scholarly journals Organo-mineral associations in chert of the 3.5 Ga Mount Ada Basalt raise questions about the origin of organic matter in Paleoarchean hydrothermally influenced sediments

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Julien Alleon ◽  
David T. Flannery ◽  
Nicola Ferralis ◽  
Kenneth H. Williford ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Mineralogical Composition ◽  
Molecular Characteristics ◽  
Reducing Conditions ◽  
Mineral Associations ◽  
Alteration Processes ◽  
Molecular Information ◽  
Organic Precursors ◽  
Pool Formation

Abstract Hydrothermal and metamorphic processes could have abiotically produced organo-mineral associations displaying morphological and isotopic characteristics similar to those of fossilized microorganisms in ancient rocks, thereby leaving false-positive evidence for early life in the geological record. Recent studies revealed that geologically-induced alteration processes do not always completely obliterate all molecular information about the original organic precursors of ancient microfossils. Here, we report the molecular, geochemical, and mineralogical composition of organo-mineral associations in a chert sample from the ca. 3.47 billion-year-old (Ga) Mount Ada Basalt, in the Pilbara Craton, Western Australia. Our observations indicate that the molecular characteristics of carbonaceous matter are consistent with hydrothermally altered biological organics, although significantly distinct from that of organic microfossils discovered in a chert sample from the ca. 3.43 Ga Strelley Pool Formation in the same area. Alternatively, the presence of native metal alloys in the chert, previously believed to be unstable in such hydrothermally influenced environments, indicates strongly reducing conditions that were favorable for the abiotic formation of organic matter. Drawing definitive conclusions about the origin of most Paleoarchean organo-mineral associations therefore requires further characterization of a range of natural samples together with experimental simulations to constrain the molecular composition and geological fate of hydrothermally-generated condensed organics.

scholarly journals Purification and characterization of subcomponent C1q of the first component of bovine complement

1979 ◽  
Vol 177 (2) ◽  
pp. 531-540 ◽  
Author(s):  
R. Duncan Campbell ◽  
Nuala A. Booth ◽  
John E. Fothergill
Keyword(s):  
Sodium Dodecyl ◽  
Molar Ratio ◽  
High Yield ◽  
Molecular Characteristics ◽  
Haemolytic Activity ◽  
Reducing Conditions ◽  
Equilibrium Sedimentation ◽  
Triple Helices ◽  
Polypeptide Chains

Bovine C1q, a subcomponent of the first component of complement, was purified in high yield by a combination of euglobulin precipitation, and ion-exchange and molecularsieve chromatography on CM-cellulose and Ultrogel AcA 34. Approx. 12–16mg can be isolated from 1 litre of serum, representing a yield of 13–18%. The molecular weight of undissociated subcomponent C1q, as determined by equilibrium sedimentation, is 430000. On sodium dodecyl sulphate/polyacrylamide gels under non-reducing conditions, subcomponent C1q was shown to consist of two subunits of mol.wts. 69000 and 62000 in a molar ratio of 2:1. On reduction, the 69000-mol.wt. subunit gave chains of mol.wts. 30000 and 25000 in equimolar ratio, and the 62000-mol.wt. subunit decreased to 25000. The amino acid composition, with a high value for glycine, and the presence of hydroxyproline and hydroxylysine, suggests that there is a region of collagen-like sequence in the molecule. This is supported by the loss of haemolytic activity and the degradation of the polypeptide chains of subcomponent C1q when digested by collagenase. All of these molecular characteristics support the structure of six subunits, each containing three different polypeptide chains, with globular heads connected by collagen triple helices as proposed by Reid & Porter (1976) (Biochem. J.155, 19–23) for human subcomponent C1q. Subcomponent C1q contains approx. 9% carbohydrate; analysis of the degree of substitution of the hydroxylysine residues revealed that 91% are modified by the addition of the disaccharide unit Gal-Glc. Bovine subcomponent C1q generates full C1 haemolytic activity when assayed with human subcomponents C1r and C1s.

Functional Characterization of PM6/13, a β3-specific (GPIIIa/CD61) Monoclonal Antibody that Shows Preferential Inhibition of Fibrinogen Binding over Fibronectin Binding to Activated Human Platelets

1998 ◽  
Vol 79 (01) ◽  
pp. 177-185 ◽  
Author(s):  
Ashia Siddiqua ◽  
Michael Wilkinson ◽  
Vijay Kakkar ◽  
Yatin Patel ◽  
Salman Rahman ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Functional Characterization ◽  
Human Platelets ◽  
Western Blots ◽  
Activated Platelets ◽  
Reducing Conditions ◽  
Fibronectin Binding

