Nutrients and antinutrient constituents of Amaranthus caudatus L. Cultivated on different soils

This study investigated variations in the concentration of nutrients, antinutrients and mineral content of Amaranthus caudatus harvested from different soil types at various stages of maturity. Four out the five soils namely; sandy clay loam, silty clay loam, clayey loam and loam were experimentally formulated from primary particles of silt, clay and sand in line with the United State Department of Agriculture’s (USDA) soil triangle protocol. The unfractionated soil was used as the control. After harvesting at pre-flowering (61 days after planting), flowering (71 days after planting) and post-flowering (91 days after planting) stages, nutrient and antinutrient analyses were carried out following Association of Official Analytical Chemists (AOAC) and other referenced methods while the Inductively Coupled Plasma- Optical Emission Spectrometer was used to determine mineral compositions of the plant samples. The results of the study revealed that particle size and physicochemical properties of the soil influenced the number of minerals deposited in plant tissues. It was further observed that the nutritional properties of the plant change as plant ages. For an optimal yield of vitamins A and E, clayey loam proved to be the best soil particularly when A. caudatus is harvested before flowering but for vitamin C, sandy clayey loam yielded the highest output at the same stage. Similarly, clayey loam and loam soils yielded the highest proximate compositions at flowering and pre-flowering; however, mineral elements (micro and macro) were highest in control and loam soils.     

Synthesis, structure and magnetic properties of a two-dimensional manganese(II) complex with a maximum denticity of ethylenediaminetetraacetic ligand

A new Mn(II) complex, [Mn₂(edta)(H₂O)]_n·nH₂O (1) (H₄edta = ethylenediaminetetraacetic acid) has been synthesized by the reaction of MnCl₂·4H₂O and H₄edta under hydrothermal conditions, and was characterized by single-crystal X-ray diffraction study, variable temperature (1.8-300 K) magnetic measurement, and thermal gravity analysis. The result of X-ray crystallographic analysis reveals that complex 1 is the first two-dimensional (2D) Mn-edta coordination polymer with a grid-like (4,4)-topology, which is built from Mn-carboxylate chains and entirely deprotonated edta⁴⁻ ligands with a maximum denticity. The variable temperature magnetic data indicate that complex 1 exhibits strong antiferromagnetic couplings.     

Whey Protein/Arabic Gum Gels Formed by Chemical or Physical Gelation Process

Whey proteins (WP) gelation process with addition of Arabic gum (AG) was studied. Two different driving processes were employed to induce gelation: (1) heating of 12% whey protein isolate (WPI) solutions (w/w) or (2) acidification of previous thermal denatured WPI solutions (5% w/w) with glucono-δ-lactone (GDL). Protein concentrations were different because they were minimal to form gel in these two processes, but denaturation conditions were the same (90 °C/30 min). Water-holding capacity and mechanical properties of the gels were evaluated. The BST equation was used to evaluate the nonlinear part of the stress–strain data. Cold-set gels were weaker than heat-set gels at the pH range near the isoelectric point (pI) of the main whey proteins, but heated gels were more deformable (did not exhibit rupture point) and showed greater elasticity modulus. However, gels formed by heating far from the pI (pH 6.7 or 3.5) showed more fragile structure, indicating that, in these mixed gels, there are prevailing biopolymers interactions. Cold-set and heat-set gels at pH near or below the WP pI showed strain-weakening behavior, but heated gels at neutral pH showed strong strain-hardening behavior. Such results suggest that differences in stress–strain curve at the nonlinear part of the data could be correlated to structure particularities obtained from different gelation processes.     

Mn/Fe superoxide dismutase interaction fingerprints and prediction of oligomerization and metal cofactor from sequence

Fe- and Mn-containing superoxide dismutase (sod) enzymes are closely related and similar in both amino acid sequence and structure, but differ in their mode of oligomerization and in their specificity for the Fe or Mn cofactor. The goal of the present work is to identify and analyze the sequence and structure characteristics that ensure the cofactor specificities and the oligomerization modes. For that purpose, 374 sod sequences and 17 sod crystal structures were collected and aligned. These alignments were searched for residues and inter-residue interactions that are conserved within the whole sod family, or alternatively, that are specific to a given sod subfamily sharing common characteristics. This led us to define key residues and inter-residue interaction fingerprints in each subfamily. The comparison of these fingerprints allows, on a rational basis, the design of mutants likely to modulate the activity and/or specificity of the target sod, in good agreement with the available experimental results on known mutants. The key residues and interaction fingerprints are furthermore used to predict if a novel sequence corresponds to a sod enzyme, and if so, what type of sod it is. The predictions of this fingerprint method reach much higher scores and present much more discriminative power than the commonly used method that uses pairwise sequence comparisons.     

