Amino-N compounds found in soil organic matter hydrolysates of a loamy sand using an immobilized protease reactor column

Summary Soil organic matter (OM) from seven different fertility plots of a loamy sand was extracted and fractionated into high- and low-molecular-weight (HMW, LMW) fractions using gel filtration. The fractions were acid-hydrolyzed to determine the amino sugar and amino acid contents. The same fractions were hydrolyzed with an immobilized protease reactor column. Reverse-phase high-performance liquid chromatography (HPLC) was used to identify the soil amino-N compounds. With the HMW fraction as substrate, the enzyme released less than 1% of 11 amino-N compounds determined by acid hydrolysis. Phenylalanine and leucine, however, were recovered in quantities of 2% and 4%, respectively. Immobilized protease hydrolysis of the LMW fraction recovered considerably more amino-N compounds compared with acid hydrolysis of the same fractions. Each system of hydrolysis produced some amino-N compounds not found in the other. We conclude that an immobilized enzyme reactor column will allow a researcher to perform time-course hydrolysis, so that hydrolysis intermediates, e.g. peptides, can be separated and identified.     

Effect of the Molecular Weight Distribution of Glutenin Protein from an Extra‐Strong Wheat Flour on Rheological and Breadmaking Properties Through Reconstitution Studies

Ten glutenin fractions were separated by sequential extraction of wheat gluten protein with dilute hydrochloric acid from defatted glutenin‐rich wheat gluten of the Canadian hard red spring wheat (HRSW) cultivar Glenlea. The molecular weight distribution (MWD) of 10 different soluble glutenin fractions was examined by multistacking SDS‐PAGE under nonreduced conditions. Also, the subunit composition of the different glutenin fractions was determined by SDS‐PAGE under reduced conditions. The MWD of the fractions (especially HMW glutenins) varied from fraction to fraction. From early to later fractions, the MWD shifted from low to high. The early extracted fractions contained more LMW glutenin subunits (LMW‐GS) and less HMW glutenin subunits (HMW‐GS). The later extracted fractions and the residue fraction contained much more HMW‐GS (2*, 5, and 7 subunits) than the early extracted fractions. The trend in the amounts of 2*, 5, and 7 subunits in each fraction from low to high matched the extraction solvent sequence containing from lower to higher levels of HCl. The influence of glutenin protein fractions from the extra‐strong mixing cultivar, Glenlea, on the breadmaking quality of the weak HRSW, McVey, was assessed by enriching (by 1%) the McVey base flour with isolated glutenin protein fractions from Glenlea. The mixograph peak development times and loaf volumes of enriched flour were measured in an optimized baking test. The results indicated that the higher content in Glenlea glutenin of HMW‐GS with higher molecular weight, such as 2*, 5, and 7, seem to be the critical factor responsible for the strong mixing properties of Glenlea. Our results confirmed that subunit 7 occurred in the highest quantity of all the HMW‐GS. Therefore, it seems that the greater the content of larger molecular weight glutenin subunits, the larger the glutenin polymers and the stronger the flour.     

低分子量有机酸对石灰性土壤有机磷组成及有效性的影响

为探索提高土壤磷素有效性的途径,采用室内培养的方法,研究不同有机酸对土壤速效磷含量及有机磷组分的影响。结果表明,添加有机酸后土壤速效磷含量发生显著变化,其中草酸处理下土壤速效磷含量显著高于其他处理,而柠檬酸和苹果酸对土壤速效磷含量具有抑制作用,其活化量为负值;随着培养时间的延长,速效磷含量缓慢降低。速效磷含量随着草酸浓度的升高而升高,随着苹果酸、柠檬酸浓度的升高而降低;有机酸处理后,土壤活性、中活性、中稳性有机磷升高,高稳性有机磷降低,这说明有机酸能促进土壤有机磷由有效性低的形态逐步向有效性高的形态转化,其中草酸的作用效果总体上较柠檬酸和苹果酸强。     

Screening spring wheat for midge resistance in relation to ferulic acid content

The concentration of ferulic acid (FA), the major phenolic acid in the wheat kernel, was found to differ significantly in the mature grain of six wheat cultivars known to have a range of tolerance to the orange wheat blossom midge (Sitodiplosis mosellana). Differences in FA content were correlated with floret infestation level of the cultivars. The wheat cultivars ranked similarly in FA content at the four locations where they were tested, despite a significant effect of environment. Ferulic acid was synthesized mainly during the early stages of grain filling but at different rates among cultivars. Ferulic acid was concentrated primarily in the shorts and bran fractions in an insoluble-bound form. A high correlation was obtained between FA contents as determined by GLC, fluorometry, UV, and colorimetry. The colorimetric procedure was modified as a qualitative, simple, and rapid test for identifying midge-resistant wheat and evaluated in several field trials. The method should provide a rapid tool in the preliminary screening of experimental lines in the development of midge-resistant wheat cultivars.     

