有机蒙脱土的差热分析曲线形状因子解析

用十八烷基三甲基溴化铵（STAB）、双-十八烷基二甲基溴化铵（DOAB）、三-十八烷基甲基溴化铵（TOAB）和蒙脱土（MMT）制备有机蒙脱土（OMMT）,在采用热质量-差热（TG-DTA）研究OMMT热分解动力学基础上,计算差热分析（DTA）曲线形状因子（Ф）。结果表明：OMMT插层改性效果好,MMT/STAB,MMT/DOAB和MMT/TOAB热分解动力学机理函数的差异源于STAB,DOAB和TOAB在OMMT晶体片层中采取的排列方式不同,且MMT/STAB的差热分析曲线对称性较好,MMT/DOAB和MMT/TOAB的差热分析曲线对称性较差,Ф值与其TG-DTG-DTA中差热分析曲线吻合。     

Mode of bleaching phytotoxicity of herbicidal diphenylpyrrolidinones

A mode of action study of herbicidal diphenylpyrrolidinones was carried out through carotenoid analyses in intact Scenedesmus cells and by a cell‐free plant‐type phytoene desaturase assay using Escherichia coli transformants. A series of forty‐eight diphenylpyrrolidinones decreased the carotenoid content of Scenedesmus cells in the light and inhibited phytoene desaturase. The relationship between substituents at various positions and inhibition of phytoene desaturase is discussed. Using very active bleaching diphenylpyrrolidinones, a 10⁻⁵ M concentration affected neither the ζ‐carotene desaturase nor the protoporphyrinogen‐IX oxidase. Although some differences in their inhibitory activity were found between the in vivo and cell‐free assays, it is concluded that the compounds are essentially bleachers affecting carotenoid biosynthesis in plants. Enzyme kinetics studies with recombinant phytoene desaturase revealed a non‐competitive inhibition with respect to the substrate phytoene. A competition against the inhibitor was shown by the cofactor NADP⁺, suggesting an interaction of pyrrolidinones at the cofactor‐binding site of phytoene desaturase. © 2001 Society of Chemical Industry     

Kinetics of Antioxidant-Producing Maillard Reaction in the Mixture of Ribose and Sea Cucumber (Stichopus japonicus) Gut Hydrolysates

Maillard reaction products (MRPs) were produced in sea cucumber gut hydrolysates (SCGHs)-ribose system at 75°C, 85°C, and 95°C with a pH value of 7.0 or 8.0 for 12 hour. The parameters of amount of intermediate products, fluorescence intensity, browning development, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability showed a positive correlation with each other in SCGHs-ribose system. The amount of intermediate products, fluorescence intensity, and browning development followed the zero-order kinetic with activation energy from 62 to 91 kJ/mol in the Maillard reaction of SCGHs-ribose system. Moreover, 2-methyl-butanal has positive and significant correlation with DPPH radical scavenging ability of SCGHs-ribose MRPs. These results suggest that Maillard reaction improves the antioxidant activity of SCGHs, which contributes to the generation of intermediate, fluorescent, browning, and volatile products of SCGHs-ribose system.     

