized. Black-Right-Pointing-Pointer Thermal degradation of the complexes provides an indication of long range electronic communication between metal to ligand. Black-Right-Pointing-Pointer On inclusion of Ni(II) into 1-D coordination polymer of Cu(II). (a) Cu(II) and Ni(II) ions exhibit non-integral oxidation state. (b) resulting heterobimetallic complex 4 exhibits metallic behaviour at all temperature range of the present study whereas monometallic complexes are semiconductor.« less

Charge Transfer Between Quantum Dots and Peptide-Coupled Redox Complexes

DTIC Science & Technology

2009-01-01

labeled with reactive metal complexes includ- ing a ruthenium chelate (Ru), a bis-bipyridine ruthe- nium chelate (ruthenium-bpy), and a ferrocene metal...of unconjugated QDs and the metal complex–labeled peptides immobilized on indium tin oxide (ITO) electrodes. The ruthenium and ferrocene peptide...Ag/AgCI E v s. N H E E v s. v ac uu m (e V ) Ruthenium Ferrocene Ruthenium-bpy DHLA QDs DHLA-PEG QDs Quantum dot Metal complex CB VB E0X of QDs Fe

Bifunctional chelating agent for the design and development of site specific radiopharmaceuticals and biomolecule conjugation strategy

DOEpatents

Katti, Kattesh V.; Prabhu, Kandikere R.; Gali, Hariprasad; Pillarsetty, Nagavara Kishore; Volkert, Wynn A.

2003-10-21

There is provided a method of labeling a biomolecule with a transition metal or radiometal in a site specific manner to produce a diagnostic or therapeutic pharmaceutical compound by synthesizing a P.sub.2 N.sub.2 -bifunctional chelating agent intermediate, complexing the intermediate with a radio metal or a transition metal, and covalently linking the resulting metal-complexed bifunctional chelating agent with a biomolecule in a site specific manner. Also provided is a method of synthesizing the --PR.sub.2 containing biomolecules by synthesizing a P.sub.2 N.sub.2 -bifunctional chelating agent intermediate, complexing the intermediate with a radiometal or a transition metal, and covalently linking the resulting radio metal-complexed bifunctional chelating agent with a biomolecule in a site specific manner. There is provided a therapeutic or diagnostic agent comprising a --PR.sub.2 containing biomolecule.

Modelling of trace metal uptake by roots taking into account complexation by exogenous organic ligands

NASA Astrophysics Data System (ADS)

Jean-Marc, Custos; Christian, Moyne; Sterckeman, Thibault

2010-05-01

The context of this study is phytoextraction of soil trace metals such as Cd, Pb or Zn. Trace metal transfer from soil to plant depends on physical and chemical processes such as minerals alteration, transport, adsorption/desorption, reactions in solution and biological processes including the action of plant roots and of associated micro-flora. Complexation of metal ions by organic ligands is considered to play a role on the availability of trace metals for roots in particular in the event that synthetic ligands (EDTA, NTA, etc.) are added to the soil to increase the solubility of the contaminants. As this role is not clearly understood, we wanted to simulate it in order to quantify the effect of organic ligands on root uptake of trace metals and produce a tool which could help in optimizing the conditions of phytoextraction.We studied the effect of an aminocarboxilate ligand on the absorption of the metal ion by roots, both in hydroponic solution and in soil solution, for which we had to formalize the buffer power for the metal. We assumed that the hydrated metal ion is the only form which can be absorbed by the plants. Transport and reaction processes were modelled for a system made up of the metal M, a ligand L and the metal complex ML. The Tinker-Nye-Barber model was adapted to describe the transport of solutes M, L and ML in the soil and absorption of M by the roots. This allowed to represent the interactions between transport, chelating reactions, absorption of the solutes at the root surface, root growth with time, in order to simulate metal uptake by a whole root system.Several assumptions were tested such as i) absorption of the metal by an infinite sink and according to a Michaelis-Menten kinetics, solutes transport by diffusion with and without ii) mass flow and iii) soil buffer power for the ligand L. In hydroponic solution (without soil buffer power), ligands decreased the trace metal flux towards roots, as they reduced the concentration of hydrated metal ion. In soil, depending on the L/M ratio, the presence of metal complexes could increase the metal flux taken up by roots since the ligand desorbed the metal on soil solid phase while the complex dissociated and provided metal ions to the solution in the vicinity of the root.The model enabled to surround the conditions in which phytoextraction is thus optimized. In addition of complexation by organic ligands added to the soil, we expect to integrate complexation by roots organic exudates and by soil organic matter, as well as the competition of the metal ions with Ca2+ et H+.

Ammonia release method for depositing metal oxides

DOEpatents

Silver, G.L.; Martin, F.S.

1994-12-13

A method is described for depositing metal oxides on substrates which is indifferent to the electrochemical properties of the substrates and which comprises forming ammine complexes containing metal ions and thereafter effecting removal of ammonia from the ammine complexes so as to permit slow precipitation and deposition of metal oxide on the substrates. 1 figure.

Synthesis and Properties of Ortho-Nitro-Fe Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, A.; Mishra, Niyati; Sharma, R.

2011-07-15

Ortho-Nitro-Fe complex (Transition metal complex) has synthesized by chemical route method and properties of made complex has characterized by X-Ray diffraction (XRD), Moessbauer spectroscopy, Fourier transformation infra-red spectroscopy (FTIR) and X-Ray photoelectron spectroscopy (XPS). XRD analysis shows that sample is crystalline in nature and having particle size in the range of few nano meters. Moessbauer spectroscopy at room temperature shows the oxidation state of Iron (central metal ion) after complaxasion. FTIR spectra of the complex confirms the coordination of metal ion with ligand.

Fabrication of carbon nanotube films from alkyne-transition metal complexes

DOEpatents

Iyer, Vivekanantan S [Delft, NL; Vollhardt, K Peter C. [Oakland, CA

2007-08-28

A simple method for the production or synthesis of carbon nanotubes as free-standing films or nanotube mats by the thermal decomposition of transition metal complexed alkynes with aryl, alkyl, alkenyl, or alkynyl substituents. In particular, transition metal (e.g. Co, Ni, Fe, Mo) complexes of diarylacetylenes, e.g. diphenylacetylene, and solid mixtures of these complexes with suitable, additional carbon sources are heated in a vessel. More specifically, the heating of the transition metal complex is completed at a temperature between 400-800.degree. C. and more particularly 550-700.degree. C. for between 0.1 to 24 hours and more particularly 0.5-3 hours in a sealed vessel under a partial pressure of argon or helium.

Homo- and Heterometallic Bis(Pentafluorobenzoyl)Methanide Complexes of Copper(II) and Cobalt(II)

NASA Astrophysics Data System (ADS)

Crowder, Janell M.

beta-Diketones are well known to form metal complexes with practically every known metal and metalloid. Metal complexes of fluorinated beta-diketones generally exhibit increased volatility and thermal stability compared to the non-fluorinated analogues, and thus are used extensively in various chemical vapor deposition (CVD) processes for the deposition of metal, simple or mixed metal oxides, and fluorine-doped metal oxide thin films. Furthermore, the electron-withdrawing nature of the fluorinated ligand enhances the Lewis acidity of a coordinatively unsaturated metal center which facilitates additional coordination reactions. The physical and structural properties of fluorinated beta-diketonate complexes are discussed in Chapter 1 and a few key application examples are given. The focus of this work is the synthesis and single crystal X-ray structural characterization of unsolvated and coordinatively unsaturated metal complexes of bis(pentafluorobenzoyl)- methanide (L, C6F5COCHCOC 6F5-). In Chapter 2, we present the preparation and isolation of the unsolvated complex [Cu(L)2] in pure crystalline form for the first time. We subsequently investigated the reaction of unsolvated [Cu(L)2] with sodium hexafluoroacetylacetonate [Na(hfac)] in a solvent-free environment. This reaction allowed the isolation of the first heterometallic Na-Cu diketonate [Na2Cu2(L) 4(hfac)2] structurally characterized by single crystal X-ray crystallography. Thermal decomposition of [Na2Cu2(L) 4(hfac)2] was investigated for its potential application in MOCVD processes. In the final chapter, we present the first exploration of the anhydrous synthesis of Co(II) complexed with bis(pentafluorobenzoyl)methanide in order to produce a complex without ligated water. Single crystal X-ray crystallographic investigations revealed the isolation of the ethanol adduct, [Co2(L)4(C2H5OH)2], and following the removal of ethanol, a 1,4-dioxane adduct, [{Co 2(L)4}2(C4H8O2)]. In this work, we have provided the first investigation of the synthesis, isolation and single crystal X-ray structural characterization of unsolvated and coordinatively unsaturated Cu(II) and Co(II) complexes of bis(pentafluorobenzoyl)methanide ligand. These studies demonstrate how the electrophilicity of a coordinatively unsaturated metal complexed to highly-fluorinated â-diketone ligands can be utilized for the formation of new adducts or new and interesting heterometallic complexes. This body of work provides a basis upon which future research into unsolvated and unligated bis(pentafluorobenzoyl)methanide metal complexes can expand.

Surface Modification and Nanojunction Fabrication with Molecular Metal Wires

DTIC Science & Technology

2014-02-17

Title: Transition Metal Complexes of a Super Rigid Anthyridine Ligand: Structural, Magnetic and DFT Studies. Transition metal complexes of iron ( II ...Compounds with Masked Diazonium Capping Groups (J. Organomet. Chem. 2013, 745, 93). (3) New Diruthenium( II ,III) Compounds Bearing Terminal Olefin Groups...2012, 36, 2340). (2) Synthesis , Structure, Magnetism, and Single Molecular Conductance of Linear Trinickel String Complexes with Sulfur-Containing

Transition Metal d-Orbital Splitting Diagrams: An Updated Educational Resource for Square Planar Transition Metal Complexes

ERIC Educational Resources Information Center

Bo¨rgel, Jonas; Campbell, Michael G.; Ritter, Tobias

2016-01-01

The presentation of d-orbital splitting diagrams for square planar transition metal complexes in textbooks and educational materials is often inconsistent and therefore confusing for students. Here we provide a concise summary of the key features of orbital splitting diagrams for square planar complexes, which we propose may be used as an updated…

Electrolyte salts for nonaqueous electrolytes

DOEpatents

Amine, Khalil; Zhang, Zhengcheng; Chen, Zonghai

2012-10-09

Metal complex salts may be used in lithium ion batteries. Such metal complex salts not only perform as an electrolyte salt in a lithium ion batteries with high solubility and conductivity, but also can act as redox shuttles that provide overcharge protection of individual cells in a battery pack and/or as electrolyte additives to provide other mechanisms to provide overcharge protection to lithium ion batteries. The metal complex salts have at least one aromatic ring. The aromatic moiety may be reversibly oxidized/reduced at a potential slightly higher than the working potential of the positive electrode in the lithium ion battery. The metal complex salts may also be known as overcharge protection salts.

Labile Low-Molecular-Mass Metal Complexes in Mitochondria: Trials and Tribulations of a Burgeoning Field.

PubMed

Lindahl, Paul A; Moore, Michael J

2016-08-02

Iron, copper, zinc, manganese, cobalt, and molybdenum play important roles in mitochondrial biochemistry, serving to help catalyze reactions in numerous metalloenzymes. These metals are also found in labile "pools" within mitochondria. Although the composition and cellular function of these pools are largely unknown, they are thought to be comprised of nonproteinaceous low-molecular-mass (LMM) metal complexes. Many problems must be solved before these pools can be fully defined, especially problems stemming from the lability of such complexes. This lability arises from inherently weak coordinate bonds between ligands and metals. This is an advantage for catalysis and trafficking, but it makes characterization difficult. The most popular strategy for investigating such pools is to detect them using chelator probes with fluorescent properties that change upon metal coordination. Characterization is limited because of the inevitable destruction of the complexes during their detection. Moreover, probes likely react with more than one type of metal complex, confusing analyses. An alternative approach is to use liquid chromatography (LC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). With help from a previous lab member, the authors recently developed an LC-ICP-MS approach to analyze LMM extracts from yeast and mammalian mitochondria. They detected several metal complexes, including Fe580, Fe1100, Fe1500, Cu5000, Zn1200, Zn1500, Mn1100, Mn2000, Co1200, Co1500, and Mo780 (numbers refer to approximate masses in daltons). Many of these may be used to metalate apo-metalloproteins as they fold inside the organelle. The LC-based approach also has challenges, e.g., in distinguishing artifactual metal complexes from endogenous ones, due to the fact that cells must be disrupted to form extracts before they are passed through chromatography columns prior to analysis. Ultimately, both approaches will be needed to characterize these intriguing complexes and to elucidate their roles in mitochondrial biochemistry.

Headgroup interactions and ion flotation efficiency in mixtures of a chelating surfactant, different foaming agents, and divalent metal ions.

PubMed

Svanedal, Ida; Boija, Susanne; Norgren, Magnus; Edlund, Håkan

2014-06-10

The correlation between interaction parameters and ion flotation efficiency in mixtures of chelating surfactant metal complexes and different foaming agents was investigated. We have recently shown that chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) forms strong coordination complexes with divalent metal ions, and this can be utilized in ion flotation. Interaction parameters for mixed micelles and mixed monolayer formation for Mg(2+) and Ni(2+) complexes with the chelating surfactant 4-C12-DTPA and different foaming agents were calculated by Rubingh's regular solution theory. Parameters for the calculations were extracted from surface tension measurements and NMR diffusometry. The effects of metal ion coordination on the interactions between 4-C12-DTPA and the foaming agents could be linked to a previously established difference in coordination chemistry between the examined metal ions. As can be expected from mixtures of amphoteric surfactants, the interactions were strongly pH-dependent. Strong correlation was found between interaction parameter β(σ) for mixed monolayer formation and the phase-transfer efficiency of Ni(2+) complexes with 4-C12-DTPA during flotation in a customized flotation cell. In a mixture of Cu(2+) and Zn(2+), the significant difference in conditional stability constants (log K) between the metal complexes was utilized to selectively recover the metal complex with the highest log K (Cu(2+)) by ion flotation. Flotation experiments in an excess concentration of metal ions confirmed the coordination of more than one metal ion to the headgroup of 4-C12-DTPA.

Spectral and in vitro antimicrobial properties of 2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid transition metal complexes

NASA Astrophysics Data System (ADS)

Dhankar, Raksha P.; Rahatgaonkar, Anjali M.; Chorghade, Mukund S.; Tiwari, Ashutosh

2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid (ADP) was complexed with acetates of Mn(II), Ni(II), Cu(II) and Zn(II). The structures of the ligand and its metal complexes were characterized by microanalysis, IR, NMR, UV-vis spectroscopy, magnetic susceptibility and TGA-DTA analyses. Octahedral and square planar geometries were suggested for the complexes in which the central metal ion coordinated with sbnd O donors of ligand and acetate ions. Each ligand binds the metal using carboxylate oxygens. The ligand and complexes were evaluated for their antimicrobial activities against different species of pathogenic bacteria and fungi. The present novel pyrimidine containing complexes could constitute a new group of antibacterial and antifungal agents.

Features of proteolytic properties of tetraphenylporphyrin complex with lanthanide group metals

NASA Astrophysics Data System (ADS)

Tobolkina, Elena A.; Skripnikova, Tatiana A.; Starikova, Anna A.; Shumilova, Galina I.; Pendin, Andrey A.

2018-01-01

Demetallation of metalloporphyrin molecules is one of the essential degradation reactions in photosynthesis. The effect of metalloporphyrin nature on removal of central metals from tetraphenylporphyrin complexes based on lanthanide group metals (Dy, Er, Lu, Ho) has been studied. pH values, at which the metal ions leave the metalloporphyrin complex were established using two-phase spectrophotometric titration with potentiometric pH-control. The pH values decrease with the increase of atomic numbers of lanthanide groups, as well as with increase of 4f-electrons. The reaction of an extra ligand exchange for the hydroxide ion was studied. For Dy-, Er- and Ho-tetraphenylporphyrin complexes one particle of extra ligand coordinates with one porphyrin complex. A complex with dimeric particles can be formed for the system of Lu-tetraphenylporphyrin. Constants of the ion exchange reactions were calculated.

Metal-organic complexes in geochemical processes: Estimation of standard partial molal thermodynamic properties of aqueous complexes between metal cations and monovalent organic acid ligands at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Shock, Everetr L.; Koretsky, Carla M.

1995-04-01

Regression of standard state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state allows evaluation of standard partial molal entropies ( overlineSo) of aqueous metal-organic complexes involving monovalent organic acid ligands. These values of overlineSo provide the basis for correlations that can be used, together with correlation algorithms among standard partial molal properties of aqueous complexes and equation-of-state parameters, to estimate thermodynamic properties including equilibrium constants for complexes between aqueous metals and several monovalent organic acid ligands at the elevated pressures and temperatures of many geochemical processes which involve aqueous solutions. Data, parameters, and estimates are given for 270 formate, propanoate, n-butanoate, n-pentanoate, glycolate, lactate, glycinate, and alanate complexes, and a consistent algorithm is provided for making other estimates. Standard partial molal entropies of association ( Δ -Sro) for metal-monovalent organic acid ligand complexes fall into at least two groups dependent upon the type of functional groups present in the ligand. It is shown that isothermal correlations among equilibrium constants for complex formation are consistent with one another and with similar correlations for inorganic metal-ligand complexes. Additional correlations allow estimates of standard partial molal Gibbs free energies of association at 25°C and 1 bar which can be used in cases where no experimentally derived values are available.

Quantitative description and local structures of trivalent metal ions Eu(III) and Cm(III) complexed with polyacrylic acid.

PubMed

Montavon, G; Bouby, M; Huclier-Markai, S; Grambow, B; Geckeis, H; Rabung, T; Pashalidis, I; Amekraz, B; Moulin, C

2008-11-15

The trivalent metal ion (M(III)=Cm, Eu)/polyacrylic acid (PAA) system was studied in the pH range between 3 and 5.5 for a molar PAA-to-metal ratio above 1. The interaction was studied for a wide range of PAA (0.05 mg L(-1)-50 g L(-1)) and metal ion concentrations (2x10(-9)-10(-3) M). This work aimed at 3 goals (i) to determine the stoichiometry of M(III)-PAA complexes, (ii) to determine the number of complexed species and the local environment of the metal ion, and (iii) to quantify the reaction processes. Asymmetric flow-field-flow fractionation (AsFlFFF) coupled to ICP-MS evidenced that size distributions of Eu-PAA complexes and PAA were identical, suggesting that Eu bound to only one PAA chain. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements performed with Eu and Cm showed a continuous shift of the spectra with increasing pH. The environment of complexed metal ions obviously changes with pH. Most probably, spectral variations arose from conformational changes within the M(III)-PAA complex due to pH variation. Complexation data describing the distribution of complexed and free metal ion were measured with Cm by TRLFS. They could be quantitatively described in the whole pH-range studied by considering the existence of only a single complexed species. This indicates that the slight changes in M(III) speciation with pH observed at the molecular level do not significantly affect the intrinsic binding constant. The interaction constant obtained from the modelling must be considered as a mean interaction constant.

Electrochemistry of mixed-metal bimetallic complexes containing the pentacyanoferrate(II) or pentaammineruthenium(II) metal center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, K.J.; Lee, L.; Mabbott, G.A.

1983-03-30

The electrochemistry of a series of mixed-metal bimetallic complexes of the type B/sub 5/MLM'B'/sub 5/, where B/sub 5/M = (CNN)/sub 5/Fe/sup II/ or (NH/sub 3/)/sub 5/Ru/sup II/, L = pyrazine, 4,4'-bipyridine, or 4-cyanopyridine, M'B'/sub 5/ = Rh/sup III/(NH/sub 3/)/sub 5/ or Co/sup III/(CN)/sub 5/, is reported. The bimetallic complexes all have metal-to-ligand charge-transfer (MLCT) bands associated with the M-B unit (d/sub ..pi../M ..-->.. p/sub ..pi../*L). The effect of the remote metal center, M'B'/sub 5/, is to function as a Lewis acid, shifting the MLCT maximum to lower energy and shifting the M/sup III///sup II/ reduction potential more positive with respectmore » to free B/sub 5/ML. The remote metal influence is attenuated by longer bridging ligands and by reduced ..pi..-overlap. A comparison of the electrochemical data of the mixed-valence Fe(II)/Fe(III) and Ru(II)/Ru(III) complexes to the mixed-metal Fe(II)/Co(III) and Ru(II)/Rh(III) complexes has enabled a quantitative measure of the stabilization due to electron delocalization in the mixed-valence complexes. The results show that electron delocalization is greater for the ruthenium complexes than for the iron complexes, is a small contributor to the total stabilization of the mixed-valence state, and even in ruthenium drops off rapidly as the length of the bridge increases.« less

Synthesis, spectral, thermal and antimicrobial studies of transition metal complexes of 14-membered tetraaza[N4] macrocyclic ligand

NASA Astrophysics Data System (ADS)

Shankarwar, Sunil G.; Nagolkar, Bhagwat B.; Shelke, Vinod A.; Chondhekar, Trimbak K.

2015-06-01

A series of metal complexes of Mn(II), Co(II), Ni(II), Cu(II), have been synthesized with newly synthesized biologically active macrocyclic ligand. The ligand was synthesized by condensation of β-diketone 1-(4-chlorophenyl)-3-(2-hydroxyphenyl)propane-1,3-dione and o-phenylene diamine. All the complexes were characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, 1H-NMR, UV-Vis spectroscopy and mass spectroscopy. From the analytical data, stoichiometry of the complexes was found to be 1:2 (metal:ligand). Thermal behavior (TG/DTA) and kinetic parameters suggest more ordered activated state in complex formation. All the complexes are of high spin type and six coordinated. On the basis of IR, electronic spectral studies and magnetic behavior, an octahedral geometry has been assigned to these complexes. The antibacterial and antifungal activities of the ligand and its metal complexes, has been screened in vitro against Staphylococcus aureus, Escherichia coli and Aspergillus niger, Trichoderma respectively.

Affinity to bovine serum albumin and anticancer activity of some new water-soluble metal Schiff base complexes

NASA Astrophysics Data System (ADS)

Asadi, Mozaffar; Asadi, Zahra; Zarei, Leila; Sadi, Somaye Barzegar; Amirghofran, Zahra

2014-12-01

Metal Schiff-base complexes show biological activity but they are usually insoluble in water so four new water-soluble metal Schiff base complexes of Na2[M(5-SO3-1,2-salben]; (5-SO3-1,2-salben denoted N,N";-bis(5-sulphosalicyliden)-1,2-diaminobenzylamine and M = Mg, Mn, Cu, Zn) were synthesized and characterized. The formation constants of the metal complexes were determined by UV-Vis absorption spectroscopy. The interaction of these complexes with bovine serum albumin (BSA) was studied by fluorescence spectroscopy. Type of quenching, binding constants, number of binding sites and binding stoichiometries were determined by fluorescence quenching method. The results showed that the mentioned complexes strongly bound to BSA. Thermodynamic parameters indicated that hydrophobic association was the major binding force and that the interaction was entropy driven and enthalpically disfavoured. The displacement experiment showed that these complexes could bind to the subdomain IIA (site I) of albumin. Furthermore the synchronous fluorescence spectra showed that the microenvironment of the tryptophan residues was not apparently changed. Based on the Förster theory of non-radiation energy transfer, the distance between the donor (Trp residues) and the acceptor metal complexes was obtained. The growth inhibitory effect of complexes toward the K562 cancer cell line was measured.

Preparation of nanoporous metal foam from high nitrogen transition metal complexes

DOEpatents

Tappan, Bryce C.; Huynh, My Hang V.; Hiskey, Michael A.; Son, Steven F.; Oschwald, David M.; Chavez, David E.; Naud, Darren L.

2006-11-28

Nanoporous metal foams are prepared by ignition of high nitrogen transition metal complexes. The ammonium salts of iron(III) tris[bi(tetrazolato)-amine], cobalt(III) tris(bi(tetrazolato)amine), and high nitrogen compounds of copper and silver were prepared as loose powders, pressed into pellets and wafers, and ignited under an inert atmosphere to form nanoporous metal foam monoliths having very high surface area and very low density.

A low-spin Fe(III) complex with 100-ps ligand-to-metal charge transfer photoluminescence

NASA Astrophysics Data System (ADS)

Chábera, Pavel; Liu, Yizhu; Prakash, Om; Thyrhaug, Erling; Nahhas, Amal El; Honarfar, Alireza; Essén, Sofia; Fredin, Lisa A.; Harlang, Tobias C. B.; Kjær, Kasper S.; Handrup, Karsten; Ericson, Fredric; Tatsuno, Hideyuki; Morgan, Kelsey; Schnadt, Joachim; Häggström, Lennart; Ericsson, Tore; Sobkowiak, Adam; Lidin, Sven; Huang, Ping; Styring, Stenbjörn; Uhlig, Jens; Bendix, Jesper; Lomoth, Reiner; Sundström, Villy; Persson, Petter; Wärnmark, Kenneth

2017-03-01

Transition-metal complexes are used as photosensitizers, in light-emitting diodes, for biosensing and in photocatalysis. A key feature in these applications is excitation from the ground state to a charge-transfer state; the long charge-transfer-state lifetimes typical for complexes of ruthenium and other precious metals are often essential to ensure high performance. There is much interest in replacing these scarce elements with Earth-abundant metals, with iron and copper being particularly attractive owing to their low cost and non-toxicity. But despite the exploration of innovative molecular designs, it remains a formidable scientific challenge to access Earth-abundant transition-metal complexes with long-lived charge-transfer excited states. No known iron complexes are considered photoluminescent at room temperature, and their rapid excited-state deactivation precludes their use as photosensitizers. Here we present the iron complex [Fe(btz)3]3+ (where btz is 3,3‧-dimethyl-1,1‧-bis(p-tolyl)-4,4‧-bis(1,2,3-triazol-5-ylidene)), and show that the superior σ-donor and π-acceptor electron properties of the ligand stabilize the excited state sufficiently to realize a long charge-transfer lifetime of 100 picoseconds (ps) and room-temperature photoluminescence. This species is a low-spin Fe(III) d5 complex, and emission occurs from a long-lived doublet ligand-to-metal charge-transfer (2LMCT) state that is rarely seen for transition-metal complexes. The absence of intersystem crossing, which often gives rise to large excited-state energy losses in transition-metal complexes, enables the observation of spin-allowed emission directly to the ground state and could be exploited as an increased driving force in photochemical reactions on surfaces. These findings suggest that appropriate design strategies can deliver new iron-based materials for use as light emitters and photosensitizers.