Hydrolysis of low-molecular-weight soil peptides by immobilized proteases in column and batch reaction systems

Summary Organic matter was extracted from three soils, a cultivated Berwick sandy loam, a cultivated Franklin loamy sand, and an uncultivated Cumberland silty loam. Gel-permeation chromatography was used to separate organic matter extracts into high- (HMW) and low-molecular-weight (LMW) fractions. Reversed-phase high performance liquid chromatography was used to separate and collect the LMW peptide fractions. Peptide samples were hydrolyzed with immobilized proteases attached to beaded agarose and carboxymethyl cellulose in column and batch reaction systems. The chromatograms suggested that peptides are bound to common soil components. The amino acids released in the greatest percentages were relatively non-polar. Large percentages of serine, glycine, alanine, threonine, and valine were observed in the LMW soil peptides. Little aspartic acid, asparagine, glutamic acid, glutamine, arginine, and no histidine was detected in the LMW soil peptides. The soil peptides released different amino acid percentages and quantities when hydrolyzed by immobilized proteases attached to different supports. The quanitities of amino acids released by batch hydrolysis differed from those obtained with column hydrolysis. Greater quantities of amino acids were released (by both types of immobilized protease) from the LMW peptide hydrolysates of the two cultivated soils than from the uncultivated soil.     

施用有机物料对土壤镉形态的影响

采用室内培养试验,研究作物新鲜秸秆和腐熟猪粪对模拟镉（Cd）污染的土壤中Cd形态转化的动态影响。结果表明,各处理土壤交换态Cd含量随培养时间均逐渐降低。碳酸盐结合态和铁锰氧化物结合态Cd含量先增加后降低, 而有机质结合态和残渣态Cd含量则逐渐增加。添加秸秆可增加土壤交换态Cd含量,但随时间延长,增幅逐渐降低, 猪粪则可降低土壤交换态Cd含量。添加有机物后土壤交换态Cd含量的变化主要是由有机质结合态或残渣态Cd含量的变化而引起。秸秆和猪粪对土壤Cd形态的转化与土壤胡敏酸（HA）和富里酸（FA）的变化有关。秸秆对能活化土壤Cd的FA增加幅度大于对能钝化土壤Cd的HA增加幅度,降低HA/FA比,但降幅随时间逐渐减少; 猪粪在整个培养阶段对HA增加幅度均大于FA的增加幅度,增加HA/FA比。秸秆和猪粪均可降低潮土pH而提高红壤pH,但只有猪粪可通过提高红壤pH降低Cd向交换态转化。添加秸秆和猪粪后,Cd由低活性态向交换态转化与HA/FA呈显著负相关。     

trans-C18:1 isomers in cheeses enriched in unsaturated fatty acids and manufactured with different milk fat globule sizes

Increasing the knowledge on dietary fat composition, mainly the minor components, will improve the nutritional value of foods and their labeling. In this study, we examined the trans-octadecenoic acid (C18:1) composition of Emmental cheeses enriched in unsaturated fatty acids (FA) and manufactured with milks produced by cows selected to produce small and large fat globules. The FA composition of the milks was not significantly ( P > 0.05) different from the FA composition of the corresponding Emmental cheeses. Increasing the unsaturated FA content of the cheeses using dietary manipulations lead to an increase in the trans-C18:1 and changed their isomeric profiles. In milk fat produced with the linseed-enriched diet, the trans-10 C18:1 concentration was greater than trans-11 C18:1 (vaccenic acid), which is classically the major trans-C18:1 in milk fat. The content in trans-C18:1 and more particularly in trans-10 C18:1 was negatively correlated with the size of fat globules ( r (2) = 0. 82 and 0.87, respectively) and related to milk fat depression. The trans-C18:1 content was negatively correlated with the saturated FA (slope = -0.35; r (2) = 0.81) and positively correlated with the unsaturated (slope = 0.29; r (2) = 0.85) and monounsaturated (slope = 0.32; r (2) = 0.81) FA. Focusing on the health-related considerations of fat in food products, further nutritional studies are needed to elucidate the role of trans-C18:1 isomers.     