Neuroglobin基因体内转染对水杨酸钠给药后小鼠下丘核神经元听反应的影响

实验以48只成年健康昆明小鼠为实验对象,研究GeneJamer转染试剂介导的neuroglobin(NGB)基因体内转染对水杨酸钠给药后小鼠下丘核区听反应的影响。实验分4组,每组12只。A1组:对照组1(阴性对照,将GeneJamer转染试剂6μl和pEGFP-C12μg混合后注入下丘核脑区);A2组:对照组2[阳性对照,将GeneJamer转染试剂(6μl)和pEGFP-NGB(质粒载体pEGFP-C1与NGB基因全编码序列构建的重组子2μg)混合后注入下丘核脑区];B组:水杨酸钠给药组(450mg/kg·d-1)+pEGFP-C1;C组:水杨酸钠(450mg/kg.d-1)+pEGFP-NGB组。以直接注射法将GeneJamer转染试剂和重组质粒pEGFP-NGB混合后注入小鼠下丘核区。采用RT-PCR和Westernblot技术检测小鼠下丘核区NGBmRNA和蛋白的表达;采用细胞外记录技术,研究小鼠下丘核区神经元在水杨酸钠给药后转染重组质粒pEGFP-NGB对强度-发放率函数(刺激声强与实验鼠下丘核区神经元在接受声刺激所产生的电发放的关系曲线)、强度-潜伏期函数(刺激声强与实验鼠下丘核区神经元在接受声刺激至产生电发放潜伏期之间的关系曲线)和频率调谐曲线(实验鼠下丘核区神经元在各个频率纯音刺激下起反应的阈值绘制的曲线)的影响。实验观察到:(1)经GeneJamer转染试剂介导NGB基因可有效地转染小鼠下丘核区脑组织并得到表达。(2)水杨酸钠给药后神经元的强度-发放率函数曲线升高。对照组A1、A2各项指标进行比较均无统计学意义。对照组A1、A2和水杨酸钠+pEGFP-NGB组神经元的强度-发放率函数以非单调型(随刺激强度增加时,发放率表现为先降后升呈“V”形或“U”形)为主,分别占74.6%、72.2%和59.3%,水杨酸钠给药组以不规则型强度-发放率函数为主,占47%,与对照组A1、A2和水杨酸钠+pEGFP-NGB组比较,有显著性差异(P<0.01、P<0.01、P<0.05)。(3)水杨酸钠给药后神经元的强度-潜伏期函数曲线降低。对照组A1、A2各项指标进行比较均无统计学意义。水杨酸钠给药组以非单调型强度-潜伏期率函数为主,与对照组A1、A2和水杨酸钠+pEGFP-NGB组比较,有显著性差异(P<0.01、P<0.05)。(4)A1和A2对照组听反应神经元的调谐曲线,Q-10dB值均大于5.00,其调谐曲线为狭窄型。记录水杨酸钠给药组72个听神经元的调谐曲线,有53个神经元的Q-10dB值小于5.00,Q-10dB值最小为2.12,其调谐曲线为宽阔型;其余19个神经元的Q-10dB值大于5.00,属于狭窄型调谐曲线。水杨酸钠+pEGFP-NGB组67个听神经元的调谐曲线,有12个神经元的Q-10dB值小于5.00,Q-10dB值最小为2.87,其调谐曲线为宽阔型,其它的神经元的值大于5.00。它们的调谐曲线均属狭窄型。以上结果提示外源性NGB基因在水杨酸钠给药后小鼠下丘核区局部高表达,提示GeneJamer转染试剂介导NGB体内转基因治疗水杨酸钠引起的下丘核区的损伤的方法是可行的。实验小鼠转染NGB基因后可逆转因水杨酸钠给药引起的强度-发放率函数曲线升高以及强度-潜伏期函数曲线降低,并可逆转水杨酸钠引起的部分听神经元对声刺激强度的编码类型。     

