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  • 1.
    Jonsson, Sofi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Nilsson, Mats B
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Skyllberg, Ulf
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Schaefer, Jeffra K
    Department of Geosciences, Princeton University.
    Åkerblom, Staffan
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Impact of nutrient and humic matter loadings on methylmercury formation and bioaccumulation in estuarine ecosystemsManuskript (preprint) (Övrigt vetenskapligt)
  • 2.
    Jonsson, Sofi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skyllberg, Ulf
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Nilsson, Mats B
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Differentiated reactivity of geochemical mercury pools control methylmercury levels in sediment and biotaManuskript (preprint) (Övrigt vetenskapligt)
  • 3.
    Jonsson, Sofi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skyllberg, Ulf
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nilsson, Mats B
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Westlund, Per-Olof
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mercury methylation rates for geochemically relevant HgII species in sediments2012Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, nr 21, s. 11653-11659Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Monomethylmercury (MeHg) in fish from freshwater, estuarine and marine environments are a major global environmental issue. Mercury levels in biota are mainly controlled by the methylation of inorganic mercuric mercury (HgII) to MeHg in water, sediments and soils. There is, however, a knowledge gap concerning the mechanisms and rates of methylation of specific geochemical HgII species. Such information is crucial for a better understanding of variations in MeHg concentrations among ecosystems and, in particular, for predicting the outcome of currently proposed measures to mitigate mercury emissions and reduce MeHg concentrations in fish. To fill this knowledge gap we propose an experimental approach using HgII isotope tracers, with defined and geochemically important adsorbed and solid HgII forms in sediments, to study MeHg formation. We report HgII methylation rate constants, km, in estuarine sediments which span over two orders of magnitude depending on chemical form of added tracer: metacinnabar (β-201HgS(s)) < cinnabar (α-199HgS(s)) < HgII reacted with mackinawite (≡FeS-202HgII) < HgII bonded to natural organic matter (NOM-196HgII) < a typical aqueous tracer (198Hg(NO3)2(aq)). We conclude that a combination of thermodynamic and kinetic effects of HgII solid-phase dissolution and surface desorption control the HgII methylation rate in sediments and causes the large observed differences in km-values. The selection of relevant solid-phase and surface adsorbed HgII tracers will therefore be crucial to achieving biogeochemically accurate estimates of ambient HgII methylation rates.

  • 4.
    Liem-Nguyen, Van
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jonsson, Sofi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Skyllberg, Ulf
    Nilsson, Mats B.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Effects of Nutrient Loading and Mercury Chemical Speciation on the Formation and Degradation of Methylmercury in Estuarine Sediment2016Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, nr 13, s. 6983-6990Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Net formation of methylmercury (MeHg) in sediments is known to be affected by the availability of inorganic divalent mercury (HgII) and by the activities of HgII methylating and MeHg demethylating bacteria. Enhanced autochthonous organic matter deposition to the benthic zone, following increased loading of nutrients to the pelagic zone, has been suggested to increase the activity of HgII methylating bacteria and thus the rate of net methylation. However, the impact of increased nutrient loading on the biogeochemistry of mercury (Hg) is challenging to predict as different geochemical pools of Hg may respond differently to enhanced bacterial activities. Here, we investigate the combined effects of nutrient (N and P) supply to the pelagic zone and the chemical speciation of HgII and of MeHg on MeHg formation and degradation in a brackish sediment-water mesocosm model ecosystem. By use of Hg isotope tracers added in situ to the mesocosms or ex situ in incubation experiments, we show that the MeHg formation rate increased with nutrient loading only for HgII tracers with a high availability for methylation. Tracers with low availability did not respond significantly to nutrient loading. Thus, both microbial activity (stimulated indirectly through plankton biomass production by nutrient loading) and HgII chemical speciation were found to control the MeHg formation rate in marine sediments. 

  • 5.
    Linderholm, Johan
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Chemical characterisation of various archaeological soil samples using main and trace elements determined by inductively coupled plasma atomic emission spectrometry1994Ingår i: Journal of Archaeological Science, ISSN 0305-4403, E-ISSN 1095-9238, Vol. 21, nr 3, s. 303-314Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study a method has been developed to classify archaeologically related soil samples by means of multivariate statistical analysis (principal component analysis) of determined trace and main component concentrations. The Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) technique was used for the determination of Fe, As, Cu, P, Mn, V, Co, Mo, Zn, Cr, Pb and Ca, and good accuracy was achieved by calibration against a certified reference material. It was shown that Cu, P, Mn, Zn and Ca were accumulated in feature and dwelling samples from a late bronze age site, Vistad, in southeast Sweden. Elements like Fe, V, Co and Cr characterized the control samples (from a surrounding field). It was also demonstrated that in this case, a simpler pretreatment procedure—acid extraction—could be used instead of total dissolution of the samples. Microwave heating was utilized for both procedures.

