超高压微射流对花生蛋白结构的影响（简报）

为了探讨超高压微射流对花生蛋白理化性质和结构的影响,该文研究了花生蛋白溶液经超高压微射流处理后的颗粒大小、游离巯基基团、疏水基团和紫外吸收基团的变化规律。结果表明：花生蛋白的颗粒尺寸和游离巯基基团含量随着超高压微射流均质压力的增大而显著减小;疏水基团和紫外吸收基团的含量则随着均质压力的增大而显著增大,说明超高压微射流处理可破坏花生蛋白的内部基团,使蛋白的结构发生变化。     

超高压微射流对花生蛋白结构的影响

为了探讨超高压微射流对花生蛋白理化性质和结构的影响.该文研究了花生蛋白溶液经超高压微射流处理后的颗粒大小、游离巯墓基团、疏水基团和紫外吸收基团的变化规律.结果表明:花生蛋白的颗粒尺寸和游离巯基基团含量随着超高压微射流均质压力的增大而显著减小;疏水基团和紫外吸收基团的含量则随着均质压力的增大而显著增大,说明超高压微射流处理可破坏花生蛋白的内部基团,使蛋白的结构发生变化.     

Effect of preparation conditions on protein secondary structure and biofilm formation of kafirin

Various extraction and drying conditions for the isolation of kafirin from dry-milled, whole grain sorghum have been investigated, with a view to optimizing extraction of the protein for commercial food coatings and packaging films. The addition of sodium hydroxide to an aqueous ethanol extractant increased the yield and solubility of kafirin. Subsequent heat drying at 40 degrees C was shown to cause the kafirin to aggregate as indicated by an increase in intermolecular beta-sheets. Extraction of the flour using ethanol (70%, w/w) with 0.5% (w/w) sodium metabisulfite and 0.35% (w/w) sodium hydroxide at 70 degrees C followed by freeze-drying of the protein was found to produce a yield of 54% kafirin with good film-forming properties. The kafirin films were assessed for their sensory properties, tensile strength, strain, and water vapor permeability. Fourier transform infrared spectroscopy was used to study the secondary structure of the extracted kafirins. The best films were made with kafirin containing a large proportion of nativelike alpha-helical structures with little intermolecular beta-sheet content as indicated by the Fourier transform infrared reflectance peak intensity ratios associated with these secondary structures. The principal factor affecting the secondary structure of the protein appeared to be the temperature at which the protein was dried. Heat drying resulted in a greater proportion of intermolecular beta-sheets. Any industrial-scale extraction must therefore minimize protein aggregation and maximize native alpha-helical structures to achieve optimal film quality.     

巴氏杀菌和超巴氏杀菌对牛乳清蛋白结构及热稳定性的影响

为了研究巴氏杀菌与超巴氏杀菌处理对牛乳清蛋白结构的影响,采用热力学和光谱学等方法测定乳清蛋白结构及稳定性。红外光谱分析结果显示巴氏杀菌处理对乳清蛋白二级结构影响不显著,而经超巴氏杀菌处理后的乳清蛋白中α-螺旋结构含量显著减少,无规则卷曲结构含量显著增多,结构转变的更为无序,其稳定性更好;荧光光谱分析结构表明经121℃、5 s超巴氏杀菌处理的乳清蛋白样品发生红移,说明超巴氏杀菌改变了乳清蛋白二级和三级结构;差示扫描量热法分析结果显示121℃、5 s热处理的乳清蛋白样品热变性温度为99.9℃,高于巴氏杀菌处理的乳清蛋白样品,表明超巴氏杀菌处理后的乳清蛋白样品的稳定性显著提高,期望为制备高品质乳提供理论基础。     