SummaryWe report the characterization of a monoclonal antibody (MAb) PM6/13 which recognises glycoprotein IIIa (GPIIIa) on platelet membranes and in functional studies inhibits platelet aggregation induced by all agonists examined. In platelet-rich plasma, inhibition of aggregation induced by ADP or low concentrations of collagen was accompanied by inhibition of 5-hydroxytryptamine secretion. EC50 values were 10 and 9 [H9262]g/ml antibody against ADP and collagen induced responses respectively. In washed platelets treated with the cyclooxygenase inhibitor, indomethacin, PM6/13 inhibited platelet aggregation induced by thrombin (0.2 U/ml), collagen (10 [H9262]g/ml) and U46619 (3 [H9262]M) with EC50 = 4, 8 and 4 [H9262]g/ml respectively, without affecting [14C]5-hydroxytryptamine secretion or [3H]arachidonate release in appropriately labelled cells. Studies in Fura 2-labelled platelets revealed that elevation of intracellular calcium by ADP, thrombin or U46619 was unaffected by PM6/13 suggesting that the epitope recognised by the antibody did not influence Ca2+ regulation. In agreement with the results from the platelet aggregation studies, PM6/13 was found to potently inhibit binding of 125I-fibrinogen to ADP activated platelets. Binding of this ligand was also inhibited by two other MAbs tested, namely SZ-21 (also to GPIIIa) and PM6/248 (to the GPIIb-IIIa complex). However when tested against binding of 125I-fibronectin to thrombin stimulated platelets, PM6/13 was ineffective in contrast with SZ-21 and PM6/248, that were both potent inhibitors. This suggested that the epitopes recognised by PM6/13 and SZ-21 on GPIIIa were distinct. Studies employing proteolytic dissection of 125I-labelled GPIIIa by trypsin followed by immunoprecipitation with PM6/13 and analysis by SDS-PAGE, revealed the presence of four fragments at 70, 55, 30 and 28 kDa. PM6/13 did not recognize any protein bands on Western blots performed under reducing conditions. However Western blotting analysis with PM6/13 under non-reducing conditions revealed strong detection of the parent GP IIIa molecule, of trypsin treated samples revealed recognition of an 80 kDa fragment at 1 min, faint recognition of a 60 kDa fragment at 60 min and no recognition of any product at 18 h treatment. Under similar conditions, SZ-21 recognized fragments at 80, 75 and 55 kDa with the 55kDa species persisting even after 18 h trypsin treatment. These studies confirm the epitopes recognised by PM6/13 and SZ-21 to be distinct and that PM6/13 represents a useful tool to differentiate the characteristics of fibrinogen and fibronectin binding to the GPIIb-IIIa complex on activated platelets.

Characterization of dissolved organic matter (DOM) extracted from soils by hot water percolation (HWP)

2010 ◽  
Vol 59 (1) ◽  
pp. 99-108 ◽  
Author(s):  
M. Takács ◽  
Gy. Füleky
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Natural Organic Matter ◽  
Extraction Methods ◽  
Soil Samples ◽  
Hot Water ◽  
Soil Extracts ◽  
Water Percolation ◽  
Soil Humic Acid

The Hot Water Percolation (HWP) technique for preparing soil extracts has several advantages: it is easily carried out, fast, and several parameters can be measured from the same solution. The object of this study was to examine the possible use of HWP extracts for the characterization of soil organic matter. The HPLC-SEC chromatograms, UV-VIS and fluorescence properties of the HWP extracts were studied and the results were compared with those of the International Humic Substances Society (IHSS) Soil Humic Acid (HA), IHSS Soil Fulvic Acid (FA) and IHSS Suwannee Natural Organic Matter (NOM) standards as well as their HA counterparts isolated by traditional extraction methods from the original soil samples. The DOM of the HWP solution is probably a mixture of organic materials, which have some characteristics similar to the Soil FA fractions and NOM. The HWP extracted organic material can be studied and characterized using simple techniques, like UV-VIS and fluorescence spectroscopy.

Particle Size Effects on Concentration of Metals in Lake Erie Bottom Sediments

1984 ◽  
Vol 19 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Alena Mudroch
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Clay Minerals ◽  
Surface Sediment ◽  
Size Effects ◽  
Lake Erie ◽  
Size Fraction ◽  
Mineralogical Composition ◽  
Major Elements ◽  
Sediment Samples

Abstract Surface sediment samples obtained at the offshore and nearshore area of Lake Erie were separated into eight different size fractions ranging from <2 µm to 250 µm. The concentration of major elements (Si, Al, Ca, Mg, K, Na, Fe, Mn and P), metals (Zn, Cu, Cr, Ni, V, Co and Pb) and organic matter was determined together with the mineralogical composition and morphology of the particles in each size fraction. The distribution of the metals in the offshore sediment was bimodal with the majority of the metals divided between the 63 to 250 um size fraction which also contained the highest concentration of organic matter (about 20%) and the <4 µm fraction containing up to 60% of clay minerals. However, the metals in the nearshore sediment were associated mainly with the clay minerals.