Metal-isonitrile adducts for preparing radionuclide complexes for labelling and imaging agents

DOEpatents

Jones, Alun G.; Davison, Alan; Abrams, Michael J.

1987-01-01

A method for preparing a coordination complex of an isonitrile ligand and radionuclide such as Tc, Ru, Co, Pt, Fe, Os, Ir, W, Re, Cr, Mo, Mn, Ni, Rh, Pd, Nb and Ta is disclosed. The method comprises preparing a soluble metal adduct of said isonitrile ligand by admixing said ligand with a salt of a displaceable metal having a complete d-electron shell selected from the group consisting of Zn, Ga, Cd, In, Sn, Hg, Tl, Pb and Bi to form a soluble metal-isonitrile salt, and admixing said metal isonitrile salt with a salt comprising said radioactive metal in a suitable solvent to displace said displaceable metal with the radioactive metal thereby forming said coordination. The complex is useful as a diagnostic agent for labelling liposomes or vesicles, and selected living cells containing lipid membranes, such as blood clots, myocardial tissue, gall bladder tissue, etc.

Group transfer and electron transfer reactions of organometallic complexes

NASA Astrophysics Data System (ADS)

Atwood, Jim D.

During 1994, despite the disruptions, the authors have made progress in several aspects of their research on electron transfer reactions between organometallic complexes. This summary covers three areas that are relatively complete: (1) reactions between metal carbonyl anions and metal carbonyl halides, (2) reactions of hydrido- and alkyl-containing anions (RFe(CO)4(-) and RW(CO)5(-) with metal carbonyl cations; and (3) reactions of a seventeen-electron complex (Cp* Cr(CO)3*) with metal carbonyl derivatives. Two areas of examination that have just begun (possible carbene transfer and the possible role of metal carbonyl anions in carbon-hydrogen bond activation) will also be described.

Syntheses, spectroscopic characterization, thermal study, molecular modeling, and biological evaluation of novel Schiff's base benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) with Ni(II), and Cu(II) metal complexes.

PubMed

Chandra, Sulekh; Gautam, Seema; Rajor, Hament Kumar; Bhatia, Rohit

2015-02-25

Novel Schiff's base ligand, benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) was synthesized by the condensation of benzil and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio. The structure of ligand was determined on the basis of elemental analyses, IR, (1)H NMR, mass, and molecular modeling studies. Synthesized ligand behaved as tetradentate and coordinated to metal ion through sulfur atoms of thiol ring and nitrogen atoms of imine group. Ni(II), and Cu(II) complexes were synthesized with this nitrogen-sulfur donor (N2S2) ligand. Metal complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic spectra, EPR, thermal, and molecular modeling studies. All the complexes showed molar conductance corresponding to non-electrolytic nature, expect [Ni(L)](NO3)2 complex, which was 1:2 electrolyte in nature. [Cu(L)(SO4)] complex may possessed square pyramidal geometry, [Ni(L)](NO3)2 complex tetrahedral and rest of the complexes six coordinated octahedral/tetragonal geometry. Newly synthesized ligand and its metal complexes were examined against the opportunistic pathogens. Results suggested that metal complexes were more biological sensitive than free ligand. Copyright © 2014 Elsevier B.V. All rights reserved.

New technique for heterogeneous vapor-phase synthesis of nanostructured metal layers from low-dimensional volatile metal complexes

NASA Astrophysics Data System (ADS)

Badalyan, A. M.; Bakhturova, L. F.; Kaichev, V. V.; Polyakov, O. V.; Pchelyakov, O. P.; Smirnov, G. I.

2011-09-01

A new technique for depositing thin nanostructured layers on semiconductor and insulating substrates that is based on heterogeneous gas-phase synthesis from low-dimensional volatile metal complexes is suggested and tried out. Thin nanostructured copper layers are deposited on silicon and quartz substrates from low-dimensional formate complexes using a combined synthesis-mass transport process. It is found that copper in layers thus deposited is largely in a metal state (Cu0) and has the form of closely packed nanograins with a characteristic structure.

Fabrication of transparent ceramics using nanoparticles

DOEpatents

Cherepy, Nerine J; Tillotson, Thomas M; Kuntz, Joshua D; Payne, Stephen A

2012-09-18

A method of fabrication of a transparent ceramic using nanoparticles synthesized via organic acid complexation-combustion includes providing metal salts, dissolving said metal salts to produce an aqueous salt solution, adding an organic chelating agent to produce a complexed-metal sol, heating said complexed-metal sol to produce a gel, drying said gel to produce a powder, combusting said powder to produce nano-particles, calcining said nano-particles to produce oxide nano-particles, forming said oxide nano-particles into a green body, and sintering said green body to produce the transparent ceramic.

Vanadium and nickel complexes in petroleum resid acid, base, and neutral fractions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pearson, C.D.; Green, J.D.

1993-01-01

Acid and base fractions from petroleum vacuum resids with no detectable (by visible spectrophotometry) quantities of porphyrinic Ni or V complexes were hydrotreated under various conditions to determine if significant amounts of porphyrinic metals were released, via disassociation or other means, upon hydrotreating. No significant quantities were observed, thereby indicating that nonporphyrinic metals were not simply associated, complexed or otherwise masked (in terms of visible spectrophotometric response) porphyrinic metal complexes. However, it is possible that hydrotreating was simply not effective in breaking up these associates and/or that some porphyrinic forms of metal were in fact released but were rapidly destroyedmore » by hydrotreating. In addition, three liquid chromatographic (LC) separation methods were sequentially applied to Cerro Negro (Orinoco belt Venezuelan heavy crude) >700[degree]C resid in an effort to separate and concentrate the metal complexes present. Nonaqueous ion exchange chromatography was used initially to separate the resid into acid, base and neutral types. Two concentrates containing 19,500 and 13,500 ppm total V, or an estimated 19 and 13 wt % V-containing compounds respectively, were obtained. The degree of enrichment of Ni compounds obtained was significantly lower. By visible spectrophotometry, using vanadyl etioporphyrin as a standard, each of the concentrates contained near a 1:1 ratio of porphyrinic:nonporphyrinic V complexes. Analogous separation behavior for porphyrinic versus nonporphyrinic metal forms was observed throughout much of the work, thereby suggesting that a comparable diversity of structures existed within each general class of metal compounds. The generally wide dispersion of both Ni and V over the LC separation scheme suggests a structural variety of metal complexes that is comparable to that observed for other heteroatoms (N, S, O) in petroleum.« less

Vanadium and nickel complexes in petroleum resid acid, base, and neutral fractions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pearson, C.D.; Green, J.D.

1993-01-01

Acid and base fractions from petroleum vacuum resids with no detectable (by visible spectrophotometry) quantities of porphyrinic Ni or V complexes were hydrotreated under various conditions to determine if significant amounts of porphyrinic metals were released, via disassociation or other means, upon hydrotreating. No significant quantities were observed, thereby indicating that nonporphyrinic metals were not simply associated, complexed or otherwise masked (in terms of visible spectrophotometric response) porphyrinic metal complexes. However, it is possible that hydrotreating was simply not effective in breaking up these associates and/or that some porphyrinic forms of metal were in fact released but were rapidly destroyedmore » by hydrotreating. In addition, three liquid chromatographic (LC) separation methods were sequentially applied to Cerro Negro (Orinoco belt Venezuelan heavy crude) >700{degree}C resid in an effort to separate and concentrate the metal complexes present. Nonaqueous ion exchange chromatography was used initially to separate the resid into acid, base and neutral types. Two concentrates containing 19,500 and 13,500 ppm total V, or an estimated 19 and 13 wt % V-containing compounds respectively, were obtained. The degree of enrichment of Ni compounds obtained was significantly lower. By visible spectrophotometry, using vanadyl etioporphyrin as a standard, each of the concentrates contained near a 1:1 ratio of porphyrinic:nonporphyrinic V complexes. Analogous separation behavior for porphyrinic versus nonporphyrinic metal forms was observed throughout much of the work, thereby suggesting that a comparable diversity of structures existed within each general class of metal compounds. The generally wide dispersion of both Ni and V over the LC separation scheme suggests a structural variety of metal complexes that is comparable to that observed for other heteroatoms (N, S, O) in petroleum.« less

Metal species involved in long distance metal transport in plants

PubMed Central

Álvarez-Fernández, Ana; Díaz-Benito, Pablo; Abadía, Anunciación; López-Millán, Ana-Flor; Abadía, Javier

2014-01-01

The mechanisms plants use to transport metals from roots to shoots are not completely understood. It has long been proposed that organic molecules participate in metal translocation within the plant. However, until recently the identity of the complexes involved in the long-distance transport of metals could only be inferred by using indirect methods, such as analyzing separately the concentrations of metals and putative ligands and then using in silico chemical speciation software to predict metal species. Molecular biology approaches also have provided a breadth of information about putative metal ligands and metal complexes occurring in plant fluids. The new advances in analytical techniques based on mass spectrometry and the increased use of synchrotron X-ray spectroscopy have allowed for the identification of some metal-ligand species in plant fluids such as the xylem and phloem saps. Also, some proteins present in plant fluids can bind metals and a few studies have explored this possibility. This study reviews the analytical challenges researchers have to face to understand long-distance metal transport in plants as well as the recent advances in the identification of the ligand and metal-ligand complexes in plant fluids. PMID:24723928

Speciation of heavy metals in landfill leachate: a review.

PubMed

Baun, Dorthe L; Christensen, Thomas H

2004-02-01

The literature was reviewed with respect to metal speciation methods in aquatic samples specifically emphasizing speciation of heavy metals in landfill leachate. Speciation here refers to physical fractionation (particulate, colloidal, dissolved), chemical fractionation (organic complexes, inorganic complexes, free metal ions), as well as computer-based thermodynamic models. Relatively few landfill leachate samples have been speciated in detail (less than 30) representing only a few landfills (less than 15). This suggests that our knowledge about metal species in landfill leachate still is indicative. In spite of the limited database and the different definitions of the dissolved fraction (< 0.45 microm or < 0.001 microm) the studies consistently show that colloids as well as organic and inorganic complexes are important for all heavy metals in landfill leachate. The free metal ion constitutes less than 30%, typically less than 10%, of the total metal concentration. This has significant implications for sampling, since no standardized procedures exist, and for assessing the content of metals in leachate in the context of its treatment, toxicity and migration in aquifers.

Prebiotic coordination chemistry: The potential role of transition-metal complexes in the chemical evolution

NASA Technical Reports Server (NTRS)

Beck, M.

1979-01-01

In approaching the extremely involved and complex problem of the origin of life, consideration of the coordination chemistry appeared not only as a possibility but as a necessity. The first model experiments appear to be promising because of prebiotic-type synthesis by means of transition-metal complexes. It is especially significant that in some instances various types of vitally important substances (nucleic bases, amino acids) are formed simultaneously. There is ground to hope that systematic studies in this field will clarify the role of transition-metal complexes in the organizatorial phase of chemical evolution. It is obvious that researchers working in the fields of the chemistry of cyano and carbonyl complexes, and of the catalytic effect of transition-metal complexes are best suited to study these aspects of the attractive and interesting problem of the origin of life.

Synthesis, structure and DFT study of cymantrenyl Fischer carbene complexes of group VI and VII transition metals

NASA Astrophysics Data System (ADS)

Fraser, Roan; van Rooyen, Petrus H.; Landman, Marilé

2016-02-01

Bi- and trimetallic carbene complexes of group VI and VII transition metals (Cr, Mo, W, Mn and Re), with CpMn(CO)3 as the initial synthon, have been synthesised according to the classical Fischer methodology. Crystal structures of the novel carbene complexes with general formula [Mx(CO)y-1{C(OEt)(MnCp(CO)3)}], where x = 1 then y = 3 or 6; x = 2 then y = 10, of the complexes are reported. A density functional theory (DFT) study was undertaken to determine natural bonding orbitals (NBOs) and conformational as well as isomeric aspects of the polymetallic complexes. Application of the second-order perturbation theory (SOPT) of the natural bond orbital (NBO) method revealed stabilizing interactions between the methylene C-H bonds and the carbonyl ligands of the carbene metal moiety. These stabilization interactions show a linear decrease for the group VI metal carbene complexes down the group.

Multi Service Tactics, Techniques, and Procedures for Treatment of Chemical Warfare Agent Casualties and Conventional Military Chemical Injuries

DTIC Science & Technology

2016-08-02

at mechanical ventilation of a severely exposed casualty until atropine takes effect . Administering supplemental oxygen as available. Chapter 3 3-10...Scavengers; hydroxocobalamin, and dicobalt edetate (2) Provision of S-Groups, thiosulfate (3) Assisted ventilation (4) Oxygen cyanogen... temperature index for light work. Refer to table 1-3 on page 1-12 for work and rest cycles and also water consumption chart. Chapter 1 1-12 ATP 4

Synthesis of Donor/Acceptor-Substituted Diazo Compounds in Flow and Their Application in Enantioselective Dirhodium-Catalyzed Cyclopropanation and C-H Functionalization.

PubMed

Rackl, Daniel; Yoo, Chun-Jae; Jones, Christopher W; Davies, Huw M L

2017-06-16

A tandem reaction system has been developed for the preparation of donor/acceptor-substituted diazo compounds in continuous flow coupled to dirhodium-catalyzed C-H functionalization or cyclopropanation. Hydrazones were oxidized in flow by solid-supported N-iodo-p-toluenesulfonamide potassium salt (PS-SO 2 NIK) to generate the diazo compounds, which were then purified by passing through a column of molecular sieves/sodium thiosulfate.

Self-templated formation of uniform NiCo2O4 hollow spheres with complex interior structures for lithium-ion batteries and supercapacitors.

PubMed

Shen, Laifa; Yu, Le; Yu, Xin-Yao; Zhang, Xiaogang; Lou, Xiong Wen David

2015-02-02

Despite the significant advancement in preparing metal oxide hollow structures, most approaches rely on template-based multistep procedures for tailoring the interior structure. In this work, we develop a new generally applicable strategy toward the synthesis of mixed-metal-oxide complex hollow spheres. Starting with metal glycerate solid spheres, we show that subsequent thermal annealing in air leads to the formation of complex hollow spheres of the resulting metal oxide. We demonstrate the concept by synthesizing highly uniform NiCo2O4 hollow spheres with a complex interior structure. With the small primary building nanoparticles, high structural integrity, complex interior architectures, and enlarged surface area, these unique NiCo2O4 hollow spheres exhibit superior electrochemical performances as advanced electrode materials for both lithium-ion batteries and supercapacitors. This approach can be an efficient self-templated strategy for the preparation of mixed-metal-oxide hollow spheres with complex interior structures and functionalities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of herbaspirillum- and limnobacter-related strains isolated from young volcanic deposits in miyake-jima island, Japan.

PubMed

Lu, Hongsheng; Fujimura, Reiko; Sato, Yoshinori; Nanba, Kenji; Kamijo, Takashi; Ohta, Hiroyuki

2008-01-01

The role of microbes in the early development of ecosystems on new volcanic materials seems to be crucial to primary plant succession but is not well characterized. Here we analyzed the bacterial community colonizing 22-year-old volcanic deposits of the Miyake-jima Island (Japan) using culture-based and 16S rRNA gene clone library methods. The majority of 91 bacterial isolates were placed phylogenetically in two clusters (A and B) of the Betaproteobacteria. Cluster A (82% of isolates) was related to the genus Limnobacter and Cluster B (9%) was affiliated with the Herbaspirillum clade. The clone library analysis supported the predominance of Cluster B rather than Cluster A. Strain KP1-50 of Cluster B was able to grow on a mineral medium under an atmosphere of H(2), O(2), and CO(2) (85:5:10), and characterized by its large-subunit gene of ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL) and nitrogenase reductase gene (nifH). In contrast, strains of Cluster A did not grow chemolithoautotrophically with H(2), O(2), and CO(2) but increased their cell biomass with the addition of thiosulfate to the succinate medium, suggesting the use of thiosulfate as an energy source. From phenotypic characterization, it was suggested that the Cluster A and B strains were novel species in the genus Limnobacter and Herbaspirillum, respectively.

Sulfur redox chemistry governs diurnal antimony and arsenic cycles at Champagne Pool, Waiotapu, New Zealand

NASA Astrophysics Data System (ADS)

Ullrich, Maria K.; Pope, James G.; Seward, Terry M.; Wilson, Nathaniel; Planer-Friedrich, Britta

2013-07-01

Champagne Pool, a sulfidic hot spring in New Zealand, exhibits distinct diurnal variations in antimony (Sb) and arsenic (As) concentrations, with daytime high and night-time low concentrations. To identify the underlying mobilization mechanisms, five sites along the drainage channel of Champagne Pool were sampled every 2 h during a 24 h period. Temporal variations in elemental concentrations and Sb, As, and sulfur (S) speciation were monitored in the discharging fluid. Total trace element concentrations in filtered and unfiltered samples were analyzed using ICP-MS, and Sb, As and S species were determined by IC-ICP-MS. Sulfur speciation in the drainage channel was dominated by thiosulfate and sulfide at night, while sulfate dominated during the day. The distinct diurnal changes suggest that the transformations are caused by phototrophic sulfur-oxidizing bacteria. These bacteria metabolize thiosulfate and sulfide in daylight to form sulfate and, as suggested by modeling with PhreeqC, elemental sulfur. Sulfide consumption during the day results in undersaturation of antimony sulfides, which triggers the additional release of dissolved Sb. For As, diurnal cycles were much more pronounced in speciation than in total concentrations, with di- and trithioarsenate forming at night due to excess sulfide, and monothioarsenate forming from arsenite and elemental sulfur during the day. Sulfur speciation was thus found to control Sb and As in terms of both solubility and speciation.

L-Cysteine Metabolism and Fermentation in Microorganisms.

PubMed

Takagi, Hiroshi; Ohtsu, Iwao

L-Cysteine is an important amino acid both biologically and commercially. Although most amino acids are industrially produced by microbial fermentation, L-cysteine has been mainly produced by protein hydrolysis. Due to environmental and safety problems, synthetic or biotechnological products have been preferred in the market. Here, we reviewed L-cysteine metabolism, including biosynthesis, degradation, and transport, and biotechnological production (including both enzymatic and fermentation processes) of L-cysteine. The metabolic regulation of L-cysteine including novel sulfur metabolic pathways found in microorganisms is also discussed. Recent advancement in biochemical studies, genome sequencing, structural biology, and metabolome analysis has enabled us to use various approaches to achieve direct fermentation of L-cysteine from glucose. For example, worldwide companies began to supply L-cysteine and its derivatives produced by bacterial fermentation. These companies successfully optimized the original metabolism of their private strains. Basically, a combination of three factors should be required for improving L-cysteine fermentation: that is, (1) enhancing biosynthesis: overexpression of the altered cysE gene encoding feedback inhibition-insensitive L-serine O-acetyltransferase (SAT), (2) weakening degradation: knockout of the genes encoding L-cysteine desulfhydrases, and (3) exploiting export system: overexpression of the gene involved in L-cysteine transport. Moreover, we found that "thiosulfate" is much more effective sulfur source than commonly used "sulfate" for L-cysteine production in Escherichia coli, because thiosulfate is advantageous for saving consumption of NADPH and relating energy molecules.

Synthesis, characterization, spectroscopic and antioxidation studies of Cu(II)-morin complex

NASA Astrophysics Data System (ADS)

Panhwar, Qadeer Khan; Memon, Shahabuddin; Bhanger, M. I.

2010-04-01

Complex formation between copper (II) sulfate and morin (3,5,7,2',4'-pentahydroxyflavone) have been studied in methanol. Structure of the complex was determined through various analytical techniques including UV-vis, IR, 1H NMR, thermal, gravimetric and elemental analyses. The stoichiometric ratio for the reaction between the flavonoid and the metal ion in methanol has been determined by Job's method and elemental analysis for metal content of complex by titration with EDTA, which confirm that morin forms a 1:1 metal:ligand complex. 1H NMR study reveals that, 3OH and 4CO groups of morin take part in complexation with a copper ion. Individual stress was given to the site of central ion and composition of the complex. Antioxidant activity of the complex was evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method, which showed that the antioxidant activity of complexed morin has higher value as compared to the free morin. Moreover, it was observed that the metal complex is sufficiently stable as well as the data indicates the spontaneous formation of complex (-Δ G) that is exothermic in nature (-Δ H) and entropically unfavourable (-Δ S).

General Synthesis of Transition-Metal Oxide Hollow Nanospheres/Nitrogen-Doped Graphene Hybrids by Metal-Ammine Complex Chemistry for High-Performance Lithium-Ion Batteries.

PubMed

Chen, Jiayuan; Wu, Xiaofeng; Gong, Yan; Wang, Pengfei; Li, Wenhui; Mo, Shengpeng; Peng, Shengpan; Tan, Qiangqiang; Chen, Yunfa

2018-02-09

We present a general and facile synthesis strategy, on the basis of metal-ammine complex chemistry, for synthesizing hollow transition-metal oxides (Co 3 O 4 , NiO, CuO-Cu 2 O, and ZnO)/nitrogen-doped graphene hybrids, potentially applied in high-performance lithium-ion batteries. The oxygen-containing functional groups of graphene oxide play a prerequisite role in the formation of hollow transition-metal oxides on graphene nanosheets, and a significant hollowing process occurs only when forming metal (Co 2+ , Ni 2+ , Cu 2+ , or Zn 2+ )-ammine complex ions. Moreover, the hollowing process is well correlated with the complexing capacity between metal ions and NH 3 molecules. The significant hollowing process occurs for strong metal-ammine complex ions including Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ ions, and no hollow structures formed for weak and/or noncomplex Mn 2+ and Fe 3+ ions. Simultaneously, this novel strategy can also achieve the direct doping of nitrogen atoms into the graphene framework. The electrochemical performance of two typical hollow Co 3 O 4 or NiO/nitrogen-doped graphene hybrids was evaluated by their use as anodic materials. It was demonstrated that these unique nanostructured hybrids, in contrast with the bare counterparts, solid transition-metal oxides/nitrogen-doped graphene hybrids, perform with significantly improved specific capacity, superior rate capability, and excellent capacity retention. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solar chemistry of metal complexes

NASA Astrophysics Data System (ADS)

Gray, H. B.; Maverick, A. W.

1981-12-01

Electronic excited states of certain transition metal complexes undergo oxidation-reduction reactions that store chemical energy. Such reactions have been extensively explored for mononuclear complexes. Two classes of polynuclear species exhibit similar properties, and these complexes are now being studied as possible homogeneous sensitizer-catalysts for hydrogen production from aqueous solutions.

Synthesis, characterization of 1,2,4-triazole Schiff base derived 3d-metal complexes: Induces cytotoxicity in HepG2, MCF-7 cell line, BSA binding fluorescence and DFT study

NASA Astrophysics Data System (ADS)

Tyagi, Prateek; Tyagi, Monika; Agrawal, Swati; Chandra, Sulekh; Ojha, Himanshu; Pathak, Mallika

2017-01-01

Two novel Schiff base ligands H2L1 and H2L2 have been synthesized by condensation reaction of amine derivative of 1,2,4-triazole moiety with 2-hydroxy-4-methoxybenzaldehyde. Co(II), Ni(II), Cu(II) and Zn(II) of the synthesized Schiff bases were prepared by using a molar ratio of ligand:metal as 1:1. The structure of the Schiff bases and synthesized metal complexes were established by 1H NMR, UV-Vis, IR, Mass spectrometry and molar conductivity. The thermal stability of the complexes was study by TGA. Fluorescence quenching mechanism of metal complexes 1-4 show that Zn(II) and Cu(II) complex binds more strongly to BSA. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31 + g(d,p) basis set. The spectral data shows that the ligands behaves as binegative tridentate. On the basis of the spectral studies, TGA and DFT data an octahedral geometry has been assigned for Co(II), Ni(II), square planar for Cu(II) and tetrahedral for Zn(II) complexes. The anticancer activity were screened against human breast cancer cell line (MCF-7) and human hepatocellular liver carcinoma cell line (Hep-G2). Result indicates that metal complexes shows increase cytotoxicity in proliferation to cell lines as compared to free ligand.

Synthesis and antimalarial activity of metal complexes of cross-bridged tetraazamacrocyclic ligands.