Role of Gluten and Its Components in Determining Durum Semolina Dough Viscoelastic Properties

Gluten was isolated from three durum wheat cultivars with a range in strength. Gluten was further fractionated to yield gliadin, glutenin and high molecular weight (HMW) and low molecular weight (LMW) glutenin subunits (GS). The gluten and various fractions were used to enrich a base semolina. Enriched dough samples were prepared at a fixed protein content using a 2‐g micromixograph. Mixing strength increased with addition of gluten. Dynamic and creep compliance responses of doughs enriched with added gluten ranked in order according to the strength of the gluten source. Gliadin addition to dough resulted in weaker mixing curves. Gliadin was unable to form a network structure, having essentially no effect on dough compliance, but it did demonstrate its contribution to the viscous nature of dough (increased tan δ). Source of the gliadin made no difference in response of moduli or compliance. Addition of glutenin to the base semolina increased the overall dough strength properties. Glutenin source did influence both dynamic and compliance results, indicating there were qualitative differences in glutenin among the three cultivars. Enrichment with both HMW‐GS and LMW‐GS increased overall dough strength. Source of HMW‐GS did not affect compliance results; source of LMW‐GS, however, did have an effect. The LMW‐2 proteins strengthened dough to a greater extent than did LMW‐1. Mechanisms responsible for dough viscoelastic properties are described in terms of reversible physical cross‐links.     

Properties of neutral phosphate buffer extractable organic matter in soils revealed using size exclusion chromatography and fractionation with polyvinylpyrrolidone

Abstract

A neutral phosphate buffer (NPB) extraction method has been used to estimate the amount of available N in soil. However, the properties of soil NPB-extractable organic N have not been fully elucidated. The purpose of the present study was to characterize the properties of organic matter in the NPB extracts of soils. The NPB extracts were obtained from three soil samples, and the organic matter in the extracts was separated into three fractions according to its solubility in acid and adsorption onto polyvinylpyrrolidone (PVP). High-performance size exclusion chromatography (HPSEC) with ultraviolet (UV) and fluorescence detections was applied to the NPB extracts and their fractions. The HPSEC analysis of the NPB extract revealed the presence of a single broad peak, irrespective of the detection methods. The broad peak was identified as humic substances using the on-flow measurements of UV absorption spectra and fluorescence emission spectra. Among the fractions, the PVP-non-adsorbed fulvic acid (FA) fraction accounted for the largest proportion of organic C or N in the NPB extract, followed by the PVP-adsorbed FA and humic acid (HA) fractions. The peak of humic substances was observed for all fractions using HPSEC with the on-flow measurement of UV absorption and fluorescence emission spectra. The molecular weight of the humic substances varied with each fraction. When the Coomassie Blue-reactive substances (CBRS) were quantified using a Bradford protein assay, they were detected in the NPB extract and almost half were distributed in the PVP-non-adsorbed FA fraction. However, humic substances were considered to be the main constituents of CBRS in the soil NPB extract because of their reactivity with Coomassie Blue and the absence of proteinaceous materials. Furthermore, an incubation experiment revealed that the organic matter available to microorganisms was included in the HA and PVP-non-adsorbed FA fractions. Based on the HPSEC analysis of the NPB extracts and their fractions, it was observed that the humic substances in the NPB extract, particularly in the HA and PVP-non-adsorbed FA fractions, were available to microorganisms.     

Forms and Uptake of Manganese in Relation to Soil Taxonomic Orders in Alluvial Soils of Punjab,India

