scholarly journals Radiocarbon analysis of isoprenoid and branched Glycerol Dialkyl Glycerol Tetraethers in soils and fluvial sediments

2020 ◽  
Author(s):  
Hannah Gies ◽  
Daniel Montluçon ◽  
Maarten Lupker ◽  
Tessa van der Voort ◽  
Frank Hagedorn ◽  
...  
Keyword(s):  
Membrane Lipids ◽  
Similar Rate ◽  
Subalpine Forest ◽  
Soil Core ◽  
Separation Procedure ◽  
Fluvial Sediments ◽  
Geophysical Research ◽  
Radiocarbon Age ◽  
Transport Dynamics ◽  
Glycerol Dialkyl Glycerol Tetraethers

<p>Glycerol dialkyl glycerol tetraethers (GDGTs), membrane lipids synthesized by archaea (isoprenoid GDGTs) and bacteria (branched GDGTs), form the basis of a suite of molecular proxies used in terrestrial as well as marine environments. Compound-specific radiocarbon analysis has provided valuable insights into the sources and yielded constraints on transport dynamics of different biomarkers in the context of carbon cycle processes. To complement the existing biomarker radiocarbon toolbox, and to shed new light on the sources and fate of GDGTs, we developed a new method to measure GDGT radiocarbon compositions in natural samples.</p><p>Isoprenoid and branched GDGTs are isolated using two UHPLC silica columns in series coupled to a fraction collector set to eluent recovery at different time intervals. The accuracy of the method was tested using a modern and a radiocarbon-dead reference material. Procedural blanks show that the separation procedure adds less than 3 µg carbon with a Fm of 0.64.</p><p>The method is first applied to determine the Δ<sup>14</sup>C composition of isoprenoid and branched GDGTs in two soil core profiles from a temperate and subalpine forest ecosystem in order to explore the range of typical values encountered in natural systems.  The cores, which reach a depth of 80 cm and 40 cm respectively, have previously been analyzed with respect to radiocarbon characteristics of long-chain n-alkanes and fatty acids as well as bulk particulate and dissolved organic carbon (OC) [1]. For each core, GDGTs were separated and analyzed from 3 different depth intervals. The Δ<sup>14</sup>C of both isoprenoid and branched GDGTs decreases, at a similar rate as the bulk, by -350‰ and -200‰ along the temperate and the subalpine core respectively, hence confirming their potential for constraining transport-dynamics of soil-derived matter in rivers.</p><p>The radiocarbon age of GDGTs in a suite of fluvial sediments is older than expected under the assumption that topsoil-derived organic matter is the main source of the compounds. Potentially, this offset could be caused by rapid degradation of the compounds during transport and therefore alter the proxy signal on the way to sedimentary archives.</p><p> </p><p>[1] van der Voort, T. S., et al., 2017 - Geophysical Research Letters 44, 23</p>

scholarly journals Radiocarbon Analysis of Isoprenoid and Branched Glycerol Dialkyl Glycerol Tetraethers in Soils and Fluvial Sediments

2019 ◽  
Author(s):  
H. Gies ◽  
D. Montlucon ◽  
N. Haghipour ◽  
M. Lupker ◽  
T.S. van der Voort ◽  
...  
Keyword(s):  
Fluvial Sediments ◽  
Glycerol Dialkyl Glycerol Tetraethers

scholarly journals Millennial-age glycerol dialkyl glycerol tetraethers (GDGTs) in forested mineral soils: <sup>14</sup>C-based evidence for stabilization of microbial necromass

2021 ◽  
Vol 18 (1) ◽  
pp. 189-205
Author(s):  
Hannah Gies ◽  
Frank Hagedorn ◽  
Maarten Lupker ◽  
Daniel Montluçon ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Direct Evidence ◽  
Membrane Lipids ◽  
Soil Depth ◽  
Mineral Surfaces ◽  
Carbon Cycle Model ◽  
Model Predictions ◽  
Microbial Products ◽  
Mineral Soils ◽  
Glycerol Dialkyl Glycerol Tetraethers

Abstract. Understanding controls on the persistence of soil organic matter (SOM) is essential to constrain its role in the carbon cycle and inform climate–carbon cycle model predictions. Emerging concepts regarding the formation and turnover of SOM imply that it is mainly comprised of mineral-stabilized microbial products and residues; however, direct evidence in support of this concept remains limited. Here, we introduce and test a method for the isolation of isoprenoid and branched glycerol dialkyl glycerol tetraethers (GDGTs) – diagnostic membrane lipids of archaea and bacteria, respectively – for subsequent natural abundance radiocarbon analysis. The method is applied to depth profiles from two Swiss pre-Alpine forested soils. We find that the Δ14C values of these microbial markers markedly decrease with increasing soil depth, indicating turnover times of millennia in mineral subsoils. The contrasting metabolisms of the GDGT-producing microorganisms indicates it is unlikely that the low Δ14C values of these membrane lipids reflect heterotrophic acquisition of 14C-depleted carbon. We therefore attribute the 14C-depleted signatures of GDGTs to their physical protection through association with mineral surfaces. These findings thus provide strong evidence for the presence of stabilized microbial necromass in forested mineral soils.