PubMed

Hubin, Timothy J; Amoyaw, Prince N-A; Roewe, Kimberly D; Simpson, Natalie C; Maples, Randall D; Carder Freeman, TaRynn N; Cain, Amy N; Le, Justin G; Archibald, Stephen J; Khan, Shabana I; Tekwani, Babu L; Khan, M O Faruk

2014-07-01

Using transition metals such as manganese(II), iron(II), cobalt(II), nickel(II), copper(II), and zinc(II), several new metal complexes of cross-bridged tetraazamacrocyclic chelators namely, cyclen- and cyclam-analogs with benzyl groups, were synthesized and screened for in vitro antimalarial activity against chloroquine-resistant (W2) and chloroquine-sensitive (D6) strains of Plasmodium falciparum. The metal-free chelators tested showed little or no antimalarial activity. All the metal complexes of the dibenzyl cross-bridged cyclam ligand exhibited potent antimalarial activity. The Mn(2+) complex of this ligand was the most potent with IC50s of 0.127 and 0.157μM against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) P. falciparum strains, respectively. In general, the dibenzyl hydrophobic ligands showed better anti-malarial activity compared to the activity of monobenzyl ligands, potentially because of their higher lipophilicity and thus better cell penetration ability. The higher antimalarial activity displayed by the manganese complex for the cyclam ligand in comparison to that of the cyclen, correlates with the larger pocket of cyclam compared to that of cyclen which produces a more stable complex with the Mn(2+). Few of the Cu(2+) and Fe(2+) complexes also showed improvement in activity but Ni(2+), Co(2+) and Zn(2+) complexes did not show any improvement in activity upon the metal-free ligands for anti-malarial development. Published by Elsevier Ltd.

Structure-activity relationships of mononuclear metal-thiosemicarbazone complexes endowed with potent antiplasmodial and antiamoebic activities.

PubMed

Bahl, Deepa; Athar, Fareeda; Soares, Milena Botelho Pereira; de Sá, Matheus Santos; Moreira, Diogo Rodrigo Magalhães; Srivastava, Rajendra Mohan; Leite, Ana Cristina Lima; Azam, Amir

2010-09-15

A useful concept for the rational design of antiparasitic drug candidates is the complexation of bioactive ligands with transition metals. In view of this, an investigation was conducted into a new set of metal complexes as potential antiplasmodium and antiamoebic agents, in order to examine the importance of metallic atoms, as well as the kind of sphere of co-ordination, in these biological properties. Four functionalized furyl-thiosemicarbazones (NT1-4) treated with divalent metals (Cu, Co, Pt, and Pd) to form the mononuclear metallic complexes of formula [M(L)2Cl2] or [M(L)Cl2] were examined. The pharmacological characterization, including assays against Plasmodium falciparum and Entamoeba histolytica, cytotoxicity to mammalian cells, and interaction with pBR 322 plasmid DNA was performed. Structure-activity relationship data revealed that the metallic complexation plays an essential role in antiprotozoal activity, rather than the simple presence of the ligand or metal alone. Important steps towards identification of novel antiplasmodium (NT1Cu, IC50 of 4.6 microM) and antiamoebic (NT2Pd, IC50 of 0.6 microM) drug prototypes were achieved. Of particular relevance to this work, these prototypes were able to reduce the proliferation of these parasites at concentrations that are not cytotoxic to mammalian cells. Copyright (c) 2010. Published by Elsevier Ltd.

Neutralization by Metal Ions of the Toxicity of Sodium Selenide

PubMed Central

Dauplais, Marc; Lazard, Myriam; Blanquet, Sylvain; Plateau, Pierre

2013-01-01

Inert metal-selenide colloids are found in animals. They are believed to afford cross-protection against the toxicities of both metals and selenocompounds. Here, the toxicities of metal salt and sodium selenide mixtures were systematically studied using the death rate of Saccharomyces cerevisiae cells as an indicator. In parallel, the abilities of these mixtures to produce colloids were assessed. Studied metal cations could be classified in three groups: (i) metal ions that protect cells against selenium toxicity and form insoluble colloids with selenide (Ag+, Cd2+, Cu2+, Hg2+, Pb2+ and Zn2+), (ii) metal ions which protect cells by producing insoluble metal-selenide complexes and by catalyzing hydrogen selenide oxidation in the presence of dioxygen (Co2+ and Ni2+) and, finally, (iii) metal ions which do not afford protection and do not interact (Ca2+, Mg2+, Mn2+) or weakly interact (Fe2+) with selenide under the assayed conditions. When occurring, the insoluble complexes formed from divalent metal ions and selenide contained equimolar amounts of metal and selenium atoms. With the monovalent silver ion, the complex contained two silver atoms per selenium atom. Next, because selenides are compounds prone to oxidation, the stabilities of the above colloids were evaluated under oxidizing conditions. 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), the reduction of which can be optically followed, was used to promote selenide oxidation. Complexes with cadmium, copper, lead, mercury or silver resisted dissolution by DTNB treatment over several hours. With nickel and cobalt, partial oxidation by DTNB occurred. On the other hand, when starting from ZnSe or FeSe complexes, full decompositions were obtained within a few tens of minutes. The above properties possibly explain why ZnSe and FeSe nanoparticles were not detected in animals exposed to selenocompounds. PMID:23342137

Transition Metal Intercalators as Anticancer Agents—Recent Advances

PubMed Central

Deo, Krishant M.; Pages, Benjamin J.; Ang, Dale L.; Gordon, Christopher P.; Aldrich-Wright, Janice R.

2016-01-01

The diverse anticancer utility of cisplatin has stimulated significant interest in the development of additional platinum-based therapies, resulting in several analogues receiving clinical approval worldwide. However, due to structural and mechanistic similarities, the effectiveness of platinum-based therapies is countered by severe side-effects, narrow spectrum of activity and the development of resistance. Nonetheless, metal complexes offer unique characteristics and exceptional versatility, with the ability to alter their pharmacology through facile modifications of geometry and coordination number. This has prompted the search for metal-based complexes with distinctly different structural motifs and non-covalent modes of binding with a primary aim of circumventing current clinical limitations. This review discusses recent advances in platinum and other transition metal-based complexes with mechanisms of action involving intercalation. This mode of DNA binding is distinct from cisplatin and its derivatives. The metals focused on in this review include Pt, Ru and Cu along with examples of Au, Ni, Zn and Fe complexes; these complexes are capable of DNA intercalation and are highly biologically active. PMID:27809241

Simultaneous separation of inorganic anions and metal-citrate complexes on a zwitterionic stationary phase with on-column complexation.

PubMed

Nesterenko, Ekaterina P; Nesterenko, Pavel N; Paull, Brett

2008-12-05

The retention and separation selectivity of inorganic anions and on-column derivatised negatively charged citrate or oxalate metal complexes on reversed-phase stationary phases dynamically coated with N-(dodecyl-N,N-dimethylammonio)undecanoate (DDMAU) has been investigated. The retention mechanism for the metal-citrate complexes was predominantly anion exchange, although the amphoteric/zwitterionic nature of the stationary phase coating undoubtedly also contributed to the unusual separation selectivity shown. A mixture of 10 inorganic anions and metal cations was achieved using a 20 cm monolithic DDMAU modified column and a 1 mM citrate eluent, pH 4.0, flow rate equal to 0.8 mL/min. Selectivity was found to be strongly pH dependent, allowing additional scope for manipulation of solute retention, and thus application to complex samples. This is illustrated with the analysis of an acidic mine drainage sample with a range of inorganic anions and transition metal cations, varying significantly in their concentrations levels.

Synthesis and characterization of a metal complex containing naringin and Cu, and its antioxidant, antimicrobial, antiinflammatory and tumor cell cytotoxicity.

PubMed

Pereira, Regina M S; Andrades, Norma E D; Paulino, Niraldo; Sawaya, Alexandra C H F; Eberlin, Marcos N; Marcucci, Maria C; Favero, Giovani Marino; Novak, Estela Maria; Bydlowski, Sérgio Paulo

2007-07-09

The antioxidant activity of flavonoids is believed to increase when they are coordinated with transition metal ions. However, the literature on this subject is contradictory and the outcome seems to largely depend on the experimental conditions. In order to understand the contribution of the metal coordination and the type of interaction between a flavonoid and the metal ion, in this study a new metal complex of Cu (II) with naringin was synthesized and characterized by FT-IR, UV-VIS, mass spectrometry (ESI-MS/MS), elemental analysis and 1H-NMR. The results of these analyses indicate that the complex has a Cu (II) ion coordinated via positions 4 and 5 of the flavonoid. The antioxidant, anti-inflammatory and antimicrobial activities of this complex were studied and compared with the activity of free naringin. The Naringin-Cu (II) complex 1 showed higher antioxidant, anti-inflammatory and tumor cell cytotoxicity activities than free naringin without reducing cell viability.

The QSAR study of flavonoid-metal complexes scavenging rad OH free radical

NASA Astrophysics Data System (ADS)

Wang, Bo-chu; Qian, Jun-zhen; Fan, Ying; Tan, Jun

2014-10-01

Flavonoid-metal complexes have antioxidant activities. However, quantitative structure-activity relationships (QSAR) of flavonoid-metal complexes and their antioxidant activities has still not been tackled. On the basis of 21 structures of flavonoid-metal complexes and their antioxidant activities for scavenging rad OH free radical, we optimised their structures using Gaussian 03 software package and we subsequently calculated and chose 18 quantum chemistry descriptors such as dipole, charge and energy. Then we chose several quantum chemistry descriptors that are very important to the IC50 of flavonoid-metal complexes for scavenging rad OH free radical through method of stepwise linear regression, Meanwhile we obtained 4 new variables through the principal component analysis. Finally, we built the QSAR models based on those important quantum chemistry descriptors and the 4 new variables as the independent variables and the IC50 as the dependent variable using an Artificial Neural Network (ANN), and we validated the two models using experimental data. These results show that the two models in this paper are reliable and predictable.

Curcumin derivatives as metal-chelating agents with potential multifunctional activity for pharmaceutical applications.

PubMed

Ferrari, Erika; Benassi, Rois; Sacchi, Stefania; Pignedoli, Francesca; Asti, Mattia; Saladini, Monica

2014-10-01

Curcuminoids represent new perspectives for the development of novel therapeutics for Alzheimer's disease (AD), one probable mechanism of action is related to their metal complexing ability. In this work we examined the metal complexing ability of substituted curcuminoids to propose new chelating molecules with biological properties comparable with curcumin but with improved stability as new potential AD therapeutic agents. The K2T derivatives originate from the insertion of a -CH2COOC(CH3)3 group on the central atom of the diketonic moiety of curcumin. They retain the diketo-ketoenol tautomerism which is solvent dependent. In aqueous solution the prevalent form is the diketo one but the addition of metal ion (Ga(3+), Cu(2+)) causes the dissociation of the enolic proton creating chelate complexes and shifting the tautomeric equilibrium towards the keto-enol form. The formation of metal complexes is followed by both NMR and UV-vis spectroscopy. The density functional theory (DFT) calculations on K2T21 complexes with Ga(3+) and Cu(2+) are performed and compared with those on curcumin complexes. [Ga(K2T21)2(H2O)2](+) was found more stable than curcumin one. Good agreement is detected between calculated and experimental (1)H and (13)C NMR data. The calculated OH bond dissociation energy (BDE) and the OH proton dissociation enthalpy (PDE), allowed to predict the radical scavenging ability of the metal ion complexed with K2T21, while the calculated electronic affinity (EA) and ionization potential (IP) represent yardsticks of antioxidant properties. Eventually theoretical calculations suggest that the proton-transfer-associated superoxide-scavenging activity is enhanced after binding metal ions, and that Ga(3+) complexes display possible superoxide dismutase (SOD)-like activity. Copyright © 2014 Elsevier Inc. All rights reserved.

The preparation and use of metal salen complexes derived from cyclobutane diamine

NASA Astrophysics Data System (ADS)

Patil, Smita

The helix is an important chiral motif in nature, there is increasing development in field of helical transition metal complexes and related supramolecular structures. Hence, the goals of this work are to apply the principles of helicity in order to produce metal complexes with predictable molecular shapes and to study their properties as asymmetric catalysts. Computational studies suggest that the (1R,2 R)-cyclobutyldiamine unit can produce highly twisted salen complexes with a large energy barrier between the M and P helical forms. To test this prediction, the tartrate salt of (1R,2R)-cyclobutyldiamine was synthesized and condensed with a series of saliclaldehydes to produce novel salen ligands. The salicylaldehydes chosen have extended phenanthryl or benz[a]anthryl sidearms to encourage formation of helical coordination complexes. These ligands were metallated with zinc, iron and manganese salts to produce salen metal complexes which were characterized by NMR analysis, high-resolution mass spectrometry, and IR spectroscopy. A second ligand type, neutral bis(pyridine-imine) has also been synthesized from (1R,2R)-cyclobutyldiamine and quinolylaldehydes. The synthesis of bis(pyridine-imine) ligands was conducted using greener method, solvent assisted grinding. These ligands, in-situ with nickel metal salts, showed good catalytic activity for asymmetric Diels-Alder reactions. The third ligand type studied was chiral acid-functionalized Schiff-base ligands. These were synthesized by the condensation of 3-formyl-5-methyl salicylic acid and (1R,2R)-cyclobutyldiamine. With this type of ligand, there is possibility of producing both mono and dinuclear metal complexes. In our studies, we were only able to synthesize mononuclear complexs. These were tested as catalysts for asymmetric direct Mannich-type reaction, but were found to be ineffective.

Identification of different coordination geometries by XAFS in copper(II) complexes with trimesic acid

NASA Astrophysics Data System (ADS)

Gaur, A.; Klysubun, W.; Soni, Balram; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

2016-10-01

X-ray absorption spectroscopy (XAS) is very useful in revealing the information about geometric and electronic structure of a transition-metal absorber and thus commonly used for determination of metal-ligand coordination. But XAFS analysis becomes difficult if differently coordinated metal centers are present in a system. In the present investigation, existence of distinct coordination geometries around metal centres have been studied by XAFS in a series of trimesic acid Cu(II) complexes. The complexes studied are: Cu3(tma)2(im)6 8H2O (1), Cu3(tma)2(mim)6 17H2O (2), Cu3(tma)2(tmen)3 8.5H2O (3), Cu3(tma) (pmd)3 6H2O (ClO4)3 (4) and Cu3(tma)2 3H2O (5). These complexes have not only Cu metal centres with different coordination but in complexes 1-3, there are multiple coordination geometries present around Cu centres. Using XANES spectra, different coordination geometries present in these complexes have been identified. The variation observed in the pre-edge features and edge features have been correlated with the distortion of the specific coordination environment around Cu centres in the complexes. XANES spectra have been calculated for the distinct metal centres present in the complexes by employing ab-initio calculations. These individual spectra have been used to resolve the spectral contribution of the Cu centres to the particular XANES features exhibited by the experimental spectra of the multinuclear complexes. Also, the variation in the 4p density of states have been calculated for the different Cu centres and then correlated with the features originated from corresponding coordination of Cu. Thus, these spectral features have been successfully utilized to detect the presence of the discrete metal centres in a system. The inferences about the coordination geometry have been supported by EXAFS analysis which has been used to determine the structural parameters for these complexes.

Metal (II) Complexes Derived from Naphthofuran-2-carbohydrazide and Diacetylmonoxime Schiff Base: Synthesis, Spectroscopic, Electrochemical, and Biological Investigation

PubMed Central

Sumathi, R. B.; Halli, M. B.

2014-01-01

A new Schiff base and a new series of Co(II), Ni(II), Cu(II), Cd(II), and Hg(II) complexes were synthesized by the condensation of naphthofuran-2-carbohydrazide and diacetylmonoxime. Metal complexes of the Schiff base were prepared from their chloride salts of Co(II), Ni(II), Cu(II), Cd(II), and Hg(II) in ethanol. The ligand along with its metal complexes have been characterized on the basis of analytical data, IR, electronic, mass, 1HNMR, ESR spectral data, thermal studies, magnetic susceptibility, and molar conductance measurements. The nonelectrolytic behaviour of the complexes was assessed from the measured low conductance data. The elemental analysis of the complexes confirm the stoichiometry of the type CuL2Cl2 and MLCl2 where M = Ni(II), Co(II), Cd(II), and Hg(II) and L = Schiff base. The redox property of the Cu(II) complex was investigated by electrochemical method using cyclic voltammetry. In the light of these results, Co(II), Ni(II), and Cu(II) complexes are assigned octahedral geometry, Cd(II), and Hg(II) complexes tetrahedral geometry. In order to evaluate the effect of metal ions upon chelation, both the ligand and its metal complexes were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleaving capacity of all the complexes was analysed by agarose gel electrophoresis method. PMID:24592203

Solvation Effect on Complexation of Alkali Metal Cations by a Calix[4]arene Ketone Derivative.

PubMed

Požar, Josip; Nikšić-Franjić, Ivana; Cvetnić, Marija; Leko, Katarina; Cindro, Nikola; Pičuljan, Katarina; Borilović, Ivana; Frkanec, Leo; Tomišić, Vladislav

2017-09-14

The medium effect on the complexation of alkali metal cations with a calix[4]arene ketone derivative (L) was systematically examined in methanol, ethanol, N-methylformamide, N,N-dimethylformamide, dimethyl sulfoxide, and acetonitrile. In all solvents the binding of Na + cation by L was rather efficient, whereas the complexation of other alkali metal cations was observed only in methanol and acetonitrile. Complexation reactions were enthalpically controlled, while ligand dissolution was endothermic in all cases. A notable influence of the solvent on NaL + complex stability could be mainly attributed to the differences in complexation entropies. The higher NaL + stability in comparison to complexes with other alkali metal cations in acetonitrile was predominantly due to a more favorable complexation enthalpy. The 1 H NMR investigations revealed a relatively low affinity of the calixarene sodium complex for inclusion of the solvent molecule in the calixarene hydrophobic cavity, with the exception of acetonitrile. Differences in complex stabilities in the explored solvents, apart from N,N-dimethylformamide and acetonitrile, could be mostly explained by taking into account solely the cation and complex solvation. A considerable solvent effect on the complexation equilibria was proven to be due to an interesting interplay between the transfer enthalpies and entropies of the reactants and the complexes formed.

Molecular Speciation of Trace Metal Organic Complexes in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Repeta, D.; Boiteau, R. M.; Bundy, R. M.; Babcock-Adams, L.

2017-12-01

Microbial production across approximately one third of the surface ocean is limited by extraordinarily low (picomolar) concentrations of dissolved iron, essentially all of which is complexed to strong organic ligands of unknown composition. Other biologically important trace metals (cobalt, copper, zinc, nickel) are also complexed to strong organic ligands, which again have not been extensively characterized. Nevertheless, organic ligands exert a strong influence on metal bioavailability and toxicity. For example, amendment experiments using commercially available siderophores, organic compounds synthesized by microbes to facilitate iron uptake, show these ligands can both facilitate or impede iron uptake depending on the siderophore composition and available uptake pathways. Over the past few years we have developed analytical techniques using high pressure liquid chromatography interfaced with inductively coupled plasma and electrospray ionization mass spectrometry to identify and quantify trace metal organic complexes in laboratory cultures of marine microbes and in seawater. We found siderophores to be widely distributed in the ocean, particularly in regions characterized by low iron concentrations. We also find chemically distinct complexes of copper, zinc, colbalt and nickel that we have yet to fully characterize. We will discuss some of our recent work on trace metal organic speciation in seawater and laboratory cultures, and outline future efforts to better understand the microbial cycling of trace metal organic complexes in the sea.

Understanding M-ligand bonding and mer-/fac-isomerism in tris(8-hydroxyquinolinate) metallic complexes.

PubMed

Lima, Carlos F R A C; Taveira, Ricardo J S; Costa, José C S; Fernandes, Ana M; Melo, André; Silva, Artur M S; Santos, Luís M N B F

2016-06-28

Tris(8-hydroxyquinolinate) metallic complexes, Mq3, are one of the most important classes of organic semiconductor materials. Herein, the nature of the chemical bond in Mq3 complexes and its implications on their molecular properties were investigated by a combined experimental and computational approach. Various Mq3 complexes, resulting from the alteration of the metal and substitution of the 8-hydroxyquinoline ligand in different positions, were prepared. The mer-/fac-isomerism in Mq3 was explored by FTIR and NMR spectroscopy, evidencing that, irrespective of the substituent, mer- and fac-are the most stable molecular configurations of Al(iii) and In(iii) complexes, respectively. The relative M-ligand bond dissociation energies were evaluated experimentally by electrospray ionization tandem mass spectrometry (ESI-MS-MS), showing a non-monotonous variation along the group (Al > In > Ga). The results reveal a strong covalent character in M-ligand bonding, which allows for through-ligand electron delocalization, and explain the preferred molecular structures of Mq3 complexes as resulting from the interplay between bonding and steric factors. The mer-isomer reduces intraligand repulsions, being preferred for smaller metals, while the fac-isomer is favoured for larger metals where stronger covalent M-ligand bonds can be formed due to more extensive through-ligand conjugation mediated by metal "d" orbitals.

Compartmentation of metals in foliage of Populus tremula grown on soils with mixed contamination. II. Zinc binding inside leaf cell organelles.

PubMed

Vollenweider, Pierre; Bernasconi, Petra; Gautschi, Hans-Peter; Menard, Terry; Frey, Beat; Günthardt-Goerg, Madeleine S

2011-01-01

The phytoextraction potential of plants for removing heavy metals from polluted soils is determined by their capacity to store contaminants in aboveground organs and complex them safely. In this study, the metal compartmentation, elemental composition of zinc deposits and zinc complexation within leaves from poplars grown on soil with mixed metal contamination was analysed combining several histochemical and microanalytical approaches. Zinc was the only heavy metal detected and was stored in several organelles in the form of globoid deposits showing β-metachromasy. It was associated to oxygen anions and different cations, noteworthy phosphorous. The deposit structure, elemental composition and element ratios indicated that zinc was chelated by phytic acid ligands. Maturation processes in vacuolar vs. cytoplasmic deposits were suggested by differences in size and amounts of complexed zinc. Hence, zinc complexation by phytate contributed to metal detoxification and accumulation in foliage but could not prevent toxicity reactions therein. Copyright © 2010 Elsevier Ltd. All rights reserved.

Metal-promoted binuclear C-H activation of ethylene and formation of a novel heterobimetallic Ir-Pt complex. X-ray crystal structure of ((Ph sub 3 P) sub 2 (CO)Ir(. mu. -H)(. mu. -. eta. sup 2 :. eta. sup 1 -CH double bond CH sub 2 )Pt(PPh sub 3 ) sub 2 ) sup + CF sub 3 SO sub 3 sup minus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Yohsin; Stang, P.J.; Arif, A.M.

1990-07-04

Heterobimetallic complexes containing asymmetric metal-metal bonds as well as homogeneous C-H bond activation by organometallic compounds are of considerable current interest largely because of their relevance to catalysis. Although coordination of an alkene to transition metal systems is generally considered a necessary activation step in many catalytic and stoichiometric organometallic reactions, little is known about alkene C-H bond activation of precomplexed olefin substrates. In this paper the authors report the first intermolecular example of olefin C-H activation by a second, different metal system of a precomplexed {pi}-ethylene transition-metal complex and the concomitant formation of a novel alkene-bridged heterobimetallic Ir-Pt complex.

Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands. Tuning Redox Potentials and Small Molecule Activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Christine M.

2015-08-01

Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO2, H2O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, withmore » the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in multicomponent systems.« less

Atypical behavior in the electron capture induced dissociation of biologically relevant transition metal ion complexes of the peptide hormone oxytocin

NASA Astrophysics Data System (ADS)

Kleinnijenhuis, Anne J.; Mihalca, Romulus; Heeren, Ron M. A.; Heck, Albert J. R.

2006-07-01

Doubly protonated ions of the disulfide bond containing nonapeptide hormone oxytocin and oxytocin complexes with different transition metal ions, that have biological relevance under physiological conditions, were subjected to electron capture dissociation (ECD) to probe their structural features in the gas phase. Although, all the ECD spectra were strikingly different, typical ECD behavior was observed for complexes of the nonapeptide hormone oxytocin with Ni2+, Co2+ and Zn2+, i.e., abundant c/z' and a'/y backbone cleavages and ECD characteristic S-S and S-C bond cleavages were observed. We propose that, although in the oxytocin-transition metal ion complexes the metal ions serve as the main initial capture site, the captured electron is transferred to other sites in the complex to form a hydrogen radical, which drives the subsequent typical ECD fragmentations. The complex of oxytocin with Cu2+ displayed noticeably different ECD behavior. The fragment ions were similar to fragment ions typically observed with low-energy collision induced dissociation (CID). We propose that the electrons captured by the oxytocin-Cu2+ complex might be favorably involved in reducing the Cu2+ metal ion to Cu+. Subsequent energy redistribution would explain the observed low-energy CID-type fragmentations. Electron capture resulted also in quite different specific cleavage sites for the complexes of oxytocin with Ni2+, Co2+ and Zn2+. This is an indication for structural differences in these complexes possibly linked to their significantly different biological effects on oxytocin-receptor binding, and suggests that ECD may be used to study subtle structural differences in transition metal ion-peptide complexes.

A label-free colorimetric sensor for Pb2+ detection based on the acceleration of gold leaching by graphene oxide.

PubMed

Shi, Xinhao; Gu, Wei; Zhang, Cuiling; Zhao, Longyun; Peng, Weidong; Xian, Yuezhong

2015-03-14

In this work, we developed a novel, label-free, colorimetric sensor for Pb(2+) detection based on the acceleration of gold leaching by graphene oxide (GO) at room temperature. Gold nanoparticles (AuNPs) can be dissolved in a thiosulfate (S2O3(2-)) aqueous environment in the presence of oxygen; however, the leaching rate is very slow due to the high activation energy (27.99 kJ mol(-1)). In order to enhance the reaction rate, some accelerators should be added. In comparison with the traditional accelerators (metal ions or middle ligands), we found that GO could efficiently accelerate the gold leaching reaction. Kinetic data demonstrate that the dissolution rate of gold in the Pb(2+)-S2O3(2-)-GO system is 5 times faster than that without GO at room temperature. In addition, the effects of surface modification and the nanoparticle size on the etching of AuNPs were investigated. Based on the GO-accelerated concentration-dependent colour changes of AuNPs, a colorimetric sensor for Pb(2+) detection was developed with a linear range from 0.1 to 20 μM and the limit of detection (LOD) was evaluated to be 0.05 μM. This colorimetric assay is simple, low-cost, label-free, and has numerous potential applications in the field of environmental chemistry.

