臭氧化降解除草剂2,4-D的机理研究(Ⅱ):降解路径

为了考察除草剂2,4-D在臭氧化反应过程中的降解机理,在前文分析中间产物的基础上,进一步跟踪反应溶液中几个主要中间产物和氯离子的浓度变化趋势,由此提出可能的降解路径。结果说明,2,4-D臭氧化降解过程主要是羟基自由基的间接氧化起作用,臭氧分子的直接氧化所占比重很小。对前文分析出的主要中间产物进行分类,并通过判断反应溶液中中间产物和氯离子浓度随反应时间变化的趋势,可知2,4-D在羟基自由基作用下,主要先产生了2,4-二氯苯酚等含氯的酚类,再经过脱氯,形成无氯的芳香族化合物。苯环结构开裂后,形成了大部分有机酸,另一小部分有机酸在2,4-D初步降解为含氯芳香族化合物时即可产生。脱氯过程有一个初始较慢后来较快的趋势,这说明2,4-D直接脱氯较少,大部分脱氯过程发生在形成2,4-DCP等含氯芳香族中间产物后,此时,脱氯产生无氯的芳香族中间产物。在最后的深度氧化阶段,经过一系列中间产物反应之后,部分2,4-D能降解为水、二氧化碳等终产物。     

Efficient activation of aromatic C-H bonds for addition to C-C multiple bonds

Efficient electrophilic metalation of aromatic C-H bonds leading to new C-C bond formation through regio- and stereoselective addition to alkynes and alkenes has been realized by a catalytic amount (0.02 to 5 mole percent) of palladium(II) or platinum(II) compounds in a mixed solvent containing trifluoroacetic acid at room temperature. Various arenes undergo unexpected selective trans hydroarylation to terminal or internal C&cjs0812;C bonds inter- and intramolecularly with high efficiency (up to a turnover number of 4500 for palladium), especially for electron-rich arenes, giving thermodynamically unfavorable cis-alkenes, and the oxygen- and nitrogen-containing heterocycles. The simplicity, generality, and efficiency of this process should be very attractive to the possible industrial application for the functionalization of arenes.     

Tyrosinase reactivity in a model complex: an alternative hydroxylation mechanism

The binuclear copper enzyme tyrosinase activates O2 to form a mu-eta2:eta2-peroxodicopper(II) complex, which oxidizes phenols to catechols. Here, a synthetic mu-eta2:eta2-peroxodicopper(II) complex, with an absorption spectrum similar to that of the enzymatic active oxidant, is reported to rapidly hydroxylate phenolates at -80 degrees C. Upon phenolate addition at extreme temperature in solution (-120 degrees C), a reactive intermediate consistent with a bis-mu-oxodicopper(III)-phenolate complex, with the O-O bond fully cleaved, is observed experimentally. The subsequent hydroxylation step has the hallmarks of an electrophilic aromatic substitution mechanism, similar to tyrosinase. Overall, the evidence for sequential O-O bond cleavage and C-O bond formation in this synthetic complex suggests an alternative intimate mechanism to the concerted or late stage O-O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase.     

Deconstruction of iterative multidomain polyketide synthase function

PksA, which initiates biosynthesis of the environmental carcinogen aflatoxin B1, is one of the multidomain iterative polyketide synthases (IPKSs), a large, poorly understood family of biosynthetic enzymes. We found that dissection of PksA and its reconstitution from selected sets of domains allows the accumulation and characterization of advanced octaketide intermediates bound to the enzyme, permitting the reactions controlled by individual catalytic domains to be identified. A product template (PT) domain unites with the ketosynthase and thioesterase in this IPKS system to assemble precisely seven malonyl-derived building blocks to a hexanoyl starter unit and mediate a specific cyclization cascade. Because the PT domain is common among nonreducing IPKSs, these mechanistic features should prove to be general for IPKS-catalyzed production of aromatic polyketides.     

