共查询到20条相似文献，搜索用时 109 毫秒
1.
辐照西洋参培养物皂苷次生代谢调控的研究 总被引：6，自引：0，他引：6
研究了不同前体、前体浓度、前体加入时期、前体作用时间、ATP浓度、烟酸浓度对西洋参芽胞愈伤组织生长及皂苷合成的影响。结果表明 :0 1 %甲羟戊酸对生长有抑制作用 ,对皂苷合成有明显的促进作用 ;1 0 0mg L亮氨酸对生长无明显影响 ,对皂苷合成有促进作用 ;444mg L的醋酸镁对培养物生长和皂苷合成都有促进作用 ;在继代开始时加入前体皂苷含量最高 ;甲羟戊酸作用 6h皂苷产量最高 ;1 60mg LATP对生长和皂苷合成均有促进作用 ;1 0mg L烟酸利于培养物生长和皂苷合成 ;用6 0 Coγ射线辐照培养物 ,剂量为 40 0 0Gy时得到皂苷含量高于原愈伤组织 1倍的细胞系。 相似文献
2.
3.
~(110m)Ag在牡蛎中的积累和分布 总被引：2，自引：0，他引：2
研究了1 1 0mAg通过海水途径和食物途径在牡蛎中的积累和分布。结果表明 ,牡蛎能快速并大量吸收海水中的1 1 0mAg ,在实验期间的 2 3d内 ,整体浓集系数 (CF)最高可达 2 4 67。各软组织中鳃的浓集系数最大 ( 33661 ) ,其余器官的CF按降序排列分别为 :外套膜 ( 2 31 1 9) ,>水管( 2 1 81 8) ,剩余部分 ( 1 7685 ) ,>闭壳肌 ( 991 5 ) ,壳的CF也高达 1 89。投喂标记扁藻的实验结果表明 ,牡蛎也能通过食物途径吸收环境中的1 1 0mAg ,投喂 2d后 ,仍有超过 80 %的放射性1 1 0mAg留在牡蛎体内。1 1 0mAg经食物途径进入牡蛎后 ,主要分布于剩余部分 (含性腺和胃消化腺 ) 相似文献
4.
5.
6.
水稻无侧根突变体RM109冠根的解剖学观察 总被引：1，自引：1，他引：1
对水稻无侧根突变体RM1 0 9与原品种大力 (OryzasativaL .,cv .Oochikara)的冠根组织形态进行比较 ,结果表明 ,大力品种可观察到侧根原基及侧根 ,而RM1 0 9均无 ;RM1 0 9的原生木质部间中柱鞘细胞数目减少 ,为大力的 77% ;后生木质部导管数增加 ,其导管I的数量为大力的 1 4 9% ,其导管Ⅱ的数量为大力的 3 2 1 % ,且导管排列散乱。推测其原因在于根尖生长点细胞分化异常和IAA合成能力低下 相似文献
7.
8.
9.
用3H TdR标记小麦种胚 ,研究了质子处理的种胚萌发早期DNA合成动态 ,并与γ射线辐照进行对比。表明质子处理能引起肿胚DNA损伤修复合成 ,即DNA非按期合成 ,京 41 1与原冬 977的修复复制峰期分别出现在正常的DNA合成峰期前 4h与 2h。以京 41 1为例 ,比较质子处理与γ射线辐照的种胚DNA损伤修复特点的差异 ,质子的DNA非按期合成峰期出现时间早于γ射线处理的 2h ,正常的DNA合成峰期晚于γ射线处理的 4h ,且在DNA非按期合成峰期后的DNA合成量明显低于γ射线。 相似文献
10.
用~3H-TdR研究混合重金属对鲫鱼DNA合成的影响 总被引：12，自引：0，他引：12
应用3 H 胸腺嘧啶核苷 ( 3 H TdR)示踪法研究混合重金属对鲫鱼 (Carassiusaura tus)遗传毒性的影响。结果表明 ,最佳取样时间为注射3 H TdR后 6h。鱼体各组织对混合重金属的毒性反应呈现双向效应 ,即低浓度时 ,表现出损伤、修复作用 ;高浓度时 ,DNA合成受到抑制。鱼卵、鱼鳃对重金属最敏感 ,损伤浓度为 0 0 773mg L ;而大脑对混合重金属耐受性最强。DNA损伤修复作用和DNA合成作用都存在剂量效应 ,随着暴露时间的延长 ,毒性作用增大。鱼体各组织对重金属的毒性反应可由DNA损伤修复变成合成抑制。经过 72h暴露后 ,3 H TdR在肝脏、鱼鳃、鱼卵中掺入量约低于对照的 5 0 %。 相似文献
11.