  • 6.
    Lundberg, Erik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Olofsson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Westermark, Gunilla T
    Sauer-Eriksson, A Elisabeth
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Stability and fibril formation properties of human and fish transthyretin, and of the Escherichia coli transthyretin-related protein2009Ingår i: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 276, nr 7, s. 1999-2011Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Human transthyretin (hTTR) is one of several proteins known to cause amyloid disease. Conformational changes in its native structure result in aggregation of the protein, leading to insoluble amyloid fibrils. The transthyretin (TTR)-related proteins comprise a protein family of 5-hydroxyisourate hydrolases with structural similarity to TTR. In this study, we tested the amyloidogenic properties, if any, of sea bream TTR (sbTTR) and Escherichia coli transthyretin-related protein (ecTRP), which share 52% and 30% sequence identity, respectively, with hTTR. We obtained filamentous structures from all three proteins under various conditions, but, interestingly, different structures displayed different tinctorial properties. hTTR and sbTTR formed thin, curved fibrils at low pH (pH 2-3) that bound thioflavin-T (thioflavin-T-positive) but did not stain with Congo Red (CR) (CR-negative). Aggregates formed at the slightly higher pH of 4.0-5.5 had different morphology, displaying predominantly amorphous structures. CR-positive material of hTTR was found in this material, in agreement with previous results. ecTRP remained soluble at pH 2-12 at ambient temperatures. By raising of the temperature, fibril formation could be induced at neutral pH in all three proteins. Most of these temperature-induced fibrils were thicker and straighter than the in vitro fibrils seen at low pH. In other words, the temperature-induced fibrils were more similar to fibrils seen in vivo. The melting temperature of ecTRP was 66.7 degrees C. This is approximately 30 degrees C lower than the melting temperatures of sbTTR and hTTR. Information from the crystal structures was used to identify possible explanations for the reduced thermostability of ecTRP.

  • 7.
    Nydahl, Anna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Tengberg, Anders
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Båmstedt, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Wikner, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Precise microbial respiration rate in coastal waters by a contiuous multi-sample sensorManuskript (preprint) (Övrigt vetenskapligt)
  • 8.
    Sauer-Eriksson, Elisabeth
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Linusson, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Transthyretin-related and transthyretin-like proteins2009Ingår i: Recent advances in Transthyretin evolution, structure and biological functions / [ed] Dr. Samantha J. Richardson, Dr. Vivian Cody, Springer Berlin/Heidelberg, 2009, s. 109-122Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Bioinformatics programs are highly accurate in identifying protein families directly from protein sequences, even when the sequence identity is very low. The transthyretin-related proteins (TRPs) are one example of a protein family that has been identified. Whereas transthyretin (TTR) is well-characterized both in vivo and in vitro, only recently has research focused on the TRPs. Their structural similarity to TTR has been verified, and their function as a 5-hydroxyisourate (HIU) hydrolase has been established. In this review we discuss structural aspects of TRP function. We also discuss the still unknown transthyretin-like proteins (TLPs) that are seemingly unique to nematodes.

  • 9.
    Wikner, Johan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Panigrahi, Satya
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Nydahl, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Båmstedt, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Tengberg, Anders
    Göteborgs universitet.
    Precise continuous measurements of pelagic respiration in coastal waters with Oxygen Optodes2013Ingår i: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 11, s. 1-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An analytical setup for respiration rate measurements was developed and evaluated in pelagic water samples using a commercially available optical oxygen sensor (Optode (TM)). This setup required the development of a gas tight stopper to connect the sensors to a 1 dm(3) glass sample bottle, precise temperature control (+/- 0.05 degrees C), and proper stirring of samples. The detection limit and precision of the method was 0.3 mmol O-2 m(-3) d(-1). This was similar to the detection limit for the high-precision Winkler titration method reported in field studies. When compared with the Winkler method, the Optode sensor enabled operator-independent, high temporal resolution measurement of respiration, better coverage of plankton groups and detection of non-linear oxygen decline, without the need for wet chemistry. Respiration rates measured by the Optodes showed good accuracy when compared with measurements made with the Winkler titration method (3% deviation), followed the expected temperature response (Q(10) = 3.0), were correlated with chlorophyll a and were congruent with earlier reported values in the literature. The main source of uncertainty was a necessary correction for system drift during the incubation period, due to oxygen release from the plastic components. Additionally, less stringent temperature control on board research vessels during rough seas reduced the precision. We conclude that the developed Optode system can be used to measure respiration in productive coastal waters. Samples from cold or deep waters were, however, often below the detection limit.

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