超高压处理对大黄鱼鱼糜水分状态和蛋白质结构的影响

为了研究超高压处理大黄鱼鱼糜的凝胶特性,该文利用低场核磁共振、拉曼光谱研究了水浴加热和超高压处理鱼糜凝胶化过程中水分存在状态和蛋白质结构的变化,并分析了它们和鱼糜凝胶特性指标的相关性。结果表明,与水浴加热处理相比,超高压处理能改善鱼糜凝胶特性,使其保水率、弹性、内聚性增大（P<0.05）,硬度下降（P<0.05）。但随压力增大,鱼糜的内聚性、弹性、咀嚼性呈下降趋势（P<0.05）,保水率变化不显著（P>0.05）;低场核磁共振分析显示超高压使鱼糜自由水组分消失,不易流动水的流动性增强（P<0.05）,结合水的含量增加（P<0.05）;拉曼光谱分析显示超高压使鱼糜蛋白α-螺旋含量显著增加（P<0.05）,无规卷曲和β-转角含量显著下降（P<0.05）,三级结构也发生变化;相关性分析表明,蛋白质结构、水分状态及含量与鱼糜的质构、保水率之间存在特定相关性。说明不同处理条件下,鱼糜的蛋白质结构和水分状态发生改变,从而表现出相应的质构、保水率等凝胶特性。以上结果可为鱼糜凝胶特性的评价及改进提供检测方法及理论依据。     

Enzymatic oligomerization of vanillic acid

When vanillic acid was incubated with an extracellular laccase from the fungus Rhizoctonia praticola, the formation of various oligomeric products was observed ranging from dimers to pentamers. The three dimers isolated by thin-layer chromatography had molecular ions of 304, 304 and 334, respectively, which corresponded to two dimers (methoxy-p-benzoquinone-vanillic acid) with C-O (2-methoxy-6-(2'-methoxy-4'-carboxyphenoxy)-1,4-benzoquinone) and C-C (2-methoxy-6-(2'-hydroxy-3'-methoxy-5'-carboxyphenyl)-1,4-benzoquinone) coupling, and dehydrodivanillic acid (m/z 334) (2,2'-dihydroxy-3, 3'-dimethoxy-5,5'-dicarboxybiphenyl). The identity of these compounds and their methylated derivatives was confirmed by mass and NMR spectrometric analysis. The oxidative coupling of vanillic acid is also catalyzed by peroxidase but not by tyrosinase.     

冷冻方式对醛交联大豆蛋白多孔材料结构及吸附特性的影响

为制备纳米级孔径的大豆蛋白多孔材料,研究了冰箱和液氮冷冻处理的醛交联大豆蛋白多孔材料的结构及吸附性能。结果表明:戊二醛对大豆蛋白的交联效果优于甲醛和乙二醛。液氮冷冻处理的多孔材料比表面积和孔容均较大,而平均孔径较小;纳米级孔的孔径都分布在80 nm以内,介孔总孔容占比超过50%,大孔次之,微孔占比最小;冰箱冷冻样品纳米级孔的孔径主要分布在70 nm以内,且微孔和介孔孔容都小于采用液氮冷冻处理的样品。场发射扫描电镜分析表明,大豆蛋白多孔材料的孔形态为微米级圆孔和纳米级狭缝孔。冷冻处理比醛类交联剂对孔结构的影响大,合适的冷冻方式能替代或超过交联剂种类变化取得的效果。热重分析表明液氮冷冻处理的戊二醛交联大豆蛋白多孔材料热稳定性好;该多孔材料对对硝基苯酚和六价铬离子具有一定的吸附效果,是制备大豆蛋白多孔材料较合适的方法。研究结果为植物蛋白多孔材料的制备提供参考。     

Peroxidase-catalyzed oligomerization of ferulic acid esters

Valuable information about possible types of linkages, reaction mechanisms, and sequences for oxidative coupling of phenolic compounds in planta is available from in vitro model systems. Ferulate oligomers were generated in a system using ethyl ferulate, peroxidase, and hydrogen peroxide under various conditions. A molar ferulate/H2O2 ratio of 1:1, an ethanol level of 30% in an aqueous sodium phosphate buffer (pH 6.0), and a reaction time of 10 min were considered to be ideal to produce maximal proportions of ferulate trimers and tetramers from ethyl ferulate as starting material. The dominant trimer and tetramer were each isolated from the reaction mixture and identified as 8-O-4/8-5(cyclic)-dehydrotriferulic acid triethyl ester and 8-5(cyclic)/4-O-5/8-5(cyclic)-dehydrotetraferulic acid tetraethyl ester. The structure of the 8-O-4/8-5(cyclic)-dehydrotriferulic acid triethyl ester revealed that a third ferulate unit is bound to a preformed 8-O-4-diferulate dimer, a surprising reaction sequence considering the dominance of 8-5-coupled dimers among dehydrodiferulates in H2O2/peroxidase-based model reactions. As 4-O-5-coupling is not favored in the dimerization process of ferulates, the main tetramer isolated in this study is probably formed by 4-O-5-coupling of two preformed 8-5(cyclic)-diferulates, a logical step in analogy with reactions occurring in lignin biosynthesis.     