Different forms of manganese (Mn) were investigated, including total, diethylenetriamine penta-acetic acid (DTPA) extractable, soil solution plus exchangeable (Mn), Mn adsorbed onto inorganic sites, Mn bound by organic sites, and Mn adsorbed onto oxide surfaces, from four soil taxonomic orders in northwestern India. The total Mn content was 200–950 mg kg^?1, DTPA-extractable Mn content was 0.60–5.80 mg kg^?1, soil solution plus exchangeable Mn content was 0.02–0.80 mg kg^?1, Mn adsorbed onto inorganic sites was 2.46–90 mg kg^?1, and Mc adsorbed onto oxide surfaces was 6.0–225.0 mg kg^?1. Irrespective of the different fractions of Mn their content was generally greater in the fine-textured Alfisols and Inceptisols than in coarse-textured Entisols and Aridisols. The proportion of the Mn fractions extracted from the soil was in the order as follows: Adsorbed onto oxide surfaces > adsorbed onto inorganic site > organically bound > DTPA > soil solution + exchangeable. Based on coefficient of correlation, the soil solution plus exchangeable Mn, held onto organic site and oxide surface (amorphous) and DTPA-extractable Mn, increased with increase in organic carbon of the soil. The two forms, adsorbed onto inorganic site (crystalline) and DTPA extractable, along with organic carbon, increased with increase in clay content of the soil. DTPA-Mn and Mn adsorbed onto oxide surfaces and held on organic site decreased with increased with an increase in calcium carbonate and pH. Total Mn was strongly correlated with organic carbon and clay content of soil. Among the forms, Mn held on the organic site, water soluble + exchangeable and adsorbed onto oxide surface were positively correlated with DTPA-extractable Mn. DTPA-extractable Mn seems to be a good index of Mn availability in soils and this form is helpful for correction of Mn deficiency in the soils of the region. The uptake of Mn was greater in fine-textured Inceptisols and Alfisols than in coarse-textured Entisols and Aridisols. Among the different forms only DTPA-extractable Mn was positively correlated with total uptake of Mn. Among soil properties Mn uptake was only significantly affected by pH of the soil.     

Changes in Fatty Acid Composition and Content of Two Plants (Lolium perenne and Trifolium repens) Grown During 6 and 18 Months in a Metal (Pb, Cd, Zn) Contaminated Field

The aim of this in situ study was to investigate the fatty acid (FA) composition and content in roots and shoots of Lolium perenne and Trifolium repens, grown under heavy metal stress (Cd, Pb, Zn). The composition of FA was quite similar for the two plants and the two organs; main FA were palmitic acid (C16:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). For both plants, the major FA that characterized the roots was C18:2 whereas C18:3 was the prominent FA in shoots. For the first sampling (S1), in the roots of L. perenne and T. repens, polyunsaturated fatty acids (PUFA) were affected by metal contamination while, in the second sampling (S2), PUFA were affected in the shoots of the two plants. This alteration of PUFA was well correlated with the bioaccumulation factor of metals which decreased in roots and increased in shoots with the time. Moreover, a positive correlation was found between the PUFA decrease and the malondialdehyde (MDA) content, indicating the occurrence of a lipid peroxidation induced by the metal stress.     

长期施肥对小麦-玉米作物系统土壤腐殖质组分碳和氮的影响

通过对华北平原小麦–玉米轮作农田生态系统18年田间施肥试验,研究了长期不同施肥处理对耕层（0—20 cm）土壤腐殖质及活性腐殖质组分碳和氮的影响。试验设化肥NPK不同组合（NPK、NP、NK、PK）,全部施用有机肥（OM）,一半有机肥+化肥NPK（1/2OMN）及不施肥（CK）共7个处理。结果表明,各施肥处理均能在不同程度上增加土壤腐殖质（胡敏酸、富里酸和胡敏素）及活性腐殖质（活性胡敏酸和活性富里酸）组分碳和氮含量,提高可浸提腐殖质（胡敏酸和富里酸）及活性腐殖质组分碳和氮分配比例;但施肥对土壤活性腐殖质组分碳和氮含量的增加率均分别高于腐殖质组分碳和氮。各处理土壤腐殖质及活性腐殖质组分碳和氮含量均为OM处理最高,且有机肥与化肥NPK配施高于单施化肥各处理;而化肥处理中NPK均衡施用效果最好。说明施用有机肥、有机肥与化肥NPK配施及化肥NPK均衡施用是增加土壤腐殖质及活性腐殖质组分碳和氮的关键;活性腐殖质组分碳和氮较腐殖质组分碳和氮对施肥措施的响应更灵敏。     

