Influence of Clay Minerals and Exchangeable Cations on the Formation of Humic-Like Substances (Melanoidins) from D-glucose and L-tyrosine

Arfaioli, P.

doi:10.1180/claymin.1999.034.3.10

Cited by 4 publications

(7 citation statements)

References 21 publications

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“…While the Maillard reaction is well known in medicine and nutrition (Ikan 1996), the extent to which it can stabilize or protect proteins in soils has not been studied. Previously considered to require too extreme a temperature to occur extensively in soils (Arfaioli et al 1999;Bosetto et al 2002), recent in vitro work has shown that, at least for free amino acids, the Maillard reaction can be catalyzed by clays (Arfaioli et al 1999;Bosotto et al, 2002), common minerals (Jokic et al 2001) and polyphenols (Jokic et al 2004). Maillard products occur extensively in soil char, however (review by Knicker (2006, this volume).…”

Section: Carbohydratesmentioning

confidence: 96%

Role of proteins in soil carbon and nitrogen storage: controls on persistence

et al. 2007

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Mechanisms of soil organic carbon (C) and nitrogen (N) stabilization are of great interest, due to the potential for increased CO 2 release from soil organic matter (SOM) to the atmosphere as a result of global warming, and because of the critical role of soil organic N in controlling plant productivity. Soil proteins are recognized increasingly as playing major roles in stabilization and destabilization of soil organic C and N. Two categories of proteins are proposed: detrital proteins that are released upon cell death and functional proteins that are actively released into the soil to fulfill specific functions. The latter include microbial surface-active proteins (e.g., hydrophobins, chaplins, SC15, glomalin), many of which have structures that promote their persistence in the soil, and extracellular enzymes, responsible for many decomposition and nutrient cycling transformations. Here we review information on the nature of soil proteins, particularly those of microbial origin, and on the factors that control protein persistence and turnover in the soil. We discuss first the intrinsic properties of the protein molecule that affect its stability, next possible extrinsic stabilizing influences that arise as the proteins interact with other soil constituents, and lastly controls on accessibility of proteins at coarser spatial scales involving microbial cells, clay particles, and soil aggregates. We conclude that research at the interface between soil science and microbial physiology will yield rapid advances in our understanding of soil proteins. We suggest as research priorities determining the relative abundance and turnover time (age) of microbial versus plant proteins and of functional microbial proteins, including surfaceactive compounds.

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Section: Carbohydratesmentioning

confidence: 96%

Role of proteins in soil carbon and nitrogen storage: controls on persistence

et al. 2007

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“…These dark colored substances may be complex, insoluble, and nonhydrolysable polymers called melanoidins. Melanoidins are N-rich, humic-like products of the Maillard reaction formed from the condensation of amino acids and reducing sugars with an affinity for clay mineral surfaces (Arfaioli et al 1999(Arfaioli et al , 2003Derenne and Largeau 2001;Hedges 1978). Presence of these dark-colored substances formed during extraction may bias the results of the colorimetric Bradford assay and result in an overestimation of soil protein when tannins are present.…”

Section: Effects Of Tanninmentioning

confidence: 97%

Bradford reactive soil protein in Appalachian soils: distribution and response to incubation, extraction reagent and tannins

Halvorson¹,

Gonzalez²

2006

Plant Soil

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Bradford reactive soil protein (BRSP) is thought to correlate to glomalin, an important soil glycoprotein that promotes soil aggregate formation and may represent a significant pool of stable soil organic matter (SOM). However, more information is needed about its importance in Appalachian soils and its relationships with other soil properties. We measured BRSP in 0-20 cm soil from pastures, hayfields, cultivated fields or forest areas in southern West Virginia. Highest amounts of BRSP were found near the soil surface and decreased significantly with depth for all land uses except cultivated sites. Forest and pasture sites contained more BRSP than hayfields or cultivated fields but these differences occurred only in the 0-5 cm depth. Overall averages of C and N in BRSP represented about 4.0 and 6.5% of the total soil C and N respectively. During a 395 day soil incubation, we found CO 2 -C evolution rates comparable to other studies but only small changes in BRSP ( < 10%) including some evidence for increases during incubation. Sodium citrate, sodium pyrophosphate, and sodium oxalate recovered significantly more BRSP from soil than the other extractants we tested with highest extraction efficiencies observed for sodium citrate and pyrophosphate. Recovery of BRSP appears related to negative charge and buffering capacity of both the soil and extractant. Extractants with low negative charge had little buffering capacity and yielded little BRSP. Tannic acid appeared to increase extraction of BRSP but less soluble-N was recovered from tannin-treated samples than from untreated controls and E4/E6, the ratio of absorbance at 465 and 665 nm, decreased, evidence for the formation of larger or heavier molecules. Formation of dark-colored substances during extraction suggests the colorimetric Bradford assay may overestimate soil protein when tannins are present. Recovery of less soluble-N from soil extracts and lower E4/E6 ratios suggests tannins may bind with soil constituents themselves or form non-extractable N-containing complexes.

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“…Condensation of glucose and tyrosine/glycine/ tryptophan at 70 ° C: FTIR spectra resembling natural humic substances; yields of humic substances; XRD investigation into change in d -spacings Arafaioli et al (1997Arafaioli et al ( , 1999 ; Bosetto et al (1995Bosetto et al ( , 1997Bosetto et al ( , 2002 Smectites Condensation of arginine and glucose at 37 ° C; C and N fractions yields; FTIR spectra of solid residue and supernatant humic substances; XRD investigation into change in d -spacings Gonzalez and Laird (2004) …”

Section: Clay -Size Layer Silicatesmentioning

confidence: 99%