Observation of individual chemical reactions in solution

Discrete chemical reaction events occurring in solution have been observed by single photon detection of a bimolecular, chemiluminescent reaction. The reactants were generated from 9,10-diphenylanthracene in acetonitrile with potential pulses applied to an ultramicroelectrode. Electrogenerated radical ions of opposite sign react to yield the excited singlet state of the parent compound. The chemical reactions were restricted to a 20-femtoliter volume adjacent to the electrode by the use of rapid potential pulses. Individual chemical reaction events were stochastic and followed the Poisson distribution, and the interarrival time between successive reaction events was exponentially distributed.     

木材酸性液化条件下苯酚的作用机理

论述了酸性条件下木材液化中苯酚的作用机理.苯酚作为亲核试剂,引起了木材组分一些主要化学键的断裂,使得木材组分大分子降解为小分子;苯酚作为反应试剂,与其中一些降解生成的小分子反应生成具有酚类结构的化合物;苯酚作为溶剂,使生成的酚类结构化合物溶解,并减缓或阻止了已生成的活性小分子之间的缩聚反应.催化剂酸提供质子(H )以及酸性环境,使化学键的断裂更为容易,同时也改变了液化反应途径.     

工业副产物硒的氧化

在化学反应中，二氧化硒作为温和的氧化剂，可以将羟基、甲基等基团氧化为醛基，而本身被还原为硒，成为废弃物。以合成反应中生成的硒为原料，用浓硝酸和浓硫酸的混合物进行氧化反应，使其氧化为可以重复使用的二氧化硒，反应收率为94％，并用滴定法测定其含量为96％，符合工业化生产的要求。     

荞麦壳水不溶性膳食纤维提取工艺的优化

[目的]确定化学浸提法提取荞麦壳水不溶性膳食纤维的最佳工艺参数,为合理利用养麦壳资源提供参考依据.[方法]采用化学浸提法对荞麦壳水不溶性膳食纤维进行提取,探讨料液比、碱解时间、碱解温度和NaOH浓度对水不溶性膳食纤维提取率的影响,并采用正交试验设计优化提取工艺.[结果]NaOH浓度对水不溶性膳食纤维提取的影响最大,其次是碱解温度和碱解时间,料液比影响最小;化学浸提法提取荞麦壳水不溶性膳食纤维的最佳工艺条件为:料液比1.0∶15.5,碱解时间60 min,碱解温度45℃,NaOH浓度4%.从荞麦壳中提取的水不溶性膳食纤维持水力300.25g/g,膨胀力5.57 mL/g,色泽为焦黄色,可用作食品添加剂.[结论]化学浸提法能有效提取出荞麦壳水不溶性膳食纤维,且方法简单、可控、耗时短,适用于工厂化大规模生产,但必须控制好NaOH浓度.     

天然产物中抗变态反应活性物质的研究进展

综述了天然产物中抗变态反应活性物质的化学成分及其药理作用。天然产物中抗变态反应活性物质能够抗Ⅰ型～Ⅳ型变态反应,抗过敏反应的作用机理呈现多环节特性,它们有望作为先导化合物开发为新型抗变态反应天然药物     

类蛋白反应在食品蛋白质和活性肽研究中的应用

文章综述类蛋白反应的化学机制,以及其在食品蛋白质研究工作中的应用。同时,介绍类蛋白反应在改善生物活性肽的ACE抑制作用和抗氧化活性方面的新应用,以及可能的机制—肽分子结构重组机制。     

Water catalysis of a radical-molecule gas-phase reaction

There has been considerable speculation about the role of water and water complexes in chemical gas-phase reactions, including the conjecture that water may act as a molecular catalyst through its ability to form hydrogen bonds. Here, we present kinetic studies in which the effect of water on the rate of the reaction between hydroxyl radicals and acetaldehyde has been measured directly in Laval nozzle expansions at low temperatures. An increasing enhancement of the reaction rate by added water was found with decreasing temperatures between 300 and 60 kelvin. Quantum chemical calculations and statistical rate theory support our conclusions that this observation is due to the reduction of an intrinsic reaction barrier caused by specific water aggregation. The results suggest that even single water molecules can act as catalysts in radical-molecule reactions.     