不同基因型烤烟化学成分与中性香气物质含量的相关分析

研究73个基因型烤烟常规化学成分与中性香气物质含量的相关关系,结果表明:主要化学成分在不同基因型间存在广泛的变异;烟碱、总氮、氮碱比、钾氯比与中性香气物质含量呈显著正相关;典型相关分析表明中性香气物质的显著性指标为芳香族氨酸类、类胡萝卜素类、新植二烯和类西柏烷类,常规化学指标中的显著性指标为还原糖、氮碱比、糖碱比、钾氯比、烟碱和氯。     

杨木木粉在酸性氯化胆碱/丙三醇中的快速液化研究

将可再生的木质纤维生物质进行液化转化制备高分子化合物可减少化石资源的消耗。以氯化胆碱/丙三醇低共熔溶剂为液化试剂,硫酸为催化剂,研究不同的反应条件包括液化温度、液化时间、催化剂浓度、液固比等对杨木木粉液化率的影响,并借助傅里叶变换红外（FTIR）、凝胶渗透色谱（GPC）和气相色谱-质谱（GC-MS）对水溶性、丙酮溶和丙酮不溶（液化残渣）3个组分液化产物进行分析。结果表明,反应条件为240℃、15 min、硫酸质量浓度8%、液固比10∶1时,木材液化率达到最大值78.13%。在液化剂氯化胆碱/丙三醇作用下,木质素和半纤维素可以快速发生液化,水溶性液化产物组分主要包括醛、酮、酸、酯以及芳香衍生物等,丙酮溶组分液化产物主要为木质素降解产物,液化残渣主要为不溶的纤维素。研究表明氯化胆碱/丙三醇是一种高效的木材液化试剂,且液化组分主要为木质素和半纤维素。     

3，5，6-三氯吡啶-2-酚的合成优化

[目的]进一步优化三氯乙酰氯合成三氯吡啶酚的工艺。[方法]以三氯乙酰氯、丙烯腈为原料,在催化剂作用下,通过加成环化、芳构化2步法合成3,5,6-三氯吡啶-2-酚,考察溶剂类型、催化剂用量、助催化剂类型和反应压力对三氯吡啶酚收率的影响。[结果]三氯乙酰氯路线合成三氯吡啶酚的优化工艺为：三氯乙酰氯、丙烯腈为原料,1．3g／46g（三氯乙酰氯）氯化亚铜为催化剂,二氯苯为溶剂,此条件下三氯吡啶酚的收率可达55％。微负压条件有利于及时排除反应过程中产生的氯化氢,降低安全隐患,而添加助催化剂对反应效果无显著促进作用。[结论]该研究确定了三氯乙酰氯路线合成三氯吡啶酚的最佳工艺。     

氯化铵和氯化钾对太湖黄泥土磷的吸持动力学影响的研究

土壤中磷的移动性、植物有效性和对水体环境的潜在危害性与土壤对磷的吸持反应有关,而铵钾磷共施是农业生产中的普遍现象,因此,本文通过批量培养法,研究了相同摩尔数的氯化铵和氯化钾对磷的吸持动力学的影响,并对磷的吸持动力学进行了不同模型的拟合.结果表明,氯化铵、氯化钾均显著增加了土壤对磷的吸持,在培养初期(5 min),相同摩尔数的氯化铵、氯化钾对磷的吸持量无显著差异,但在15 min ～ 10 d阶段,相同摩尔数的氯化钾对磷吸持量的影响显著大于相同摩尔数的氯化铵.而铵钾共施时,两者对磷的吸持具有协同作用,并主要表现为氯化钾的作用.氯化铵对土壤磷吸持总量无显著影响,氯化钾则显著增加了土壤磷吸持总量,氯化钾和氯化铵处理土壤磷吸收总量则无显著差异.通过比较不同模型拟合的决定系数(R2)大小,不同模型拟合效果顺序为Elovich方程＞双常数方程＞Parabolic扩散方程＞零级方程＞一级方程＞二级方程.     

用第8染色体的SSR标记分析香稻居群遗传多样性

用5对与香味基因连锁的SSR标记对广西种植的香稻、非香地方籼型栽培稻、非香地方粳型栽培稻以及南亚香稻UPRB系列、UPRH系列、B系列共6个居群进行遗传多样性分析。结果表明,6个居群在第8染色体的遗传多样性以南亚香稻B系列居群的最大;聚类表明,南亚香稻居群与广西水稻居群(包括香稻与非香稻居群)各自聚为一类,说明南亚香稻与广西水稻种质在第8染色体上存在遗传差异,证明了南亚香稻类群的独特性。     

Lead effects on corn mitochondrial respiration

Oxidation of exogenous nicotinamide-adenine dinucleotide and succinate by corn mitochondria was measured as a function of lead chloride concentration. Lead chloride (50 to 62 micromoles per liter) stimulated oxidation of exogenous reduced nicotinamide-adenine dinucleotide by 174 to 640 percent depending on the reaction mediums, whereas lead chloride (12.5 micromoles per liter) inhibited succinate oxidation by more than 80 percent. When inorganic phosphate was included in reaction mediums the subsequent addition of lead was without effect due to the low solubility of lead phosphate. If addition of lead was followed by addition of phosphate the inhibition of succinate oxidation by lead was released, but there was no reduction in the stimulation of oxidation of reduced nicotinamide-adenine dinucleotide by lead. The effects of lead on plant growth might be accentuated under conditions of phosphate deficiency.     

