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1.
The volatiles in the headspace above a solution of [(13)C(6)]fructose and alanine in glycerol/water, heated in a closed vial at 130 degrees C for 2 h, were analyzed by solid-phase microextraction in tandem with GC-MS. Carbonyl compounds and pyrazines were among the detected components. The examination of their mass spectra showed that most of the 1-hydroxy-2-propanone and 2,3-pentanedione were (13)C(3)-labeled, the majority of the 2-methylpyrazine and 2-ethyl-3-methylpyrazine were (13)C(5)-labeled, and 2,5-dimethylpyrazine and 3-ethyl-2,5-dimethylpyrazine were mainly (13)C(6)-labeled. This is in agreement with the literature, and corresponds to the incorporation of fructose carbons, and in the case of 2,3-pentanedione, 2-ethyl-3-methylpyrazine, and 3-ethyl-2,5-dimethylpyrazine alanine carbons, into the molecules. However, minority fractions of 1-hydroxy-2-propanone (10%) and 2,3-pentanedione (14%) were found unlabeled, 2-methylpyrazine (10%) and 2-ethyl-3-methylpyrazine (11%) only doubly labeled, and 2,5-dimethylpyrazine (20%) and 3-ethyl-2,5-dimethylpyrazine (27%) only triply labeled, suggesting they contain carbons originating from the solvent glycerol. This could be confirmed by reaction of fructose and alanine in [(13)C(3)]glycerol/water, which produced the same volatiles, with 11-27% existent in their (13)C(3)-labeled form. Hence, glycerol participated not only as a solvent but also as a precursor in the reaction.  相似文献   

2.
Estuarine ecosystems are becoming increasingly altered by the concentration of human populations near the coastline, however a robust indicator of this change is lacking. We developed an index of waterbird community integrity (IWCI) and tested its sensitivity to anthropogenic activities within 28 watersheds and associated subestuaries of Chesapeake Bay, USA. The IWCI was used as a tool to gain insight into how human land use affects estuarine ecosystem integrity. Based on Akaike’s information criteria (AIC), a single variable model including percent developed land in estuarine watersheds was thirteen (2002) and twenty-six (2003) times more likely than models including percent agriculture and forest cover to fit the IWCI data. Consequently, we examined how suburban, urban, and total development shaped IWCI scores at three spatial scales: (1) watershed; (2) inverse-distance-weighted (IDW) watershed (land cover near the coastline weighted proportionally greater than that farther away); (3) local (land cover within 500 m of the coastline). Suburban, urban, and total development were all significant predictors of IWCI scores. Relationships were stronger at the IDW and local scales than at the whole watershed scale. Nonparametric changepoint analysis revealed a >80% probability of a threshold in IWCI scores when as little as 3.7% (2002) and 3.5% (2003) of the IDW land cover within the watershed was urban. Our results indicate that, of the landscape stressors we examined, development near estuarine coastlines is the primary stressor to estuarine waterbird community integrity, and that estuarine ecosystem integrity may be impaired by even extremely low levels of coastal urbanization.  相似文献   

3.
Within the framework of the Dutch Priority Program on Acidification, 10 yr of research was conducted in a Douglas fir stand at Speulder forest. Research was conducted to establish the loads and levels of acidifying and eutrophying pollutants and ozone, to determine forest vitality characteristics and follow growth parameters and nutrient status in time and to determine the effects of reduction of loads and levels by manipulation experiments. Results indicate that during the last 20 yr critical levels for air pollutants have hardly been exceeded except for ozone, which slightly affected assimilation. Elevated nitrogen deposition has caused several adverse effects including (i) inhibited mycorrhizal development, leading to a decreased base cation and phosphorus uptake; (ii) elevated foliage/root (fine and coarse) ratios, making the forest more sensitive to drought and windthrow; (iii) elevated nitrogen and arginine concentrations in the foliage, associated with relative base cation and phosphorus deficiency, and (iv) elevated nitrate leaching polluting the groundwater. High inputs of acidity have caused elevated ratios of Al to base cations, affecting fine root (uptake) and depletion of the readily available Al pool, thus affecting the long-term sustainability. Despite these effects, forest vitality, in terms of defoliation/discoloration, is reasonable and forest growth even increased in response to nitrogen. The exceedances of critical loads for nitrogen and acidity, however, implies a (large) risk for the long-term sustainability of the Speulder forest.  相似文献   