Soil Properties and their Spatial Pattern in a Degraded Sandy Grassland under Post-grazing Restoration, Inner Mongolia, Northern China

In this study, we use classical and geostatistical methods to identify characteristics of some selected soil properties including soil particle size distribution, soil organic carbon, total nitrogen, pH and electrical conductivity and their spatial variation in a 5-year recovery degraded sandy grassland after two different grazing intensity disturbance: post-heavy-grazing restoration grassland (HGR) and post-moderately grazing restoration grassland (MGR), respectively, in Horqin steppe, Inner Mongolia, northern China. The objective was to examine effect of grazing intensity on spatial heterogeneity of soil properties. One hundred soil samples were taken from the soil layer 0–15 cm in depth of a grid of 10 m×10 m under each treatment. The results showed that soil fine fractions (very fine sand, 0.1–0.05 mm and silt + clay, <0.05 mm), soil organic carbon and total nitrogen concentrations were significant lower and their coefficients of variation significant higher under the HGR than under the MGR. Geostatistical analysis of soil heterogeneity revealed that soil particle size fractions, organic carbon and total nitrogen showed different degree of spatial dependence with exponential or spherical semivariograms on the scale measured under HGR and MGR. The spatial structured variance account for a large proportion of the sample variance in HGR plot ranging from 88% to 97% for soil particle fractions, organic C and total N, however, except for organic C (88.8%), the structured variance only account for 50% of the sample variance for soil particle fractions and total N in the MGR plot. The ranges of spatial autocorrelation for coarse-fine sand, very fine sand, silt + clay, organic C and total N were 13.7 m, 15.8 m, 15.2 m, 22.2 m and 21.9 m in HGR plot, respectively, and was smaller than in MGR plot with the corresponding distance of 350 m, 144.6 m, 45.7 m, 27.3 m and 30.3 m, respectively. This suggested that overgrazing resulted in an increase in soil heterogeneity. Soil organic C and total N were associated closely with soil particle fractions, and the kriging-interpolated maps showed that the spatial distribution of soil organic C and total N corresponded to the distribution patterns of soil particle fractions, indicating that high degree of spatial heterogeneity in soil properties was linked to the distribution of vegetative and bare sand patches. The results suggested that the degree of soil heterogeneity at field scale can be used as an index for indicating the extent of grassland desertification. Also, the changes in soil heterogeneity may in turn influence vegetative succession and restoration process of degraded sandy grassland ecosystem.     

我国23个土壤磷素淋失风险评估Ⅱ.淋失临界值与土壤理化性质和磷吸附特性的关系

从13个省（市）采取23个耕地表层土壤,通过室内模拟试验测定其磷素淋失临界值和pH、有机质、＜0.01mm、＜0.002mm、交换性钙镁、活性铁铝、磷等温吸附特性等,以建立土壤磷素淋失临界值与土壤基本理化性质和磷吸附特性之间的关系.结果表明：土壤pH＜6.0时,随土壤pH提高临界值增加,土壤pH与临界值之间呈显著的指数关系;而当土壤pH＞6.0时,随土壤pH提高临界值减小,在pH6.5左右土壤磷素淋失临界值最高.土壤磷素淋失临界值与土壤有机质、活性铁（铝）、交换性钙之间存在显著的相关,而与交换性镁、CEC、＜0.01mm、＜0.002mm、K、Qm的相关性受土壤酸碱度影响.可以通过测定土壤有机质或活性铁的含量,来计算土壤磷素淋失临界值,评价土壤磷素淋失的风险.供试的23个土壤,除了采自湖北潜江的20号水稻土存在比较大的磷素淋失风险,其余土壤发生磷素淋失的风险很小.     