黄绿木霉T1010对樱桃番茄横向土壤环境性状改良效果研究

为了研究黄绿木霉(Trichoderma aureoviride)T1010对土壤微生物群落、物理性状、化学性状的作用,评价T1010调整土壤环境性状生态效应的潜力,采用土壤稀释法测定土壤中微生物群落数,土壤称重法测定物理性状,无机化学反应法测定土壤中主要化学指标含量,结果表明:T1010促进土壤中细菌、放线菌、固氮菌的生长,与土壤处理前相比,固氮菌数量最大提高6.04倍,比对照提高58.02%;T1010抑制其他真菌的生长,比初始值下降52.99%,比对照下降79.47%;T1010改良物理性状,比重、容重比对照下降,总孔隙度趋近50%;水解氮、有机质比对照提高,与T1010的增殖正相关,有效磷比对照降低,与T1010的增殖负相关;T1010处理组侧根数比常规化肥处理组增加144%,立枯病感病指数降低36.36%。T1010具有改良土壤物理性状、提高微生物群体量、促进化学物质的可溶性等多种功能,是一种潜在、有效的土壤改良菌株。     

化学杀雄剂EXP对油菜膜脂过氧化及保护酶活性的影响(英文)

[Objective] The aim of this study was to investigate the characteristics and mechanism of chemical emasculation in rapeseed and to provide the theoretical basis for development and utilization of new chemical gametocides.[Method] The activity of peroxidase,catalase and the content of hydrogen peroxide,malondialdehyde in leaves and flower buds of Brassica napus cultivars Qinyou No.3 and L89 induced by the chemical gametocide EXP in the course of male sterility were studied.[Result] Protective enzyme activity and the content of hydrogen peroxide,malondialdehyde in rapeseed treated with EXP changed significantly,which indicated that active oxygen metabolism was abnormal.Furthermore,there was a significant difference in the reaction degree of different cultivars and organs treated by EXP.[Conclusion] There was a correlation between the disturbance of active oxygen metabolism and the male sterility induced by chemical gametocide EXP.     

Effect of Chemical Gametocide EXP on Membrane Lipid Peroxidation and Protective Enzyme Activity in Rapeseed (Brassica napus)

[Objective] The aim of this study was to investigate the characteristics and mechanism of chemical emasculation in rapeseed and to provide the theoretical basis for development and utilization of new chemical gametocides.[Method] The activity of peroxidase,catalase and the content of hydrogen peroxide,malondialdehyde in leaves and flower buds of Brassica napus cultivars Qinyou No.3 and L89 induced by the chemical gametocide EXP in the course of male sterility were studied.[Result] Protective enzyme activity and the content of hydrogen peroxide,malondialdehyde in rapeseed treated with EXP changed significantly,which indicated that active oxygen metabolism was abnormal.Furthermore,there was a significant difference in the reaction degree of different cultivars and organs treated by EXP.[Conclusion] There was a correlation between the disturbance of active oxygen metabolism and the male sterility induced by chemical gametocide EXP.     

化学杀雄剂EXP对油菜膜脂过氧化及保护酶活性的影响

[目的]为探讨油菜化学杀雄作用特征与机理,为新型化学杀雄剂的开发利用提供理论依据。[方法]对化学杀雄剂EXP诱导甘蓝型油菜品种秦油3号、L89雄性不育过程中叶片和花蕾中过氧化物酶、过氧化氢酶活性以及过氧化氢、丙二醛含量进行了测定。[结果]EXP处理后的油菜体内保护酶活性及过氧化氢、丙二醛含量发生显著变化,说明活性氧代谢出现了异常。同时,不同品种及器官对EXP处理的反应程度表现出较大差异。[结论]活性氧代谢失调与化学杀雄剂EXP诱导雄性败育具有关联性。     

化学动力学法预测炒制葵花籽货架期

用化学动力学法以过氧化值为表征参数预测几种贮存条件下炒制葵花籽货架期。以生葵花籽为原料,炒制后去壳,分别在4℃、25℃和40℃温度及10.5 k Pa和21.0 k Pa氧分压条件下贮存,测定贮存期间其过氧化值变化,进行动力学回归,求算化学反应动力学参数,进而结合感官评定预测炒制葵花籽的货架期。结果表明,葵花籽仁油脂氧化劣变呈一级化学反应特征,反应速率常数随温度的升高而增大,半衰期随温度的升高而下降,用过氧化值预测的货架期与感官评定结果接近。研究证明,用过氧化值法可预测炒制葵花籽的货架期,在低温、低氧分压贮存条件下可延长炒制葵花籽的货架期。     

化学杀雄剂EXP对油菜膜脂过氧化及保护酶活性的影响(英文)

[Objective] The aim of this study was to investigate the characteristics and mechanism of chemical emasculation in rapeseed and to provide the theoretical basis for development and utilization of new chemical gametocides.[Method] The activity of peroxidase,catalase and the content of hydrogen peroxide,malondialdehyde in leaves and flower buds of Brassica napus cultivars Qinyou No.3 and L89 induced by the chemical gametocide EXP in the course of male sterility were studied.[Result] Protective enzyme activity and the content of hydrogen peroxide,malondialdehyde in rapeseed treated with EXP changed significantly,which indicated that active oxygen metabolism was abnormal.Furthermore,there was a significant difference in the reaction degree of different cultivars and organs treated by EXP.[Conclusion] There was a correlation between the disturbance of active oxygen metabolism and the male sterility induced by chemical gametocide EXP.     

