碱性蛋白酶Alcalase凝固大豆分离蛋白的分子间作用力

为了进一步揭示蛋白酶凝固豆乳的机理,该文通过添加不同化学试剂研究碱性蛋白酶Alcalase凝固大豆分离蛋白(SPI)过程中的分子间作用力。结果发现凝固过程中的分子间作用力主要是氢键和疏水作用,而离子键和二硫键对凝固过程影响不大。大豆蛋白质分子间的交联主要由次级键起作用,同时需要克服由负电荷引起的静电斥力,这就解释了为什么与无机盐和酸相比,Alcalase得到的SPI凝固物强度低。根据以上结论,该文还对豆乳凝固酶当前的筛选策略进行了评价。     

Effect of interfacial protein cross-linking on the in vitro digestibility of emulsified corn oil by pancreatic lipase

The objective of this study was to investigate the influence of globular protein interfacial cross-linking on the in vitro digestibility of emulsified lipids by pancreatic lipase. 3% (wt/wt) corn oil-in-water emulsions stabilized by either lecithin or beta-lactoglobulin were prepared (pH 7). A portion of the beta-lactoglobulin stabilized emulsions was subjected to a heat treatment known to cross-link the adsorbed globular proteins (85 degrees C, 20 min). Pancreatic lipase and bile extract were then added to each emulsion at 37 degrees C (pH 7) and the evolution of the particle charge, particle size, appearance and free fatty acids released were measured over a period of 2 h. The rate and extent of lipid digestion did not differ greatly between lecithin and beta-lactoglobulin stabilized emulsions, nor did it differ greatly for unheated (BLG-U) or heated (BLG-H) beta-lactoglobulin stabilized emulsions. For example, the initial rate of lipid digestion was found to be 3.1, 3.4, and 2.3 mM fatty acids s(-1) m(-2) of lipid surface for droplets stabilized by BLG-U, BLG-H, and lecithin, respectively. Pancreatic lipase was able to adsorb to the droplet surfaces and access the emulsified lipids, regardless of the initial interfacial composition and the fact that some of the original emulsifier appeared to remain at the oil-water interface during digestion. These results help to explain why the human body is so efficient at digesting dietary triacylglycerols.     

温室覆盖材料传热系数测试台的研究开发

研究开发了基于热箱法原理的园艺设施覆盖材料传热系数测试台,这是适应于园艺设施覆盖材料传热方式和工作环境特点的专用实验设备。该测试台依靠制冷、加热、风机、整流和除湿等调控装置,可全面稳定地模拟实现接近园艺设施覆盖材料实际工作的环境,包括设施内外气温、室外风速和天空辐射背景等条件,可以真实地反映各因素对覆盖材料传热的影响。测试台的测试条件可方便地调节,同时具有较高的测试精度。     

Quantitative structure-activity relationship modeling of peptide and protein behavior as a function of amino acid composition

A quantitative structure-activity relationship (QSAR) modeling approach based on the location of each amino acid along three axes obtained by principal component analysis (called z scores) was extended to physical and functional properties of proteins, where the proportion of particular amino acids rather than a precise sequence is the determining factor. Coomassie Brilliant Blue spectral responses to amino acid homopolymers (R = 0.926) and proteins, either as a function of their contents of six basic and aromatic amino acids (R = 0.976) or as a function of the contributions of these amino acids to the three z scores (R = 0.935), were modeled. The ultraviolet absorbance of proteins was modeled in terms of the z score contributions of tyrosine, tryptophan, and cysteine (R = 0.995). Modeling many protein functional properties in this manner appears to be possible. An approach to modeling peptide behaviors that depend on short sequences of amino acids was also considered.     

Study on the binding of propiconazole to protein by molecular modeling and a multispectroscopic method

Propiconazole (PCZ) is an N-substituted triazole used as a fungicide on fruits, grains, seeds, hardwoods, and conifers. Although the triazole fungicides have shorter half-lives and lower bioaccumulation than the organochlorine pesticides, possible detrimental effects on the aquatic ecosystem and human health also exist. To evaluate the toxicity of PCZ at the protein level, its effects on human serum albumin (HSA) were characterized by molecular modeling and multispectroscopic method. On the basis of the fluorescence spectra, PCZ exhibited remarkable fluorescence quenching, which was attributed to the formation of a complex. The thermodynamic parameters ΔH and ΔS were calculated to be -14.980 KJ/mol and 26.966 J/(mol K), respectively, according to the van't Hoff equation, which suggests hydrophobic and electrostatic interactions are the predominant intermolecular forces in stabilizing the PCZ-protein complex. Furthermore, HSA conformation was slightly altered in the presence of PCZ. These results indicated that PCZ indeed affected the conformation of HSA.     