Response surface methodology was successfully employed to optimize lipase-catalyzed synthesis of feruloyl butyryl glycerides (FBGs). The effects of the reaction parameters, including the reaction time, reaction temperature, enzyme concentration, substrate molar ratio, and water activity, and the interaction parameters were examined. The analysis suggested that the conversion of the FBGs was significantly (p < 0.05) affected by independent factors of reaction time, reaction temperature, substrate molar ratio, and water activity as well as interactive terms of reaction temperature/reaction time, reaction temperature/enzyme concentration, substrate molar ratio/reaction temperature, water activity/reaction temperature, reaction time/enzyme concentration, and enzyme concentration/water activity. The highest conversion yield of FBGs was 81.2% at the following optimized reaction conditions: reaction temperature of 53.6 degrees C, reaction time of 5.5 days, enzyme concentration of 50.8 mg/mL, water activity of 0.14, and substrate molar ratio of 2.9. The conversion is higher as compared to that at the conditions before optimization. 相似文献
12.
In the present study, a kinetic model of the Maillard reaction occurring in heated monosaccharide-casein systems was proposed. Its parameters, the reaction rate constants, were estimated via multiresponse modeling. The determinant criterion was used as the statistical fit criterion instead of the familiar least squares to avoid statistical problems. The kinetic model was extensively tested by varying the reaction conditions. Different sugars (glucose, fructose, galactose, and tagatose) were studied regarding their effect on the reaction kinetics. This study has shown the power of multiresponse modeling for the unraveling of complicated reaction routes as occur in the Maillard reaction. The iterative process of proposing a model, confronting it with experiments, and criticizing the model was passed through four times to arrive at a model that was largely consistent with all results obtained. A striking difference was found between aldose and ketose sugars as suggested by the modeling results: not the ketoses themselves but only their reaction products were found to be reactive in the Maillard reaction. 相似文献
13.
土壤在淹水条件下 ,氧化铁是土壤中主要的电子接受者之一。本文利用抗坏血酸和针铁矿模拟研究了土壤中的有机还原性物质与氧化铁之间的反应。结果表明 :在抗坏血酸与针铁矿作用的过程中 ,由于溶液中质子被消耗 ,溶液的pH上升 ,质子的消耗量随着抗坏血酸加入量的增加而增加。质子消耗的动力学曲线表明 ,抗坏血酸与针铁矿之间的作用属于异相反应 ,达到平衡所需要的时间较长。在反应的初期 ,二价铁的还原溶出速率很慢 ,在较长的时间内溶液中二价铁浓度不发生变化。pH对抗坏血酸与针铁矿之间的反应有影响 ,pH上升 ,反应速率受抑制 ,pH下降 ,反应速率加快。从不同pH条件下的抗坏血酸的峰电位的测定结果推断 ,pH对抗坏血酸与针铁矿反应的影响可能通过影响针铁矿表面化学性质来实现的。 相似文献
14.
The reaction of malondialdehyde with casein was studied in aqueous solution to evaluate the impact of this lipid oxidation product on food protein modification. By using multiresponse modeling, a kinetic model was developed for this reaction. The influence of temperature and pH on protein browning and malondialdehyde degradation was evaluated. The hypothesis that one malondialdehyde unit leads to the cross-linking of two casein-bound lysine residues was in accordance with the data. At higher malondialdehyde concentrations, a different reaction mechanism was operative, probably involving a dihydropyridine cross-link. The results obtained were compared with the reaction of casein with 2-oxopropanal, a well-studied alpha-dicarbonyl compound. The reaction of casein with 2-oxopropanal followed a different reaction pathway. Comparison of the degree of browning of casein by reaction with malondialdehyde and 2-oxopropanal showed a considerably higher degree of browning induced by malondialdehyde. This research has shown that kinetic modeling is a useful tool to unravel reaction mechanisms. Clearly, the contribution of lipid oxidation products, such as malondialdehyde, to protein modification (both in food and in vivo) can be substantial and needs to be taken into account in future studies. 相似文献
15.
鸡蛋壳直接中和制取乳酸钙的工艺 总被引：3，自引：1，他引：2
该文利用鸡蛋壳制取乳酸钙。采用直接中和法,将经过预处理的蛋壳粉碎至一定细度,加入乳酸进行中和反应制取乳酸钙。试验过程中对直接中和反应过程中各影响因素进行了研究探讨,筛选出最佳中和反应条件。并采用了三元线性回归正交试验对试验结果进行了显著性分析。试验结果表明,加入蛋壳粉10 g、乳酸18.5 mL、蒸馏水100 mL,在中和反应温度35℃、反应时间2 h的条件下,制取乳酸钙的产率可达79.23%,质量分数达到86.93%。通过这种方法制取乳酸钙,既充分挖掘了鸡蛋壳中潜在的利用价值,又解决了蛋壳造成的环境污染问题。 相似文献
16.