Effect of nitrification inhibitors on rice protein

Abstract

The effects of ammonium sulfate and urea nitrogen (150 kg N/ha) applied with three levels (5, 10 and 15% of N) of the nitrification inhibitors karanjin and nitrapyrin on grain protein of rice (Oryza sativa L. cv. Bala) were studied in pot experiment. Karanjin at the 10 and 15 per cent levels and nitrapyrin at the 10 per cent level significantly increased grain protein. Rice protein levels were highest at the 15 per cent karanjin level.     

植物多酚-牛血清白蛋白相互作用及对蛋白质结构的影响

多酚与蛋白质的相互作用取决于蛋白质和多酚的结构与类型,为研究不同植物多酚与牛血清白蛋白（bovine serum albumin,BSA）之间的相互作用,探明不同植物多酚对BSA结构的影响,进而筛选出稳定的植物多酚-BSA复合物。该研究采用原花青素（proanthocyanidins,PC）、儿茶素（catechin,C）、表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)、茶多酚（tea polyphenol,TP）,通过紫外光谱法、荧光光谱法、红外光谱法和分子对接研究植物多酚与BSA相互作用及其对蛋白质结构的影响。结果表明：4种植物多酚-BSA复合物的紫外最大波长红移由大到小为EGCG（365 nm）＞PC（364 nm）、C（364 nm）＞TP（363 nm）;红外光谱发现,酰胺Ⅰ带的吸收峰（1 657.44 cm^-1）发生蓝移由大到小为PC（1 656.15 cm^-1）＞TP（1 632.07 cm^-1）＞EGCG（1 631.49 cm^-1）＞C（1 631.44 cm^-1）,烟酰胺II带峰形变宽;BSA二级结构由β-转角、无规卷曲转变为β-折叠、ɑ-螺旋,β-折叠含量增加C-BSA（40.20%）>PC-BSA（39.50%）>EGCG-BSA（39.32%）>TP-BSA（34.04%）,表明C更能促进BSA的二级结构稳定;荧光光谱表明4种多酚对BSA的猝灭类型均为静态猝灭,且结合位点约为1,表明存在一个结合位点;分子对接结果表明该结合位点位于Sub-domain IIA的疏水腔中,分子间相互作用力主要是氢键、疏水作用力,结合能由小到大为C（-3.72 kJ/mol）＜EGCG（-1.77 kJl/mol）＜PC（-1.02 kJ/mol）＜TP（-0.38 kJ/mol）;4种多酚中C和EGCG与BSA相互作用程度较大,C与BSA的结合能最小,形成的复合物最稳定。通过多酚与蛋白相互作用研究,更好地发挥多酚和蛋白两种组分的功能作用,可为开发功能性多酚-蛋白质复合物产品提供参考。     