The preparation of unsmeared soil surfaces and an improved apparatus for infiltration measurements

A method is described for using a quick setting epoxy resin to prepare a soil surface for infiltration measurements. It gives an unsmeared soil surface where the biological pores and structural surfaces are revealed. Experiments with an alluvial Prairie Soil and a Red Podzolic Soil, comparing steady state infiltration rates through cut smeared surfaces and resin treated ones, showed that the resin-prepared surface permits 2.5–6 times more rapid entry of water. It is postulated that the greater rate more closely reflects the field structural condition. Apparatus, with a water reservoir remote from the hole, is also described for measuring constant head subsoil infiltration through a specially prepared auger hole.     

Construction and evaluation of a reference electrode assembly for use in monitoring in situ soil redox potentials

Abstract

A simple procedure for the construction of inexpensive Ag,AgCl reference electrode assemblies is described. Disposable plastic syringes (60‐cm) were used to form the bodies of the electrode assemblies and small Ag,AgCl internal reference elements were made from silver wire. The internal reference elements were immersed in a solution of AgCl‐saturated KCl, which also served as the salt bridge. Contact between the salt bridge and test solution or soil was made through a ceramic microtensiometer cup. This procedure yields reference electrode assemblies that perform as well as commercially available reference electrodes in terms of their stability and reproducibility. Because of their rugged construction and ease of maintenance, these reference electrode assemblies are ideal for use in the field. Moreover, they proved to be particularly useful when in situ soil redox potentials were monitored for 84 h.     

Bulk density by Proctor test as a function of texture for agricultural soils in Maputo province of Mozambique

Soil degradation processes may be of various kinds, including soil compaction. The present study was carried out with the objective of assessing the sensitivity of agricultural or recently abandoned soils in Maputo province of Mozambique to compaction. The assessment is based on the maximum of bulk density attained using the Proctor test (MBD).

In this study the soil texture is expressed by silt plus clay (S + C) or clay (C). The relations between the soil texture and MBD, and between soil texture and critical water content (CWC—soil water at which MBD is attained) were determined. Selected soils range from 10 to 74% of S + C and 9 to 60% of C.

The results suggest there is a relationship between the considered parameters, being that between S + C and MBD or CWC, the best. For MBD the relationship is represented by two quadratic equations with the boundary in between these being a S + C value of 25% and C value of 20%.

Based on the obtained results, one can conclude that the selected parameters may be a useful basis for estimation of the sensitivity to compaction of the Maputo province's soils. It is recommended that similar studies be carried out for soils under forest land and for soil of other provinces to establish the national physical degradation hazard as a function of soil parameters determined routinely and at low cost. The suggested parameters are texture and soil organic matter (SOM).     

Dynamic interfacial rheology as a tool for the characterization of whey protein isolates gelation at the oil-water interface.

Heat-induced interfacial aggregation of a whey protein isolate (WPI), previously adsorbed at the oil-water interface, was studied by interfacial dynamic characteristics coupled with microscopic observation and image analysis of the drop after heat treatment. The experiments were carried out at temperatures ranging from 20 to 80 degrees C with different thermal regimes. During the heating period, competition exists between the effect of temperature on the film fluidity and the increase in mechanical properties associated with the interfacial gelation process. During the isothermal treatment, the surface dilational modulus, E, increases, and the phase angle, delta, decreases with time to a plateau value. The frequency dependence of E and delta is characteristic of viscoelastic films with increasing delta and decreasing E at lower frequencies. The effects of heat treatment depend on the conditions at which the gelation process takes place. Microscopic observation of gelled films gives complementary information on the effect of heat treatment on WPI adsorbed films.     