Properties of humic substances from the baltic sea and lake ermistu mud

Scope and Goal  Humic substances (HSs) are the product of microbial degradation, chemical polymerisation and oxidation of organic matter. HSs can be divided into different fractions: humic acid (HA), hymatomelanic acid (HMA), fulvic acid (FA) and humin. HSs play a fundamental role in accumulation and exchange processes of chemical compounds (metals and organic pollutants) in the environment. HSs can form soluble complexes that migrate long distances or precipitate, carrying bound cations with them. The migration/precipitation abilities depend on the metal ion, the ion charge, the degree of ionisation of the organic molecule, the ionic strength of the media, and the location of the metal ion. Objective  Estonia is rich in the Baltic Sea and lake sediments. Historically, mud has been used in human treatment as a curative mud. High-molecular HSs are an important part of curative mud and they have a strong effect on its properties. The curative mud which is used in human therapy may not be polluted with different organic and inorganic contaminants. The aim of this work is to characterise and compare HSs isolated from the Baltic Sea mud (Haapsalu Bay) and from the sediments of Lake Ermistu (Estonia). Results and Conclusions  We determined the yield of basic extraction of different HSs components from mud in the course of separation. We found that acid pre-treatment of mud increased the amount of extracted HSs more in the sea mud than in the lake mud. These results show that HSs are bound to the inorganic/organic structure of mud and are released during prolonged treatment with an acid. We performed elemental analysis of the different fractions of HS extracts. HMA fractions had the highest carbon content and the lowest nitrogen content. HMA contains more polysaccharides than amino acid residues. These subunits may cause a better solubility of HMA in water as compared to HA. Acid pre-treatment of the natural sea and the lake mud diminished the content of carbon in most of the HS fractions. The content of nitrogen in the sea and in lake FA diminished by about two times. We determined the metal content in the mud and its HS fractions. We found that the concentration of heavy metals Pb and Cr is lower than <0.08 mg/kg. As expected, the total metal concentration is considerably lower in the lake than in the sea mud. Acid pre-treatment of mud shows that the sea HA forms more stable Fe and Mg complexes, while the sea HMA contains more stable Zn and Cu complexes. The lake HSs result in more stable Mg complexes with HA and HMA fractions. Sea FA binds Cu and Mg better, but lake FA is more effective in binding Zn. To compare the amount of metals extracted from HA, HMA, FA (with that, remains in HS fractions), the metal concentration in the alkaline full extract of the sea mud was determined. Alkaline treatment removed 0.8% Mg, 7.9% Cu, 5.2% Zn and 3.8% Fe together with HSs from the sea mud, the rest remained in humin and in the mineral part of the mud. The following work-up was additionally carried out for most of the metals. So, we found that there was only 1.7% of Fe, 2.1 % of Mg, 23.2% of Zn and 45.2% of Cu left in HA, HMA and the FA fraction (as a sum) from the total amount of those metals in HSs. This means that Cu is the metal most strongly bound to HSs. On the bases of HS separation data we found that the order of stability of the metal-humate complexes is Cu>Zn>Mg>Fe. The ultraviolet spectra of HA, HMA and FA revealed that HMA had the biggest molar absorption and calculated aromaticity. Recommendations and Outlook. The characteristics of HSs, isolated from the Baltic Sea and Lake Ermistu mud reveal the difference of HSs from the sea and the lake mud. Also, different properties of HS fractions are observed. Metals are concentrated variously in different HS fractions. In all cases the content of Pb and Cr was low, meaning that the mud preparations are nontoxic in respect to these metals. The order of stability of metal-humate complexes is Cu>Zn>Mg>Fe. The order of affinity of metals to HS fractions obtained have to be extended to other metals of environmental interest. The ability of HSs to bind metals may make them a candidate for natural, environmentally safe substances to concentrate hazardous metals and to remove them from natural water reservoirs.     

Amino acid composition of soil peptides chromatographed by high performance liquid chromatography on C18 and C8 columns

Summary Low molecular weight fractions (LMW; <5000 daltons) of organic matter were isolated from three soils by a mild extraction procedure and gel-permeation chromatography. The peptides present in the LMW soil extracts were separated on a Whatman Partisphere C18 and a Beckman Ultrapore C8 column by reverse-phase high performance liquid chromatography (HPLC). The peptide fractions were collected, acid hydrolyzed, and analyzed for amino acid composition. The C8 bonded-phase column gave better separation of the LMW soil peptide material than the C18 column. The total quantities of amino acids released from LMW peptides by acid hydrolysis were greater than the quantities released by immobilized protease hydrolysis (Warman and Isnor 1990). Total soil N present in the form of LMW peptides in these three soils ranged from 4 to 15%. The total recovery of peptide amino acid-N showed little difference between the C18 and C8 columns for two of the soils tested.     