厌氧菌Sunxiuqinia sp. SH-52外切型海藻酸裂解酶的异源表达及酶学特征

【背景】目前已报道的海藻酸分解菌多数为好氧菌,未见有关厌氧菌的报道。从分离的海藻酸分解菌中表征的海藻酸裂解酶大多为内切型海藻酸裂解酶,外切型较少。【目的】研究来自厌氧海藻酸分解菌的海藻酸裂解酶基因,表征新型海藻酸裂解酶并阐明其酶学性质,为海藻酸裂解酶的多样性和微生物降解海藻酸机制提供理论依据。【方法】对来自厌氧海藻酸分解菌Sunxiuqinia sp. SH-52的海藻酸裂解酶SHA-4编码基因进行克隆,分析基因序列,构建重组质粒PGEX-4T-1-SHA-4并在大肠杆菌中实现异源表达,经纯化后对其酶学性质及降解特征进行研究。【结果】该酶在28°C、用0.1 mmol/L IPTG (异丙基-β-D-硫代半乳糖苷)条件下诱导6 h达到最大表达量,纯化后酶的比活力达到21 U/mg。酶学性质分析表明SHA-4的最适温度为37°C;最适pH为7.5;对PolyMG (杂聚古罗糖醛酸-甘露糖醛酸嵌段)具有底物偏好性;Na+对该酶的活性具有抑制作用,而金属离子Cu~(2+)具有明显促进作用,使活性提高了约168%;SHA-4催化海藻酸的Km值为2.5 mg/mL,Vmax为8.7 mg/(mL·min);SHA-4为外切型海藻酸裂解酶,降解海藻酸终产物为单糖。【结论】异源表达了来自一株厌氧海藻酸分解菌Sunxiuqiniasp.SH-52的海藻酸裂解酶SHA-4,该酶是PL6家族中第一个对PolyMG有底物偏好性的外切型海藻酸裂解酶,而且活性较高,作为工具酶有很好的应用前景,为海藻酸降解机制的探索提供了新的线索。     

Representing an ensemble of NMR-derived protein structures by a single structure.

The usefulness of representing an ensemble of NMR-derived protein structures by a single structure has been investigated. Two stereochemical properties have been used to assess how a single structure relates to the ensemble from which it was derived, namely the distribution of phi psi torsion angles and the distribution of chi 1 torsion angles. The results show that the minimized average structure derived from the ensemble (a total of 11 ensembles from the Brookhaven Protein Data Bank were analyzed) does not always correspond well with this ensemble, particularly for those ensembles generated with a smaller number of experimentally derived restraints per residue. An alternative method that selects the member of the ensemble which is closest to the "average" of the ensemble has been investigated (a total of 23 ensembles from the Brookhaven Protein Data Bank were analyzed). Although this method selected a structure that on the whole corresponded more closely to the ensemble than did the minimized average structure, this is still not a totally reliable means of selecting a single structure to represent the ensemble. This suggests that it is advisable to study the ensemble as a whole. A study has also been made of the practice of selecting the "best" rather than the most representative member of the ensemble. This too suggests that the ensemble should be studied as a whole. A study of the conformational space occupied by the ensemble also suggests the need to consider the ensemble as a whole, particularly for those ensembles generated with a smaller number of experimentally derived restraints per residue.     

Two new end-to-end single dicyanamide bridged Cu(II) complexes with Schiff base ligands: Structural, electrochemical and magnetic properties

The synthesis, crystal structures and magnetic properties of two different copper(II) complexes of formula [Cu(L¹)(dca)]_n · nClO₄ (1) and [Cu(L²)]₂(dca)(ClO₄) (2) [L¹ = N,N-dimethylethylene-N′-(pyridine-2-carbaldiiminato), HL² = N,N-dimethylethylene-N′-salicylaldiiminato, dca = dicyanamide anion] are described. Spectroscopic and electrochemical properties have also been discussed. A one-dimensional chain structure with single, symmetrical, μ_1,5-dca bridges is found in compound 1. The copper atom in 1 has a square pyramidal geometry. A tridentate Schiff base ligand, having NNN donor sites, and one nitrogen atom from dca occupy the basal plane. N(18) of a neighbouring unit occupies the apical site. The Schiff base used in compound 2 is a tridentate anion with NNO donor sites, which changes the structure in a dinuclear unit of copper atoms bridged by single end-to-end dicyanamide ion. The environment around copper in 2 is square planar. Magnetic susceptibility measurements for 1 and 2 reveal the occurrence of weak antiferromagnetic interaction through the dca ligand.