黑色素自组装薄膜制备的研究

采用自组装技术,在碱性溶液中制备黑色素自组装薄膜。利用扫描电镜、红外光谱、光电子能谱和X射线衍射仪对其进行表征。结果表明,黑色素溶液在带有负电荷的基底(硅片)上,通过自组装技术组装,得到均匀和形貌一致的黑色素薄膜。由红外光谱和光电子能谱可知,黑色素成分通过N-O-Si形式与基底结合。X-射线衍射结果显示,组装在硅片上的自组装薄膜在2个方向上都是有序的结构。这对理解黑色素薄膜的微观结构是非常有用的一个研究。     

Effects of particle size on the quality attributes of reconstituted whole-wheat flour and tortillas made from it

The objective of this study was to examine the effects of whole-wheat flour (WWF) particle size on the quality attributes of WWF tortillas. WWF samples of different particle size distributions from commercial U.S. hard white (median diameters: 175.7, 128.6, 120.0, 108.5 and 102.4 μm), hard red winter (median diameters: 173.7, 133.6, 124.3, 110.8 and 104.2 μm) and hard red spring (median diameters: 173.7, 132.1, 124.7, 112.9, 106.3 μm) wheat classes were obtained by fine grinding of bran and shorts and re-combining with the rest of fractions. For all three wheat classes, as WWF median particle size decreased, the L* (lightness) value decreased but the adjusted damaged starch, polyphenol oxidase activity, and a* and b* values increased. Mixolab data showed that development time decreased as WWF particle size was reduced, while stability time and starch retrogradation increased. As for WWF tortilla quality, the breaking force and extensibility increased with decreasing particle size from ∼175 to 129–134 μm, but diameter and thickness were not significantly affected. The results indicated that reducing the median particle sizes of WWFs from ∼175 μm to ∼130 μm would significantly improve the WWF tortilla quality.     

Adsorption and Transformation Reactions of L-DOPA in Soils

3-(3′,4′-Dihydroxyphenyl)-L-alanine (L-DOPA), which is a component of velvetbean (Mucuna pruriens), displays a high inhibitory activity to plant growth. The inhibitory activity is influenced by the presence of soils, because L-DOPA is eliminated in soils. In the present study, the effect of several soil types (volcanic ash, calcareous, and alluvial soils) on the L-DOPA disappearance was investigated at constant equilibrium pH values. In the presence of soils, L-DOPA disappeared with the reaction time, and the disappearance was associated with three reactions: adsorption reaction (characterized by fast and sudden disappearance of L-DOPA within the initial 8 h period), catalytic transformation reaction (constant L-DOPA disappearance throughout the reaction period), and biotransformation caused by microbial activity (accelerated L-DOPA disappearance observed after 72 h of reaction time). The adsorption and transformation reactions consisted of physicochemical reactions mediated by the presence of soils. The amount of L-DOPA adsorbed was largest in the presence of volcanic ash soil among the three soil types. It is likely that the mechanism of L-DOPA adsorption includes a ligand exchange reaction. In the presence of soils, L-DOPA transformation was observed at equilibrium pH values higher than 4 and it increased with increasing equilibrium pH values. In the absence of soil, however, L-DOPA transformation did not occur at an equilibrium pH value lower than 6.0, indicating that L-DOPA transformation was accelerated by the presence of soil. The rate of L-DOPA transformation mediated by soils at constant equilibrium pH value was in the following order: alluvial soil > calcareous soil > volcanic ash soil. The plant-growth-inhibitory activity of L-DOPA was also reduced by the presence of soils, and the reduction in the case of L-DOPA was more obvious than in the case of 2,4-dichlorophenoxyacetic acid (2,4-D). Based on the reduction effect of soils on the plant-growth-inhibitory activity of L-DOPA (without pH-adjustment), calcareous soil ranked first, followed by volcanic ash soil, then alluvial soil. This was because the calcareous soil showed the highest soil pH value (7.8), and thereby the L-DOPA transformation reaction was accelerated. In soils with high pH values, the plant-growth-inhibitory activity of L-DOPA could therefore not be detected.     