Effect of habitat spatiotemporal structure on collembolan diversity

Landscape fragmentation is a major threat to biodiversity. It results in the transformation of continuous (hence large) habitat patches into isolated (hence smaller) patches, embedded in a matrix of another habitat type. Many populations are harmed by fragmentation because remnant patches do not fulfil their ecological and demographic requirements. In turn, this leads to a loss of biodiversity, especially if species have poor dispersal abilities. Moreover, landscape fragmentation is a dynamic process in which patches can be converted from one type of habitat to another. A recently created habitat might suffer from a reduced biodiversity because of the absence of adapted species that need a certain amount of time to colonize the new patch (e.g. direct meta-population effect). Thus landscape dynamics lead to complex habitat spatiotemporal structured, in which each patch is more or less continuous in space and time. In this study, we define habitat spatial structure as the degree to which a habitat is isolated from another habitat of the same kind and temporal structure as the time since the habitat is in place. Patches can also display reduced biodiversity because their spatial or temporal structures are correlated with habitat quality (e.g. indirect effects). We discriminated direct meta-community effects from indirect (habitat quality) effects of the spatiotemporal structure of habitats on biodiversity using Collembola as a model. We tested the relative importance of spatial and temporal structure of habitats for collembolan diversity, taking soil properties into account. In an agroforested landscape, we set up a sampling design comprised of two types of habitats (agriculture versus forest), a gradient of habitat isolation (three isolation classes) and two contrasting ages of habitats. Our results showed that habitat temporal structure is a key factor shaping collembolan diversity. A reduced diversity was detected in recent habitats, especially in forests. Interactions between temporal continuity and habitat quality were also detected by taking into account soil properties: diversity increased with soil carbon content, especially in old forests. Negative effects of habitat age on diversity were stronger in isolated patches. We conclude that habitat temporal structure is a key factor shaping collembolan diversity, while direction and amplitude of its effect depend on land use type and spatial isolation.     

Effect of soil structure on soil water status

Although the need for research into soil structural features responsible for water loss from soil is recognised, the research has been hampered by the lack of suitable techniques for measuring in situ soil macrostructure. Therefore, in a field experiment, structural parameters obtained from eight differently tilled (loam) soils in winter and spring were correlated with gravimetric soil water content (at 5 and 10-cm depths) and evaporative water loss during daylight hours. Percentage of voids and aggregates of different sizes, mean aggregate size, mean void size and macroporosity percentage were all calculated from structural data obtained from sectioned blocks of soil that were impregnated with paraffin wax in the field.Significant negative correlations were observed between soil water content, and percentage of 4–8 and 8–16-nm voids, mean aggregate size and macroporosity percentage, especially in winter when there are long periods without precipitation. However, inverse relationships were detected between evaporative water loss during daylight hours on selected days and mean aggregate size, mean void size and macroporosity percentage. But evaporative water loss during daylight hours apparently did not influence water content of bare soil with coarse structure at the surface.     

超声处理对菜籽蛋白酶解效果的影响

以双低菜籽饼粕蛋白为原料,以常规酶解为对照,以酶解产物的抑制活性为指标,分别考察了超声预处理蛋白酶、超声预处理蛋白原料和酶解过程前期施加超声3种超声处理方式对双低菜籽蛋白酶解制备ACEI 活性肽效果的影响。结果表明,3种超声辅助方式都能有效地促进菜籽饼粕蛋白的酶解,提高产物的ACE抑制活性,其中超声预处理蛋白原料效果最为明显。这种方式的最佳参数为：超声频率20 kHz、超声时间 30 min、超声功率1250 W、作用时间4 s、间歇时间2 s,该条件下酶解产物对ACE的抑制率从对照组的70.83%提高到92.97%,肽得率从29.6%提高到41.4%,半抑制浓度IC50从3.57 mg/mL降到2.48 mg/mL。这表明脉冲超声辅助酶解法是一种高效制备双低菜籽ACEI肽的方法。     