"Turn-on" fluorescence detection of lead ions based on accelerated leaching of gold nanoparticles on the surface of graphene.

PubMed

Fu, Xiuli; Lou, Tingting; Chen, Zhaopeng; Lin, Meng; Feng, Weiwei; Chen, Lingxin

2012-02-01

A novel platform for effective "turn-on" fluorescence sensing of lead ions (Pb(2+)) in aqueous solution was developed based on gold nanoparticle (AuNP)-functionalized graphene. The AuNP-functionalized graphene exhibited minimal background fluorescence because of the extraordinarily high quenching ability of AuNPs. Interestingly, the AuNP-functionalized graphene underwent fluorescence restoration as well as significant enhancement upon adding Pb(2+), which was attributed to the fact that Pb(2+) could accelerate the leaching rate of the AuNPs on graphene surfaces in the presence of both thiosulfate (S(2)O(3)(2-)) and 2-mercaptoethanol (2-ME). Consequently, this could be utilized as the basis for selective detection of Pb(2+). With the optimum conditions chosen, the relative fluorescence intensity showed good linearity versus logarithm concentration of Pb(2+) in the range of 50-1000 nM (R = 0.9982), and a detection limit of 10 nM. High selectivity over common coexistent metal ions was also demonstrated. The practical application had been carried out for determination of Pb(2+) in tap water and mineral water samples. The Pb(2+)-specific "turn-on" fluorescence sensor, based on Pb(2+) accelerated leaching of AuNPs on the surface of graphene, provided new opportunities for highly sensitive and selective Pb(2+) detection in aqueous media.

Using a plant hormone and a thioligand to improve phytoremediation of Hg-contaminated soil from a petrochemical plant.

PubMed

Cassina, L; Tassi, E; Pedron, F; Petruzzelli, G; Ambrosini, P; Barbafieri, M

2012-09-15

Mercury-contaminated soils from a petrochemical plant in southern Italy were investigated to assess the phytoextraction efficiency of crop plants treated with the phytohormone, cytokinine (CK foliar treatment), and with the thioligand, ammonium thiosulfate (TS, soil application). Plant biomass, evapotranspiration, Hg uptake and distribution in plant tissues following treatment were compared. Results indicate the effectiveness of CK in increasing plant biomass and the evapotranspiration rate while TS treatment promoted soil Hg solubility and availability. The simultaneous addition of CK and TS treatments increased Hg uptake and translocation in both tested plants with up to 248 and 232% in Brassica juncea (Indian mustard) and Helianthus annuus (sunflower) respectively. B. juncea was more effective in Hg uptake, whereas H. annuus gave better response regarding plant biomass production. The effectiveness of the treatments was confirmed by the calculation of Hg phytoextraction and evaluation of labile-Hg residue in the soil after plant growth. In one growing cycle the plants subject to simultaneous CK and TS treatment significantly reduced labile-Hg pools that were characterized by the soil sequential extraction, but did not significantly affect the pseudototal metal content in the soil. Results support the use of plant growth regulators in the assisted phytoextraction process for Hg-contaminated soils. Copyright © 2012 Elsevier B.V. All rights reserved.

Diverse reactivity of a tricoordinate organoboron L2PhB: (L = oxazol-2-ylidene) towards alkali metal, group 9 metal, and coinage metal precursors† †Electronic supplementary information (ESI) available: Experimental and calculation details, and crystallographic information for 2, 3, 4, 6, 8. CCDC 1038665, 1038666, 1038667, 1011534, and 1011533. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc00404g Click here for additional data file. Click here for additional data file.

PubMed Central

Kong, Lingbing; Ganguly, Rakesh; Li, Yongxin

2015-01-01

The reactivity of a tricoordinate organoboron L2PhB: (L = oxazol-2-ylidene) 1 towards metal precursors and its coordination chemistry were comprehensively studied. While the boron center in 1 is reluctant to coordinate to the alkali metals in their trifluoromethanesulfonate salts (MOTf) (M = Li, Na, K), the unprecedented compound 2 containing two L2PhB: units linked by a cyclic Li(OTf)2Li spacer was obtained from the reaction of 1 with LiOTf. Treatment of 1 with group 9 metal complexes [MCl(COD)]2 (M = Rh, Ir) afforded the first zwitterionic rhodium(i)–boronium complex 3 and the iridium(iii)–borane complex 4, respectively. The reaction pathway may involve C–H activation followed by proton migration from the metals to the boron center, demonstrating the first example of the deprotonation of metal hydrides by a basic boron. In the reactions with coinage metals, 1 could act as a two-electron reducing agent towards the metal chlorides MCl (M = Cu, Ag, Au). Meanwhile, the reaction of 1 with gold chloride supported by a N-heterocyclic carbene (NHC) produced a heteroleptic cationic gold complex [(L2PhB)Au(NHC)]Cl (6) featuring both carbene and L2PhB: ligands on the gold atom. In contrast, an isolable gold chloride complex (L2PhB)AuCl (8) was obtained by direct complexation between 1 and triphenylphosphine-gold chloride via ligand exchange. X-ray diffraction analysis and computational studies revealed the nature of the B:→Au bonding interaction in complexes 6 and 8. Natural Population Analysis (NPA) and Natural Bond Orbital (NBO) analysis support the strong σ-donating property of the L2PhB: ligand. Moreover, preliminary studies showed that complex 8 can serve as an efficient precatalyst for the addition of X–H (X = N, O, C) to alkynes under ambient conditions, demonstrating the first application of a metal complex featuring a neutral boron-based ligand in catalysis. PMID:29308167

METAL PHTHALOCYANINES

DOEpatents

Frigerio, N.A.

1962-03-27

A process is given for preparing heavy metal phthalocyanines, sulfonated or not. The process comprises mixing an inorganic metal salt with dimethyl formamide or methyl sulfoxide; separating the metal complex formed from the solution; mixing the complex with an equimolar amount of sodium, potassium, lithium, magnesium, or beryllium sulfonated or unsulfonated phthalocyanine whereby heavy-metal phthalocyanine crystals are formed; and separating the crystals from the solution. Uranyl, thorium, lead, hafnium, and lanthanide rare earth phthalocyanines can be produced by the process. (AEC)

Influence of Structural Defects on Biomineralized ZnS Nanoparticle Dissolution: An in-Situ Electron Microscopy Study.

PubMed

Eskelsen, Jeremy R; Xu, Jie; Chiu, Michelle; Moon, Ji-Won; Wilkins, Branford; Graham, David E; Gu, Baohua; Pierce, Eric M

2018-02-06

The dissolution of metal sulfides, such as ZnS, is an important biogeochemical process affecting fate and transport of trace metals in the environment. However, current studies of in situ dissolution of metal sulfides and the effects of structural defects on dissolution are lacking. Here we have examined the dissolution behavior of ZnS nanoparticles synthesized via several abiotic and biological pathways. Specifically, we have examined biogenic ZnS nanoparticles produced by an anaerobic, metal-reducing bacterium Thermoanaerobacter sp. X513 in a Zn-amended, thiosulfate-containing growth medium in the presence or absence of silver (Ag), and abiogenic ZnS nanoparticles were produced by mixing an aqueous Zn solution with either H 2 S-rich gas or Na 2 S solution. The size distribution, crystal structure, aggregation behavior, and internal defects of the synthesized ZnS nanoparticles were examined using high-resolution transmission electron microscopy (TEM) coupled with X-ray energy dispersive spectroscopy. The characterization results show that both the biogenic and abiogenic samples were dominantly composed of sphalerite. In the absence of Ag, the biogenic ZnS nanoparticles were significantly larger (i.e., ∼10 nm) than the abiogenic ones (i.e., ∼3-5 nm) and contained structural defects (e.g., twins and stacking faults). The presence of trace Ag showed a restraining effect on the particle size of the biogenic ZnS, resulting in quantum-dot-sized nanoparticles (i.e., ∼3 nm). In situ dissolution experiments for the synthesized ZnS were conducted with a liquid-cell TEM (LCTEM), and the primary factors (i.e., the presence or absence structural defects) were evaluated for their effects on the dissolution behavior using the biogenic and abiogenic ZnS nanoparticle samples with the largest average particle size. Analysis of the dissolution results (i.e., change in particle radius with time) using the Kelvin equation shows that the defect-bearing biogenic ZnS nanoparticles (γ = 0.799 J/m 2 ) have a significantly higher surface energy than the abiogenic ZnS nanoparticles (γ = 0.277 J/m 2 ). Larger defect-bearing biogenic ZnS nanoparticles were thus more reactive than the smaller quantum-dot-sized ZnS nanoparticles. These findings provide new insight into the factors that affect the dissolution of metal sulfide nanoparticles in relevant natural and engineered scenarios, and have important implications for tracking the fate and transport of sulfide nanoparticles and associated metal ions in the environment. Moreover, our study exemplified the use of an in situ method (i.e., LCTEM) to investigate nanoparticle behavior (e.g., dissolution) in aqueous solutions.

Heavy ligand atom induced large magnetic anisotropy in Mn(ii) complexes.

PubMed

Chowdhury, Sabyasachi Roy; Mishra, Sabyashachi

2017-06-28

In the search for single molecule magnets, metal ions are considered pivotal towards achieving large magnetic anisotropy barriers. In this context, the influence of ligands with heavy elements, showing large spin-orbit coupling, on magnetic anisotropy barriers was investigated using a series of Mn(ii)-based complexes, in which the metal ion did not have any orbital contribution. The mixing of metal and ligand orbitals was achieved by explicitly correlating the metal and ligand valence electrons with CASSCF calculations. The CASSCF wave functions were further used for evaluating spin-orbit coupling and zero-field splitting parameters for these complexes. For Mn(ii) complexes with heavy ligand atoms, such as Br and I, several interesting inter-state mixings occur via the spin-orbit operator, which results in large magnetic anisotropy in these Mn(ii) complexes.

Luminescent Rhenium(I) and Iridium(III) Polypyridine Complexes as Biological Probes, Imaging Reagents, and Photocytotoxic Agents.

PubMed

Lo, Kenneth Kam-Wing

2015-12-15

Although the interactions of transition metal complexes with biological molecules have been extensively studied, the use of luminescent transition metal complexes as intracellular sensors and bioimaging reagents has not been a focus of research until recently. The main advantages of luminescent transition metal complexes are their high photostability, long-lived phosphorescence that allows time-resolved detection, and large Stokes shifts that can minimize the possible self-quenching effect. Also, by the use of transition metal complexes, the degree of cellular uptake can be readily determined using inductively coupled plasma mass spectrometry. For more than a decade, we have been interested in the development of luminescent transition metal complexes as covalent labels and noncovalent probes for biological molecules. We argue that many transition metal polypyridine complexes display triplet charge transfer ((3)CT) emission that is highly sensitive to the local environment of the complexes. Hence, the biological labeling and binding interactions can be readily reflected by changes in the photophysical properties of the complexes. In this laboratory, we have modified luminescent tricarbonylrhenium(I) and bis-cyclometalated iridium(III) polypyridine complexes of general formula [Re(bpy-R(1))(CO)3(py-R(2))](+) and [Ir(ppy-R(3))2(bpy-R(4))](+), respectively, with reactive functional groups and used them to label the amine and sulfhydryl groups of biomolecules such as oligonucleotides, amino acids, peptides, and proteins. Additionally, using a range of biological substrates such as biotin, estradiol, and indole, we have designed luminescent rhenium(I) and iridium(III) polypyridine complexes as noncovalent probes for biological receptors. The interesting results generated from these studies have prompted us to investigate the possible applications of luminescent transition metal complexes in intracellular systems. Thus, in the past few years, we have developed an interest in the cytotoxic activity, cellular uptake, and bioimaging applications of these complexes. Additionally, we and other research groups have demonstrated that many transition metal complexes have facile cellular uptake and organelle-localization properties and that their cytotoxic activity can be readily controlled. For example, complexes that can target the nucleus, nucleolus, mitochondria, lysosomes, endoplasmic reticulum, and Golgi apparatus have been identified. We anticipate that this selective localization property can be utilized in the development of intracellular sensors and bioimaging reagents. Thus, we have functionalized luminescent rhenium(I) and iridium(III) polypyridine complexes with various pendants, including molecule-binding moieties, sugar molecules, bioorthogonal functional groups, and polymeric chains such as poly(ethylene glycol) and polyethylenimine, and examined their potentials as biological reagents. This Account describes our design of luminescent rhenium(I) and iridium(III) polypyridine complexes and explains how they can serve as a new generation of biological reagents for diagnostic and therapeutic applications.

A Simple Method for Drawing Chiral Mononuclear Octahedral Metal Complexes

ERIC Educational Resources Information Center

Mohamadou, Aminou; Haudrechy, Arnaud

2008-01-01

Octahedral transition-metal complexes are involved in a number of reactions and octahedral coordination geometry, frequently observed for metallic centers, includes important topographical stereochemistry. Depending on the number and nature of different ligands, octahedral coordination units with at least two different monodentate ligands give…

Synthesis and Characterization of Heterobimetallic Iridium-Aluminum and Rhodium-Aluminum Complexes.

PubMed

Brewster, Timothy P; Nguyen, Tan H; Li, Zhongjing; Eckenhoff, William T; Schley, Nathan D; DeYonker, Nathan J

2018-02-05

We demonstrate the synthesis and characterization of a new class of late-transition-metal-aluminum heterobimetallic complexes via a novel synthetic pathway. Complexes of this type are exceedingly rare. Joint experimental and theoretical data sheds light on the electronic effect of ligands containing aluminum moieties on late-transition-metal complexes.

Exploring Trends in Metal-Metal Bonding, Spectroscopic Properties, and Conformational Flexibility in a Series of Heterobimetallic Ti/M and V/M Complexes (M = Fe, Co, Ni, and Cu).

PubMed

Wu, Bing; Wilding, Matthew J T; Kuppuswamy, Subramaniam; Bezpalko, Mark W; Foxman, Bruce M; Thomas, Christine M

2016-12-05

To understand the metal-metal bonding and conformational flexibility of first-row transition metal heterobimetallic complexes, a series of heterobimetallic Ti/M and V/M complexes (M = Fe, Co, Ni, and Cu) have been investigated. The titanium tris(phosphinoamide) precursors ClTi(XylNP i Pr 2 ) 3 (1) and Ti(XylNP i Pr 2 ) 3 (2) have been used to synthesize Ti/Fe (3), Ti/Ni (4, 4 THF ), and Ti/Cu (5) heterobimetallic complexes. A series of V/M (M = Fe (7), Co (8), Ni (9), and Cu (10)) complexes have been generated starting from the vanadium tris(phosphinoamide) precursor V(XylNP i Pr 2 ) 3 (6). The new heterobimetallic complexes were characterized and studied by NMR spectroscopy, X-ray crystallography, electron paramagnetic resonance, and Mössbauer spectroscopy, where applicable, and computational methods (DFT). Compounds 3, 4 THF , 7, and 8 are C 3 -symmetric with three bridging phosphinoamide ligands, while compounds 9 and 10 adopt an asymmetric geometry with two bridging phosphinoamides and one phosphinoamide ligand bound η 2 to vanadium. Compounds 4 and 5, on the other hand, are asymmetric in the solid state but show evidence for fluxional behavior in solution. A correlation is established between conformational flexibility and metal-metal bond order, which has important implications for the future reactivity of these and other heterobimetallic molecules.

Templated synthesis of copper(II) azacyclam complexes using urea as a locking fragment and their metal-enhanced binding tendencies towards anions.

PubMed

Boiocchi, Massimo; Fabbrizzi, Luigi; Garolfi, Mauro; Licchelli, Maurizio; Mosca, Lorenzo; Zanini, Cristina

2009-10-26

Copper(II) azacyclam complexes 3(2+) and 4(2+) were obtained through a metal-templated procedure involving the pertinent open-chain tetramine, formaldehyde and a phenylurea derivative as a locking fragment. Both metal complexes can establish interactions with anions through the metal centre and the amide NH group. Equilibrium studies in DMSO by a spectrophotometric titration technique were carried out to assess the affinity of 3(2+) and 4(2+) towards anions. While the NH group of an amide model compound and the metal centre of the plain Cu(II)(azacyclam)(2+) complex do not interact at all with anions, 3(2+) and 4(2+) establish strong interactions with oxo anions, profiting from a pronounced cooperative effect. In particular, 1) they form stable 1:1 and 1:2 complexes with H(2)PO(4) (-) ions in a stepwise mode with both hydrogen-bonding and metal-ligand interactions, and 2) in the presence of CH(3)COO(-), they undergo deprotonation of the amido NH group and thus profit from axial coordination of the partially negatively charged carbonyl oxygen atom in a scorpionate binding mode.

Infrared Multiple-Photon Dissociation spectroscopy of group II metal complexes with salicylate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryan P. Dain; Gary Gresham; Gary S. Groenewold

2011-07-01

Ion-trap tandem mass spectrometry with collision-induced dissociation, and the combination of infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations were used to characterize singly-charged, 1:1 complexes of Ca2+, Sr2+ and Ba2+ with salicylate. For each metal-salicylate complex, the CID pathways are: (a) elimination of CO2 and (b) formation of [MOH]+ where M=Ca2+, Sr2+ or Ba2+. DFT calculations predict three minima for the cation-salicylate complexes which differ in the mode of metal binding. In the first, the metal ion is coordinated by O atoms of the (neutral) phenol and carboxylate groups of salicylate. In the second, the cationmore » is coordinated by phenoxide and (neutral) carboxylic acid groups. The third mode involves coordination by the carboxylate group alone. The infrared spectrum for the metal-salicylate complexes contains a number of absorptions between 1000 – 1650 cm-1, and the best correlation between theoretical and experimental spectra for the structure that features coordination of the metal ion by phenoxide and the carbonyl group of the carboxylic acid group, consistent with calculated energies for the respective species.« less

Infrared multiple-photon dissociation spectroscopy of group II metal complexes with salicylate.

PubMed

Dain, Ryan P; Gresham, Gary; Groenewold, Gary S; Steill, Jeffrey D; Oomens, Jos; van Stipdonk, Michael J

2011-07-15

Ion trap tandem mass spectrometry with collision-induced dissociation, and the combination of infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations, were used to characterize singly charged, 1:1 complexes of Ca(2+), Sr(2+) and Ba(2+) with salicylate. For each metal-salicylate complex, the CID pathways are: (a) elimination of CO(2) and (b) formation of [MOH](+) where M = Ca(2+), Sr(2+) or Ba(2+). DFT calculations predict three minima for the cation-salicylate complexes which differ in the mode of metal binding. In the first, the metal ion is coordinated by O atoms of the (neutral) phenol and carboxylate groups of salicylate. In the second, the cation is coordinated by phenoxide and (neutral) carboxylic acid groups. The third mode involves coordination by the carboxylate group alone. The infrared spectrum for the metal-salicylate complexes contains a number of absorptions between 1000 and 1650 cm(-1), and the best correlation between theoretical and experimental spectra is found for the structure that features coordination of the metal ion by phenoxide and the carbonyl O of the carboxylic acid group, consistent with the calculated energies for the respective species. Copyright © 2011 John Wiley & Sons, Ltd.

Selective synthesis of a series of isostructural MIICuI heterobimetallic complexes spontaneously assembled by an unsymmetrical naphthyridine-based ligand.

PubMed

Nicolay, Amélie; Tilley, T Don

2018-05-31

Metal-metal cooperation is integral to the function of many enzymes and materials, and model complexes hold enormous potential for providing insights into the capabilities of analogous multimetallic cores. However, the selective synthesis of heterobimetallic complexes still presents a significant challenge, especially for systems that hold the metals in close proximity and feature open or reactive coordination sites for both metals. To address this issue, a rigid, naphthyridine-based dinucleating ligand featuring distinct binding environments was synthesized. This ligand enables the selective synthesis of a series of MIICuI bimetallic complexes (M = Mn, Fe, Co, Ni, Cu, Zn), in which each metal center exclusively occupies its preferred binding pocket, from simple chloride salts. The precision of this selectivity is evident from cyclic voltammetry, ESI-MS and anomalous X-ray diffraction measurements. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Discovery and development of microporous metal carboxylates.

PubMed

Mori, Wasuke; Sato, Tomohiko; Kato, Chika Nozaki; Takei, Tohru; Ohmura, Tetsushi

2005-01-01

We have found a form of copper(II) terephthalate that occluded an enormous amount of gases such as N2, Ar, O2, and Xe. Copper(II) terephthalate is the first metal complex found capable of adsorbing gases. This complex has opened a new field of adsorbent chemistry and is recognized as a leader in the construction of microporous metal complexes. In extending the route for the synthesis of microporous complexes, we obtained many new porous materials that are widely recognized as useful materials for applications in areas such as gas storage, molecular sieves, catalysis, inclusion complexes, and surface science. 2005 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Mechanics of metal-catecholate complexes: The roles of coordination state and metal types

PubMed Central

Xu, Zhiping

2013-01-01

There have been growing evidences for the critical roles of metal-coordination complexes in defining structural and mechanical properties of unmineralized biological materials, including hardness, toughness, and abrasion resistance. Their dynamic (e.g. pH-responsive, self-healable, reversible) properties inspire promising applications of synthetic materials following this concept. However, mechanics of these coordination crosslinks, which lays the ground for predictive and rational material design, has not yet been well addressed. Here we present a first-principles study of representative coordination complexes between metals and catechols. The results show that these crosslinks offer stiffness and strength near a covalent bond, which strongly depend on the coordination state and type of metals. This dependence is discussed by analyzing the nature of bonding between metals and catechols. The responsive mechanics of metal-coordination is further mapped from the single-molecule level to a networked material. The results presented here provide fundamental understanding and principles for material selection in metal-coordination-based applications. PMID:24107799

Carbon quantum dots and a method of making the same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zidan, Ragaiy; Teprovich, Joseph A.; Washington, Aaron L.

The present invention is directed to a method of preparing a carbon quantum dot. The carbon quantum dot can be prepared from a carbon precursor, such as a fullerene, and a complex metal hydride. The present invention also discloses a carbon quantum dot made by reacting a carbon precursor with a complex metal hydride and a polymer containing a carbon quantum dot made by reacting a carbon precursor with a complex metal hydride.

New trends in the optical and electronic applications of polymers containing transition-metal complexes.

PubMed

Liu, Shu-Juan; Chen, Yang; Xu, Wen-Juan; Zhao, Qiang; Huang, Wei

2012-04-13

Polymers containing transition-metal complexes exhibit excellent optical and electronic properties, which are different from those of polymers with a pure organic skeleton and combine the advantages of both polymers and metal complexes. Hence, research about this class of polymers has attracted more and more interest in recent years. Up to now, a number of novel polymers containing transition-metal complexes have been exploited, and significant advances in their optical and electronic applications have been achieved. In this article, we summarize some new research trends in the applications of this important class of optoelectronic polymers, such as chemo/biosensors, electronic memory devices and photovoltaic devices. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DNA binding of supramolecular mixed-metal complexes

NASA Astrophysics Data System (ADS)

Swavey, Shawn; Williams, Rodd L.; Fang, Zhenglai; Milkevitch, Matthew; Brewer, Karen J.

2001-10-01

The high binding affinity of cisplatin toward DNA has led to its popularity as an anticancer agent. Due to cumulative drug resistance and toxic side effects, researchers are exploring related metallodrugs. Our approach involves the use of supramolecular complexes. These mixed-metal complexes incorporate a reactive platinum moiety bridged by a polyazine ligand to a light absorbing metal-based chromophore. The presence of the light absorber allows excitation of these systems, opening up the possibility of photoactivation. The use of a supramolecular design allows components of the assembly to be varied to enhance device function and light absorbing properties. Aspects of our molecular design process and results on the DNA binding properties for a number of these mixed-metal complexes will be discussed.

Photodissociation Studies of Metal-Containing Clusters and Complexes

NASA Astrophysics Data System (ADS)

Pilgrim, Jeffrey Scott

1995-01-01

There have been two major areas of investigation for researchers working with laser ablation in molecular beams. The first area is the study of weakly-bound complexes. These complexes are bound by electrostatic interactions. In the present study the weakly bound interactions of the rare gases with the magnesium ion are investigated with electronic spectroscopy. The second major area is the study of metal and metal-containing clusters. Examples of previous investigations are the alkali metal clusters and the fullerenes. The present investigation is on metal -carbon clusters. The so-called metallo-carbohedrenes and metal-carbon nanocrystals are studied. Resonance enhanced photodissociation spectroscopy is used to obtain electronic excitation spectra of the Mg^+-rare gas species in the ultraviolet region. This investigation is facilitated by a reflectron time-of-flight mass spectrometer. The interaction of the rare gas with the metal ion is attributed to a "solvation" of the atomic ion transition. Simple bonding arguments predict that the excited state is more bound than the ground state for these complexes. This will result in a shift of the complex vibronic origin to lower energy from the atomic ion transition. This is exactly what is observed in the experiment with progressively larger shifts for the heavier rare gases. The electronic excitation spectra allow the vibrational frequencies and anharmonicities for these complexes to be obtained for the excited state. In turn, the excited state bond dissociation energies can be determined. Finally, conservation of energy allows calculation of the ground state bond dissociation energies. In the metal-carbon systems the stability of the metallo-carbohedrene, met-car, stoichiometry is shown to extend into the transition period at least to the iron group. Photodissociation with a 532 nm laser causes a loss of metal atoms for met-cars formed with first row transition metals and a loss of metal-carbon units for met-cars formed from second-row transition metal atoms. Larger metal-carbon clusters are found to be face-centered-cubic nanocrystals. Photodissociation of these nanocrystals causes fragmentation into smaller nanocrystals. In addition, nanocrystals also dissociatively rearrange into the met -car structure. Two of the metal-carbon nanocrystals ( rm Ti_{14}C_{13 }^+ and rm V_{14 }C_{13}^+) fragment into the met-car with a trapped carbon atom.