链状亚历山大藻暴露下紫贻贝体内麻痹性贝毒蓄积转化规律

本研究将紫贻贝(Mytilus galloprovincialis)暴露于一株麻痹性贝类毒素(paralytic shellfish toxins, PSTs)优势产毒藻——链状亚历山大藻(Alexandrium catenella, GY-H25株),模拟现场赤潮藻密度,探究了紫贻贝内脏团和可食组织中蓄积代谢及生物转化过程,并通过蓄积代谢动力学,重点比较了不同细胞密度GY-H25对紫贻贝体内毒素蓄积代谢和转化情况的影响。结果显示,GY-H25生长及产毒稳定,PSTs组分主要为N-磺酰胺甲酰基类毒素(C1和C2),单细胞最高产毒能力为2.96 pg STXeq/cell。暴露实验中,紫贻贝对PSTs有较强的蓄积作用,2种暴露浓度下PSTs含量变化趋势一致,实验结束时,2种暴露组紫贻贝内脏团中PSTs均超过欧盟国际限量标准(800 μg STXeq/kg),但可食组织则均低于限量标准;比较发现,高浓度组紫贻贝内脏团最高蓄积浓度达到6 815.36 μg STXeq/kg,且高浓度组暴露期间平均蓄积速率为17.89%,显著高于低浓度组13.06%的蓄积速率。另外,紫贻贝对PSTs表现出较强的生物转化能力,在对C1、C2和GTX5三者的转化研究中发现,快速代谢时期和平稳期C2→GTX5的转化为GTX5生成的主要途径,同时期C1的相关转化中C1→GTX5途径超过C2→C1,致使C1整体占比减少。综合评估紫贻贝中PSTs转化产物和毒性当量因子(toxic equivalency factor, TEF),发现紫贻贝对PSTs代谢转化进一步促使高毒性GTX5的生成和占比提升,总体终端毒性升高,这也可能是秦皇岛紫贻贝中PSTs风险严峻的主要原因之一。因此,本研究有助于科学评估紫贻贝中PSTs风险,为建立区域性风险监测技术提供科学基础。     

热水处理对采后鲜食蚕豆荚褐变及活性氧代谢的影响

为了提高鲜食蚕豆的保鲜效果,本试验以鲜食蚕豆果实为材料,研究了 45℃热水处理10 min对鲜食蚕豆果实在常温(20℃)贮藏过程中豆荚褐变、种子品质及豆荚活性氧(ROS)代谢的影响.结果表明,45℃热水处理10 min能显著提高豆荚中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)的活性,以...     

Time-related changes of the intestinal morphology of Atlantic salmon, Salmo salar L., at two different soybean meal inclusion levels

Soybean meal (SBM) induces enteritis in the distal intestine of Atlantic salmon. The present study assesses the effects of SBM concentrations on the kinetics of the enteritis process. Fish of 300 g, kept at 12 °C, were fed diets with different SBM inclusions: 0%, 10% and 20% SBM for 57 days. Samples of the distal intestine of five fish per treatment were taken for histological and electron microscopical analysis. A semi-quantitative scoring system was used to assess the degree of the morphological changes induced by SBM feeding in the distal intestinal epithelium. The first signs of enteritis appeared earlier in the salmon fed the 20SBM diet than in those fed the 10SBM diet. Thereafter, the condition increased steadily, displaying no signs of recovery. Furthermore, at the lower concentration, the process marking the onset of enteritis began more gradually than at the higher concentration and it displayed a tendency to stabilize after 13–20 days of continuous feeding. Electron microscopy indicated that the endocytosis process was hampered at day 3 of 20SBM and at 7 days of 10SBM. Furthermore, a strong reduction of microvilli was already evident after 7 days of 20SBM feeding, thus indicating a decreased uptake capacity of the distal enterocytes. In addition, transformation and migration of eosinophilic granulocytes was observed, which, in combination with the lysozyme C immunoreactivity supports their protective role during the inflammatory process in the distal gut of Atlantic salmon. It can be concluded that the severity of enteritis and its kinetics are concentration-dependent, showing no signs of recovery during feeding with diets containing SBM.     