4.
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5.
The essential oils of Ocimum basilicum L., Origanum vulgare L., and Thymus vulgaris L. were analyzed by means of gas chromatography-mass spectrometry and assayed for their antioxidant and antimicrobial activities. The antioxidant activity was evaluated as a free radical scavenging capacity (RSC), together with effects on lipid peroxidation (LP). RSC was assessed measuring the scavenging activity of the essential oils on 2,2-diphenyl-1-picrylhydrazil (DPPH(*)) and OH(*) radicals. Effects on LP were evaluated following the activities of essential oils in Fe(2+)/ascorbate and Fe(2+)/H(2)O(2) systems of induction. Essential oils exhibited very strong RSCs, reducing the DPPH radical formation (IC(50)) in the range from 0.17 (oregano) to 0.39 microg/mL (basil). The essential oil of T. vulgaris exhibited the highest OH radical scavenging activity, although none of the examined essential oils reached 50% of neutralization (IC(50)). All of the tested essential oils strongly inhibited LP, induced either by Fe(2+)/ascorbate or by Fe(2+)/H(2)O(2). The antimicrobial activity was tested against 13 bacterial strains and six fungi. The most effective antibacterial activity was expressed by the essential oil of oregano, even on multiresistant strains of Pseudomonas aeruginosa and Escherichia coli. A significant rate of antifungal activity of all of the examined essential oils was also exhibited.  相似文献   

6.
The photodegradation of the carboxamide acaricide hexythiazox in three different solvent systems (aqueous methanolic, aqueous isopropanolic, and aqueous acetonitrilic solutions) in the presence of H(2)O(2), KNO(3), and TiO(2) under ultraviolet (UV) light (λ(max) ≥ 250 nm) and sunlight (λ(max) ≥290 nm) has been assessed in this work. The kinetics of photodecomposition of hexythiazox and the identification of photoproducts were carried out using liquid chromatography-mass spectrometry. The rate of photodecomposition of hexythiazox in different solvents followed first-order kinetics in both UV radiation and natural sunlight, and the degradation rates were faster under UV light than under sunlight. Hexythiazox was found to be more efficiently photodegraded in the presence of TiO(2) than in the presence of H(2)O(2) and KNO(3). Two major photoproducts were separated in pure form using column chromatography and identified according to IR, (1)H NMR, and mass spectral information as cyclohexylamine and 5-(4-chlorophenyl)-4-methylthiazolidin-2-one. Another nine photoproducts were identified according to LC-MS/MS spectral information. The plausible photodegradation pathways of hexythiazox were proposed according to the structures of the photoproducts.  相似文献   

7.
Rheological characteristics of dough and glutenin macropolymer (GMP) extracted thereof were investigated. Three single enzymes, pentosanase (PP), glucoseoxidase (GLZ), and laccase (LAC), and their combinations were used. GLZ gave the least extensible and most resistant dough, and pentosanase/glucoseoxidase (PPGLZ) resulted in dough with improved extensibility. The enzymes improved gluten quality. The glutenin macropolymer (GMP) was characterized in terms of wet weight, protein content, pentosan association, and dynamic rheological properties. Enzymatic addition decreased the wet weight of GMP but increased the protein content. PP decreased the content of pentosans on the GMP, but single oxidases increased the content of pentosans associated with GMP. PP did not modify the elastic modulus (G') of the GMP, whereas GLZ increased G' by increasing the polymerization of proteins and LAC diminished G'. The combination PPGLZ produced a synergic increase of G'.  相似文献   