Experimental considerations in metal mobilization from soil by chelating ligands: The influence of soil-solution ratio and pre-equilibration - A case study on Fe acquisition by phytosiderophores.

PubMed

Schenkeveld, W D C; Kimber, R L; Walter, M; Oburger, E; Puschenreiter, M; Kraemer, S M

2017-02-01

The efficiency of chelating ligands in mobilizing metals from soils and sediments is generally examined under conditions remote from those under which they are exuded or applied in the field. This may lead to incorrect estimations of the mobilizing efficiency. The aim of this study was to establish the influence of the soil solution ratio (SSR) and pre-equilibration with electrolyte solution on metal mobilization and metal displacement. For this purpose a series of interaction experiments with a calcareous clay soil and a biogenic chelating agent, the phytosiderophore 2'-deoxymugineic acid (DMA) were carried out. For a fixed ligand concentration, the SSR had a strong influence on metal mobilization and displacement. Metal complexation was faster at higher SSR. Reactive pools of metals that were predominantly mobilized at SSR 6 (in this case Cu), became depleted at SSR 0.1, whereas metals that were marginally mobilized at SSR 6, were dominantly mobilized at SSR 0.1 (in this case Fe), because of large soil reactive pools. For a fixed "amount of ligand"-to-"amount of soil"-ratio, metal complexation scaled linearly with the SSR. The efficiency of ligands in mobilizing metals under field conditions can be predicted with batch experiments, as long as the ligand-to-soil-ratio is matched. In most previously reported studies this criterion was not met. Equivalent metal-complex concentrations under field conditions can be back-calculated using adsorption isotherms for the respective metal-complexes. Drying and dry storage created labile pools of Fe, Cu and Zn, which were rapidly mobilized upon addition of DMA solution to dry soil. Pre-equilibration decreased these labile pools, leading to smaller concentrations of these metals during initial mobilization, but did not reduce the lag time between ligand addition and onset of microbial degradation of the metal-complexes. Hence SSR and pre-equilibration should be carefully considered when testing the metal mobilizing efficiency of chelating ligands. Copyright © 2016. Published by Elsevier B.V.

Plastic scintillators with high loading of one or more metal carboxylates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherepy, Nerine; Sanner, Robert Dean

According to one embodiment, a method includes incorporating a metal carboxylate complex into a polymeric matrix to form an optically transparent material. According to another embodiment, a material includes at least one metal carboxylate complex incorporated into a polymeric matrix, where the material is optically transparent.

A new metalation complex for organic synthesis and polymerization reactions

NASA Technical Reports Server (NTRS)

Hirshfield, S. M.

1971-01-01

Organometallic complex of N,N,N',N' tetramethyl ethylene diamine /TMEDA/ and lithium acts as metalation intermediate for controlled systhesis of aromatic organic compounds and polymer formation. Complex of TMEDA and lithium aids in preparation of various organic lithium compounds.

Spectral studies, thermal investigation and biological activity of some metal complexes derived from (E)-N‧-(1-(4-aminophenyl)ethylidene)morpholine-4-carbothiohydrazide

NASA Astrophysics Data System (ADS)

El-Samanody, El-Sayed A.; Polis, Magdy W.; Emara, Esam M.

2017-09-01

A new series of biologically active Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes derived from the novel thiosemicarbazone ligand; (E)-N‧-(1-(4-aminophenyl)ethylidene)morpholine-4-carbothiohydrazide (HL) were synthesized. The mode of bonding of the ligand and the geometrical structures of its metal complexes were achieved by different analytical and spectral methods. The ligand coordinated with metal ions in a neutral bidentate fashion through the thione sulfur and azomethine nitrogen atoms. All metal complexes adopted octahedral geometry, except Cu(II) complexes (3, 6, 7) which have a square planar structure. The general thermal decomposition pathways of the ligand along with its metal complexes were explained. The thermal stability of the complexes is controlled by the number of outer and inner sphere water molecules, ionic radii and the steric hindrance. The activation thermodynamic parameters; (activation energy (E*), enthalpy of activation (ΔH*), entropy of activation (ΔS*) and Gibbs free energy (ΔG*)) along with order of reaction (n) were estimated from DTG curves. The ESR spectra of Cu(II) complexes indicated that (dx2-y2)1 is the ground state with covalence character of metal-ligand bonds. The molluscicidal and biochemical effects of the ligand and its Ni(II); Cu(II) complexes (2; 3, 5, 7) along with their combinations with metaldehyde were screened in vitro on the mucous gland of Eobania vermiculata. The tested compounds exhibited a significant toxicity against the tested animals and have almost the same toxic effect of metaldehyde which increases the mucous secretion of the snails and leads to death.

Platinated DNA oligonucleotides: new probes forming ultrastable conjugates with graphene oxide

NASA Astrophysics Data System (ADS)

Wang, Feng; Liu, Juewen

2014-05-01

Metal containing polymers have expanded the property of polymers by involving covalently associated metal complexes. DNA is a special block copolymer. While metal ions are known to influence DNA, little is explored on its polymer property when strong metal complexes are associated. In this work, we study cisplatin modified DNA as a new polymer and probe. Out of the complexes formed between cisplatin-A15, HAuCl4-A15, Hg2+-T15 and Ag+-C15, only the cisplatin adduct is stable under the denaturing gel electrophoresis condition. Each Pt-nucleobase bond gives a positive charge and thus makes DNA a zwitterionic polymer. This allows ultrafast adsorption of DNA by graphene oxide (GO) and the adsorbed complex is highly stable. Non-specific DNA, protein, surfactants and thiolated compounds cannot displace platinated DNA from GO, while non-modified DNA is easily displaced in most cases. The stable GO/DNA conjugate is further tested for surface hybridization. This is the first demonstration of using metallated DNA as a polymeric material for interfacing with nanoscale materials.Metal containing polymers have expanded the property of polymers by involving covalently associated metal complexes. DNA is a special block copolymer. While metal ions are known to influence DNA, little is explored on its polymer property when strong metal complexes are associated. In this work, we study cisplatin modified DNA as a new polymer and probe. Out of the complexes formed between cisplatin-A15, HAuCl4-A15, Hg2+-T15 and Ag+-C15, only the cisplatin adduct is stable under the denaturing gel electrophoresis condition. Each Pt-nucleobase bond gives a positive charge and thus makes DNA a zwitterionic polymer. This allows ultrafast adsorption of DNA by graphene oxide (GO) and the adsorbed complex is highly stable. Non-specific DNA, protein, surfactants and thiolated compounds cannot displace platinated DNA from GO, while non-modified DNA is easily displaced in most cases. The stable GO/DNA conjugate is further tested for surface hybridization. This is the first demonstration of using metallated DNA as a polymeric material for interfacing with nanoscale materials. Electronic supplementary information (ESI) available: Methods, additional gels, kinetics, mass spectrum. See DOI: 10.1039/c4nr00867g

Complexation- and ligand-induced metal release from 316L particles: importance of particle size and crystallographic structure.

PubMed

Hedberg, Yolanda; Hedberg, Jonas; Liu, Yi; Wallinder, Inger Odnevall

2011-12-01

Iron, chromium, nickel, and manganese released from gas-atomized AISI 316L stainless steel powders (sized <45 and <4 μm) were investigated in artificial lysosomal fluid (ALF, pH 4.5) and in solutions of its individual inorganic and organic components to determine its most aggressive component, elucidate synergistic effects, and assess release mechanisms, in dependence of surface changes using atomic absorption spectroscopy, Raman, XPS, and voltammetry. Complexation is the main reason for metal release from 316L particles immersed in ALF. Iron was mainly released, while manganese was preferentially released as a consequence of the reduction of manganese oxide on the surface. These processes resulted in highly complexing media in a partial oxidation of trivalent chromium to hexavalent chromium on the surface. The extent of metal release was partially controlled by surface properties (e.g., availability of elements on the surface and structure of the outermost surface) and partially by the complexation capacity of the different metals with the complexing agents of the different media. In general, compared to the coarse powder (<45 μm), the fine (<4 μm) powder displayed significantly higher released amounts of metals per surface area, increased with increased solution complexation capacity, while less amounts of metals were released into non-complexing solutions. Due to the ferritic structure of lower solubility for nickel of the fine powder, more nickel was released into all solutions compared with the coarser powder.

Physicochemical impact studies of gamma rays on "aspirin" analgesics drug and its metal complexes in solid form: Synthesis, spectroscopic and biological assessment of Ca(II), Mg(II), Sr(II) and Ba(II) aspirinate complexes

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Sharshar, T.; Elsabawy, Khaled M.; Heiba, Zein K.

2013-09-01

Metal aspirinate complexes, M2(Asp)4, where M is Mg(II), Ca(II), Sr(II) or Ba(II) are formed by refluxed of aspirin (Asp) with divalent non-transition metal ions of group (II) and characterized by elemental analysis and spectroscopic measurements (infrared, electronic, 1H NMR, Raman, X-ray powder diffraction and scanning electron microscopy). Elemental analysis of the chelates suggests the stoichiometry is 1:2 (metal:ligand). Infrared spectra of the complexes agree with the coordination to the central metal atom through three donation sites of two oxygen atoms of bridge bidentate carboxylate group and oxygen atom of sbnd Cdbnd O of acetyl group. Infrared spectra coupled with the results of elemental analyzes suggested a distorted octahedral structure for the M(II) aspirinate complexes. Gamma irradiation was tested as a method for stabilization of aspirin as well as their complexes. The effect of gamma irradiation, with dose of 80 Gy, on the properties of aspirinate complexes was studied. The aspirinate chelates have been screened for their in vitro antibacterial activity against four bacteria, gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two strains of fungus (Aspergillus flavus and Candida albicans). The metal chelates were shown to possess more antibacterial activity than the free aspirin chelate.

Use of Molecular Typing Methods To Trace the Dissemination of Listeria monocytogenes in a Shrimp Processing Plant

PubMed Central

Destro, M. T.; Leitao, M.; Farber, J. M.

1996-01-01

Volume 62, no. 2, p. 705, column 2, line 5 from bottom: "neutralized with chlorine" should read "chlorine neutralized by the addition of 5 ml of a 1% solution of sodium thiosulfate." Page 706, Table 1, footnote b: Footnote b should read "The designation in parentheses is the area or type of sample collected as indicated in Table 3." Page 709, Tables 3 and 4: Tables 3 and 4 should read as shown below. PMID:16535326

Hydroxocobalamin Versus Sodium Thiosulfate for the Treatment of Acute Cyanide Toxicity in a Swine (Sus scrofa) Model

DTIC Science & Technology

2012-06-01

effects, but vomiting , arthralgias, and injection site pain have been reported in humans.7,26,38,39 In addition, animal studies have reported a higher...treatment of acute cyanide poisoning in adult beagle dogs . Clin Toxicol (Phila). 2006;44(suppl 1):5-15. 15. Posner MA, Tobey RE, McElroy H...cobalamine and acute cyanide poisoning in dogs . Life Sci. 1965;4:1785-1789. 18. Borron SW, Baud FJ, Barriot P, et al. Prospective study of hydroxocobalamin

Development and Evaluation of Integrity Assessment Tests for Polymeric Hermetic Seals

DTIC Science & Technology

2006-02-19

Knoxville, the wires were pulled from the seals and then the packages were dipped in the microorganism Enterobacter aerogene . The polytrays were exposed for...inoculated) 5 samples Total Polytrays 80 Microorganism Washes 1. Prepare Cultures of Enterobacter aerogenes a. 5 tubes (10 mL each) in...initial number – 6 log CFU/mL a. Add two tubes (20 mL) of Enterobacter aerogenes culture to 5 gallons of water with sodium thiosulfate b. Ca. 9 log CFU

[Glutamate dehydrogenase activity in the pancreatic tissue in acute experimental pancreatitis and under the action of sodium thiosulphate].

PubMed

Simavorian, P S; Saakian, I L; Gevorkian, D A

1991-04-01

It has been established that the development of acute pancreatitis is accompanied by the reduced activity of glutamate dehydrogenase in the mitochondrial fraction of pancreas, pronounced in the focus of tissue necrosis and less expressed in the reactive inflammation focus. Besides this in the pancreas redistribution of enzyme, activity in the subcellular organelles takes place and enzyme activity emerges in the cytosol and further--in the blood and peritoneum liquid. Sodium thiosulfate has a marked correlation effect.

Synthesis, spectroscopic, thermal and DFT calculations of 2-(3-amino-2-hydrazono-4-oxothiazolidin-5-yl) acetic acid binuclear metal complexes

NASA Astrophysics Data System (ADS)

Hassan, Walid M. I.; Badawy, M. A.; Mohamed, Gehad G.; Moustafa, H.; Elramly, Salwa

2013-07-01

The binuclear complexes of 2-(3-amino-2-hydrazono-4-oxothiazolidin-5-yl) acetic acid ligand (HL) with Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) ions were prepared and their stoichiometry was determined by elemental analysis. The stereochemistry of the studied series of metal complexes was established by analyzing their infrared, 1H NMR spectra and the magnetic moment measurements. According to the elemental analysis data, the complexes were found to have the formulae [Fe2L(H2O)8]Cl5 and [M2L(H2O)8]Cl3 (M = Co(II), Ni(II), Cu(II) and Zn(II)). The present analyses demonstrate that all metal ions coordinated to the ligand via O(9), O(11), N(16) and N(18) atoms. Thermal decomposition studies of the ligand-metal complexes have been performed to verify the status of water molecules present in these metal complexes and their general decomposition pattern. Density Functional Theory (DFT) calculations at the B3LYP/6-31G* level of theory have been carried out to investigate the equilibrium geometry of the ligand and complexes. Moreover, charge density distribution, extent of distortion from regular geometry, dipole moment and orientation have been performed and discussed.

Properties- and applications of quasicrystals and complex metallic alloys.

PubMed

Dubois, Jean-Marie

2012-10-21

This article aims at an account of what is known about the potential for applications of quasicrystals and related compounds, the so-called family of Complex Metallic Alloys (CMAs‡). Attention is focused at aluminium-based CMAs, which comprise a large number of crystalline compounds and quasicrystals made of aluminium alloyed with transition metals (like Fe or Cu) or normal metals like Mg. Depending on composition, the structural complexity varies from a few atoms per unit cell up to thousands of atoms. Quasicrystals appear then as CMAs of ultimate complexity and exhibit a lattice that shows no periodicity anymore in the usual 3-dimensional space. Properties change dramatically with lattice complexity and turn the metal-type behaviour of simple Al-based crystals into a far more complex behaviour, with a fingerprint of semi-conductors that may be exploited in various applications, potential or realised. An account of the ones known to the author is given in the light of the relevant properties, namely light absorption, reduced adhesion and friction, heat insulation, reinforcement of composites for mechanical devices, and few more exotic ones. The role played by the search for applications of quasicrystals in the development of the field is briefly addressed in the concluding section.

Metal-metal bond lengths in complexes of transition metals.

PubMed

Pauling, L

1976-12-01

In complexes of the transition metals containing clusters of metal atoms the cobalt-cobalt bond lengths are almost always within 1 pm of the single-bond value 246 pm given by the enneacovalent radius of cobalt, whereas most of the observed iron-iron bond lengths are significantly larger than the single-bond value 248 pm, the mean being 264 pm, which corresponds to a half-bond. A simple discussion of the structures of these complexes based on spd hybrid orbitals, the electroneutrality principle, and the partial ionic character of bonds between unlike atoms leads to the conclusion that resonance between single bonds and no-bonds would occur for iron and its congeners but not for cobalt and its congeners, explaining the difference in the bond lengths.

Regio- and Stereochemical Control in Ocimene Polymerization by Half-Sandwich Rare-Earth Metal Dialkyl Complexes.

PubMed

Peng, Deqian; Du, Gaixia; Zhang, Pengfei; Yao, Bo; Li, Xiaofang; Zhang, Shaowen

2016-06-01

The polymerization of ocimene has been first achieved by half-sandwich rare-earth metal dialkyl complexes in combination with activator and Al(i) Bu3 . The regio- and stereoselectivity in the ocimene polymerization can be controlled by tuning the cyclopentadienyl ligand and the central metal of the complex. The chiral cyclopentadienyl-ligated Sc complex 1 prepares syndiotactic cis-1,4-polyocimene (cis-1,4-selectivity up to 100%, rrrr = 100%), while the corresponding Lu, Y, and Dy complexes 2-4 and the achiral pentamethylcyclopentadienyl Sc, Lu, and Y complexes 5-7 afford isotactic trans-1,2-polyocimenes (trans-1,2-selectivity up to 100%, mm = 100%). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Activation of carbon-hydrogen bonds and dihydrogen by 1,2-CH-addition across metal-heteroatom bonds.

PubMed

Webb, Joanna R; Burgess, Samantha A; Cundari, Thomas R; Gunnoe, T Brent

2013-12-28

The controlled conversion of hydrocarbons to functionalized products requires selective C-H bond cleavage. This perspective provides an overview of 1,2-CH-addition of hydrocarbons across d(0) transition metal imido complexes and compares and contrasts these to examples of analogous reactions that involve later transition metal amide, hydroxide and alkoxide complexes with d(6) and d(8) metals.

Handheld Delivery System for Modified Boron-Type Fire Extinguishment Agent

DTIC Science & Technology

1993-11-01

was to develop and test a handheld portable delivery system for use with the modified boron-type fire extinguishing agent for metal fires . B...BACKGROUND A need exists for an extinguishing agent and accompanying delivery system that are effective against complex geometry metal fires . A modified...agent and its delivery system have proven effective against complex geometry metal fires containing up to 200 pounds of magnesium metal. Further

Method of stripping metals from organic solvents

DOEpatents

Todd, Terry A [Aberdeen, ID; Law, Jack D [Pocatello, ID; Herbst, R Scott [Idaho Falls, ID; Romanovskiy, Valeriy N [St. Petersburg, RU; Smirnov, Igor V [St.-Petersburg, RU; Babain, Vasily A [St-Petersburg, RU; Esimantovski, Vyatcheslav M [St-Petersburg, RU

2009-02-24

A new method to strip metals from organic solvents in a manner that allows for the recycle of the stripping agent. The method utilizes carbonate solutions of organic amines with complexants, in low concentrations, to strip metals from organic solvents. The method allows for the distillation and reuse of organic amines. The concentrated metal/complexant fraction from distillation is more amenable to immobilization than solutions resulting from current practice.

An absorption spectral study of Nd (III) with glutathione (reduced), GSH in aqueous and aquated organic solvent in presence and absence of Zn (II)

NASA Astrophysics Data System (ADS)

Mehta, Jignasu P.; Bhatt, Prashant N.; Misra, Sudhindra N.

2003-02-01

The coordination chemistry of glutathione (reduced) GSH is of great importance as it acts as an excellent model system for the binding of metal ions. The GSH complexation with metal ions is involved in the toxicology of different metal ions. Its coordination behaviour for soft metal ions and hard metal ions is found different because of the structure of GSH and its different potential binding sites. We have studied two chemically dissimilar metal ions viz. Nd (III) being hard metal ion, which will prefer hard donor sites like carboxylic groups, and Zn (II) the soft metal ion more suited to peptide-NH and sulfhydryl groups. The absorption difference and comparative absorption spectroscopy involving 4f-4f transitions of the heterobimetallic complexation of GSH with Nd (III) and Zn (II) has been explored in aqueous and aquated organic solvents. The changes in the oscillator strengths of different 4f-4f bands and Judd-Ofelt intensity (Tλ) parameters determined experimentally is being used to investigate the complexation of GSH. The in vivo intracellular complexation of GSH with Ca (II) in presence of Zn (II) ion has been mimicked through Nd (III)-GSH-Zn (II) absorption spectral studies in vitro.

Ternary metal complexes of guaifenesin drug: Synthesis, spectroscopic characterization and in vitro anticancer activity of the metal complexes.

PubMed

Mahmoud, W H; Mahmoud, N F; Mohamed, G G; El-Sonbati, A Z; El-Bindary, A A

2015-01-01

The coordination behavior of a series of transition metal ions named Cr(III), Fe(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with a mono negative tridentate guaifenesin ligand (GFS) (OOO donation sites) and 1,10-phenanthroline (Phen) is reported. The metal complexes are characterized based on elemental analyses, IR, (1)H NMR, solid reflectance, magnetic moment, molar conductance, UV-vis spectral studies, mass spectroscopy, ESR, XRD and thermal analysis (TG and DTG). The ternary metal complexes were found to have the formulae of [M(GFS)(Phen)Cl]Cl·nH2O (M=Cr(III) (n=1) and Fe(III) (n=0)), [M(GFS)(Phen)Cl]·nH2O (M=Mn(II) (n=0), Zn(II) (n=0) and Cu(II) (n=3)) and [M(GFS)(Phen)(H2O)]Cl·nH2O (M=Co(II) (n=0), Ni(II) (n=0) and Cd(II) (n=4)). All the chelates are found to have octahedral geometrical structures. The ligand and its ternary chelates are subjected to thermal analyses (TG and DTG). The GFS ligand, in comparison to its ternary metal complexes also was screened for their antibacterial activity on gram positive bacteria (Bacillus subtilis and Staphylococcus aureus), gram negative bacteria (Escherichia coli and Neisseria gonorrhoeae) and for in vitro antifungal activity against (Candida albicans). The activity data show that the metal complexes have antibacterial and antifungal activity more than the parent GFS ligand. The complexes were also screened for its in vitro anticancer activity against the Breast cell line (MFC7) and the results obtained show that they exhibit a considerable anticancer activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Density functional theory study on Herzberg-Teller contribution in Raman scattering from 4-aminothiophenol-metal complex and metal-4-aminothiophenol-metal junction

NASA Astrophysics Data System (ADS)

Liu, Shasha; Zhao, Xiuming; Li, Yuanzuo; Zhao, Xiaohong; Chen, Maodu

2009-06-01

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag2-PATP and PATP-Au2) and the two junctions (Ag2-PATP-Au2 and Au2-PATP-Ag2) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 102. We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S1 electronic transition energy of complexes and junctions. Ag2-PATP-Au2 and Au2-PATP-Ag2 junctions yield higher Raman intensities than those of Ag2-PATP and PATP-Au2 complexes, especially for b2 modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.

Metal-metal interactions in tetrakis(diphenylphosphino)benzene-bridged dimetallic complexes and their related coordination polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Pei-Wei; Fox, M.A.

1994-06-22

Electrochemical, EPR, and spectroelectrochemical methods have been used to probe electronic coupling through a 1,2,4,5-tetrakis(diphenylphosphino)benzene bridging ligand connecting metal centers in several Ni-, Pd-, and Pt-containing dimetallic complexes. These dimetalated complexes showed weak intervalence charge transfer (IT) bands and slightly shifted redox potentials in comparison with their monometallic models. A Marcus-Hush analysis of the energies of the IT bands for the electrochemically generated mixed-valence heterodimetallic complexes (Ni{sup o}-Pd{sup II} and Ni{sup o}-Pt{sup II}, respectively) established the magnitude of intermetallic electronic coupling. The weak thermal coupling observed in these dimetalated complexes is consistent with the very low conductivities (10{sup {minus}8}-10{sup {minus}10}{omega}{supmore » -1} cm{sup {minus}1}) observed in the polymeric analogs of these complexes, namely, the newly prepared metal coordination polymers (M = Ni{sup II}, Pd{sup II}, Pt{sup II}) with 1,2,4,5-tetrakis(diphenylphosphino)benzene.« less

Spectral, optical and cytotoxicity studies on 2-isonicotinoyl-N-phenylhydrazine-1-carboxamide(H3L) and some of its metal complexes

NASA Astrophysics Data System (ADS)

Hosny, Nasser M.; Hassan, Nader Y.; Mahmoud, Heba M.; Abdel-Rhman, Mohamed H.

2018-03-01

The ligand 2-isonicotinoyl-N-phenylhydrazine-1-carboxamide (H3L) and its metal complexes with Co(II), Ni(II), Cu(II) and Zn(II) acetates have been synthesized. The isolated compounds have been characterized by elemental analyses, FT-IR, 1H NMR, 13C NMR, ESR, mass, electronic spectra, electrical conductivity, effective magnetic moments and thermal analyses. The free organic ligand exists in the keto form, but in the metal complexes, it coordinates in the enol form. Four coordinated species were suggested for all the isolated metal complexes. The measured optical band gap values confirmed the presence of direct electronic transition and the semi-conductivity of the compounds. The ligand and its Zn(II) complex were examined as cytotoxic agent against HCT-116 and HePG-2. The ligand showed very strong cytotoxic effect against HePG-2, but moderate cytotoxicity against HCT-116. Zn(II) complex showed weak cytotoxicity against the two cell lines.