植物多酚类物质的络合萃取

为提高农业植物资源的开发利用效率和改进植物多酚类物质的提取分离技术,采用苹果多酚模型溶液,对以可逆络合反应为基础的植物多酚类物质络合萃取工艺技术进行研究。结果表明,以磷酸三丁酯(TBP)为萃取剂、煤油(Ker)或正辛醇(Oct)为溶剂,可实现对植物多酚类物质的络合萃取;通过pH值和温度的"摆动效应",在得到目标物质的同时,完成混合萃取剂的回收利用。研究指出,采用络合萃取工艺技术,可以实现植物多酚类物质及相关组分的提取分离。     

Femtosecond clocking of the chemical bond

When a chemical bond is broken in a direct dissociation reaction, the process is so rapid that it has generally been considered instantaneous and thus unmeasurable. However, the bond does persist for times on the order of 10(-13) seconds after the photon has been absorbed. Femtosecond (10(-15) second) laser techniques can be used to directly clock this process, which describes the dynamics of the chemical bond. The time required to break the chemical bond in an elementary reaction has been measured and the characteristic repulsion length for the potential governing fragment separation has been obtained.     

马丁草化学鉴别的初步研究

[目的]研究马丁草的化学成分。[方法]采用化学反应鉴别方法,分析马丁草的化学成分。[结果]酚类、香豆素、萜类、内酯、糖及其苷类、皂苷和有机酸出现正反应;其余项目均出现负反应现象。[结论]该试验为马丁草的生物活性成分研究提供了物质基础。     

链霉菌702所产抑真菌物质理化性质的初步研究

用链霉菌702所产的抑真菌物质纯品进行了极性试验和官能团反应。极性试验表明该物质属于中性的非水溶性Ⅰ型抗生素;在官能团反应中,Molisch反应和Hopkins—Col反应呈阳性,表明该物质含有糖基和色氨酸,为进一步对该抑菌物质进行结构鉴定,提供了有益的实验依据。     

扰动扩散流动分析法测定土壤氮、磷技术研究

随着国家对农业面源氮、磷污染防治力度的加大,土壤氮、磷测定技术迫切需要改善。本研究在对常规的扩散对流（Dispersion convection）和强迫对流（Forced convection）流动分析方法基础上,提出了扰动扩散（Perturbation diffusion）流动分析方法,以实现土壤氮、磷全自动化快速测定与分析。扰动扩散流动分析方法是将样品和试剂定量化后集中在化学反应腔中进行反应,然后程序控制蠕动泵对化学反应腔中反应物进行反复扰动,待化学反应完全稳定后流入光电探测单元完成土壤氮、磷含量测定。采用取自湖北潜江的土壤样品对扰动扩散流动分析方法进行了系统验证,实验结果表明,本研究提出的方法与常规紫外可见分光光度法对氮、磷测定相比,基于硫酸钠和碳酸氢钠联合浸提的土壤铵态氮测量值相关系数为0.915 5,基于氯化钙浸提的土壤铵态氮、硝态氮和水溶性磷测量值相关系数分别为0.998 5、0.990 1和0.991 1。铵态氮、硝态氮和水溶性磷的检出限分别为0.055 4、0.020 3 mg·L^-1和0.008 4 mg·L^-1,相对标准偏差（RSD,n=7）分别为1.8%、4.8%和1.0%。     

An unexpectedly efficient catalytic antibody operating by ping-pong and induced fit mechanisms

A transition state analogue was used to produce a mouse antibody that catalyzes transesterification in water. The antibody behaves as a highly efficient catalyst with a covalent intermediate and the characteristic of induced fit. While some features of the catalytic pathway were programmed when the hapten was designed and reflect favorable substrate-antibody interactions, other features are a manifestation of the chemical potential of antibody diversity. The fact that antibodies recapitulate mechanisms and pathways previously thought to be a characteristic of highly evolved enzymes suggests that once an appropriate binding cavity is achieved, reaction pathways commensurate with the intrinsic chemical potential of proteins ensue.     

TiO2对苯酚光化学反应的影响

采用高压汞灯作光源,用GC-MS研究了TiO2对苯酚光化学反应的影响．结果表明,TiO2对苯酚的硝化反应起催化作用,对苯酚的氯代反应无催化作用;有氧条件比无氧条件下的光化学反应产物复杂,产生的污染更为严重．TiO2存在时苯酚和NaNO2光化学产物有硝基苯酚、醇、酮、联苯和多环芳烃．TiO2和NaCl活化后,苯酚的光反应较暗反应更为复杂,可生成毒性更大的污染化合物。