发芽蚕豆左旋多巴超声强化提取及其动力学过程

为了充分提取和利用高生物活性的天然左旋多巴(L-DOPA),研究了超声波强化提取发芽蚕豆L-DOPA的工艺条件,并初步探讨了超声浸提动力学过程。基于单因素试验,以超声功率、液固比、萃取时间为考察因素,采用Box-Behnken试验设计进行了工艺参数优化,结果表明,超声功率对发芽蚕豆L-DOPA得率的影响较大;原料用量2.0g,采用含30%乙醇的0.1mol/L醋酸溶液为提取溶剂,其较佳提取工艺条件为:超声功率257W、液固比31mL/g、萃取时间为37.4min。在此条件下,发芽蚕豆L-DOPA的平均得率为1.47%,较未发芽蚕豆增加0.58倍,略高于传统提取法,且超声强化提取显著缩短了浸提时间。对最优提取条件下L-DOPA得率随时间变化的动力学分别用Film模型、非稳态扩散理论和Ponomaryov经验方程进行拟合,其中Film理论模型的拟合度较好,其决定系数R2值最大,为0.9928。研究结果为天然L-DOPA制备提供了参考。     

Changes in Chemical Structure and Biological Activity of L-DOPA as Influenced by an Andosol and Its Components

Velvetbean ( Mucuna pruriens ) has been reported to release 3-(3',4'-dihydroxyphenyl)-L-alanine (L-DOPA) as an allelochemical that inhibits the growth of other plants, although the inhibitory activity depends on the soil type and it is extremely reduced in Andosols. To clarify the effects of Andosols and their components on the chemical structure and plant-growth-inhibitory activity of L-DOPA, an L-DOPA solution was reacted with an Andosol and its components (weathered pumice and purified allophane), and the resultant solution was subjected to ¹H nuclear magnetic resonance and ultraviolet-visible spectral analyses, and plant-growth-inhibitory activity tests. When the L-DOPA solution was added to the soil components, the concentration of L-DOPA in the solution decreased by adsorption and transformation (polymerization) reactions. The adsorption mechanism included a ligand exchange reaction. The rate of L-DOPA transformation was faster at higher pH values. The soil components displayed a catalytic activity and accelerated the transformation of L-DOPA. Similar transformation occurred when light was irradiated. At pH values higher than 4.0, the transformed products from L-DOPA consisted of humic substances-like heterogeneous components, whereas specific components with low molecular weight were included when L-DOPA was transformed at a pH value of 9.7 or higher. The plant-growth-inhibitory activity of L-DOPA was extremely weakened when L-DOPA was adsorbed on or transformed (polymerized) by soil components. Therefore, in soils with high abilities of adsorption and transformation of L-DOPA such as in Andosols, it was likely that the L-DOPA concentration in the soil solution decreased quickly by adsorption and transformation reactions and the allelopathic activity of L-DOPA was lost.     

大田蚕豆各器官中左旋多巴含量的分析

以青海大田栽培的蚕豆品种166植株为试材,采用紫外可见分光光度法,测定其茎、叶、花、籽粒、荚、种皮6个器官左旋多巴(L-DOPA)含量及其变化趋势。结果表明:蚕豆品种166各器官间L-DOPA含量平均含量从高到低顺序为花叶茎荚籽粒种皮,平均含量分别为6.516%、5.740%、1.988%、0.031%、0.030%、0.025%。     

Variation of favism-inducing factors (vicine,convicine and L-DOPA) during pod development inVicia faba L.

Changes in the concentrations of vicine, convicine and L-DOPA in two cultivars ofVicia faba L. seeds in different stages of pod development were determined by high performance liquid chromatography (HPLC). The vicine and convincine conent was highest in fresh green cotyledons (moisture content about 80%) and gradually declined until a constant level was reached when seed dry matter percentage was around 40%. A similar pattern of variation in glucoside concentration was observed for the seed coat. The pods contained neither vicine nor convicine but they were particularly rich in L-DOPA. These compounds were not homogeneously distributed in the seeds.     

浸种与光照时间对蚕豆芽苗菜生长与品质的影响

为确定适宜蚕豆芽苗菜生产的浸种和光照时间,以小蚕豆品种‘监利’为材料,设置不同浸种时间(12、16、20、24和28 h)和光照时间(8、9、10、11和12 h/d),分析对蚕豆芽苗菜生长指标和营养指标的影响。结果显示:随浸种时间增加,蚕豆芽苗菜苗长、茎鲜重和可食率均增加;浸种16 h时,蚕豆芽苗菜的生长指标和可溶性蛋白含量均显著高于12 h;除16 h外,其他浸种时间的左旋多巴含量均显著12 h。随光照时间延长,蚕豆芽苗菜的生长显著变慢,在光照时间为9 h/d时,左旋多巴含量显著高于8 h/d,且与其他处理并无显著差异;可溶性蛋白和可溶性糖均在9 h/d光照时间时达到最优含量。以左旋多巴含量为主要指标,兼顾营养和生长指标,蚕豆芽苗菜生产的最适浸种和光照时间为浸种时间16 h,光照时间9 h/d。