8.
The properties, hydrological features, and genesis of the solods occurring in the Baraba Lowland and Priobskoe Plateau were studied. Methods for determining the hydromorphism degree are considered; the features of the similarity and differences between the solods and other soils with textural profile differentiation are shown. Depending on the reasons for the waterlogging, the solods should be divided into two groups: the solods of groundwater waterlogging and the solods of surface waterlogging. Criteria for their discrimination are suggested: the ratio between the contents of the clay fraction in the parent rock (or in the B2 horizon) and that in the A2 horizon, the changes in the pH values along the soil profiles, and the content of nonsilicate iron compounds. The solods studied are shown to be formed under the conditions of a stagnant-percolative regime and gleying. This circumstance is an obligatory and sufficient reason for the formation of the light-colored acid eluvial (A2) horizons. According to some basic properties of the soil solid phase (the acidity, the total chemical composition, and the clay pattern in the eluvial part), the gleyed solods are close or identical to the gleyed soddy-podzolic and gleyed chernozem-like podzolic soils. At the same time, the solods differ from the gleyed chernozem-like podzolic soils by their thicker A1 (or Ap) horizon and their higher humus content (5–7%).  相似文献   

9.
This work was focused on the relationship between the microstructure and the mechanical and barrier properties of whey protein isolate (WPI) films. Sorbitol (S) and glycerol (G) were used as plasticizers and the pH was varied between 7 and 9. The films were cast from heated aqueous solutions and dried in a climate room at 23 degrees C and 50% relative humidity for 16 h. The microstructure of the films was found to be dependent on the concentration, the plasticizers, and the pH. When the concentration increased, a more aggregated structure was formed, with a denser protein network and larger pores. This resulted in increased water vapor permeability (WVP) and decreased oxygen permeability (OP). When G was used as a plasticizer instead of S, the microstructure was different, and the moisture content and WVP approximately doubled. When the pH increased from 7 to 9, a denser protein structure was formed, the strain at break increased, and the OP decreased.  相似文献   

10.
干燥后稻米食味值的预测与分析   总被引：9，自引：3，他引：9  
为了采用神经网络方法预测干燥后稻米食味值，依据稻米的食味值与其主要成分(水分、蛋白质、直链淀粉和脂肪酸)和干燥温度有关这一研究结论，用近红外光谱谷物成分分析仪测定了稻米的主要成分值，用专家模糊评判方法确定稻米的食味值，建立了稻米食味值与其主要成分之间的网络结构模型，误差分析结果表明：该方法可以较好预测稻米的食味值，并分析了干燥条件对稻米理化指标的影响规律，影响程度为干燥温度：-0.7；水分：0.68、脂肪酸：-0.56、直链淀粉：0.48和蛋白质含量：-0.33。  相似文献   

11.
Aluminum (Al) and chromium (Cr) stresses often occur simultaneously in agricultural soils, and pose a great damage to crop growth, yield formation and product safety. In the current study, the influence of combined Al and Cr stresses on plant biomass, metal and nutrient contents was determined in comparison with that of Al or Cr stress alone. A hydroponic experiment was conducted to investigate the effect of pH, Al and Cr in the medium solution on the uptake of mineral elements as well as Al and Cr in the two barley genotypes differing in Al tolerance. Aluminum sensitive genotype Shang 70-119 had significantly higher Cr and Al contents in plants than Al-tolerant genotype Gebeina. Barley roots had much higher Al and Cr contents than above-ground plant parts. Chromium contents were much higher in the solution with pH 4.0 than in that with pH 6.5. Aluminum stress reduced phosphorus (P), calcium (Ca), magnesium (Mg), sulfur (S), copper (Cu), manganese (Mn), zinc (Zn) and boron (B) contents in roots and restrained potassium (K) and iron (Fe) from being translocated into shoots and leaves. Chromium stress resulted in reduced P, K, Mg, S, Fe, Zn and Mn contents in roots at pH 6.5 and P, K, Ca, Mg, S, Zn and Mn contents at pH 4.0. Translocation of all nutrients from roots to upper parts of plants was inhibited except Ca in pH 6.5 with Cr addition. Lower contents of all nutrients were observed at pH 4.0 as compared to pH 6.5. Combined stress of Cr and Al, on the whole, caused further reduction in mineral content in all plant parts of the two barley genotypes as compared to Al or Cr stress alone. Moreover, the reduction was more pronounced in Al sensitive genotype Shang 70-119.  相似文献   