鲤肠道对L-甲硫氨酸和L-苯丙氨酸的离体吸收动力学

采用离体灌注试验系统和茚三酮对氨基酸显色的试验方法,定量分析了鲤鱼肠道壁对氨基酸吸收和跨壁运输量,在相同的实验环境下,分别研究鲤鱼肠道对对L-甲硫氨酸和L-苯丙氨酸的吸收转运量。结果表明,在60 min内草鲤鱼道可对灌流液的氨基酸进行持续的吸收转运,并在肠道外积累;当肠道内灌流氨基酸浓度逐渐增加时,肠道外培养液中氨基酸的浓度与其起始浓度呈正相关变化,并未出高浓度氨基酸对吸收转运的“抑制”效应;通过对吸收转运量达到最大值时试验氨基酸的浓度与吸收转运量的比较,以及在氨基酸吸收转运量随时间的变化规律等的比较分析表明,鱼肠道对L-甲硫氨酸和L-苯丙氨酸的吸收。结果表明,鲤鱼肠道能有效地吸收、运输L-甲硫氨酸和L-苯丙氨酸。鲤鱼肠道对L-甲硫氨酸和L-苯丙氨酸的吸收曲线符合Michaelis-Menten方程。两种氨基酸的吸收动力学方程分别为：1/V =0.1251×1/[S] + 0.0524（R2=0.9781,P<0.05）和1/V=0.1887×1/[S]+0.0288（R2=0.9762,P<0.05）,动力学参数为：L-甲硫氨酸：Vmax=19.08µmol/g•min,Kmax=2.39mmol/L;L-苯丙氨酸：Vmax=34.72µmol/g•min,Kmax=6.55mmol/L。吸收动力学特征分析表明：鲤鱼肠道对两种氨基酸的吸收是一种逆浓度、需要转运载体的主动吸收方式,且对不同的氨基酸有不同的吸收、运输特异性,鲤鱼肠道对L-甲硫氨酸的吸收率和跨壁运输能力均强于L-苯丙氨酸（P<0.05)。     

不同碳源条件下金黄色蝶形担孢酵母发酵合成多糖的动力学及结构差异

为探究碳源对金黄色蝶形担孢酵母(Papiliotrema aurea)DF-12合成胞外多糖(EPS)的动力学及结构和功能的影响,本试验利用Logistic、Luedeking-Piret、Herbert-pirt模型拟合不同碳源条件下金黄色蝶形担孢酵母DF-12的动力学变化,并通过高效凝胶渗透色谱、红外光谱、扫描电子显微镜和气相色谱初步分析了不同碳源所得EPS的结构差异。结果表明,以葡萄糖为碳源时最大比生长速率为0.15 h^-1,高于其他碳源,而以蔗糖为碳源时多糖比生产速率较高,达11.95 h^-1。同时不同EPS均具有较好的抗氧化活性。以葡萄糖和蔗糖为碳源所得不同EPS组分表面形貌存在差异,但其分子量、官能团和化学键无较大差异。此外,不同碳源(葡萄和蔗糖)所得EPS均由岩藻糖、鼠李糖、甘露糖、葡萄糖等单糖组成,但其摩尔比存在一定的差异。本研究结果为酵母菌EPS的进一步开发和利用提供了理论依据。     

SO2熏蒸处理对龙眼褐变和SO2残留质量分数的影响

以福眼、乌龙岭、普明庵、松风本、油潭本、蕉眼和杏山晚熟等７个品种的龙眼果实为试验材料,研究了ＳＯ２处理时硫磺用量和熏蒸时间对果皮褐变、果皮与果肉中ＳＯ２残留质量分数的影响．结果表明,不同品种龙眼果实对ＳＯ２的吸收率存在显著差异．福眼果实ＳＯ２处理时,以１００ ｇ 硫磺熏蒸２０ ｍ ｉｎ 效果最佳;蕉眼果实ＳＯ２处理时,以７５ ｇ 硫磺熏蒸３０ ｍ ｉｎ 效果最佳．     

银杏愈伤组织诱导与继代培养的研究

以银杏种子子叶、幼叶片、茎段为外植体,对银杏进行愈伤组织诱导及继代培育．结果表明：不同外植体的愈伤组织的诱导能力有差异,其诱导率高低顺序依次是子叶、叶片、茎段;愈伤组织质地、颜色、生长速度与基本培养基、外源激素及培养条件有很大关系,基本培养基以高含量无机盐的Ｍ Ｓ培养基为最好;最佳诱导培养基不适合继代保存,褐变极为严重;在培养基中附加抗氧化剂并调整激素种类,可以消除褐变现象,使细胞保持旺盛生长