Induced photolysis of DDT

Photolysis of mixtures of certain alkyl halides and aromatic amines produces dehalogenation of the halide. These reactions involve a photoinduced charge transfer from the amine to the halide. Photolysis of tritolylamine and carbon tetrachloride produces tritolylaminium chloride. Photolysis of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and diethylaniline at 3100 angstroms yields 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), p,p'-dichlorobenzophenone (DDCO), and hydrogen chloride. Photolysis of DDT does not occur unless an inducer which has a low ionization potential, such as diethylaniline, is present. The DDT-diethylaniline mixture is stable in the dark, and the induced photolysis is not affected by triplet quenchers.     

冬小麦生育期间根系脱氢酶活性的初步研究

用红四氮唑法（ＴＴＣ法）对冬小麦根系脱氢酶活性进行了系统测定．结果表明：冬小麦的根系脱氢酶活性随生育进程而逐渐降低,可能与新根的比例下降和老根的比例提高有关;施氮较多的处理,各生育时期的根系脱氢酶活性均较高;播期较晚的处理,在返青期前根系脱氢酶活性高于早播处理;不同品种之间的根系脱氢酶活性也存在差异;根系脱氢酶活性与叶片的叶绿素含量呈正相关关系,与籽粒产量也呈正相关关系。文中还对脱氢酶活性作为根系活力指标的可能性及通过栽培措施调控根系和地上部协调发展的重要性进行了讨论。     

Marihuana components: effects of smoking on delta-9-tetrahydrocannabinol and cannabidiol

Cigarettes impregnated with various preparations of Delta(9)-tetrahydro-cannabinol (Delta(9)-THC) and cannabidiol were artificially smoked, and the smoke was analyzed by means of gas chromatography and a combination of gas chromatography and mass spectrometry. Retention of the two test substances in smoke was 21 to 23 percent of the starting amount. The ratio of Delta(9)-THC to cannabidiol in smoke is different from that in starting material. It is suggested that these differences are the result of partial cyclization of the cannabidiol to Delta(9)-THC. An increase in the percentage of cannabinol in smoke is the result of a partial dehydrogenation drogenation of Delta(9)-THC or cannabidiol. No evidence for the isomerization of Delta(9)-THC to Delta(8)-THC or for the formation of new pyrolyzed products was found.     

漫灌条件下增施腐殖酸对烤烟产质量的影响

为优化漫灌条件下的烤烟配套施肥措施,提高种烟收益,改善烟叶品质,以基肥的形式增施不同用量的水溶性腐殖酸,研究其对烤烟种植收益、常规化学成分、致香物质和感官质量的影响。与常规施肥相比,增施900 kg/hm²腐殖酸,烤烟产量增加12.35%,产值提高17.16%,净效益提高9.31%,综合经济性状表现最好。腐殖酸增施量与烤烟产量、产值和增施净效益符合二次相关关系,试验最高产量、产值和增施净效益对应的最优增施量分别为924.56、935.94、706.46 kg/hm²。增施腐殖酸使烤烟烟碱含量显著提高21.53%～43.06%,氯离子含量显著降低24.80%～55.20%,显著改善化学成分的协调性。对酮、醇、酸和酯(内酯)类致香物质含量和致香物质总量有提高作用,使烟叶新植二烯与其他类别致香物质总量的比值不同程度降低。增施腐殖酸有利于提高单料烟香气量,增添焦香或干草香韵,但用量高于900 kg/hm²会降低感官评吸质量。在漫灌栽培条件下,添加706～900 kg/hm²的水溶性腐殖酸可兼顾种植收益和初烤...     