Highly efficient one-step synthesis of carbon encapsulated nanocrystals by the oxidation of metal π-complexes

NASA Astrophysics Data System (ADS)

Liu, Boyang; Shao, Yingfeng; Xiang, Xin; Zhang, Fuhua; Yan, Shengchang; Li, Wenge

2017-08-01

Various carbon encapsulated nanocrystals, including MnS and MnO, Cr2O3, MoO2, Fe7S8 and Fe3O4, and ZrO2, are prepared in one step and in situ by a simple and highly efficient synthesis approach. The nanocrystals have an equiaxed morphology and a median size smaller than 30 nm. Tens and hundreds of these nanocrystals are entirely encapsulated by a wormlike amorphous carbon shell. The formation of a core-shell structure depends on the strongly exothermic reaction of metal π-complexes with ammonium persulfate in an autoclave at below 200 °C. During the oxidation process, the generated significant amounts of heat will destroy the molecular structure of the metal π-complex and cleave the ligands into small carbon fragments, which further transform into an amorphous carbon shell. The central metal atoms are oxidized to metal oxide/sulfide nanocrystals. The formation of a core-shell structure is independent of the numbers of ligands and carbon atoms as well as the metal types, implying that any metal π-complex can serve as a precursor and that various carbon encapsulated nanocrystals can be synthesized by this method.

Comparison of energy interaction parameters for the complexation of Pr(III) with glutathione reduced (GSH) in absence and presence of Zn(II) in aqueous and aquated organic solvents using 4f?4f transition spectra as PROBE

NASA Astrophysics Data System (ADS)

Singh, Th. David; Sumitra, Ch.; Yaiphaba, N.; Devi, H. Debecca; Devi, M. Indira; Singh, N. Rajmuhon

2005-04-01

The coordination chemistry of glutathione reduced (GSH) is of great importance as it acts as excellent model system for the binding of metal ions. The GSH complexation with metal ions is involved in the toxicology of different metal ions. Its coordination behaviour for soft metal ions and hard metal ions is found different because of the structure of GSH and its different potential binding sites. In our work we have studied two chemically dissimilar metal ions viz. Pr(III), which prefer hard donor site like carboxylic groups and Zn(II) the soft metal ion which prefer peptide-NH and sulphydryl groups. The absorption difference and comparative absorption spectroscopy involving 4f-4f transitions of the heterobimetallic Complexation of GSH with Pr(III) and Zn(II) has been explored in aqueous and aquated organic solvents. The variation in the energy parameters like Slater-Condon ( F K), Racah ( E K) and Lande ( ξ4f), Nephelauxetic parameter ( β) and bonding parameter ( b1/2) are computed to explain the nature of complexation.

Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: spectral, thermal, XRD and antimicrobial studies.

PubMed

Sundararajan, M L; Jeyakumar, T; Anandakumaran, J; Karpanai Selvan, B

2014-10-15

Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), Fe(III), Co(II), Mn(II) Hg(II), and Ag(I) have been synthesized from Schiff base ligand, prepared by the condensation of 3,4-(methylenedioxy)aniline and 5-bromo salicylaldehyde. All the compounds have been characterized by using elemental analysis, molar conductance, FT-IR, UV-Vis, (1)H NMR, (13)C NMR, mass spectra, powder XRD and thermal analysis (TG/DTA) technique. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The FT-IR, (1)H NMR, (13)C NMR and UV-Vis spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. Mass spectral data further support the molecular mass of the compounds and their structure. Powder XRD indicates the crystalline state and morphology of the ligand and its metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. Melting point supports the thermal stability of all the compounds. The in vitro antimicrobial effects of the synthesized compounds were tested against five bacterial and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more biological activity than the Schiff base. Copyright © 2014 Elsevier B.V. All rights reserved.

Chemistry in acetone complexes of metal dications: a remarkable ethylene production pathway.

PubMed

Wu, Jianhua; Liu, Dan; Zhou, Jian-Ge; Hagelberg, Frank; Park, Sung Soo; Shvartsburg, Alexandre A

2007-06-07

Electrospray ionization can generate microsolvated multiply charged metal ions for various metals and ligands, allowing exploration of chemistry within such clusters. The finite size of these systems permits comparing experimental results with accurate calculations, creating a natural laboratory to research ion solvation. Mass spectrometry has provided much insight into the stability and dissociation of ligated metal cations. While solvated singly charged ions tend to shrink by ligand evaporation, solvated polycations below a certain size exhibit charge reduction and/or ligand fragmentation due to organometallic reactions. Here we investigate the acetone complexes of representative divalent metals (Ca, Mn, Co, Ni, and Cu), comparing the results of collision-induced dissociation with the predictions of density functional theory. As for other solvated dications, channels involving proton or electron transfer compete with ligand loss and become dominant for smaller complexes. The heterolytic C-C bond cleavage is common, like in DMSO and acetonitrile complexes. Of primary interest is the unanticipated neutral ethylene loss, found for all metals studied except Cu and particularly intense for Ca and Mn. We focus on understanding that process in the context of competing dissociation pathways, as a function of metal identity and number of ligands. According to first-principles modeling, ethylene elimination proceeds along a complex path involving two intermediates. These results suggest that chemistry in microsolvated multiply charged ions may still hold major surprises.

Presentation on mechanisms and applications of chalcopyrite and pyrite bioleaching in biohydrometallurgy - a presentation.

PubMed

Tao, Huang; Dongwei, Li

2014-12-01

This review outlines classic and current research, scientific documents and research achievements in bioleaching, particularly in respect of the bioleaching of chalcopyrite and pyrite. The diversity and commonality of the microbial leaching process can be easily studied through comparing the bioleaching mechanism and the application of these two metal sulfides. The crystal, electronic and surface structures of chalcopyrite and pyrite are summarized in detail in this paper. It determines the specific and complicated interaction pathways, kinetics of the atmospheric/aqueous oxidation, and the control process of bioleaching of the minerals as the precondition. Bioleaching of metal sulfides is performed by a diverse group of microorganisms and microbial communities. The species of the bacteria which have a significant effect on leaching ores are miraculously diverse. The newly identified acidophilic microorganisms with unique characteristics for efficient bioleaching of sulfidic minerals are increasing sharply. The cell-to-cell communication mechanisms, which are still implicit, elusive and intangible at present day, have gradually become a research hotspot. The different mineralogy characteristics and the acid solubility of the metal sulfides (e.g., chalcopyrite and pyrite) cause two different dissolution pathways, the thiosulfate and the polysulfide pathways. The bioleaching mechanisms are categorized by contact (an electrostatic attachment) and noncontact (planktonic) process, with emphasis on the produce of extracellular polymeric substances and formation of biofilm on the surface of the metal sulfides in this paper. The division of the direct and indirect effect are not adopted due to the redox chain, the reduction of the ferric iron and oxidation of the ferrous iron. The molecular oxygen is reduced by the electrons extracted from the specific metal sulfide, via a redox chain forming a supercomplex spanning the periplasmic space and connecting both outer and inner membrane. The passivation of the mineral surface can obviously hinder the dissolution of metal sulfides during the bioleaching process, which is significantly affected by the kinetic model, microenvironment on the surface of ore and the leach conditions, such as temperature, pH and E h . The new development of mechanism research, enhanced and intensified technologies on the bioleaching of chalcopyrite and pyrite, are conducted and summarized from the different branches of natural science. Some are depicted and explained based on molecular level in this paper. Catalyst and catalytic mechanisms in bioleaching and biooxidation for this two sulfide minerals have been concluded and applied for several decades, the continuous emergence of the new material and technology are also gradually applied into the biohydrometallurgy. The industrial applications of the bioleaching on chalcopyrite and pyrite are totally based on the understanding of the interaction mechanism between microbes and minerals, the optimization of ore leaching conditions and the development of new material and the leaching equipment. It is not incredible and unimaginable to take a different bioleaching process and diagram to deal with the two sulfuric metals, which is vital to succeed in elevating the leaching rate of copper.

Infrared Spectroscopy of Metal Ion Complexes: Models for Metal Ligand Interactions and Solvation

NASA Astrophysics Data System (ADS)

Duncan, Michael

2006-03-01

Weakly bound complexes of the form M^+-Lx (M=Fe, Ni, Co, etc.; L=CO2, C2H2, H2O, benzene, N2) are prepared in supersonic molecular beams by laser vaporization in a pulsed-nozzle cluster source. These species are mass analyzed and size-selected in a reflectron time-of-flight mass spectrometer. Clusters are photodissociated at infrared wavelengths with a Nd:YAG pumped infrared optical parametric oscillator/amplifier (OPO/OPA) laser or with a tunable infrared free-electron laser. M^+-(CO2)x complexes absorb near the free CO2 asymmetric stretch near 2349 cm-1 but with an interesting size dependent variation in the resonances. Small clusters have blue-shifted resonances, while larger complexes have additional bands due to surface CO2 molecules not attached to the metal. M^+(C2H2)n complexes absorb near the C-H stretches in acetylene, but resonances in metal complexes are red-shifted with repect to the isolated molecule. Ni^+ and Co^+ complexes with acetylene undergo intracluster cyclization reactions to form cyclobutadiene. Transition metal water complexes are studied in the O-H stretch region, and partial rotational structure can be measured. M^+(benzene) and M^+(benzene)2 ions (M=V, Ti, Al) represent half-sandwich and sandwich species, whose spectra are measured near the free benzene modes. These new IR spectra and their assignments will be discussed as well as other new IR spectra for similar complexes.

[Ru(phen)2DPPZ]2+ is in contact with DNA bases when it forms a luminescent complex with single-stranded oligonucleotides.

PubMed

Moon, Seok Joon; Kim, Jong Moon; Choi, Ji Youn; Kim, Seog K; Lee, Je Seung; Jang, Ho G

2005-05-01

The luminescence intensity of the Delta- and Lambda-enantiomer of [Ru(phen)2DPPZ]2+ ([Ru(phenanthroline)2 dipyrido[3,2-a:2',3'-c]phenazine]2+) complex enhanced upon binding to double stranded DNA, which has been known as "light switch effect". The enhancement of the luminescence required the intercalation of the large ligand between DNA base pairs. In this study, we report the enhancement in the luminescence intensity when the metal complexes bind to single stranded oligonucleotides, indicating that the "light switch effect" does not require intercalation of the large DPPZ ligand. Oligonucleotides may provide a hydrophobic cavity for the [Ru(phen)2DPPZ]2+ complex to prevent the quenching by the water molecule. In the cavity, the metal complex is in contact with DNA bases as is evidenced by the observation that the excited energy of the DNA bases transfer to the bound metal complex. However, the contact of the metal complex with DNA bases is different from the stacking of DPPZ in the intercalation pocket. In addition to the normal two luminescence lifetimes, a short lifetime in the range of 1-2 ns was found for both the delta- and lambda-enantiomer of [Ru(phen)2DPPZ]2+ when complexed with single stranded oligonucleotides, which may be assigned to the metal complex that is outside of the cavity, interacting with phosphate groups of DNA.

Control of cerium oxidation state through metal complex secondary structures

DOE PAGES

Levin, Jessica R.; Dorfner, Walter L.; Carroll, Patrick J.; ...

2015-08-11

A series of alkali metal cerium diphenylhydrazido complexes, M x(py) y[Ce(PhNNPh) 4], M = Li, Na, and K, x = 4 (Li and Na) or 5 (K), and y = 4 (Li), 8 (Na), or 7 (K), were synthesized to probe how a secondary coordination sphere would modulate electronic structures at a cerium cation. The resulting electronic structures of the heterobimetallic cerium diphenylhydrazido complexes were found to be strongly dependent on the identity of the alkali metal cations. When M = Li + or Na +, the cerium(III) starting material was oxidized with concomitant reduction of 1,2-diphenylhydrazine to aniline. Reductionmore » of 1,2-diphenylhydrazine was not observed when M = K +, and the complex remained in the cerium(III) oxidation state. Oxidation of the cerium(III) diphenylhydrazido complex to the Ce( IV) diphenylhydrazido one was achieved through a simple cation exchange reaction of the alkali metals. As a result, UV-Vis spectroscopy, FTIR spectroscopy, electrochemistry, magnetic susceptibility, and DFT studies were used to probe the oxidation state and the electronic changes that occurred at the metal centre.« less

Novel metals and metal complexes as platforms for cancer therapy.

PubMed

Frezza, Michael; Hindo, Sarmad; Chen, Di; Davenport, Andrew; Schmitt, Sara; Tomco, Dajena; Dou, Q Ping

2010-06-01

Metals are essential cellular components selected by nature to function in several indispensable biochemical processes for living organisms. Metals are endowed with unique characteristics that include redox activity, variable coordination modes, and reactivity towards organic substrates. Due to their reactivity, metals are tightly regulated under normal conditions and aberrant metal ion concentrations are associated with various pathological disorders, including cancer. For these reasons, coordination complexes, either as drugs or prodrugs, become very attractive probes as potential anticancer agents. The use of metals and their salts for medicinal purposes, from iatrochemistry to modern day, has been present throughout human history. The discovery of cisplatin, cis-[Pt(II) (NH(3))(2)Cl(2)], was a defining moment which triggered the interest in platinum(II)- and other metal-containing complexes as potential novel anticancer drugs. Other interests in this field address concerns for uptake, toxicity, and resistance to metallodrugs. This review article highlights selected metals that have gained considerable interest in both the development and the treatment of cancer. For example, copper is enriched in various human cancer tissues and is a co-factor essential for tumor angiogenesis processes. However the use of copper-binding ligands to target tumor copper could provide a novel strategy for cancer selective treatment. The use of nonessential metals as probes to target molecular pathways as anticancer agents is also emphasized. Finally, based on the interface between molecular biology and bioinorganic chemistry the design of coordination complexes for cancer treatment is reviewed and design strategies and mechanisms of action are discussed.

Synthesis, spectroscopic characterization, thermal analysis and electrical conductivity studies of Mg(II), Ca(II), Sr(II) and Ba(II) vitamin B2 complexes

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Moussa, Mohamed A. A.; Mohamed, Soha F.

2011-05-01

Riboflavin (RF) complexes of Mg(II), Ca(II), Sr(II) and Ba(II) were successfully synthesized. Structures of metal complexes obtained were confirmed and characterized by elemental analysis, molar conductance, and infrared spectra. DC electrical conductivity measurements indicated that the alkaline earth metal (II) complexes of RF ligand are non-electrolytes. Elemental analysis of chelates suggest that the metal(II) ligand ratio is 1:2 with structure formula as [M(RF) 2( X) 2]· nH 2O. Infrared assignments clearly show that RF ligand coordinated as a bidentate feature through azomethine nitrogen of pyrazine ring and C dbnd O of pyrimidine-2,4-dione. Thermal analyses of Mg(II), Ca(II), Sr(II) and Ba(II) complexes were investigated using (TG/DSC) under atmospheric nitrogen between 30 and 800 °C. The surface morphology of the complexes was studied by SEM. The electrical conductivities of RF and its metal complexes were also measured with DC electrical conductivity in the temperature range from room to 483 K.

Synthesis, characterization and biological investigations of novel Schiff base ligands containing imidazoline moiety and their Co(II) and Cu(II) complexes

NASA Astrophysics Data System (ADS)

Radha, V. P.; Jone Kirubavathy, S.; Chitra, S.

2018-08-01

Novel imidazoline based Schiff base ligands L1 and L2 were synthesized from o-phenylenediamine/o-aminophenol with creatinine. The ligands were complexed with Co(II) and Cu(II) by direct reaction with metal salts. The synthesized ligands and the metal complexes were characterized by elemental analysis, FT-IR, 1H NMR, mass, electronic, thermal analyses, conductivity and magnetic susceptibility measurements. The conductivity measurements showed the non-electrolytic nature of the complexes. The thermogravimetric analyses confirmed the presence of lattice and coordinated water molecules in the complexes. The DFT calculations were carried out at B3LYP/6-31G(d,p) level for the determination of the optimized structure of the ligands. The synthesized ligands and the metal complexes were screened for their antimicrobial activity against two gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and two fungal strains (Aspergillus niger and Candida albicans). The outcomes revealed that the metal complexes showed pronounced activity than the ligands.

Designed topology and site-selective metal composition in tetranuclear [MM'...M'M] linear complexes.

PubMed

Barrios, Leoní A; Aguilà, David; Roubeau, Olivier; Gamez, Patrick; Ribas-Ariño, Jordi; Teat, Simon J; Aromí, Guillem

2009-10-26

The ligand 1,3-bis[3-oxo-3-(2-hydroxyphenyl)propionyl]benzene (H(4)L), designed to align transition metals into tetranuclear linear molecules, reacts with M(II) salts (M=Ni, Co, Cu) to yield complexes with the expected [MMMM] topology. The novel complexes [Co(4)L(2)(py)(6)] (2; py=pyridine) and [Na(py)(2)][Cu(4)L(2)(py)(4)](ClO(4)) (3) have been crystallographically characterised. The metal sites in complexes 2 and 3, together with previously characterised [Ni(4)L(2)(py)(6)] (1), favour different coordination geometries. These have been exploited for the deliberate synthesis of the heterometallic complex [Cu(2)Ni(2)L(2)(py)(6)] (4). Complexes 1, 2, 3 and 4 exhibit antiferromagnetic interactions between pairs of metals within each cluster, leading to S=0 spin ground states, except for the latter cluster, which features two quasi-independent S=1/2 moieties within the molecule. Complex 4 gathers the structural and physical conditions, thus allowing it to be considered as prototype of a two-qbit quantum gate.

Effect of the type of metal on the electrical conductivity and thermal properties of metal complexes: The relation between ionic radius of metal complexes and electrical conductivity

NASA Astrophysics Data System (ADS)

Morgan, Sh. M.; El-Ghamaz, N. A.; Diab, M. A.

2018-05-01

Co(II) complexes (1-4) and Ni(II) complexes (5-8) were prepared and characterized by elemental analysis, IR spectra and thermal analysis data. Thermal decomposition of all complexes was discussed using thermogravimetric analysis. The dielectric properties and alternating current conductivity were investigated in the frequency range 0.1-100 kHz and temperature range 300-660 K. The thermal activation energies of electrical conductivity (ΔE1 and ΔE2) values for complexes were calculated and discussed. The values of ΔE1 and ΔE2 for complexes (1-8) were found to decrease with increasing the frequency. Ac electrical conductivity (σac) values increases with increasing temperatures and the values of σac for Co(II) complexes are greater than Ni(II) complexes. Co(II) complexes showed a higher conductivity than other Ni(II) complexes due to the higher crystallinity as confirmed by X-ray diffraction analysis.

Thermometric titration of beta-aryl-alpha-mercaptopropenoic acids and determination of the stoichiometry of their metal complexes.

PubMed

Izquierdo, A; Carrasco, J

1981-05-01

Automatic thermometric titration was applied to some beta-aryl-alpha-mercaptopropenoic acids and the stoichiometry of their complexes with several metal ions was investigated. The heats of neutralization of the mercapto-acids with sodium hydroxide and the heats of their reaction with metal ions were calculated.

Manipulation of a Schlenk Line: Preparation of Tetrahydrofuran Complexes of Transition-Metal Chlorides

ERIC Educational Resources Information Center

Davis, Craig M.; Curran, Kelly A.

2007-01-01

Before taking an inorganic laboratory course few students have experience handling air-sensitive materials using Schlenk techniques. This exercise introduces them to techniques they will employ in later syntheses. The procedure involves the formation of anhydrous tetrahydrofuran complexes of transition-metal chlorides from metal-chloride hydrates;…

Combined effects of metal complexation and size expansion in the electronic structure of DNA base pairs

NASA Astrophysics Data System (ADS)

Brancolini, Giorgia; Di Felice, Rosa

2011-05-01

Novel DNA derivatives have been recently investigated in the pursuit of modified DNA duplexes to tune the electronic structure of DNA-based assemblies for nanotechnology applications. Size-expanded DNAs (e.g., xDNA) and metalated DNAs (M-DNA) may enhance stacking interactions and induce metallic conductivity, respectively. Here we explore possible ways of tailoring the DNA electronic structure by combining the aromatic size expansion with the metal-doping. We select the salient structures from our recent study on natural DNA pairs complexed with transition metal ions and consider the equivalent model configurations for xDNA pairs. We present the results of density functional theory electronic structure calculations of the metalated expanded base-pairs with various localized basis sets and exchange-correlation functionals. Implicit solvent and coordination water molecules are also included. Our results indicate that the effect of base expansion is largest in Ag-xGC complexes, while Cu-xGC complexes are the most promising candidates for nanowires with enhanced electron transfer and also for on-purpose modification of the DNA double-helix for signal detection.

A simple model for metal cation-phosphate interactions in nucleic acids in the gas phase: alkali metal cations and trimethyl phosphate.

PubMed

Ruan, Chunhai; Huang, Hai; Rodgers, M T

2008-02-01

Threshold collision-induced dissociation techniques are employed to determine the bond dissociation energies (BDEs) of complexes of alkali metal cations to trimethyl phosphate, TMP. Endothermic loss of the intact TMP ligand is the only dissociation pathway observed for all complexes. Theoretical calculations at the B3LYP/6-31G* level of theory are used to determine the structures, vibrational frequencies, and rotational constants of neutral TMP and the M+(TMP) complexes. Theoretical BDEs are determined from single point energy calculations at the B3LYP/6-311+G(2d,2p) level using the B3LYP/6-31G* optimized geometries. The agreement between theory and experiment is reasonably good for all complexes except Li+(TMP). The absolute M+-(TMP) BDEs are found to decrease monotonically as the size of the alkali metal cation increases. No activated dissociation was observed for alkali metal cation binding to TMP. The binding of alkali metal cations to TMP is compared with that to acetone and methanol.

Structural and Spectral Properties of Curcumin and Metal- Curcumin Complex Derived from Turmeric (Curcuma longa)

NASA Astrophysics Data System (ADS)

Bich, Vu Thi; Thuy, Nguyen Thi; Binh, Nguyen Thanh; Huong, Nguyen Thi Mai; Yen, Pham Nguyen Dong; Luong, Tran Thanh

Structural and spectral properties of curcumin and metal- curcumin complex derived from turmeric (Curcuma longa) were studied by SEM and vibrational (FTIR and Raman) techniques. By comparison between curcumin commercial, fresh turmeric and a yellow powder obtained via extraction and purification of turmeric, we have found that this insoluble powder in water is curcumin. The yellow compound could complex with certain ion metal and this metal-curcumin coloring complex is water soluble and capable of producing varying hues of the same colors and having antimicrobial, cytotoxicity activities for use in foodstuffs and pharmacy. The result also demonstrates that Micro-Raman spec-troscopy is a valuable non-destructive tool and fast for investigation of a natural plant even when occurring in low concentrations.

Metal complexes of substituted Gable porphyrins as oxidation catalysts

DOEpatents

Lyons, James E.; Ellis, Jr., Paul E.; Wagner, Richard W.

1996-01-01

Transition metal complexes of Gable porphyrins having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

Synthesis, Spectroscopic, and Antimicrobial Studies on Bivalent Nickel and Copper Complexes of Bis(thiosemicrbazone)

PubMed Central

Chandra, Sulekh; Raizada, Smriti; Tyagi, Monika; Gautam, Archana

2007-01-01

A series of metal complexes of Cu(II) and Ni(II) having the general composition [M(L)X2] with benzil bis(thiosemicarbazone) has been prepared and characterized by element chemical analysis, molar conductance, magnetic susceptibility measurements, and spectral (electronic, IR, EPR, mass) studies. The IR spectral data suggest the involvement of sulphur and azomethane nitrogen in coordination to the central metal ion. On the basis of spectral studies, an octahedral geometry has been assigned for Ni(II) complexes but a tetragonal geometry for Cu(II) complexes. The free ligand and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties. PMID:18273385

Quinonoid metal complexes: toward molecular switches.

PubMed

Dei, Andrea; Gatteschi, Dante; Sangregorio, Claudio; Sorace, Lorenzo

2004-11-01

The peculiar redox-active character of quinonoid metal complexes makes them extremely appealing to design materials of potential technological interest. We show here how the tuning of the properties of these systems can be pursued by using appropriate molecular synthetic techniques. In particular, we focus our attention on metal polyoxolene complexes exhibiting intramolecular electron transfer processes involving either the ligand and the metal ion or the two dioxolene moieties of a properly designed ligand thus inducing electronic bistability. The transition between the two metastable electronic states can be induced by different external stimuli such as temperature, pressure, light, or pH suggesting the use of these systems for molecular switches.

Revisiting Mn and Fe removal in humic rich estuaries

NASA Astrophysics Data System (ADS)

Oldham, Véronique E.; Miller, Megan T.; Jensen, Laramie T.; Luther, George W.

2017-07-01

Metal removal by estuarine mixing has been studied for several decades, but few studies emphasize dissolved metal speciation and organic ligand complexation. Findings from the last decade indicate that metal-humic complexation can be significant for dissolved metals including Cu(II), Al(III) and Fe(III), but little consideration is given to the precipitation of these complexes with humic material at pH < 2. Given that total soluble metal analysis involves an acidification step for sample preservation, we show that Mn and other metal concentrations may have been underestimated in estuaries, especially when humic substance concentrations are high. A competitive ligand assay of selected samples from our study site, a coastal waterway bordered by wetlands (Broadkill River, DE), showed that Mn(III)-humic complexation is significant, and that some Mn(III)-L complexes precipitate during acidification. In the oxygenated surface waters of the Broadkill River, total dissolved Mn (dMnT) was up to 100% complexed to ambient ligands as Mn(III)-L, and we present evidence for humic-type Mn(III)-L complexes. The Mn(III) complexes were kinetically stabilized against Fe(II) reduction, even when [Fe(II)] was 17 times higher than [dMnT]. Unlike typical oceanic surface waters, [Fe(II)] > [Fe(III)-L] in surface waters, which may be attributed to high rates of photoreduction of Fe(III)-L complexes. Total [Mn(III)-L] ranged from 0.22 to 8.4 μM, in excess of solid MnOx (below 0.28 μM in all samples). Filtration of samples through 0.02 μm filters indicated that all Mn(III)-L complexes pass through the filters and were not colloidal species in contrast to dissolved Fe. Incubation experiments indicated that the reductive dissolution of solid MnOx by ambient ligands may be responsible for Mn(III) formation in this system. Unlike previous studies of estuarine mixing, which demonstrated metal removal during mixing, we show significant export of dMn and dissolved Fe (dFe) in the summer and fall of 2015. Thus, we propose that estuarine removal should be considered seasonal for dMn and dFe, with export in the summer and fall and removal during the winter.