The impact of different land uses in urban area on humus quality

Purpose

In urban areas, humus quantity and quality depend less on natural environmental factors than on anthropogenic ones. The aim of the study was to assess the impact of different land use types of urban soils on the properties of soil organic matter (SOM).

Materials and methods

Thirty-five sites involving four ways of soil use were examined: lawns, allotment gardens, fallows, and arable lands. The study was conducted in Pruszków Town in the Warsaw Agglomeration, Central Poland. Lawns and allotment gardens were located in the central part of the town, whereas fallows and arable lands were in the peripheral zones. Humus horizons, to a depth of 0–20 cm, were analyzed. Using Na-pyrophosphate extraction, we determined the soluble SOM compounds (PY), and the organic matter in the extraction residue, considered as humins (HM). In a separate extraction (with 0.05 M H₂SO₄), low molecular weight (LMW) humus compounds were determined. The quantity of humic acids (HA) precipitated during Na-pyrophosphate extraction was determined as well. A spectroscopic method (UV-Vis) was used to characterize HA properties. The absorption coefficients E4/E6 were calculated based on the results of absorbance measurements involving 465- and 665-nm wavelengths of UV-Vis light. Statistical analyses were performed to find similarities and differences between soils differently used in Pruszków.

Results and discussion

The dominant part of the humus in the studied soils were humins HMs. There were two times more HM in the central part of the town than that in the peripheral zones. The same observation was made for soluble humus compounds (PY). The amount of LMW fractions was similar in soils of all uses. The degree of humification was small and averaged about 30% for all soils. Fulvic acid (FA) concentrations predominated over HA concentrations in all soils. The least condensed HA occurred in the allotment gardens with an E4/E6 ratio of 5.7, whereas the most condensed HAs were present in soil on arable lands (E4/E6 ratio of 4.7).

Conclusions

The studies have shown that the type of land use affects humus properties. The main differences were found to be in the quantity of humus compounds. Soils from the central part of the town contained more stable (HM) and soluble (PY) compounds than soils in the outskirts of town. PY compounds were characterized by a simple structure. Fulvic acids (FA) dominated in all of the studied soils (low HA/FA ratio). A high E4/E6 ratio indicates low maturity of humic fractions with low molecular weight compounds.

     

Characterization of humic substances derived from swine manure-based compost and correlation of their characteristics with reactivities with heavy metals

Various composts contain a significant amount of humic substances including humic acid (HA) and fulvic acids (FAs). The FA fraction in soils is considered to be sensitive to agronomic and environmental factors. In this study, three fractions of humic substances, HA (MW > 1000 Da), FA (MW > 1000 Da), and FA (MW < 1000 Da) were extracted from swine manure-based compost and characterized, and then, their reactivities were correlated with heavy metals. Compositions of the three fractions of humic substances were characterized by elemental and total acidity analyses and electron spin resonance (ESR), Fourier transform infrared (FTIR), and 13C nuclear magnetic resonance with cross-polarization and magic-angle spinning spectroscopic techniques. Elemental analyses indicated that HA has higher contents of C, H, N, and S than those of FAs. However, FA (MW > 1000) and especially FA (MW < 1000) have higher contents of O than that of HA (MW > 1000). The g values of the ESR spectra of the three fractions showed that the organic free radical characteristics and the widths of the spectra and free radical concentrations of the three fractions are significantly different. The FTIR spectra indicated that HA (MW > 1000) is abundant in C=C bonds while FA (MW > 1000), especially FA (MW < 1000), are abundant in C=O bonds. In addition, 13C NMR spectra indicate that carboxyl contents of FA (MW > 1000), especially FA (MW < 1000), are higher than that of HA (MW > 1000). The sequence of the reactivity in terms of acidic functional groups was FA (MW < 1000) > FA (MW > 1000) > HA (MW > 1000). Elemental and functional group compositions of the three fractions significantly correlated with reported reactivities with heavy metals. The application of swine manure-based compost containing HA and FAs fractions to soil and associated environments may thus significantly affect the concerned reactions with organic and inorganic compounds including pollutants.     