Tracking natural organic carbon in the River Clyde, UK, using glycerol dialkyl glycerol tetraethers

2017 ◽  
Vol 108 (2-3) ◽  
pp. 289-298 ◽  
Author(s):  
Raquel A. Lopes dos Santos ◽  
Christopher H. Vane
Keyword(s):  
Organic Carbon ◽  
Surface Sediments ◽  
Membrane Lipids ◽  
Stable Carbon Isotope ◽  
Bacterial Membrane ◽  
Stable Carbon ◽  
Outer Estuary ◽  
The Impact ◽  
Marine Archaea ◽  
Glycerol Dialkyl Glycerol Tetraethers

ABSTRACTSurface sediments from a 100-km stretch of the River Clyde, UK, and its estuary were analysed for glycerol dialkyl glycerol tetraethers (GDGTs) to track the downstream changes in the source of organic matter (OM) and to evaluate the impact of urbanisation. Bacterial membrane lipids, named branched GDGTs (brGDGTs), produced in soils and rivers ranged from 1.6 to 58μgg−1 organic carbon (OC) and the isoprenoid GDGT crenarchaeol, mainly from marine archaea, ranged from 0.01 to 42μgg−1 OC. The highest brGDGT concentrations were in the upper river, in Glasgow city and in the outer estuary, suggesting higher soil-derived OM input. By contrast, crenarchaeol concentrations gradually increased from the tidal weir in Glasgow towards the sea. This spatial distribution of the tetraethers was reflected in the branched and isoprenoid tetraether (BIT) index, a proxy for soil versus marine carbon. The highest BIT values (1.0) occurred upstream, estuarine values ranged from 0.9 to 0.6 and the lowest values (0.4) were found in the outer estuary. An independent proxy for soil-derived OM, stable carbon isotope (δ13C) values, showed a comparable decrease in terrigenous OM contribution towards the sea, but was more variable compared to the BIT. Conversely, carbon/nitrogen (C/N) showed a constant trend, suggesting that it is not a reliable indicator of OM source in the Clyde. Neither BIT, δ13C nor C/N were able to reflect the input of urban effluents from Glasgow.

scholarly journals Distribution of Intact and Core Membrane Lipids of Archaeal Glycerol Dialkyl Glycerol Tetraethers among Size-Fractionated Particulate Organic Matter in Hood Canal, Puget Sound

2012 ◽  
Vol 78 (5) ◽  
pp. 1480-1490 ◽  
Author(s):  
Anitra E. Ingalls ◽  
Carme Huguet ◽  
Laura T. Truxal
Keyword(s):  
Natural Waters ◽  
Membrane Lipids ◽  
Puget Sound ◽  
Size Fraction ◽  
Free Living ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Aggregate Fraction ◽  
Hood Canal ◽  
Glycerol Dialkyl Glycerol Tetraethers

ABSTRACTThere is great interest in the membrane lipids of archaea (glycerol dialkyl glycerol tetraethers [GDGTs]) as tracers of archaeal biomass because of their utility as paleoproxies and because of the biogeochemical importance of archaea. While core GDGTs (formed by hydrolysis of polar head groups of intact GDGTs after cell death) are appropriate for paleostudies, they have also been used to trace archaeal populations. Also, despite the small size (0.2 by 0.7 μm) of cultivated marine archaea, 0.7-μm glass-fiber filters (GFFs) are typically used to collect GDGTs from natural waters. We quantified both core and intact GDGTs in free-living (0.2- to 0.7-μm), suspended (0.7- to 60-μm), and aggregate (>60-μm) particle size fractions in Puget Sound (Washington State). On average, the free-living fraction contained 36% of total GDGTs, 90% of which were intact. The intermediate-size fraction contained 62% of GDGTs, and 29% of these were intact. The aggregate fraction contained 2% of the total GDGT pool, and 29% of these were intact. Our results demonstrate that intact GDGTs are largely in the free-living fraction. Because only intact GDGTs are present in living cells, protocols that target this size fraction and analyze the intact GDGT pool are necessary to track living populations in marine waters. Core GDGT enrichment in larger-size fractions indicates that archaeal biomass may quickly become attached or entrained in particles once the archaea are dead or dying. While the concentrations of the two pools were generally not correlated, the similar sizes of the core and intact GDGT pools suggest that core GDGTs are removed from the water column on timescales similar to those of cell replication, on timescales of days to weeks.

The organization of cell surface membrane domains

1989 ◽  
Vol 47 ◽  
pp. 804-805
Author(s):  
Michael Edidin
Keyword(s):  
Cell Surface ◽  
Membrane Lipids ◽  
Surface Membrane ◽  
Lateral Diffusion ◽  
Cell Types ◽  
Membrane Domains ◽  
Membrane Biology ◽  
Morphological Polarity ◽  
Discrete Domains ◽  
Membrane Components

Cell surface membranes are based on a fluid lipid bilayer and models of the membranes' organization have emphasised the possibilities for lateral motion of membrane lipids and proteins within the bilayer. Two recent trends in cell and membrane biology make us consider ways in which membrane organization works against its inherent fluidity, localizing both lipids and proteins into discrete domains. There is evidence for such domains, even in cells without obvious morphological polarity and organization [Table 1]. Cells that are morphologically polarised, for example epithelial cells, raise the issue of membrane domains in an accute form.The technique of fluorescence photobleaching and recovery, FPR, was developed to measure lateral diffusion of membrane components. It has also proven to be a powerful tool for the analysis of constraints to lateral mobility. FPR resolves several sorts of membrane domains, all on the micrometer scale, in several different cell types.