Syntheses, structures, and properties of trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)], constructed with the complexed bridging ligand [M(bpca)(2)] [M, M' = Ni(II), Mn(II); Cu(II), Mn(II); Fe(II), Mn(II); Ni(II), Fe(II); and Fe(II), Fe(II); Hbpca = Bis(2-pyridylcarbonyl)amine, Hhfac = Hexafluoroacetylacetone].

PubMed

Kamiyama, Asako; Noguchi, Tomoko; Kajiwara, Takashi; Ito, Tasuku

2002-02-11

Five trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)] (where MM'(2) = NiMn(2), CuMn(2), FeMn(2), NiFe(2), and FeFe(2); Hbpca = bis(2-pyridylcarbonyl)amine; and Hhfac = hexafluoroacetylacetone) were synthesized almost quantitatively by the reaction of [M(bpca)(2)] and [M'(hfac)(2)] in 1:2 molar ratio, and their structures and magnetic properties were investigated. Three complexes, with M' = Mn, crystallize in the same space group, Pna2(1), whereas two complexes, with M' = Fe, crystallize in P4(1), and complexes within each set are isostructural to one another. In all complexes, [M(bpca)(2)] acts as a bis-bidentate bridging ligand to form a linear trinuclear complex in which three metal ions are arranged in the manner M'-M-M'. The central metal ion is in a strong ligand field created by the N(6) donor set, and hence the Fe(II) in the [Fe(bpca)(2)] moiety is in a low-spin state. The terminal metal ions (M') are surrounded by O(6) donor sets with a moderate ligand field, which leads to the high-spin configuration of Fe(II). Three metal ions in all complexes are almost collinear, and metal-metal distances are ca. 5.5 A. The magnetic behavior of NiMn(2) and NiFe(2) shows a weak ferromagnetic interaction between the central Ni(II) ion and the terminal Mn(II) or Fe(II) ions. In these complexes, sigma-spin orbitals of the central Ni(II) ion and those of terminal metal ions have different symmetry about a 2-fold rotation axis through the Ni-N(amide)-M'(terminal) atoms, and this results in orthogonality between the neighboring sigma-spin orbitals and thus ferromagnetic interactions.

Molecular modelling, spectroscopic characterization and biological studies of tetraazamacrocyclic metal complexes

NASA Astrophysics Data System (ADS)

Rathi, Parveen; Sharma, Kavita; Singh, Dharam Pal

2014-09-01

Macrocyclic complexes of the type [MLX]X2; where L is (C30H28N4), a macrocyclic ligand, M = Cr(III) and Fe(III) and X = Cl-, CH3COO- or NO3-, have been synthesized by template condensation reaction of 1,8-diaminonaphthalene and acetylacetone in the presence of trivalent metal salts in a methanolic medium. The complexes have been formulated as [MLX]X2 due to 1:2 electrolytic nature of these complexes. The complexes have been characterized with the help of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, electronic, infrared, far infrared, Mass spectral studies and molecular modelling. Molecular weight of these complexes indicates their monomeric nature. On the basis of all these studies, a five coordinated square pyramidal geometry has been proposed for all these complexes. These metal complexes have also been screened for their in vitro antimicrobial activities.

Ga metal nanoparticle-GaAs quantum molecule complexes for Terahertz generation.

PubMed

Bietti, Sergio; Basso Basset, Francesco; Scarpellini, David; Fedorov, Alexey; Ballabio, Andrea; Esposito, Luca; Elborg, Martin; Kuroda, Takashi; Nemcsics, Akos; Toth, Lajos; Manzoni, Cristian; Vozzi, Caterina; Sanguinetti, Stefano

2018-06-18

A hybrid metal-semiconductor nanosystem for the generation of THz radiation, based on the fabrication of GaAs quantum molecules-Ga metal nanoparticles complexes through a self assembly approach, is proposed. The role of the growth parameters, the substrate temperature, the Ga and As flux during the quantum dot molecule fabrication and the metal nanoparticle alignment is discussed. The tuning of the relative positioning of quantum dot molecules and metal nanoparticles is obtained through the careful control of Ga droplet nucleation sites via Ga surface diffusion. The electronic structure of a typical quantum dot molecule was evaluated on the base of the morphological characterizations performed by Atomic Force Microscopy and cross sectional Scanning Electron Microscopy, and the predicted results confirmed by micro-photoluminescence experiments, showing that the Ga metal nanoparticle-GaAs quantum molecule complexes are suitable for terahertz generation from intraband transition. . © 2018 IOP Publishing Ltd.

Sulfur-induced structural motifs on copper and gold surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walen, Holly

The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. The experimental observations presented here—made under identical conditions—together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence ofmore » metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.« less

Evidence for single metal two electron oxidative addition and reductive elimination at uranium.

PubMed

Gardner, Benedict M; Kefalidis, Christos E; Lu, Erli; Patel, Dipti; McInnes, Eric J L; Tuna, Floriana; Wooles, Ashley J; Maron, Laurent; Liddle, Stephen T

2017-12-01

Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido complex in a reaction that satisfies all criteria of a single-metal two-electron oxidative addition. Thermolysis of this complex promotes extrusion of azobenzene, where H-/D-isotopic labelling finds no isotopomer cross-over and the non-reactivity of a nitrene-trap suggests that nitrenes are not generated and thus a reductive elimination has occurred. Though not optimally balanced in this case, this work presents evidence that classical d-block redox chemistry can be performed reversibly by f-block metals, and that uranium can thus mimic elementary transition metal reactivity, which may lead to the discovery of new f-block catalysis.

Pesticides Curbing Soil Fertility: Effect of Complexation of Free Metal Ions.

PubMed

Kaur, Sukhmanpreet; Kumar, Vijay; Chawla, Mohit; Cavallo, Luigi; Poater, Albert; Upadhyay, Niraj

2017-01-01

Researchers have suggested that the reason behind infertility is pernicious effect of broad spectrum pesticides on non target, beneficial microorganism of soil. Here, studying the chelating effect of selective organophosphate and carbamate pesticides with essential metal ions, at all possible combinations of three different pH (4 ± 0.05, 7 ± 0.05 and 9 ± 0.05) and three different temperatures (15 ± 0.5°C, 30 ± 0.5°C and 45 ± 0.5°C), shows very fast rate of reaction which further increases with increase of pH and temperature. Carbonyl oxygen of carbamate and phosphate oxygen of organophosphate were found to be common ligating sites among all the complexes. Formed metal complexes were found to be highly stable and water insoluble on interaction with essential metal ions in solvent medium as well as over silica. Density functional theory (DFT) calculations not only reinforced the experimental observations, but, after a wide computational conformational analysis, unraveled the nature of the high stable undesired species that consist of pesticides complexed by metal ions from the soil. All in all, apart from the direct toxicity of pesticides, the indirect effect by means of complexation of free metal ions impoverishes the soil.

Pesticides Curbing Soil Fertility: Effect of Complexation of Free Metal Ions

NASA Astrophysics Data System (ADS)

Kaur, Sukhmanpreet; Kumar, Vijay; Chawla, Mohit; Cavallo, Luigi; Poater, Albert; Upadhyay, Niraj

2017-07-01

Researchers have suggested that the reason behind infertility is pernicious effect of broad spectrum pesticides on non target, beneficial microorganism of soil. Here, studying the chelating effect of selective organophosphate and carbamate pesticides with essential metal ions, at all possible combinations of three different pH (4±0.05, 7±0.05 and 9±0.05) and three different temperatures (15±0.5°C, 30±0.5°C and 45±0.5°C), shows very fast rate of reaction which further increases with increase of pH and temperature. Carbonyl oxygen of carbamate and phosphate oxygen of organophosphate were found to be common ligating sites among all the complexes. Formed metal complexes were found to be highly stable and water insoluble on interaction with essential metal ions in solvent medium as well as over silica. Density functional theory (DFT) calculations not only reinforced the experimental observations, but, after a wide computational conformational analysis, unraveled the nature of the high stable undesired species that consist of pesticides complexed by metal ions from the soil. All in all, apart from the direct toxicity of pesticides, the indirect effect by means of complexation of free metal ions impoverishes the soil.

Photoactivatable metal complexes: from theory to applications in biotechnology and medicine.

PubMed

Smith, Nichola A; Sadler, Peter J

2013-07-28

This short review highlights some of the exciting new experimental and theoretical developments in the field of photoactivatable metal complexes and their applications in biotechnology and medicine. The examples chosen are based on some of the presentations at the Royal Society Discussion Meeting in June 2012, many of which are featured in more detail in other articles in this issue. This is a young field. Even the photochemistry of well-known systems such as metal-carbonyl complexes is still being elucidated. Striking are the recent developments in theory and computation (e.g. time-dependent density functional theory) and in ultrafast-pulsed radiation techniques which allow photochemical reactions to be followed and their mechanisms to be revealed on picosecond/nanosecond time scales. Not only do some metal complexes (e.g. those of Ru and Ir) possess favourable emission properties which allow functional imaging of cells and tissues (e.g. DNA interactions), but metal complexes can also provide spatially controlled photorelease of bioactive small molecules (e.g. CO and NO)--a novel strategy for site-directed therapy. This extends to cancer therapy, where metal-based precursors offer the prospect of generating excited-state drugs with new mechanisms of action that complement and augment those of current organic photosensitizers.

Bioavailability of cyanide and metal-cyanide mixtures to aquatic life.

PubMed

Redman, Aaron; Santore, Robert

2012-08-01

Cyanide can be toxic to aquatic organisms, and the U.S. Environmental Protection Agency has developed ambient water-quality criteria to protect aquatic life. Recent work suggests that considering free, rather than total, cyanide provides a more accurate measure of the biological effects of cyanides and provides a basis for water-quality criteria. Aquatic organisms are sensitive to free cyanide, although certain metals can form stable complexes and reduce the amount of free cyanide. As a result, total cyanide is less toxic when complexing metals are present. Cyanide is often present in complex effluents, which requires understanding how other components within these complex effluents can affect cyanide speciation and bioavailability. The authors have developed a model to predict the aqueous speciation of cyanide and have shown that this model can predict the toxicity of metal-cyanide complexes in terms of free cyanide in solutions with varying water chemistry. Toxicity endpoints based on total cyanide ranged over several orders of magnitude for various metal-cyanide mixtures. However, predicted free cyanide concentrations among these same tests described the observed toxicity data to within a factor of 2. Aquatic toxicity can be well-described using free cyanide, and under certain conditions the toxicity was jointly described by free cyanide and elevated levels of bioavailable metals. Copyright © 2012 SETAC.

Macrocyclic metal complexes for metalloenzyme mimicry and sensor development.

PubMed

Joshi, Tanmaya; Graham, Bim; Spiccia, Leone

2015-08-18

Examples of proteins that incorporate one or more metal ions within their structure are found within a broad range of classes, including oxidases, oxidoreductases, reductases, proteases, proton transport proteins, electron transfer/transport proteins, storage proteins, lyases, rusticyanins, metallochaperones, sporulation proteins, hydrolases, endopeptidases, luminescent proteins, iron transport proteins, oxygen storage/transport proteins, calcium binding proteins, and monooxygenases. The metal coordination environment therein is often generated from residues inherent to the protein, small exogenous molecules (e.g., aqua ligands) and/or macrocyclic porphyrin units found, for example, in hemoglobin, myoglobin, cytochrome C, cytochrome C oxidase, and vitamin B12. Thus, there continues to be considerable interest in employing macrocyclic metal complexes to construct low-molecular weight models for metallobiosites that mirror essential features of the coordination environment of a bound metal ion without inclusion of the surrounding protein framework. Herein, we review and appraise our research exploring the application of the metal complexes formed by two macrocyclic ligands, 1,4,7-triazacyclononane (tacn) and 1,4,7,10-tetraazacyclododecane (cyclen), and their derivatives in biological inorganic chemistry. Taking advantage of the kinetic inertness and thermodynamic stability of their metal complexes, these macrocyclic scaffolds have been employed in the development of models that aid the understanding of metal ion-binding natural systems, and complexes with potential applications in biomolecule sensing, diagnosis, and therapy. In particular, the focus has been on "coordinatively unsaturated" metal complexes that incorporate a kinetically inert and stable metal-ligand moiety, but which also contain one or more weakly bound ligands, allowing for the reversible binding of guest molecules via the formation and dissociation of coordinate bonds. With regards to mimicking metallobiosites, examples are presented from our work on tacn-based complexes developed as simplified structural models for multimetallic enzyme sites. In particular, structural comparisons are made between multinuclear copper(II) complexes formed by such ligands and multicopper enzymes featuring type-2 and type-3 copper centers, such as ascorbate oxidase (AO) and laccase (Lc). Likewise, with the aid of relevant examples, we highlight the importance of cooperativity between either multiple metal centers or a metal center and a proximal auxiliary unit appended to the macrocyclic ligand in achieving efficient phosphate ester cleavage. Finally, the critical importance of the Zn(II)-imido and Zn(II)-phosphate interactions in Zn-cyclen-based systems for delivering highly sensitive electrochemical and fluorescent chemosensors is also showcased. The Account additionally highlights some of the factors that limit the performance of these synthetic nucleases and the practical application of the biosensors, and then identifies some avenues for the development of more effective macrocyclic constructs in the future.

A tritopic carbanionic N-heterocyclic dicarbene and its homo- and heterometallic coinage metal complexes.

PubMed

Zhang, Fan; Cao, Xiao-Ming; Wang, Jiwei; Jiao, Jiajun; Huang, Yongming; Shi, Min; Braunstein, Pierre; Zhang, Jun

2018-05-21

Homo (Au3)- and heterotrinuclear coinage metal complexes (Au2Ag and Au2Cu) ligated by the first tritopic carbanionic N-heterocyclic carbene (NHC) have been prepared by deprotonation of ditopic NHC digold complexes and structurally characterized by single-crystal X-ray diffraction.

An Experiment on Isomerism in Metal-Amino Acid Complexes.

ERIC Educational Resources Information Center

Harrison, R. Graeme; Nolan, Kevin B.

1982-01-01

Background information, laboratory procedures, and discussion of results are provided for syntheses of cobalt (III) complexes, I-III, illustrating three possible bonding modes of glycine to a metal ion (the complex cations II and III being linkage/geometric isomers). Includes spectrophotometric and potentiometric methods to distinguish among the…

Metal complexes of substituted Gable porphyrins as oxidation catalysts

DOEpatents

Lyons, J.E.; Ellis, P.E. Jr.; Wagner, R.W.

1996-01-02

Transition metal complexes of Gable porphyrins are disclosed having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

Pharmacologically significant complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) of novel Schiff base ligand, (E)-N-(furan-2-yl methylene) quinolin-8-amine: Synthesis, spectral, XRD, SEM, antimicrobial, antioxidant and in vitro cytotoxic studies

NASA Astrophysics Data System (ADS)

Shakir, M.; Hanif, Summaiya; Sherwani, Mohd. Asif; Mohammad, Owais; Al-Resayes, Saud I.

2015-07-01

A novel series of metal complexes of the types, [ML2(H2O)2]Cl2 and [ML2]Cl2 [M = Mn(II), 1; Co(II), 2; Ni(II), 3; Cu(II), 4; and Zn(II), 5] were synthesized by the interaction of ligand, L (E)-N-(furan-2-yl methylene) quinolin-8-amine, derived from the condensation of 2-furaldehyde and 8-aminoquinoline. The synthesized ligand and its metal complexes were characterized on the basis of results obtained from elemental analysis, ESI-MS, XRD, SEM, TGA/DTA, FT-IR, UV-Vis, magnetic moment and 1H and 13C NMR spectroscopic studies. EPR parameters were recorded in case of complex 4. The comparative in-vitro antimicrobial activities against various pathogens with reference to known antibiotics and antioxidant activity against standard control at variable concentrations revealed that the metal complexes show enhanced antimicrobial and free radical scavenging activities in general as compared to free ligand. However, the complexes 1 and 5 have shown best antioxidant activity among all the metal complexes. Furthermore, comparative in-vitro antiproliferative activity on ligand and its metal chelates performed on MDA-MB-231 (breast carcinoma), KCL22 (blood lymphoid carcinoma), HeLa (cervical carcinoma) cell lines and normal cells (PBMC) revealed that metal chelates show moderate to good activity as compared to ligand where as complex 1 seems to be the most promising one possessing a broad spectrum of activity against all the selected cancer cell lines with IC50 < 2.10 μM.

Interaction of d(10) metal ions with thioether ligands: a thermodynamic and theoretical study.

PubMed

Melchior, Andrea; Peralta, Elena; Valiente, Manuel; Tavagnacco, Claudio; Endrizzi, Francesco; Tolazzi, Marilena

2013-05-07

Thermodynamic parameters of complex formation between d(10) metal ions, such as Zn(2+), Cd(2+), Hg(2+) and Ag(+), and the macrocyclic thioether 1,4,7-trithiacyclononane ([9]AneS3) or the monodentate diethylsulfide (Et(2)S), in acetonitrile (AN) at 298.15 K, were studied by a systematic methodology including potentiometry, calorimetry and polarography. [9]AneS3 is able to form complexes with all the target cations, Et(2)S only reacts with Hg(2+) and Ag(+). Mononuclear ML(j) (j = 1, 2) complexes are formed with all the metal ions investigated, where the affinity order is Hg(2+) > Ag(+) > Cd(2+) ≈ Zn(2+) when L = [9]AneS3 and Hg(2+) > Ag(+) when L = Et(2)S. Enthalpy and entropy values are generally negative, as a consequence of both metal ion interactions with neutral ligands, the reagents' loss of degrees of freedom and the release of solvating molecules. DFT calculations on the complexes formed with [9]AneS3 in vacuum and in AN are also carried out, to correlate experimental and theoretical thermodynamic values and to highlight the interplay between the direct metal-thioether interaction and the solvation effects. Trends obtained for the stability constants and enthalpies of the 1 : 1 and 1 : 2 complexes in solvent well reproduce the experimental ones for all the divalent metal ion complexes with [9]AneS3 and indicate the release of 3 AN molecules in the formation of each consecutive octahedral complex. In addition, calculated and experimental values for Ag(+) complex formation in solution suggest that in AgL(2) species [9]AneS3 ligands are not both tridentate.

Preparation, characterization and biological activity of novel metal-NNNN donor Schiff base complexes

NASA Astrophysics Data System (ADS)

Mohamed, Gehad G.; Omar, M. M.; Ibrahim, Amr A.

2010-02-01

Novel Schiff base (H 2L) ligand is prepared via condensation of benzil and triethylenetetraamine. The ligand is characterized based on elemental analysis, mass, IR and 1H NMR spectra. Metal complexes are reported and characterized based on elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). 1:1 [M]:[H 2L] complexes are found from the elemental analyses data having the formulae [M(H 2L)Cl 2]· yH 2O (M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II)), [Fe(H 2L)Cl 2]Cl·H 2O, [Th(H 2L)Cl 2]Cl 2·3H 2O and [UO 2(H 2L)](CH 3COO) 2·2H 2O. The metal chelates are found to be non-electrolytes except Fe(III), Th(IV) and UO 2(II) complexes are electrolytes. IR spectra show that H 2L is coordinated to the metal ions in a neutral tetradentate manner with 4Ns donor sites of the two azomethine N and two NH groups. The geometrical structures of these complexes are found to be octahedral. The thermal behaviour of these chelates is studied where the hydrated complexes lose water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters are calculated using Coats-Redfern method. The ligand (H 2L), in comparison to its metal complexes, is screened for its antibacterial activity. The activity data show that the metal complexes have antibacterial activity more than the parent Schiff base ligand and cefepime standard against one or more bacterial species.

Metal-metal bond lengths in complexes of transition metals*

PubMed Central

Pauling, Linus

1976-01-01

In complexes of the transition metals containing clusters of metal atoms the cobalt-cobalt bond lengths are almost always within 1 pm of the single-bond value 246 pm given by the enneacovalent radius of cobalt, whereas most of the observed iron-iron bond lengths are significantly larger than the single-bond value 248 pm, the mean being 264 pm, which corresponds to a half-bond. A simple discussion of the structures of these complexes based on spd hybrid orbitals, the electroneutrality principle, and the partial ionic character of bonds between unlike atoms leads to the conclusion that resonance between single bonds and no-bonds would occur for iron and its congeners but not for cobalt and its congeners, explaining the difference in the bond lengths. PMID:16592368

Macrocycles

DOEpatents

Raymond, Kenneth N.; Xu, Jide; Pham, Tiffany A.

2016-09-13

The invention provides macrocycles useful in chelating metal ions, particularly radionuclides, to provide metal ion complexes. The invention also provides methods of using the compounds and complexes of the invention, such as in therapeutic and diagnostic applications.

Chromium complexes for luminescence, solar cells, photoredox catalysis, upconversion, and phototriggered NO release

PubMed Central

Büldt, Laura A.

2017-01-01

Some complexes of Cr(iii) and Cr(0) have long been known to exhibit interesting photophysical and photochemical properties, but in the past few years important conceptual progress was made. This Perspective focuses on the recent developments of Cr(iii) complexes as luminophores and dyes for solar cells, their application in photoredox catalysis, their use as sensitizers in upconversion processes, and their performance as photochemical nitric oxide sources. The example of a luminescent Cr(0) isocyanide complex illustrates the possibility of obtaining photoactive analogues of d6 metal complexes that are commonly made from precious metals such as Ru(ii) or Ir(iii). The studies highlighted herein illustrate the favorable excited-state properties of robust first-row transition metal complexes with broad application potential. PMID:29163886

Chromium complexes for luminescence, solar cells, photoredox catalysis, upconversion, and phototriggered NO release.

PubMed

Büldt, Laura A; Wenger, Oliver S

2017-11-01

Some complexes of Cr(iii) and Cr(0) have long been known to exhibit interesting photophysical and photochemical properties, but in the past few years important conceptual progress was made. This Perspective focuses on the recent developments of Cr(iii) complexes as luminophores and dyes for solar cells, their application in photoredox catalysis, their use as sensitizers in upconversion processes, and their performance as photochemical nitric oxide sources. The example of a luminescent Cr(0) isocyanide complex illustrates the possibility of obtaining photoactive analogues of d 6 metal complexes that are commonly made from precious metals such as Ru(ii) or Ir(iii). The studies highlighted herein illustrate the favorable excited-state properties of robust first-row transition metal complexes with broad application potential.

Synthesis, spectroscopic characterization, electrochemistry and biological evaluation of some metal (II) complexes with ONO donor ligand containing benzo[b]thiophene and coumarin moieties

NASA Astrophysics Data System (ADS)

Mahendra Raj, K.; Mruthyunjayaswamy, B. H. M.

2014-09-01

Schiff base ligand 3-chloro-N‧-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzo[b]thiophene-2-carbohydrazide and its Cu(II), Co(II), Ni(II) and Zn(II) complexes were synthesized, characterized by elemental analysis and various physico-chemical techniques like, IR, 1H NMR, ESI-mass, UV-Visible, thermogravimetry - differential thermal analysis, magnetic measurements and molar conductance. Spectral analysis indicates octahedral geometry for all the complexes. Cu(II) complex have 1:1 stoichiometry of the type [M(L)(Cl)(H2O)2], whereas Co(II), Ni(II) and Zn(II) complexes have 1:2 stoichiometric ratio of the type [M(L)2]. The bonding sites are the oxygen atom of amide carbonyl, nitrogen of azomethine function and phenolic oxygen of the Schiff base ligand via deprotonation. The thermogravimetry - differential thermal analysis studies gave evidence for the presence of coordinated water molecules in the composition of Cu(II) complex which was further supported by IR measurements. All the complexes were investigated for their electrochemical activity, but only the Cu(II) complex showed the redox property. In order to evaluate the effect of antimicrobial potency of metal ions upon chelation, ligand and its metal complexes along with their respective metal chlorides were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The results showed that the metal complexes were found to be more active than free ligand. Ligand and its complexes were screened for free radical scavenging activity by DPPH method and DNA cleavage activity using Calf-thymus DNA (Cat. No-105850).

Genome-Enabled Studies of Anaerobic, Nitrate-Dependent Iron Oxidation in the Chemolithoautotrophic Bacterium Thiobacillus denitrificans

NASA Astrophysics Data System (ADS)

Beller, H. R.; Zhou, P.; Legler, T. C.; Chakicherla, A.; O'Day, P. A.

2013-12-01

Thiobacillus denitrificans is a chemolithoautotrophic bacterium capable of anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, both of which can strongly influence the long-term efficacy of in situ reductive immobilization of uranium in contaminated aquifers. We previously identified two c-type cytochromes involved in nitrate-dependent U(IV) oxidation in T. denitrificans and hypothesized that c-type cytochromes would also catalyze Fe(II) oxidation, as they have been found to play this role in anaerobic phototrophic Fe(II)-oxidizing bacteria. Here we report on efforts to identify genes associated with nitrate-dependent Fe(II) oxidation, namely (a) whole-genome transcriptional studies [using FeCO3, Fe2+, and U(IV) oxides as electron donors under denitrifying conditions], (b) Fe(II) oxidation assays performed with knockout mutants targeting primarily highly expressed or upregulated c-type cytochromes, and (c) random transposon-mutagenesis studies with screening for Fe(II) oxidation. Assays of mutants for 26 target genes, most of which were c-type cytochromes, indicated that none of the mutants tested were significantly defective in nitrate-dependent Fe(II) oxidation. The non-defective mutants included the c1-cytochrome subunit of the cytochrome bc1 complex (complex III), which has relevance to a previously proposed role for this complex in nitrate-dependent Fe(II) oxidation and to current concepts of reverse electron transfer. Of the transposon mutants defective in Fe(II) oxidation, one mutant with a disrupted gene associated with NADH:ubiquinone oxidoreductase (complex I) was ~35% defective relative to the wild-type strain; this strain was similarly defective in nitrate reduction with thiosulfate as the electron donor. Overall, our results indicate that nitrate-dependent Fe(II) oxidation in T. denitrificans is not catalyzed by the same c-type cytochromes involved in U(IV) oxidation, nor have other c-type cytochromes yet been implicated in the process.