香料烟致香物质的提取及测定方法研究

以云南保山香料烟为试材,研究了同时蒸馏萃取、顶空固相微萃取、乙醚溶剂萃取3种提取方法对香料烟叶片中的特征香味成分挥发性有机酸和赖百当类等香味物质的提取效率,同时应用GC/MS对香料烟叶片中的香味物质成分进行了定性定量检测。结果表明:乙醚溶剂萃取法是一种有效的提取香味物质的方法,云南保山香料烟香气属性特征明显。     

Enantioselective organocatalysis using SOMO activation

The asymmetric alpha-addition of relatively nonpolar hydrocarbon substrates, such as allyl and aryl groups, to aldehydes and ketones remains a largely unsolved problem in organic synthesis, despite the wide potential utility of direct routes to such products. We reasoned that well-established chiral amine catalysis, which activates aldehydes toward electrophile addition by enamine formation, could be expanded to this important reaction class by applying a single-electron oxidant to create a transient radical species from the enamine. We demonstrated the concept of singly occupied molecular orbital (SOMO) activation with a highly selective alpha-allylation of aldehydes, and we here present preliminary results for enantioselective heteroarylations and cyclization/halogenation cascades.     

Accumulation of Mn(II) in Deinococcus radiodurans facilitates gamma-radiation resistance

Deinococcus radiodurans is extremely resistant to ionizing radiation. How this bacterium can grow under chronic gamma radiation [50 grays (Gy) per hour] or recover from acute doses greater than 10 kGy is unknown. We show that D. radiodurans accumulates very high intracellular manganese and low iron levels compared with radiation-sensitive bacteria and that resistance exhibits a concentration-dependent response to manganous chloride [Mn(II)]. Among the most radiation-resistant bacterial groups reported, Deinococcus, Enterococcus, Lactobacillus, and cyanobacteria accumulate Mn(II). In contrast, Shewanella oneidensis and Pseudomonas putida have high iron but low intracellular manganese concentrations and are very sensitive. We propose that Mn(II) accumulation facilitates recovery from radiation injury.     

萜类的生源合成

本文简述了萜类生源学说的发展史,指出各类萜都是由其各自的特性前身合成的,而所有这些特性前身又都是由Ipp和Dpp衍生出来的。萜类生源合成的主要反应类型是①亲核取代,它主要发生在各类萜的特性前身的合成过程中;②亲电加成,它是成环的主要反应;③分子重排,主要发生在正电荷移位和不规则萜的合成过程中。本文并用反应图表的形式讨论了各类萜的生源合成路线,从而对结构复杂、变化多端的萜类化合物作出了条理化、系统化的总结。     

Redesigning metabolic routes: manipulation of TOL plasmid pathway for catabolism of alkylbenzoates

Increasing quantities of man-made organic chemicals are released each year into the biosphere. Some of these compounds are both toxic and relatively resistant to physical, chemical, or biological degradation, and they thus constitute an environmental burden of considerable magnitude. Genetic manipulation of microbial catabolic pathways offers a powerful means by which to accelerate evolution of biodegradative routes through which such compounds might be eliminated from the environment. In the experiments described here, a catabolic pathway for alkylbenzoates specified by the TOL plasmid of Pseudomonas was restructured to produce a pathway capable of processing a new substrate, 4-ethylbenzoate. Analysis of critical steps in the TOL pathway that prevent metabolism of 4-ethylbenzoate revealed that this compound fails to induce synthesis of the catabolic enzymes and that one of its metabolic intermediates inactivates catechol 2,3-dioxygenase (C23O), the enzyme that cleaves the aromatic ring. Consequently, the pathway was sequentially modified by recruitment of genes from mutant bacteria selected for their production of either an altered pathway operon regulator that is activated by 4-ethylbenzoate or an altered C23O that is less sensitive to metabolite inactivation. The redesigned pathway was stably expressed and enabled host bacteria to degrade 4-ethylbenzoate in addition to the normal substrates of the TOL pathway.     

Palladium-catalyzed aerobic dehydrogenation of substituted cyclohexanones to phenols

Aromatic molecules are key constituents of many pharmaceuticals, electronic materials, and commodity plastics. The utility of these molecules directly reflects the identity and pattern of substituents on the aromatic ring. Here, we report a palladium(II) catalyst system, incorporating an unconventional ortho-dimethylaminopyridine ligand, for the conversion of substituted cyclohexanones to the corresponding phenols. The reaction proceeds via successive dehydrogenation of two saturated carbon-carbon bonds of the six-membered ring and uses molecular oxygen as the hydrogen acceptor. This reactivity demonstrates a versatile and efficient strategy for the synthesis of substituted aromatic molecules with fundamentally different selectivity constraints from the numerous known synthetic methods that rely on substitution of a preexisting aromatic ring.