Nondestructive evaluation of anthocyanins in olive (Olea europaea) fruits by in situ chlorophyll fluorescence spectroscopy

Anthocyanins (Anths) in olive (Olea europaea L.) fruits at different degrees of pigmentation were assessed nondestructively by measuring chlorophyll fluorescence (ChlF). The method is based on the comparison of the ChlF excitation spectra from olives with different pigmentation from green to green-red, reddish-purple, and purple. The logarithm of the ratio between the fluorescence excitation spectra (logFER) from two different colored zones gave the difference in the absorption spectrum between them. The absorbance spectrum derived from the logFER between a red olive and the same olive devoid of the skin showed the typical Anth green band (at 550 nm). It matched that recorded by microspectrophotometry on a single pulp cell and the in vitro absorbance spectrum of the olive skin extract. As expected, the in vivo Anths absorption maximum increased in intensity going from less to more mature olives and was higher in the sun-exposed olive side with respect to the sun-shaded side. Absolute quantitative nondestructive determination of Anths for each olive sample was obtained by the logFER calculated for two excitation wavelengths, 550 and 625 nm, of ChlF at 740 nm. Going from green to purple skin colors, the Log[ChlF(625)/ChlF(550)] was fairly well-correlated to the extract Anths concentration. Finally, the relationship between the Anths and the other main phenolics present in the olives analyzed by high-performance liquid chromatography was evaluated. The main result was a net increase of verbascoside with increasing Anths content. On the basis of our results, the development of a new rapid and noninvasive method for the monitoring of olive development and ripening can be envisaged.     

Congener-specific evaluation of biota-sediment accumulation factor model for HCHs and DDTs under small-scale in situ riverine condition

Purpose

The congener-specific biota-sediment accumulation factors (BSAFs) model for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) was evaluated for four different freshwater fish species (Orienus plagiostomus, Tor putitora, Glyptothorax punjabensis, and Cyprinus carpio) in in situ riverine conditions of Kabul River, Pakistan.

Materials and methods

The congeners of HCH and DDT were quantified using gas chromatograph (GC-ECD). The BSAF for each congener (HCHs and DDTs) was calculated from paired observation of congener’s measured concentrations in fish and sediment taken at the same site. Pearson’s correlation and linear regression analyses were performed to determine the influence of sediment organic carbon fraction (f _soc ) and organism lipid fraction (f _lipid ) on BSAF, and the relationship between BSAFs and logarithm of octanol-water partition coefficients (log K _ows) of HCH and DDT congeners, respectively.

Results and discussion

The BSAFs for total HCH (t-HCH) and total DDT (t-DDT) ranged from 0.6 to 1.5 and from 0.2 to 1.6, respectively. The model was significantly influenced by both fish (p = 0.004) and chemical types (p = 0.002) at 95 % confidence level. The sediment organic carbon fraction (f _soc ) and fish lipid fraction (f _lipid ) had not-too-weak effects on BSAF values for all fish species. The BSAF values were linearly fitted with logarithmic octanol-water partition coefficients (log K _ows) of HCH and DDT congeners, despite the different chemical structures, and different compound class significant negative correlations between log K _ows and BSAF values were found, indicating that hydrophobicity is one of the key factors influencing the bioaccumulation potential of the investigated compounds.

Conclusions

The present study confirmed the applicability of the BSAF model as a screening tool for predicting bioaccumulation of sediment-associated HCH and DDT congeners in investigated fish species under small-scale in situ riverine conditions of Kabul River and suite the model for benthic fish (G. punjabensis) on the basis of the 25th and 75th percentiles of congener-specific BSAF values.

     

Development of continuous type apparatus for ampholyte-free isoelectric focusing (autofocusing) of peptides in protein hydrolysates

An apparatus for continuous fractionation of peptides on the basis of amphoteric nature of sample peptides was developed. A tank (66.5 cm x 8 cm x 8 cm, L x W x H) was divided into 12 compartments by a thin agarose gel layer. A drain tube (5.5 cm in length and 0.7 cm in i.d.) was fixed through the bottom of each compartment to give a height of 4 cm from the bottom. The tank with 12 compartments and electrodes was referred to as an autofocusing unit. The peptide solution or water was delivered to the sample compartments of the first unit. The solutions drained from the first unit were successively delivered to the second and third units. To the electrodes of three units, a direct electric current was applied. By using the present apparatus, peptides in casein hydrolysate can be continuously fractionated at least for 5 h. Better resolution was obtained in the second and third units.     