花生品质对其蛋白质凝胶性的影响

为了探讨不同花生品种的感官品质、理化与营养品质、加工品质与其蛋白质凝胶性之间的关系,提出适宜肉制品加工凝胶型蛋白质专用花生品种的主要特性和评价方法,构建适宜加工凝胶型蛋白质花生品质评价模型。以62个花生品种制得的分离蛋白粉为原料,采用物性仪测定其分离蛋白凝胶性,分析各品种花生的品质特性与凝胶性之间的关系,采用有监督主成分分析对41个品种的品质数据建立凝胶型蛋白质花生品质评价模型,并用另外21个品种品质数据进行验证。结果显示,不同品种花生蛋白质在相同条件下制得的凝胶特性差异显著。果形、粗蛋白、粗纤维、半胱氨酸、甘氨酸、精氨酸、亮氨酸、伴花生球蛋白Ⅰ、花生球蛋白/伴花生球蛋白、23.5kDa等10个指标与凝胶性在0.05水平上关系显著,采用有监督主成分分析建立凝胶型蛋白质花生品质评价模型,验证模型的相关系数为0.937。研究结果表明,花生的品质特性显著影响花生蛋白质的凝胶性。花生粗蛋白含量、胱氨酸含量、精氨酸及伴花生球蛋白Ⅰ含量高的品种具有更好的凝胶性。通过凝胶型蛋白质花生品质评价模型可以预测该品种花生蛋白质的凝胶性,为不同花生品种的加工利用和专用品种的选择提供依据。     

氨化秸秆还田对土壤孔隙结构的影响

【目的】土壤孔隙性质是土壤结构性的反映,直接影响着土壤的肥力和水分有效性。定量研究氨化秸秆还田对土壤不同大小等级孔隙数量和孔隙分布的影响,可以为土壤培肥提供科学依据。【方法】采用室内试验方法,设置氨化秸秆加入量为土壤总质量的 0(CK)、 0.384%(S1)、 0.575%(S2)、 0.767%(S3)4个处理,室内培养。在培养0、60、120和180 d,取样测定土壤水分特征曲线(SWRC)数据,利用双指数土壤水分特征曲线模型(DE模型,Double-exponential water retention equation),分析氨化秸秆对土壤剩余孔隙、基质孔隙和结构孔隙的影响; 基于DE模型的微分函数,探究不同氨化秸秆处理对土壤孔隙分布的影响。【结果】不同处理的土壤水分特征曲线SWRC实测值和DE模型模拟值之间的均方根误差介于0.0036和0.0041 cm3/cm3之间,R2介于0.998和0.999之间,土壤含水量模拟值和实测值非常接近1 ∶1,表明DE模型可以准确反映添加氨化秸秆后土壤含水量随吸力的变化规律,较准确地估算土壤不同大小等级孔隙数量变化。培养120 d内,氨化秸秆对土壤剩余孔隙、基质孔隙和结构孔隙影响不显著; 培养180 d时,各处理土壤结构孔隙度表现出随着氨化秸秆添加量的增加而增加的趋势; 此时S3对土壤剩余孔隙影响不显著,显著减小了土壤的基质孔隙度(P0.05),极显著地增加了土壤的结构孔隙度(P 0.01)。在孔隙分布中,氨化秸秆促进了土壤已有孔隙向较大孔隙的发育,显著增加了土壤结构孔隙分布数量; 随着氨化秸秆添加量的增加,土壤结构孔隙的分布数量越大,且峰值出现的越早。氨化秸秆增加了土壤中有机质含量; 土壤结构孔隙和总孔隙均与有机质含量呈显著的正相关关系(P 0.05); 有机质可以黏结团聚土壤的矿物颗粒,有效地促进了土壤结构孔隙的发育; 氨化秸秆对土壤孔隙的影响随着时间的进行越来越明显。【结论】氨化秸秆增加了土壤中有机质含量,促进了土壤孔隙结构的发育,增加了土壤的结构孔隙度和总孔隙度,这对改良和培肥土壤、改善土壤耕性具有重要意义。     

Effect of flavor compound chemical structure and environmental relative humidity on the binding of volatile flavor compounds to dehydrated soy protein isolates

Influence of flavor compound chemical structure, including functional group and stereochemistry, and environmental relative humidity (RH) on the binding of volatile flavor compounds to dehydrated soy protein isolates (SPIs) was evaluated by inverse gas chromatography. Binding of selected volatile flavor compounds differed slightly between SPIs of different origins. Results showed that the flavor compound chemical structure greatly determined its binding potential to SPIs. Binding of nonpolar flavor compounds (hydrocarbon) to soy proteins was attributed mainly to nonspecific van der Waals dispersion forces and was not affected by adsorbed water. The more polar flavor compounds (ester, ketone, aldehyde, and alcohol) exhibited both specific (hydrogen bonding, dipole forces) and nonspecific interactions, and their binding with soy proteins was greatly impaired by adsorbed water in the extremely low humidity region (approaching 0% RH). Further water uptake in the 30 to 50% RH region did not significantly affect the binding of polar compounds, although sorption of alcohol compounds (when present at high levels) further increased.     