Triazine herbicides are among the most widely used herbicides in the United States. Many triazine compounds are relatively stable under natural conditions and have become prominent contaminants in hydrologic systems. It was previously reported that chloro-s-triazine compounds were rapidly dechlorinated in water by polysulfides, and the reaction was assumed to be aromatic nucleophilic substitution (SNAr). In this study, we evaluated the effect of free radical inhibitors on the reaction rate of polysulfides with herbicides atrazine, simazine, and cyanazine. The reaction was significantly inhibited by radical scavengers oxygen and 1,4-benzoquinone, suggesting involvement of free radicals in the reaction. Spectral analysis of the reaction mixture using electron spin resonance showed that after the reaction, the free radical concentration in polysulfide solution substantially decreased. These evidences indicate that radical sulfur anions may also be involved in the reaction, likely via a free radical substitution reaction (SRN1) mechanism. Amendment of sodium tetrasulfide significantly reduced the leaching of atrazine or simazine from packed sand columns. Therefore, polysulfide salts may be potentially used to remove residues of triazine herbicides in environmental media. 相似文献
17.
18.
Zamora R Navarro JL Gallardo E Hidalgo FJ 《Journal of agricultural and food chemistry》2006,54(16):6101-6105
The comparative formation of phenylalanine and phenylpyruvic acid in the reaction of 4,5-epoxy-2-decenal with phenylalanine was studied to determine whether epoyalkenals may also degrade amino acids without producing their decarboxylation. Both compounds were produced in the reaction to an extent that depended on the reaction pH, the amount of lipid oxidation product, and the reaction time and temperature. The optimum pH was 3 for producing both carbonyl derivatives, and the amount of both compounds increased linearly with the amount of epoxyalkenal present in the reaction mixture. In addition, phenylpyruvic acid was produced to a higher extent than phenylacetaldehyde at 37 degrees C. However, at 60 degrees C the degradation of phenylpyruvic acid was observed and phenylacetaldehyde was usually found to a higher extent than the alpha-keto acid in the overnight-incubated reaction mixtures. The degradation of phenylpyruvic acid produced benzaldehyde and phenylacetaldehyde. All these results suggest that epoxyalkenals can not only degrade amino acids by a Strecker-type mechanism but convert them into their corresponding alpha-keto acids. This new reaction may be an alternative chemical route for the formation in foods of alpha-keto acids, which can later participate in the generation of important amino acid-derived flavor compounds. 相似文献
19.
Rutin was acylated with stearic acid in the esterification reaction catalyzed by immobilized Candida antarctica lipase B (Novozym 435) in tert-amyl alcohol with and without molecular sieves. The lipophilic rutin stearate was synthesized by this method, which had a potential use in food, cosmetics, and pharmacy. The structure of rutin stearate was characterized by spectral methods of 1H NMR and 13C NMR, Fourier transform infrared, and UV-vis. The results suggested that the regioselectivity of the lipase-catalyzed esterification of rutin was specific at the C(4')-position of the rhamnose moiety. It was found that the addition of molecular sieves increased both the reaction rate and the yield. The time effect of adding molecular sieves in the reaction system on the conversion of rutin stearate was further examined. Instead of adding molecular sieves at the beginning of the reaction, the addition of molecular sieves at 5, 18, 24, 31, and 44 h after the beginning of the reaction was also applied. The final conversion for the case to add molecular sieves at 24 h after the beginning of reaction was the highest, with the conversion yield about 46%. 相似文献
20.
The optimal conditions for the de-esterification reaction of tomato pectinesterase (PE) and citrus PE was 0.1-0.2 M NaCl and at pH 7.5-8.5, 65 degrees C, almost identical to those for the transacylation reaction as observed by turbidity (absorbance at 400 nm) change. Among the PEs tested, pea pod PE presented the most remarkable catalysis on the transacylation reaction, and 1.5% pectin solution was determined to be suitable for this reaction. Low methoxy pectin with a DE (degree of esterification) of 31% displayed a slow turbidity increase, revealing that the extent of DE was influential on the transacylation. Besides citrus pectin, apple pectin was also proved to progress transacylation reaction by PEs from tomato and citrus sources as apparently observed by turbidity method. 相似文献