Nitrogen fixation (C2H2 reduction) in a salt marsh: Its relationship to temperature and an evaluation of an in situ chamber technique

A temperature controlled chamber for the in situ measurement of nitrogen fixation (acetylene reduction) in a vegetated salt marsh is described. Rates of acetylene reduction activity (ARA) were linear during a 9 h incubation. Measurements of acetylene penetration into the sediment indicate that the chamber technique measures ARA within the top 2–4 cm of the sediment column. This depth of penetration accounted for approx. 60% of the total ARA in the sediment column. Measurements of in situ ARA in three zones of a vegetated salt marsh (tall, medium and short height Spartina alterniflora) over a year were positively correlated with seasonal temperature variations. About 70–80% of the seasonal variation in ARA was explained by the Arrhenius relationship: ARA (μmol C₂H₄m⁻²h⁻¹)=α exp(−β/fT); where T is the ambient air temperature (°C) and α and β are constants. The constant α in this model increased from 20.1 to 40.5 while β increased from 17.5 to 20.7 along a transect from the tall to short height-form S. alterniflora communities. These differences suggest that there is spatial variability within the salt marsh among the variables that affect nitrogen fixation.     

A new test method for the evaluation of total antioxidant activity of herbal products

A new test method for measuring the antioxidant power of herbal products, based on solid-phase spectrophotometry using tetrabenzo-[b,f,j,n][1,5,9,13]-tetraazacyclohexadecine-Cu(II) complex immobilized on silica gel, is proposed. The absorbance of the modified sorbent (lambda(max) = 712 nm) increases proportionally to the total antioxidant activity of the sample solution. The method represents an attractive alternative to the mostly used radical scavenging capacity assays, because they generally require complex long-lasting stages to be carried out. The proposed test method is simple ("drop and measure" procedure is applied), rapid (10 min/sample), requires only the monitoring of time and absorbance, and provides good statistical parameters (s(r)相似文献   

Critical evaluation of methods for determining total protein in soil solution

Proteins represent a significant reservoir of organic nitrogen in most terrestrial ecosystems and therefore comprise a key component of the soil N cycle. Consequently, there is a critical need to develop robust methodologies for quantifying the abundance of proteins in soil. In this study we evaluated the performance of five commercially available total protein assay kits in a contrasting range of soils. All the kits were based on the detection of proteins after conjugation with either chromophores or fluorophores. Overall, we found that all the kits suffered significant signal interference from humic substances present in solution, resulting in either a quenching or enhancement of the protein response. Inter-comparison of the kits yielded no agreement when quantifying the total amount of protein present in soil solution, with differences in concentration for individual samples ranging 20–500-fold when using the different assay kits. We concluded that none of the commercial assay kits can provide a reliable indicator of soil solution protein content. Although it may detect some non-proteinaceous material (e.g. peptidoglycan), total protein quantitation is currently best undertaken by acid hydrolysis of proteins in solution with subsequent determination of the amino acids liberated. However, there is an imperative need to develop robust methods for protein extraction, purification and analysis in soil.     

Comparison of soil nitrate extracted by potassium chloride and adsorbed on an anion exchange membrane in situ

Abstract

The 2M potassium chloride (KCl) extraction method used to measure soil nitrate (NO₃ ^‐‐N) concentrations in soils may introduce some artifacts caused by soil sampling, processing, and handling. Furthermore, this method provides soil NO₃ ^‐‐N concentrations for soil sampled at a particular time, whereas the dynamics of this anion in situ need to be better understood. In order to develop a reliable in situ method as an alternative, an anion exchange membrane (AEM) was tested for its ability to adsorb NO₃ ^‐‐N from a soil cropped to corn (Zea mays L.) and amended with manure or inorganic nitrogen (N). In a field study, we compared the amount of NO₃ ^‐‐N adsorbed on an AEM and extracted with the 2M KCl method. The AEM was calibrated in the laboratory and placed at 15‐cm soil depth for 2‐wk periods during the corn growing season. Nitrate adsorption on the AEM and KCl‐extractable NO₃ ^‐‐N were larger in the inorganic N treatment than in the manure or the control treatments throughout the growing season. The NO₃ ^‐‐N concentrations measured by the AEM method were correlated with NO₃ ^‐‐N extracted with 2M KCl (r² = 0.78***), suggesting that the AEM method could be used to measure NO₃ ^‐‐N concentrations in agricultural soils.     