Distribution of Mercury in Lake St. Clair and the St. Clair River Sediments

1989 ◽  
Vol 24 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Alena Mudroch ◽  
K. Hill
Keyword(s):  
Organic Matter ◽  
Sediment Cores ◽  
River Sediments ◽  
Size Fraction ◽  
Mineralogical Composition ◽  
Recent Sediment ◽  
Geochemical Composition ◽  
Visual Appearance ◽  
Decaying Wood ◽  
Relationship Of

Abstract Sediment cores were collected in Lake St. Clair in 1985 and in the St. Clair River in 1986 to investigate the horizontal and vertical distribution and association of Hg in the sediments. A layer of recent sediment up to about 35 cm thick was differentiated by the geochemical composition and visual appearance from the underlying glacial-lacustrine deposits. The concentration of Hg in the surficial sediments in Lake St. Clair was lower in 1985 (<0.025 to 1.200 µg/g) than that found in 1974 (<0.20 to 3.00 µg/g). Up to 8.30 µg/g of Hg were found in the sediments collected from the nearshore area at Sarnia, Ontario, in the St. Clair River in 1986. The concentrations of Hg ranged from 5.05 to 16.00 µg/g in different sand-sized fractions (0.063 to 0.350 mm) of the sediment. The concentration of Hg was 17.80 µg/g in the silt-clay size fraction (<0.063 mm). No relationship was found between the concentration of organic matter and Hg, and the concentration of silica and Hg in the St. Clair River sediments. The results indicated a relationship of Hg with particles of different mineralogical composition. Up to 3.72 µg/g Hg was found in the surface sediment in Chenal Ecarte. The greatest concentration of Hg (13.15 µg/g) existed in the 0.350 mm particle size fraction, which consisted mainly of small pieces of decaying wood. A good relationship was found between the concentration of Hg and organic matter in the sediment at this area.

scholarly journals Characterization of Soil Organic Matter Individual Fractions (Fulvic Acids, Humic Acids, and Humins) by Spectroscopic and Electrochemical Techniques in Agricultural Soils

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1067
Author(s):  
Aleksandra Ukalska-Jaruga ◽  
Romualda Bejger ◽  
Guillaume Debaene ◽  
Bożena Smreczak
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Humic Substances ◽  
Humic Acids ◽  
Agricultural Soils ◽  
Fulvic Acids ◽  
Sorption Properties ◽  
Aliphatic Chains

The objective of this paper was to investigate the molecular characterization of soil organic matter fractions (humic substances (HS): fulvic acids-FAs, humic acids-HAs, and humins-HNs), which are the most reactive soil components. A wide spectrum of spectroscopic (UV–VIS and VIS–nearIR), as well as electrochemical (zeta potential, particle size diameter, and polydispersity index), methods were applied to find the relevant differences in the behavior, formation, composition, and sorption properties of HS fractions derived from various soils. Soil material (n = 30) used for the study were sampled from the surface layer (0–30 cm) of agricultural soils. FAs and HAs were isolated by sequential extraction in alkaline and acidic solutions, according to the International Humic Substances Society method, while HNs was determined in the soil residue (after FAs and HAs extraction) by mineral fraction digestion using a 0.1M HCL/0.3M HF mixture and DMSO. Our study showed that significant differences in the molecular structures of FAs, Has, and HNs occurred. Optical analysis confirmed the lower molecular weight of FAs with high amount of lignin-like compounds and the higher weighted aliphatic–aromatic structure of HAs. The HNs were characterized by a very pronounced and strong condensed structure associated with the highest molecular weight. HAs and HNs molecules exhibited an abundance of acidic, phenolic, and amine functional groups at the aromatic ring and aliphatic chains, while FAs mainly showed the presence of methyl, methylene, ethenyl, and carboxyl reactive groups. HS was characterized by high polydispersity related with their structure. FAs were characterized by ellipsoidal shape as being associated to the long aliphatic chains, while HAs and HNs revealed a smaller particle diameter and a more spherical shape caused by the higher intermolecular forcing between the particles. The observed trends directly indicate that individual HS fractions differ in behavior, formation, composition, and sorption properties, which reflects their binding potential to other molecules depending on soil properties resulting from their type. The determined properties of individual HS fractions are presented as averaged characteristics over the examined soils with different physico-chemical properties.

Sign in / Sign up

Export Citation Format

Share Document