12.
Two Oxisols (Mena and Malanda), a Xeralf and a Xerert from Australia and an Andept (Patua) and a Fragiaqualf (Tokomaru) from New Zealand were used to examine the effect of pH and ionic strength on the surface charge of soil and sorption of cadmium. Adsorption of Cd was measured using water, 0.01 mol dmp?3 Ca(NO3)2, and various concentrations of NaNO3 (0.01–1.5 mol dm?3) as background solutions at a range of pH values (3–8). In all soils, the net surface charge decreased with an increase in pH. The pH at which the net surface charge was zero (point of net zero charge, PZC) differed between the soils. The PZC was higher for soils dominated by variable-charge components (Oxisols and Andept) than soils dominated by permanent charge (Xeralf, Xerert and Fragiaqualf). For all soils, the adsorption of Cd increased with an increase in pH and most of the variation in adsorption with pH was explained by the variation in negative surface charge. The effect of ionic strength on Cd adsorption varied between the soils and with the pH. In Oxisols, which are dominated by variable-charge components, there was a characteristic pH below which increasing ionic strength of NaNO3 increased Cd adsorption and above which the reverse occurred. In all the soils in the normal pH range (i.e. pH>PZC), the adsorption of Cd always decreased with an increase in ionic strength irrespective of pH. If increasing ionic strength decreases cation adsorption, then the potential in the plane of adsorption is negative. Also, if increasing ionic strength increases adsorption below the PZC, then the potential in the plane of adsorption must be positive. These observations suggest that, depending upon the pH and PZC, Cd is adsorbed when potential in the plane of adsorption is either positive or negative providing evidence for both specific and non-specific adsorption of Cd. Adsorption of Cd was approximately doubled when Na rather than Ca was used as the index cation.  相似文献   

13.
Milled wood lignin (MWL) and dioxane lignin (DL) from different morphological regions (nodes and internodes) of Arundo donax reed were subjected to a comprehensive structural characterization by (13)C, (1)H NMR, FTIR, and UV spectroscopies and functional analysis. The permanganate and nitrobenzene oxidation methods were also applied to the in situ lignins. Both node and internode lignins are HGS-type lignins, with a significant amount of H units (including p-coumaric acid type structures). The S/G ratio (1.13-1.32), the weight-average molecular weight (20,400-24,500), the methoxyl group content (0.90-0.98), the phenolic hydroxyl group content (0.23-0.27), and the aliphatic hydroxyl group content (1.00-1.09) are not very different in the lignins from nodes and internodes. However, some structural differences between node and internode lignins were observed. The former has much more phenolic acids (p-coumaric and ferulic), 8.8% in node versus 1.2% in internode and less beta-O-4 (0. 32 and 0.49 per aromatic unit in node and internode, respectively). In situ node lignin is more condensed than internode lignin.  相似文献   

