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  • 1
    ISSN: 1432-0789
    Keywords: Key words Copper porphyrin ; Actinomycete melanins ; Electron paramagnetic resonance spectroscopy ; Brazilian soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The coordination chemistry of iron (III) (Fe3+) and copper (II) (Cu2+) in melanins synthesized by seven actinomycetes isolated from Brazilian latosol soils under savanna (cerrado) vegetation was investigated using electron paramagnetic resonance (EPR) and ultraviolet-visible (UV-Vis) spectroscopy. The EPR spectra indicated the presence of Cu2+ ions bound to oxygenated and nitrogenous functional groups, and rhombic coordinated Fe3+ ions. In some of the actinomycete melanins the EPR hyperfine splitting of Cu+2 ion complexes was well resolved, and indicated four magnetically equivalent nitrogen atoms in a plane. This result suggested the presence of Cu+2 porphyrin complexes, which was confirmed by Soret bands in the 400-nm region of the UV-Vis spectra. The concentration of Mn in actinomycete melanins, determined by inductively coupled plasma atomic emission spectroscopy, was lower than those of Cu and Fe.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 5 (1987), S. 120-125 
    ISSN: 1432-0789
    Keywords: Fungal melanins ; Humic acid ; Infrared analysis ; Free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Humic acid-type polymers (melanins) synthesized in culture media by the fungi Aspergillus glaucus, Eurotium echinulatum, Hendersonula toruloidea, Stachybotrys atra and Aspergillus sydowi were analysed for elemental composition, functional group content, infrared (IR) and electron spin resonance (ESR) properties. Results were discussed in comparison with range values referred for soil humic acids. The fungal polymers showed significant differences in carboxyl and nitrogen content and C/H atomic ratios, reflecting a different degree of condensation (aromaticity) among the various samples. IR analysis gave evidence of: (a) the predominant aromatic character of melanins from A. glaucus, E. echinulatum and H. toruloidea; (b) the high content of aliphatic and olefinic components of S. atra melanin; (c) the typical presence of amide bonds in the nitrogen-richest melanins from A. sydowi and H. toruloidea; and (d) the generally low amount of free carboxyl groups, which often appeared involved in hydrogen bonds. ESR spectra showed that all the melanins studied contained appreciable concentrations of organic free radicals of prevailing semiquinonic nature and of the same order of magnitude commonly measured in humic acids from soil and other sources. The free electron concentration was shown to be directly related to the C/H atomic ratio and to the degree of aromaticity shown by IR analysis. This indicated that the highest free radical content in the melanins from E. echinulatum and A. glaucus was associated with the highest presence of condensed aromatic structures. Humic acid-type polymers synthesized by soil fungi may, therefore, contribute to the total free radical content of soil humic substances and play important roles in all reactions involving free radicals in soils and related environments.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0003-2670
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0003-2670
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Inorganic Biochemistry 36 (1989), S. 346 
    ISSN: 0162-0134
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Publishing Ltd/Inc.
    European journal of soil science 55 (2004), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The potential anticlastogenic and antitoxic effects of a soil humic acid (HA), a peat HA and a peat fulvic acid (FA) on the mutagen maleic hydrazide (MH) have been investigated in two legume species, Vicia faba and Pisum sativum. Both HAs and FA were tested at two different concentrations, 20 and 200 mg l−1, either alone or after 24-hour interaction with 10 mg l−1 of MH before addition to the legume seeds. Anticlastogenicity, i.e. an antimutagenic action defined as the capacity for minimizing chromosome breakages, was evaluated by counting both micronuclei (MN) and aberrant anatelophases (AAT) in root-tip cells. Length and dry weight of the seedling primary root were measured to test the antitoxic activity of HA and FA on MH. The possible occurrence and extent of adsorption or desorption of MH onto or from HA were also investigated. The two species responded differently to the anticlastogenic tests, with V. faba showing a greater number of MN and AAT anomalies than P. sativum. Peat HA and FA exhibited anticlastogenic and antitoxic activities of similar intensity and greater than those of soil HA. The adsorption capacity of both HAs for MH was small, thus suggesting that adsorption is not a major mechanism responsible for the reduction of clastogenicity and antitoxicity of MH by HA.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Analytical and Applied Pyrolysis 15 (1989), S. 121-128 
    ISSN: 0165-2370
    Keywords: Biomass ; gas chromatography ; humic acids ; lignin ; mass spectrometry ; pyrolysis ; vermicomposts.
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 52 (1998), S. 1037-1046 
    ISSN: 1572-8943
    Keywords: biosludges ; composting ; humic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Samples of pulp and paper mill biosludges with different maturation ages (fresh biosludge and composts collected after 3 weeks, 1 year and 2 years of composting) and their corresponding humic acids were analyzed by thermal analysis with DSC in association with FT-IR spectroscopy. The DSC curves obtained exhibited endotherms in the low-temperature region, assigned to dehydration processes, exotherms at around 370°C, attributed to the loss of peptidic structures, and high-temperature exotherms, assigned to the loss of functional groups; the lignins were thermostable, regardless of the maturation age of the compost. The results obtained provided evidence that, during composting, the organic matter evolved in the direction of higher molecular complexity and stability, leading to a more homogeneous product closely resembling humic-like substances.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 127 (1990), S. 41-47 
    ISSN: 1573-5036
    Keywords: alachlor ; cycluron ; humic acid ; nutrient solution ; Pisum sativum ; prometone ; root growth ; shoot growth ; 2,4-D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Slight increases in root length and dry matter production were measured in roots and shoots of Pisum sativum seedlings, when germinated seeds were grown for eight days in a controlled environment chamber, on Nitch nutrient solution to which 10 mg L-1 soil humic acid (HA) had been added. A concentration of 100 mg L-1 of HA produced a small reduction in dry matter production of shoots. In the presence of herbicides, 10 mg L-1 cycluron or 100 mg L-1 prometone, root elongation and shoot growth was reduced by varying degrees with respect to the control. Nutrient solutions containing 100 mg L-1 cycluron, 10 or 100 mg L-1 alachlor, or as little as 0.1 mg L-1 of 2,4-D resulted in an almost complete suppression of the growth of pea seedlings. The addition of 10 or 100 mg L-1 of HA to nutrient solution containing the herbicide was found to be either ineffective in enhancing growth, or even further reduced growth, compared to samples grown in the presence of the herbicide alone. The results of this preliminary study suggest that the generally accepted view that humic substances exert a positive effect on plant growth may not occur when humic substances interact with herbicides.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 69 (1982), S. 57-66 
    ISSN: 1573-5036
    Keywords: Italy ; Minor elements ; Pollution ; Regression model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A number of soil samples from south-east Italy were analyzed for As, Bi, Cd, Cu, Hg, Li, Mn, Ni, Pb, Se, Sn, and Zn contents with the aim of estimating pollution degree in cultivated lands of region. The existence of linear relations among variables was detected assuming multiple regression models and analyzing then linear correlation coefficients.
    Type of Medium: Electronic Resource
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