Molecular markers and ex situ conservation of the European elms (Ulmus spp.)

The enormous losses suffered by the European elms during recent Dutch elm disease outbreaks led to concern over the conservation of elm genetic resources, and the subsequent establishment of a series of ex situ collections. However, as ex situ collections are inevitably finite in size, some consideration needs to be given to selecting which samples to include in them. To contribute towards this process for European ex situ elm collections we have undertaken genetic studies on a Europe-wide sample of 535 individuals. A major aim has been to use genetic markers to clarify the identification of samples to ensure that the ex situ collections contain a representative spread of taxonomic diversity. This is important given the paucity of mature elms in the landscape due to Dutch elm disease. The lack of mature material (critical for identification) compounds identification problems in what was already a taxonomically difficult group. Our data (derived from random amplified polymorphic DNA and inter-simple sequence repeats) have provided a useful supplement to morphology in undertaking such sample identifications. The molecular data served to highlight mis-identified samples and led to extensive revisions of sample identities within individual countries. Our results were less useful in detecting regional intra-specific genetic structure, and do not provide sufficient information for prioritising within-species sample selections.     

六盘山森林保持水土生态功能评价

本文列举并论述了在六盘山林区进行的森林水文学定位观测与考察成果，包括林分特性，降水分配，流域径流量、径流调节及其它森林水文特性。讨论范围涉及到六盘山的不同地域，并对当地水土保持生物措施及森林经营方法作了深入的探讨。     

Immunochemical determination of 2,4,6-trichloroanisole as the responsible agent for the musty odor in foods. 1. Molecular modeling studies for antibody production

Nine antisera have been raised against 2,4,6-trichloroanisole (2,4,6-TCA) by immunizing them with three different haptens. With the spacer arm at the meta position, hapten A (3-(2,4,6-trichloro-3-methoxyphenyl)propanoic acid) preserved all of the functional groups of the target analyte. In hapten B (5-(2,4,6-trichlorophenoxy)pentanoic acid), the spacer was placed in the molecule substituting the methoxy group. Finally, hapten C (3-(3,5-dichloro-4-methoxyphenyl)propanoic acid) held the spacer arm at the para position instead of the chlorine atom of the target analyte. Using theoretical models, we have studied how the molecular geometry and the electronic distribution are affected by the introduction of the linker. The evaluation of the avidity of the resulting antibodies demonstrates that the orientation produced by the spacer arm must also be considered an essential aspect. The screening for competitive assays performed after synthesizing a battery of heterologous competitors has provided with these antibodies eight indirect enzyme-linked immunosorbent assays with acceptable properties. From the number of assays obtained, their maximal absorbance, their signal-to-noise ratio, the slope, and the IC(50) values obtained, it can be concluded that hapten C provided the best antibodies.     

非耕农用地耕种功能恢复适宜性评价模型构建

恢复非耕农用地耕种功能是落实耕地“进出平衡”政策的基础和保障耕地动态平衡的重要内容。科学确定非耕农用地耕种功能恢复适宜性等级是合理安排恢复工作进行的依据。该研究运用文献借鉴法、熵权法、限制性因子评价法、加权指数和法等方法，从生产、生态、经济3个维度构建了包含12项评价指标的非耕农用地耕种功能恢复适宜性评价模型，并选取沈阳市康平县借助ArcGIS软件完成对非耕农用地耕种功能恢复适宜性的评价过程。结果表明：康平县内生产、生态、经济3个方面的恢复适宜性情况存在明显的空间分异特征；非耕农用地耕种功能恢复适宜区域综合评价分值较为集聚，范围为[1.951，3.201]，不适宜区域赋值为0；康平县非耕农用地耕种功能恢复适宜性等级划分为高度适宜、中度适宜、低度适宜、勉强适宜及不适宜；各个行政区非耕农用地耕种功能恢复适宜性平均水平都达到了低度适宜及以上等级；低度适宜及以上等级的非耕农用地面积占比为67.68%，大多为其他林地与乔木林地，恢复难度较小；在所有等级中，勉强适宜的非耕农用地面积占比最多，为32.30%，主要土地利用类型为其他林地、乔木林地与果园，恢复难度较大；不适宜这一等级最少，全部为坡度大于25°的其他林地。研究结果可为未来非耕农用地耕种功能的实际恢复工作提供参考。