14.
Seven triterpene saponins were isolated from n-butanol fractions of blue cohosh (Caulophyllum thalictroides) roots and rhizomes. Their structures were established by spectral ((1)H NMR, (13)C NMR, 2D-NMR, and APCI-MS) techniques and chemical reactions as hederagenin 3-O-alpha-L-arabinopyranoside (1); caulophyllogenin 3-O-alpha-L-arabinopyranoside (2); hederagenin 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranoside (3); 3-O-alpha-L-arabinopyranosyl-hederagenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (4); 3-O-alpha-L-arabinopyranosyl- caulophyllogenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (5); 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl- echinocystic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (6); 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-hederagenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (7). All seven compounds were identified in this species for the first time.  相似文献   

15.
Numerical parameters of soil color were studied according to the CIE-L*a*b color system before and after the Tamm’s and Mehra-Jackson’s treatments; we also determined the total Fe content in the samples from the main genetic horizons of the alluvial gray-humus soil, two profiles of burozems, and two profiles of podzols in the Sakhalin Island. In the analyzed samples, the numerical color parameters L* (lightness), a* (redness) and b* (yellowness) are found to vary within 46–73, 3–11, and 8–28, respectively. A linear relationship is revealed between the numerical values of a* parameters and Fe content in the Mehra-Jackson extracts; the regression equations are derived with the determination coefficients (R2): 0.49 (typical burozem), 0.79 (podzolized burozem), 0.96 (shallow-podzolic mucky podzol), 0.98 (gray-humus gley alluvial soil). For the surface-podzolic mucky podzol contaminated with petroleum hydrocarbons, R2 was equal to only 0.03. In the gray humus (AY) and structural-metamorphic (BM) horizons of the studied soils, a* and b* parameters decrease after their treatment with the Tamm’s reagent by 2 points on average. After the Mehra-Jackson treatment, the a* parameter decreased by 6 (AY) and 8 (BM) points; whereas b* parameter, by 10 and 15 points, respectively. In the E horizons of podzols, the Tamm’s treatment increased a* and b* parameters by 1 point; whereas the Mehra-Jackson’s treatment decreased these parameters by only 1 and 3 points, respectively. The redness (a*) decreased maximally in the lower gley horizon of the alluvial gray humus soil, i.e., by 6 (in the Tamm’s extract) and 10 points (in the Mehra-Jackson’s) extract. Yellowness (b*) decreased by 12 and 17 points, respectively. The revealed color specifics in the untreated samples and the color transformation under the impact of reagents in the studied soils and horizons may serve as an additional parameter that characterizes quantitatively the object of investigation in the reference databases.  相似文献   

16.
The present study investigated the mechanism of the synergistic antioxidant activity of alpha-tocopherol with resveratrol (3,5,4'-trihydroxy-trans-stilbene, 3,5,4'-THS) and its synthetic analogues, that is, 3,4-dihydroxy-trans-stilbene (3,4-DHS), 4,4'-dihydroxy-trans-stilbene (4,4'-DHS), 4-hydroxy-trans-stilbene (4-HS), and 3,5-dihydroxy-trans-stilbene (3,5-DHS). The reaction kinetics of alpha-tocopheroxyl radical with resveratrol and its analogues were studied in sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB) micelles using the stopped-flow electron paramagnetic resonance (EPR) technique. It was found that resveratrol and its analogues could regenerate alpha-tocopherol with rate constants (k(REG)) in the order of 3,4-DHS > 4,4'-DHS > resveratrol > or = 4-HS > or = 3,5-DHS in SDS and CTAB micelles. It was found that the analogues bearing o-dihydroxyl groups (3,4-DHS) and p-dihydroxyl groups (4,4'-HS) exhibited remarkably higher alpha-tocopherol-regenerating activity than those bearing no such groups (resveratrol, 4-HS, and 3,5-DHS). In addition, the alpha-tocopherol-regenerating activity of resveratrol and its analogues was correlated with their electrochemical behaviors, suggesting that electron transfer might play a critical role during the regeneration reaction.  相似文献   

