Humic Substances and Humification

Ziechmann, W.; Hübner, M.; Jonassen, Kristoffer E.N.; Batsberg, W.; Nielsen, T.; Hahner, S.; Hansen, Poul Erik; Gudmundson, A.-L.

doi:10.1016/b978-1-85573-807-2.50006-0

Cited by 9 publications

(14 citation statements)

References 16 publications

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“…The proposed HA BB model (Figure 1) is based on the average structural unit of HA obtained from chemical analysis (1,22,27,29,52). The TNB structure is consistent with several of those reported previously (52,53).…”

Section: Resultsmentioning

confidence: 99%

Conformational Modeling of a New Building Block of Humic Acid: Approaches to the Lowest Energy Conformer

Sein

Varnum

Jansen

1998

Environ. Sci. Technol.

145

112

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Multiple structural models of humic acid (HA) building blocks have been reported. In this work, the modeling is based on two structural motifs: (i) the Steelink structure and (ii) a new humic acid [TNB] building block, which incorporates more fully the results of experimental data and retro-biosynthetic analyses. Both have significant conformational freedom complicated by their stereochemistry. A molecular modeling approach for the analysis of complex molecules with significant conformational freedom is described as it relates to the newly proposed humic acid building block. A potential energy surface for various conformers of the low-energy stereoisomer has been generated. Included in this discussion is the relationship of the stereochemistry to conformation and secondary structure.

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Section: Resultsmentioning

confidence: 99%

Conformational Modeling of a New Building Block of Humic Acid: Approaches to the Lowest Energy Conformer

Sein

Varnum

Jansen

1998

Environ. Sci. Technol.

145

112

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“…29 So far the structure of HS is under debated. The main obstacle is the lack of a repetitive sequences and the variety of chemical and biological reactions involved in their genesis, 30 that make HS very complex and multifaceted molecules, able to exert important signalling and nutritional functions in soil-plant system. The points of view more debated concern the polymeric nature and the supramolecular association of HS.…”

Section: Molecular Structure Of Humic Substancesmentioning

confidence: 99%

Humic substances biological activity at the plant-soil interface

Trevisan

Francioso

Quaggiotti

et al. 2010

Plant Signaling & Behavior

333

177

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Humic substances (HS) represent the organic material mainly widespread in nature. HS have positive effects on plant physiology by improving soil structure and fertility and by influencing nutrient uptake and root architecture. The biochemical and molecular mechanisms underlying these events are only partially known. HS have been shown to contain auxin and an "auxin-like" activity of humic substances has been proposed, but support to this hypothesis is fragmentary. In this review article, we are giving an overview of available data concerning molecular structures and biological activities of humic substances, with special emphasis on their hormone-like activities.

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“…As SH são misturas heterogêneas de polieletrólitos, com composição, estrutura, funcionalidades e massas moleculares variadas 1,3 . Diferem de outras classes de compostos naturais devido à sua estrutura química indefinida e gênese complexa 4,5 . O alto teor de grupos funcionais contendo oxigênio na forma de carboxilas, hidroxilas fenólicas e carbonilas 6 conferem às SH papel importante na reatividade e transporte de espécies orgânicas e inorgânicas 3,7 .…”

Section: Introductionunclassified

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares

et al. 2002

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100 - <5 kDa) and characterized by several techniques. Molar ratios H/C suggested higher aromaticity for fractions F1 and F6 whereas molar ratios C/N didn´t show any differences regarding the humification degree between the fractions. The UV-Vis absorbance a254/a436 ratio showed higher results for F4 and F5, probably by less condensed features. FTIR studies showed high similarity in the functional groups in the fractions. The highest percentage of traces of Co, Al, Fe, Mn, Cu, Zn and Ni (determined by ICP-AES) was preferably complexed by fractions F3 and F4 with a greater amount of dissolved organic carbon (DOC). In addition, the exchange constants, determined by ultrafiltration method, showed complexes AHS-Fe and AHS-Al with higher stability than complexes AHS-Co in all fractions.]]>

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Humic Substances and Humification

Cited by 9 publications

References 16 publications

Conformational Modeling of a New Building Block of Humic Acid: Approaches to the Lowest Energy Conformer

Conformational Modeling of a New Building Block of Humic Acid: Approaches to the Lowest Energy Conformer

Humic substances biological activity at the plant-soil interface

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares

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