Genome-enabled studies of anaerobic, nitrate-dependent iron oxidation in the chemolithoautotrophic bacterium Thiobacillus denitrificans

PubMed Central

Beller, Harry R.; Zhou, Peng; Legler, Tina C.; Chakicherla, Anu; Kane, Staci; Letain, Tracy E.; A. O’Day, Peggy

2013-01-01

Thiobacillus denitrificans is a chemolithoautotrophic bacterium capable of anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, both of which can strongly influence the long-term efficacy of in situ reductive immobilization of uranium in contaminated aquifers. We previously identified two c-type cytochromes involved in nitrate-dependent U(IV) oxidation in T. denitrificans and hypothesized that c-type cytochromes would also catalyze Fe(II) oxidation, as they have been found to play this role in anaerobic phototrophic Fe(II)-oxidizing bacteria. Here we report on efforts to identify genes associated with nitrate-dependent Fe(II) oxidation, namely (a) whole-genome transcriptional studies [using FeCO3, Fe2+, and U(IV) oxides as electron donors under denitrifying conditions], (b) Fe(II) oxidation assays performed with knockout mutants targeting primarily highly expressed or upregulated c-type cytochromes, and (c) random transposon-mutagenesis studies with screening for Fe(II) oxidation. Assays of mutants for 26 target genes, most of which were c-type cytochromes, indicated that none of the mutants tested were significantly defective in nitrate-dependent Fe(II) oxidation. The non-defective mutants included the c1-cytochrome subunit of the cytochrome bc1 complex (complex III), which has relevance to a previously proposed role for this complex in nitrate-dependent Fe(II) oxidation and to current concepts of reverse electron transfer. A transposon mutant with a disrupted gene associated with NADH:ubiquinone oxidoreductase (complex I) was ~35% defective relative to the wild-type strain; this strain was similarly defective in nitrate reduction with thiosulfate as the electron donor. Overall, our results indicate that nitrate-dependent Fe(II) oxidation in T. denitrificans is not catalyzed by the same c-type cytochromes involved in U(IV) oxidation, nor have other c-type cytochromes yet been implicated in the process. PMID:24065960

Quantitation of proteins using a dye-metal-based colorimetric protein assay.

PubMed

Antharavally, Babu S; Mallia, Krishna A; Rangaraj, Priya; Haney, Paul; Bell, Peter A

2009-02-15

We describe a dye-metal (polyhydroxybenzenesulfonephthalein-type dye and a transition metal) complex-based total protein determination method. The binding of the complex to protein causes a shift in the absorption maximum of the dye-metal complex from 450 to 660 nm. The dye-metal complex has a reddish brown color that changes to green on binding to protein. The color produced from this reaction is stable and increases in a proportional manner over a broad range of protein concentrations. The new Pierce 660 nm Protein Assay is very reproducible, rapid, and more linear compared with the Coomassie dye-based Bradford assay. The assay reagent is room temperature stable, and the assay is a simple and convenient mix-and-read format. The assay has a moderate protein-to-protein variation and is compatible with most detergents, reducing agents, and other commonly used reagents. This is an added advantage for researchers needing to determine protein concentrations in samples containing both detergents and reducing agents.

Applicability study of classical and contemporary models for effective complex permittivity of metal powders.

PubMed

Kiley, Erin M; Yakovlev, Vadim V; Ishizaki, Kotaro; Vaucher, Sebastien

2012-01-01

Microwave thermal processing of metal powders has recently been a topic of a substantial interest; however, experimental data on the physical properties of mixtures involving metal particles are often unavailable. In this paper, we perform a systematic analysis of classical and contemporary models of complex permittivity of mixtures and discuss the use of these models for determining effective permittivity of dielectric matrices with metal inclusions. Results from various mixture and core-shell mixture models are compared to experimental data for a titanium/stearic acid mixture and a boron nitride/graphite mixture (both obtained through the original measurements), and for a tungsten/Teflon mixture (from literature). We find that for certain experiments, the average error in determining the effective complex permittivity using Lichtenecker's, Maxwell Garnett's, Bruggeman's, Buchelnikov's, and Ignatenko's models is about 10%. This suggests that, for multiphysics computer models describing the processing of metal powder in the full temperature range, input data on effective complex permittivity obtained from direct measurement has, up to now, no substitute.

Redox activation of metal-based prodrugs as a strategy for drug delivery

PubMed Central

Graf, Nora

2012-01-01

This review provides an overview of metal-based anticancer drugs and drug candidates. In particular, we focus on metal complexes that can be activated in the reducing environment of cancer cells, thus serving as prodrugs. There are many reports of Pt and Ru complexes as redox-activatable drug candidates, but other d-block elements with variable oxidation states have a similar potential to serve as prodrugs in this manner. In this context are compounds based on Fe, Co, or Cu chemistry, which are also covered. A trend in the field of medicinal inorganic chemistry has been toward molecularly targeted, metal-based drugs obtained by functionalizing complexes with biologically active ligands. Another recent activity is the use of nanomaterials for drug delivery, exploiting passive targeting of tumors with nanosized constructs made from Au, Fe, carbon, or organic polymers. Although complexes of all of the above mentioned metals will be described, this review focuses primarily on Pt compounds, including constructs containing nanomaterials. PMID:22289471

Synthesis, Characterization and Biological Evaluation of Transition Metal Complexes Derived from N, S Bidentate Ligands

PubMed Central

Md Yusof, Enis Nadia; Ravoof, Thahira Begum S. A.; Tiekink, Edward R. T.; Veerakumarasivam, Abhimanyu; Crouse, Karen Anne; Mohamed Tahir, Mohamed Ibrahim; Ahmad, Haslina

2015-01-01

Two bidentate NS ligands were synthesized by the condensation reaction of S-2-methylbenzyldithiocarbazate (S2MBDTC) with 2-methoxybenzaldehyde (2MB) and 3-methoxybenzaldehyde (3MB). The ligands were reacted separately with acetates of Cu(II), Ni(II) and Zn(II) yielding 1:2 (metal:ligand) complexes. The metal complexes formed were expected to have a general formula of [M(NS)2] where M = Cu2+, Ni2+, and Zn2+. These compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and various spectroscopic techniques. The magnetic susceptibility measurements and spectral results supported the predicted coordination geometry in which the Schiff bases behaved as bidentate NS donor ligands coordinating via the azomethine nitrogen and thiolate sulfur. The molecular structures of the isomeric S2M2MBH (1) and S2M3MBH (2) were established by X-ray crystallography to have very similar l-shaped structures. The Schiff bases and their metal complexes were evaluated for their biological activities against estrogen receptor-positive (MCF-7) and estrogen receptor-negative (MDA-MB-231) breast cancer cell lines. Only the Cu(II) complexes showed marked cytotoxicity against the cancer cell lines. Both Schiff bases and other metal complexes were found to be inactive. In concordance with the cytotoxicity studies, the DNA binding studies indicated that Cu(II) complexes have a strong DNA binding affinity. PMID:25988384

Antimicrobial Applications of Transition Metal Complexes of Benzothiazole Based Terpolymer: Synthesis, Characterization, and Effect on Bacterial and Fungal Strains

PubMed Central

Riswan Ahamed, Mohamed A.; Azarudeen, Raja S.; Kani, N. Mujafar

2014-01-01

Terpolymer of 2-amino-6-nitro-benzothiazole-ethylenediamine-formaldehyde (BEF) has been synthesized and characterized by elemental analysis and various spectral techniques like FTIR, UV-Visible, and 1H and 13C-NMR. The terpolymer metal complexes were prepared with Cu2+, Ni2+, and Zn2+ metal ions using BEF terpolymer as a ligand. The complexes have been characterized by elemental analysis and IR, UV-Visible, ESR, 1H-NMR, and 13C-NMR spectral studies. Gel permeation chromatography was used to determine the molecular weight of the ligand. The surface features and crystalline behavior of the ligand and its complexes were analyzed by scanning electron microscope and X-ray diffraction methods. Thermogravimetric analysis was used to analyze the thermal stability of the ligand and its metal complexes. Kinetic parameters such as activation energy (E a) and order of reaction (n) and thermodynamic parameters, namely, ΔS, ΔF, S*, and Z, were calculated using Freeman-Carroll (FC), Sharp-Wentworth (SW), and Phadnis-Deshpande (PD) methods. Thermal degradation model of the terpolymer and its metal complexes was also proposed using PD method. Biological activities of the ligand and its complexes were tested against Shigella sonnei, Escherichia coli, Klebsiella species, Staphylococcus aureus, Bacillus subtilis, and Salmonella typhimurium bacteria and Aspergillus flavus, Aspergillus niger, Penicillium species, Candida albicans, Cryptococcus neoformans, Mucor species fungi. PMID:25298760

Redox-inactive metal ions modulate the reactivity and oxygen release of mononuclear non-haem iron(III)–peroxo complexes

DOE PAGES

Bang, Suhee; Lee, Yong -Min; Hong, Seungwoo; ...

2014-09-14

Redox-inactive metal ions that function as Lewis acids play pivotal roles in modulating the reactivity of oxygen-containing metal complexes and metalloenzymes, such as the oxygen-evolving complex in photosystem II and its small-molecule mimics. Here we report the synthesis and characterization of non-haem iron(III)–peroxo complexes that bind redox-inactive metal ions, (TMC)FeIII–(μ,η 2:η 2-O 2)–M n+ (M n+ = Sr 2+, Ca 2+, Zn 2+, Lu 3+, Y 3+ and Sc 3+; TMC, 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). We demonstrate that the Ca 2+ and Sr 2+ complexes showed similar electrochemical properties and reactivities in one-electron oxidation or reduction reactions. However, the properties and reactivities ofmore » complexes formed with stronger Lewis acidities were found to be markedly different. In conclusion, complexes that contain Ca 2+ or Sr 2+ ions were oxidized by an electron acceptor to release O 2, whereas the release of O 2 did not occur for complexes that bind stronger Lewis acids. Furthermore, we discuss these results in the light of the functional role of the Ca 2+ ion in the oxidation of water to dioxygen by the oxygen-evolving complex.« less

Synthesis, spectroscopic, anticancer, antibacterial and antifungal studies of Ni(II) and Cu(II) complexes with hydrazine carboxamide, 2-[3-methyl-2-thienyl methylene

NASA Astrophysics Data System (ADS)

Chandra, Sulekh; Vandana; Kumar, Suresh

2015-01-01

Schiff's base ligand(L) hydrazine carboxamide, 2-[3-methyl-2-thienyl methylene] and its metal complexes have been synthesized and characterized by elemental analysis, molar conductance, various spectroscopic techniques such as electronic, IR, 1H NMR, mass, EPR. Molar conductance of complexes in DMF solution corresponds to non-electrolyte. Complexes have general composition [M(L)2X2], where M = Ni(II) and Cu(II), X = Cl-, NO3-, CH3COO- and ½SO42-. On the basis of above spectral studies, an octahedral geometry has been assigned for Ni(II) complexes and tetragonal geometry for Cu(II) complexes except [Cu(L)2SO4] which possesses five coordinated trigonal bipyramidal geometry. These metal complexes were also tested for their anticancer, antibacterial and antifungal activities to assess their inhibition potential. Anticancer activity of ligand and its metal complexes were evaluated using SRB fluorometric assay and Adriamycin (ADR) was applied as positive control. Schiff's base ligand and its metal complexes were screened for their antibacterial and antifungal activity against Escherichia coli, Bacillus cereus and Aspergillus niger, Aspergillus flavus, respectively. Kirby-Bauer single disk susceptibility test was used for antibacterial activity and well diffusion method for antifungal activity of the compounds on the used fungi.

trans-Methylpyridine cyclen versus cross-bridged trans-methylpyridine cyclen. Synthesis, acid-base and metal complexation studies (metal = Co2+, Cu2+, and Zn2+).

PubMed

Bernier, Nicolas; Costa, Judite; Delgado, Rita; Félix, Vítor; Royal, Guy; Tripier, Raphaël

2011-05-07

The synthesis of the cross-bridged cyclen CRpy(2) {4,10-bis((pyridin-2-yl)methyl)-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane}, a constrained analogue of the previously described trans-methylpyridine cyclen Cpy(2) is reported. The additional ethylene bridge confers to CRpy(2) proton-sponge type behaviour which was explored by NMR and potentiometric studies. Transition metal complexes have been synthesized (by complexation of both ligands with Co(2+), Cu(2+) and Zn(2+)) and characterized in solution and in the solid state. The single crystal X-ray structures of [CoCpy(2)](2+), [CuCpy(2)](2+) and [ZnCpy(2)](2+) complexes were determined. Stability constants of the complexes, including those of the cross-bridged derivative, were determined using potentiometric titration data and the kinetic inertness of the [CuCRpy(2)](2+) complex in an acidic medium (half-life values) was evaluated by spectrophotometry. The pre-organized structure of the cross-bridged ligand imposes an additional strain for the complexation leading to complexes with smaller thermodynamic stability in comparison with the related non-bridged ligand. The electrochemical study involving cyclic voltammetry underlines the importance of the ethylene cross-bridge on the redox properties of the transition metal complexes.

Redox-inactive metal ions modulate the reactivity and oxygen release of mononuclear non-haem iron(III)–peroxo complexes

PubMed Central

Bang, Suhee; Lee, Yong-Min; Hong, Seungwoo; Cho, Kyung-Bin; Nishida, Yusuke; Seo, Mi Sook; Sarangi, Ritimukta; Fukuzumi, Shunichi; Nam, Wonwoo

2014-01-01

Redox-inactive metal ions that function as Lewis acids play pivotal roles in modulating the reactivity of oxygen-containing metal complexes and metalloenzymes, such as the oxygen-evolving complex in photosystem II and its small-molecule mimics. Here we report the synthesis and characterization of non-haem iron(III)–peroxo complexes that bind redox-inactive metal ions, (TMC)FeIII–(μ,η2:η2-O2)–Mn+ (Mn+ = Sr2+, Ca2+, Zn2+, Lu3+, Y3+ and Sc3+; TMC, 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). We demonstrate that the Ca2+ and Sr2+ complexes showed similar electrochemical properties and reactivities in one-electron oxidation or reduction reactions. However, the properties and reactivities of complexes formed with stronger Lewis acidities were found to be markedly different. Complexes that contain Ca2+ or Sr2+ ions were oxidized by an electron acceptor to release O2, whereas the release of O2 did not occur for complexes that bind stronger Lewis acids. We discuss these results in the light of the functional role of the Ca2+ ion in the oxidation of water to dioxygen by the oxygen-evolving complex. PMID:25242490

Physiological function of hydrogen metabolism during growth of sulfidogenic bacteria on organic substrates.

PubMed Central

Lupton, F S; Conrad, R; Zeikus, J G

1984-01-01

Desulfovibrio vulgaris Madison and Thermodesulfobacterium commune contained functionally distinct hydrogenase activities, one which exchanged 3H2 into 3H2O and was inhibited by carbon monoxide and a second activity which produced H2 in the presence of CO. Cell suspensions of D. vulgaris used either lactate, pyruvate, or CO as the electron donor for H2 production in the absence of sulfate. Both sulfidogenic species produced and consumed hydrogen as a trace gas during growth on lactate or pyruvate as electron donors and on thiosulfate or sulfate as electron acceptors. Higher initial levels of hydrogen were detected during growth on lactate-sulfate than on pyruvate-sulfate. D. vulgaris but not T. commune also produced and then consumed CO during growth on organic electron donors and sulfate or thiosulfate. High partial pressures of exogenous H2 inhibited growth and substrate consumption when D. vulgaris was cultured on pyruvate alone but not when it was metabolizing pyruvate plus sulfate or lactate plus sulfate. The data are discussed in relation to supporting two different models for the physiological function of H2 metabolism during growth of sulfidogenic bacteria on organic electron donors plus sulfate. A trace H2 transformation model is proposed for control of redox processes during growth on either pyruvate or lactate plus sulfate, and an obligate H2 cycling model is proposed for chemiosmotic energy coupling during growth on CO plus sulfate. PMID:6480553

Bioavailability of silver and silver sulfide nanoparticles to lettuce (Lactuca sativa): Effect of agricultural amendments on plant uptake.

PubMed

Doolette, Casey L; McLaughlin, Michael J; Kirby, Jason K; Navarro, Divina A

2015-12-30

Silver nanoparticles (AgNPs) can enter terrestrial systems as sulfidised AgNPs (Ag2S-NPs) through the application of biosolids to soil. However, the bioavailability of Ag2S-NPs in soils is unknown. The two aims of this study were to investigate (1) the bioavailability of Ag to lettuce (Lactuca sativa) using a soil amended with biosolids containing Ag2S-NPs and (2) the effect of commonly used agricultural fertilisers/amendments on the bioavailability of Ag, AgNPs and Ag2S-NPs to lettuce. The study used realistic AgNP exposure pathways and exposure concentrations. The plant uptake of Ag from biosolids-amended soil containing Ag2S-NPs was very low for all Ag treatments (0.02%). Ammonium thiosulfate and potassium chloride fertilisation significantly increased the Ag concentrations of plant roots and shoots. The extent of the effect varied depending on the type of Ag. Ag2S-NPs, the realistic form of AgNPs in soil, had the lowest bioavailability. The potential risk of AgNPs in soils is low; even in the plants that had the highest Ag concentrations (Ag(+)+thiosulfate), only 0.06% of added Ag was found in edible plant parts (shoots). Results from the study suggest that agricultural practises must be considered when carrying out risk assessments of AgNPs in terrestrial systems; such practises can affect AgNP bioavailability. Copyright © 2015 Elsevier B.V. All rights reserved.

Metal complexes of curcumin for cellular imaging, targeting, and photoinduced anticancer activity.

PubMed

Banerjee, Samya; Chakravarty, Akhil R

2015-07-21

Curcumin is a polyphenolic species. As an active ingredient of turmeric, it is well-known for its traditional medicinal properties. The therapeutic values include antioxidant, anti-inflammatory, antiseptic, and anticancer activity with the last being primarily due to inhibition of the transcription factor NF-κB besides affecting several biological pathways to arrest tumor growth and its progression. Curcumin with all these positive qualities has only remained a potential candidate for cancer treatment over the years without seeing any proper usage because of its hydrolytic instability involving the diketo moiety in a cellular medium and its poor bioavailability. The situation has changed considerably in recent years with the observation that curcumin in monoanionic form could be stabilized on binding to a metal ion. The reports from our group and other groups have shown that curcumin in the metal-bound form retains its therapeutic potential. This has opened up new avenues to develop curcumin-based metal complexes as anticancer agents. Zinc(II) complexes of curcumin are shown to be stable in a cellular medium. They display moderate cytotoxicity against prostate cancer and neuroblastoma cell lines. A similar stabilization and cytotoxic effect is reported for (arene)ruthenium(II) complexes of curcumin against a variety of cell lines. The half-sandwich 1,3,5-triaza-7-phosphatricyclo-[3.3.1.1]decane (RAPTA)-type ruthenium(II) complexes of curcumin are shown to be promising cytotoxic agents with low micromolar concentrations for a series of cancer cell lines. In a different approach, cobalt(III) complexes of curcumin are used for its cellular delivery in hypoxic tumor cells using intracellular agents that reduce the metal and release curcumin as a cytotoxin. Utilizing the photophysical and photochemical properties of the curcumin dye, we have designed and synthesized photoactive curcumin metal complexes that are used for cellular imaging by fluorescence microscopy and damaging the cancer cells on photoactivation in visible light while being minimally toxic in darkness. In this Account, we have made an attempt to review the current status of the chemistry of metal curcumin complexes and present results from our recent studies on curcumin complexes showing remarkable in vitro photocytotoxicity. The undesirable dark toxicity of the complexes can be reduced with suitable choice of the metal and the ancillary ligands in a ternary structure. The complexes can be directed to specific subcellular organelles. Selectivity by targeting cancer cells over normal cells can be achieved with suitable ligand design. We expect that this methodology is likely to provide an impetus toward developing curcumin-based photochemotherapeutics for anticancer treatment and cure.

Synthesis and structures of metal chalcogenide precursors

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Duraj, Stan A.; Eckles, William E.; Andras, Maria T.

1990-01-01

The reactivity of early transition metal sandwich complexes with sulfur-rich molecules such as dithiocarboxylic acids was studied. Researchers recently initiated work on precursors to CuInSe2 and related chalcopyrite semiconductors. Th every high radiation tolerance and the high absorption coefficient of CuInSe2 makes this material extremely attractive for lightweight space solar cells. Their general approach in early transition metal chemistry, the reaction of low-valent metal complexes or metal powders with sulfur and selenium rich compounds, was extended to the synthesis of chalcopyrite precursors. Here, the researchers describe synthesis, structures, and and routes to single molecule precursors to metal chalcogenides.

Divalent Metal-Ion Complexes with Dipeptide Ligands Having Phe and His Side-Chain Anchors: Effects of Sequence, Metal Ion, and Anchor.

PubMed

Dunbar, Robert C; Berden, Giel; Martens, Jonathan K; Oomens, Jos

2015-09-24

Conformational preferences have been surveyed for divalent metal cation complexes with the dipeptide ligands AlaPhe, PheAla, GlyHis, and HisGly. Density functional theory results for a full set of complexes are presented, and previous experimental infrared spectra, supplemented by a number of newly recorded spectra obtained with infrared multiple photon dissociation spectroscopy, provide experimental verification of the preferred conformations in most cases. The overall structural features of these complexes are shown, and attention is given to comparisons involving peptide sequence, nature of the metal ion, and nature of the side-chain anchor. A regular progression is observed as a function of binding strength, whereby the weakly binding metal ions (Ba(2+) to Ca(2+)) transition from carboxylate zwitterion (ZW) binding to charge-solvated (CS) binding, while the stronger binding metal ions (Ca(2+) to Mg(2+) to Ni(2+)) transition from CS binding to metal-ion-backbone binding (Iminol) by direct metal-nitrogen bonds to the deprotonated amide nitrogens. Two new sequence-dependent reversals are found between ZW and CS binding modes, such that Ba(2+) and Ca(2+) prefer ZW binding in the GlyHis case but prefer CS binding in the HisGly case. The overall binding strength for a given metal ion is not strongly dependent on the sequence, but the histidine peptides are significantly more strongly bound (by 50-100 kJ mol(-1)) than the phenylalanine peptides.

[Ultraviolet-visible spectrometry analysis of insoluble xanthate heavy metal complexes].

PubMed

Qiu, Bo; Liu, Jin-Feng; Liu, Yao-Chi; Yang, Zhao-Guang; Li, Hai-Pu

2014-11-01

A ultraviolet-visible spectrometry method of determining insoluble xanthate heavy metal complexes in flotation wastewater was the first time to be put forward. In this work, the changes of ultraviolet-visible spectra of xanthate solution after the addition of various heavy metal ions were investigated firstly. It was found that Pb2+ and Cu2+ can form insoluble complexes with xanthate, while Fe2+, Zn2+ and Mn2+ have little effect on the ultraviolet absorption of xanthate solution. Then the removal efficiencies of filter membrane with different pore sizes were compared, and the 0.22 μm membrane was found to be effective to separate copper xanthate or lead xanthate from the filtrate. Furthermore, the results of the study on the reaction of sodium sulfide and insoluble xanthate heavy metal complexes showed that S(2-) can release the xanthate ion quantitatively from insoluble complexes to solution. Based on the above research, it was concluded that the amount of insoluble xanthate heavy metal complexes in water samples can be obtained through the increase of free xanthate in the filtrate after the addition of sodium sulfide. Finally, the feasibility of this method was verified by the application to the analysis of flotation wastewater from three ore-dressing plants in the Thirty-six Coves in Chenzhou.

Structural, spectral and biological studies of binuclear tetradentate metal complexes of N 3O Schiff base ligand synthesized from 4,6-diacetylresorcinol and diethylenetriamine

NASA Astrophysics Data System (ADS)

Emara, Adel A. A.

2010-09-01

The binuclear Schiff base, H 2L, ligand was synthesized by reaction of 4,6-diacetylresorcinol with diethylenetriamine in the molar ratio 1:2. The coordination behavior of the H 2L towards Cu(II), Ni(II), Co(II), Zn(II), Fe(III), Cr(III), VO(IV) and UO 2(VI) ions has been investigated. The elemental analyses, magnetic moments, thermal studies and IR, electronic, 1H NMR, ESR and mass spectra were used to characterize the isolated ligand and its metal complexes. The ligand acts as dibasic with two N 3O-tetradentate sites and can coordinate with two metal ions to form binuclear complexes. The bonding sites are the nitrogen atoms of the azomethine and amine groups and the oxygen atoms of the phenolic groups. The metal complexes exhibit either square planar, tetrahedral, square pyramid or octahedral structures. The Schiff base ligand and its metal complexes were tested against four pathogenic bacteria ( Staphylococcus aureus and Streptococcus pyogenes) as Gram-positive bacteria, and ( Pseudomonas fluorescens and Pseudomonas phaseolicola) as Gram-negative bacteria and two pathogenic fungi ( Fusarium oxysporum and Aspergillus fumigatus) to assess their antimicrobial properties. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.