17.
The total content of phenolic compounds (TAP) in 29 different monocultivar olive oil samples from France (Aglandau and Tanche) and Spain (Cornicabra, Picual, and Verdial) was assessed by the colorimetric Folin-Ciocalteu method. Also, individual phenolic compounds were determined and quantified by liquid chromatography coupled to mass spectrometry (LC-MS). The French olive oil samples had a lower TAP compared to Spanish samples. The quantity of individual phenolics was similar except for pinoresinol, which was lower in the French olive oil samples. TAP moderately correlated to the sum of quantified compounds (r = 0.64 and p < 0.01) Partial least-squares (PLS) regression analysis emphasized the importance of hydroxytyrosol and the total amount of quantified phenolic compounds by LC-MS in the prediction of the total amount of phenolic compounds as determined by the Folin-Ciocalteu method. The amount of alpha-tocopherol was generally different among the cultivars (Tanche > Picual > Verdial > Aglandau > Cornicabra). Of all quantified phenolic compounds in French olive oil samples, only luteolin correlated well to the altitude of the olive orchards (r = 0.76, p < 0.01).  相似文献   

18.
The effects of agricultural–pastoral and tillage practices on soil microbial populations and activities have not been systematically investigated. The effect of no-tillage (NT), no-tillage agricultural–pastoral integrated systems (NT-I) and conventional tillage (CT) at soil depths of 0–10, 10–20 and 20–30 cm on the microbial populations (bacteria and fungi), biomass-C, potential nitrification, urease and protease activities, total organic matter and total N contents were investigated. The crops used were soybean (in NT, NT-I and CT systems), corn (in NT and NT-I systems) and Tanner grass (Brachiaria sp.) (in NT-I system); a forest system was used as a control. Urease and protease activities, biomass-C and the content of organic matter and total N were higher (p < 0.05) in the forest soil than the other soils. Potential nitrification was significantly higher in the NT-I system in comparison with the other systems. Bacteria numbers were similar in all systems. Fungi counts were similar in the CT and forest, but both were higher than in NT. All of these variables were dependent on the organic matter content and decreased (p < 0.05) from the upper soil layer to the deeper soil layers. These results indicate that the no-tillage agricultural–pasture-integrated systems may be useful for soil conservation.  相似文献   

19.
Two cucumber cultivars (Cucumis sativus L.) exposed to three cadmium (Cd) concentrations (0, 1, and 5 μM) were supplemented or un-supplemented with silicon (Si) (1 mM). Exposure to 1 μM Cd had no effect on shoot and root dry mass, whereas exposure to 5 μM Cd significantly reduced plant growth. Addition of Si stimulated the growth of Cd-treated cucumber. Exposure to 5 μM Cd significantly increased shoot Cd concentration and decreased iron (Fe) and zinc (Zn) concentration. Plants supplied with Si had lower Cd and higher Zn and Fe compared with unsupplied plants. Exposure to Cd resulted in a higher production of malondialdehyde (MDA). Si nutrition partly ameliorated lipid peroxidation induced by Cd toxicity. Activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX), and catalase (CAT) decreased, whereas ascorbate peroxidase (APX) activity increased in response to 5 μM Cd. Induction of APX activity might play an important role in the response of cucumber to Cd toxicity.  相似文献   

20.
Methane emission from natural mires in the middle and southern taiga zones of Tomsk oblast was studied in the summer and fall of 2006. Methane fluxes (mg C/m2 per h) from different types of mires and different microelements of the surface topography were characterized by the following median values: 0.67 for a forested bog; 4.06 and 2.67 for hollows and elevations (hillocks) of an open (nonforested) mire, respectively; and 0.74 and 2.13 for hollows and ridges of a ridged bog, respectively. Based on these and the literature data on the areas of different types of mires in Tomsk oblast, annual methane emission from mire ecosystems of Tomsk oblast was estimated at about 0.50 × 1012 Tg C. This value comprised 0.3–1.0% of the global emission of methane from wetlands or 0.1% of the global methane emission from all sources.  相似文献   

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