6-磷酸葡萄糖对鸡类囊胚发育的影响

由鸡Ⅹ期胚盘获得的类囊胚包含禽类胚胎干细胞,且具有较强的增殖与分化能力。体外培养12、24、36 h的类囊胚细胞S tathm in基因的表达高于Ⅹ期胚盘细胞,证实增殖的细胞为禽类胚胎干细胞。超微结构观察表明,类囊胚细胞在早期增殖过程中以卵黄蛋白为能量的主要来源,当卵黄蛋白消耗殆尽,则细胞出现大量死亡。胚胎干细胞培养液(ESM)能够促进类囊胚细胞的增殖却不能减少死亡。在ESM基础上添加5 mm o l/L 6-磷酸葡萄糖(G 6P),不仅各期细胞增殖显著,且24 h细胞死亡数的比例(D/T)由23%下降到5.6 7%(P<0.0 5),3 6 h细胞D/T由3 0%下降到1 5.6 3%(P<0.0 5)。结果表明,在ESM基础上添加5 mm o l/L G 6P可促进类囊胚细胞的增殖,并明显改善能量匮乏导致的细胞死亡。     

耕作方式对土壤螨类群落结构的影响

土壤螨类是土壤生态系统中重要的指示生物之一。为探讨耕作方式对土壤螨类数量、类群数、群落结构以及垂直分布的影响, 试验选取位于东北黑土区中国科学院海伦农田生态系统国家野外科学观测研究站中5种耕作方式(免耕耕作、少耕耕作、平翻耕作、组合耕作和旋耕耕作)试验区内土壤螨类为研究对象, 采用改良干漏斗(Modified Tullgren)法, 于2009年5月、6月和7月3个时期分离0~15 cm土层中的土壤螨类。结果表明: 耕作方式对土壤螨类数量和类群数存在显著影响, 3个时期共捕获土壤螨类2 441只, 免耕耕作、少耕耕作、组合耕作、旋耕耕作和平翻耕作分别捕获土壤螨类366只、436只、553只、819只和267只, 分别隶属于13科、18科、13科、14科和11科。传统的旋耕耕作具有最高的土壤螨类个体数量, 而保护性耕作中的少耕耕作具有最高的土壤螨类类群数。不同时期耕作方式对土壤螨类垂直分布的影响不同, 5月除免耕耕作外其他4种耕作方式均较好地保持了土壤螨类垂直分布的表聚特征, 即0~5 cm土层中土壤螨类的数量显著(P<0.05)高于其他两层(5~10 cm, 10~15 cm), 其中组合耕作和少耕耕作在3个时期中均较好地保持了土壤螨类的表聚特征, 且少耕耕作较好地保持了土壤螨类的多样性。MGP分析结果表明: 土壤甲螨群落随季节的变化在组成上发生变化, 从最初的高等甲螨为优势类群转化为低等甲螨为优势类群, 免耕和少耕的这种趋势较其他耕作方式更为明显, 少耕耕作3个时期土壤甲螨的组成类型分别为P型、G型和O型, 而免耕耕作3个时期土壤甲螨的组成类型分别为P型、O型和G型。少耕和免耕两种保护耕作方式较其他耕作方式更有利于土壤螨类群落结构的稳定性及多样性的保持, 有利于农田土壤生态环境的保护。     

Effect of the structure on the electrical properties of soils

It was shown by capillarimetric and dielcometric methods that Linear relationships exist between the capacitance of soils and their volumetric water content. The coefficients of proportionality in these relationships abruptly decreased upon the disturbance of the soil structure: when the volumetric water content of soils decreased by two times, their capacitance decreased by 7–15 pF for soils with a natural structure and by only 1–2 pF for soils with a degraded structure. Therefore, the proportionality coefficients in these relationships could be used as criteria for assessing the structural state of soils.