Melatonin reduces high levels of lipid peroxidation induced by potassium iodate in porcine thyroid

2019 ◽  
pp. 1-7 ◽  
Author(s):  
Paulina Iwan ◽  
Jan Stepniak ◽  
Malgorzata Karbownik-Lewinska
Keyword(s):  
Lipid Peroxidation ◽  
Oxidative Damage ◽  
Membrane Lipids ◽  
Chemical Properties ◽  
Iodine Concentration ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Protective Effects ◽  
Potassium Iodate ◽  
Hormone Synthesis

Abstract. Iodine is essential for thyroid hormone synthesis. Under normal iodine supply, calculated physiological iodine concentration in the thyroid is approx. 9 mM. Either potassium iodide (KI) or potassium iodate (KIO3) are used in iodine prophylaxis. KI is confirmed as absolutely safe. KIO3 possesses chemical properties suggesting its potential toxicity. Melatonin (N-acetyl-5-methoxytryptamine) is an effective antioxidant and free radical scavenger. Study aims: to evaluate potential protective effects of melatonin against oxidative damage to membrane lipids (lipid peroxidation, LPO) induced by KI or KIO3 in porcine thyroid. Homogenates of twenty four (24) thyroids were incubated in presence of either KI or KIO3 without/with melatonin (5 mM). As melatonin was not effective against KI-induced LPO, in the next step only KIO3 was used. Homogenates were incubated in presence of KIO3 (200; 100; 50; 25; 20; 15; 10; 7.5; 5.0; 2.5; 1.25 mM) without/with melatonin or 17ß-estradiol. Five experiments were performed with different concentrations of melatonin (5.0; 2.5; 1.25; 1.0; 0.625 mM) and one with 17ß-estradiol (1.0 mM). Malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) concentration (LPO index) was measured spectrophotometrically. KIO3 increased LPO with the strongest damaging effect (MDA + 4-HDA level: ≈1.28 nmol/mg protein, p < 0.05) revealed at concentrations of around 15 mM, thus corresponding to physiological iodine concentrations in the thyroid. Melatonin reduced LPO (MDA + 4-HDA levels: from ≈0.97 to ≈0,76 and from ≈0,64 to ≈0,49 nmol/mg protein, p < 0.05) induced by KIO3 at concentrations of 10 mM or 7.5 mM. Conclusion: Melatonin can reduce very strong oxidative damage to membrane lipids caused by KIO3 used in doses resulting in physiological iodine concentrations in the thyroid.

Functional Properties of p-Anisoylated Plasmin-Staphylokinase Complex

1993 ◽  
Vol 70 (02) ◽  
pp. 326-331 ◽  
Author(s):  
H R Lijnen ◽  
B Van Hoef ◽  
R A G Smith ◽  
D Collen
Keyword(s):  
Human Plasma ◽  
Rate Constant ◽  
Time Course ◽  
Bolus Injection ◽  
Similar Rate ◽  
Clot Lysis ◽  
Lag Phase ◽  
Plasma Clot ◽  
Rapid Clearance ◽  
Stoichiometric Complex

SummaryThe kinetic and fibrinolytic properties of a reversibly acylated stoichiometric complex between human plasmin and recombinant staphylokinase (plasmin-STAR complex) were evaluated. The acylation rate constant of plasmin-STAR by p-amidinophenyl-p’-anisate-HCI was 52 M-1 s-1 and its deacylation rate constant 1.2 × 10-4 s-1 (t½ of 95 min) which are respectively 50-fold and around 3-fold lower than for the plasmin-streptokinase complex. The acylated complex was stable as evidenced by binding to lysine-Sepharose. However, following an initial short lag phase, the acylated plasmin-STAR complex activated plasminogen at a similar rate as the unblocked complex, whereas the acylated plasmin-streptokinase complex did not activate plasminogen. These findings indicate that STAR, unlike streptokinase, dissociates from its acylated complex with plasmin in the presence of excess plasminogen. In agreement with this hypothesis, the time course of the lysis of a 125I-fibrin labeled plasma clot submerged in citrated human plasma, is similar for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR (50% clot lysis in 2 h requires 12 nM of each agent). The plasma clearances of STAR-related antigen following bolus injection in hamsters were 1.0 to 1.5 ml/min for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR, as a result of short initial half-lives of 2.0 to 2.5 min.The dissociation of the anisoylated plasmin-STAR complex and its consequent rapid clearance suggest that it has no apparent advantages as compared to free STAR for clinical thrombolysis.

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