Nutritional Composition of Iron,Zinc, Calcium,and Phosphorus in Wheat Grain Milling Fractions as Affected by Fertilizer Nitrogen Supply

Fe and Zn deficiencies are global nutritional problems. N supply could increase Fe and Zn concentrations in wheat grain. This study was conducted to determine the impacts of different N rates (0, 122, 174, and 300 kg/ha) on the distribution and speciation of Fe and Zn in wheat grain milling fractions under field conditions. Zn and protein concentrations were increased, whereas Fe was less affected in the flour fractions with increasing N rates. Further analysis with size‐exclusion chromatography coupled with inductively coupled plasma mass spectrometry revealed that Fe and Zn bound to low‐molecular‐weight (LMW) compounds in the flour fractions (probably Fe‐nicotianamine [NA], Fe‐deoxymugineic acid, or Zn‐NA) were less affected by increasing N supply, representing 3.5–10.9% of total Fe and 2.5–56.6% of total Zn. In the shorts fraction, LMW‐Fe was absent, and LMW‐Zn with higher N supply was over twice as high as that in control and 3–27 times as high as that in the other milling fractions. In the flour fractions, the molar ratios of phytic acid (PA)/Fe and PA/Zn (both less than 30.5) decreased, whereas soluble LMW‐Fe/Zn was not affected with increasing N rates.     

连续提取对土壤腐殖质组分数量与特性的影响

以暗棕壤为供试土壤,研究了NaOH和NaOH+Na4P2O7连续提取对土壤腐殖质组分数量和特性的影响。结果表明:用两种提取剂得到的土壤腐殖质组分总量相差不大,并且其中HA组分的数量均高于FA组分。随提取次数增加,胡敏酸(HA)、富里酸(FA)和胡敏素(HM)的绝对数量均下降,HA、FA的相对数量也下降,而HM的相对数量则增加。以NaOH为提取剂时,最后得到的腐殖质组分中FA的相对比例高于HA;而用NaOH+Na4P2O7为提取剂时,最后得到的腐殖质组分中HA的相对比例则高于FA。连续提取过程中,HA、FA的色调系数(Δlogk)和活化度(AD)通常呈增加趋势,而相对色度(RF)下降,说明后提取出的HA、FA的缩合度较低,脂族性较强。用RF来表征HA、FA特性变化更为合适。     

Structure of Lysophosphatidylglyceryl-Remazolbrilliant Blue (LPG-RBB) from the Surface of Dyed Wheat Starch Granules

Wheat starch granule surface was covalently stained with Remazolbrilliant blue-R dye (RBB) and then extracted with 1% SDS containing 1% 2-mercaptoethanol (2-ME) at room temperature for 14.5 hr. The extracted blue-staining material (A₆₅₀) separated into two fractions. Low molecular weight (LMW) material was further purified by Sephadex G-75 size-exclusion chromatography and thin-layer chromatography. Infrared and nuclear magnetic resonance (¹H-NMR and ¹³C-NMR) spectroscopy indicated that the structure of the purified LMW material was 18-O-(6-lysophosphatidylglyceryl)-RBB.     

Quantitative Glutenin Composition from Gel Electrophoresis of Flour Mill Streams and Relationship to Breadmaking Quality

Three samples of Nekota (hard red winter wheat) were milled, and six mill streams were collected from each sample. The 18 mill streams were analyzed separately as well as recombined to form three patent flours. The methods of multistacking (MS)‐SDS‐PAGE and SDS‐PAGE were used to separate the unreduced SDS‐soluble glutenins and the total reduced proteins, respectively. The separated proteins were quantified by densitometry. The quantity of unreduced SDS‐soluble proteins was significantly different among the mill streams at the 4% (largest molecular weight polymeric glutenins) and at the 10 and 12% (smaller molecular weight polymeric glutenins) origins of the MS‐SDS‐PAGE gels. The quantities of total HMW‐GS, LMW‐GS, 2*, 7+9, and 5+10 subunits and the ratio of HMW‐GS to LMW‐GS in polymeric protein samples isolated using preparative MS‐SDS‐PAGE and in total reduced protein extracts were significantly different among mill streams. The quantities of HMW‐GS, LMW‐GS, 2*, 7+9, and 5+10 subunits from total reduced proteins were positively and significantly correlated with loaf volume. The quantities of glutenin subunits (both HMW‐GS and LMW‐GS) from unreduced SDS‐soluble proteins were positively or negatively correlated with loaf volume at the various MS‐SDS‐PAGE gel origins but the levels of correlation were not significant. These results showed that the glutenin protein composition was different among the various mill streams and demonstrated that electrophoretic analysis of the proteins in these fractions is a useful tool for studying the variation in functional properties of flour mill streams.