4种城市绿化树种叶片PAHs含量特征与叶面结构的关系

用气质联用仪测定了长沙市樟树(Cinnamomu camphora)、广玉兰(Magnolia grandiflora)、桂花(Opsmanthus fragrans)和红檵木(Redrlowered loropetalum)4个主要绿化树种叶片中PAHs含量,同时测定了叶片的气孔密度、气孔长宽比、叶片的宽长比和叶面积等叶面结构特征值,探讨了叶面结构与叶片中PAHs含量的关系。结果表明:红檵木叶片的PAHs含量最高,为11.13mg·kg-1,16种PAHs在4树种叶片中均有不同程度的检出,其中以3环和4环为主,菲的浓度最高。除桂花外,在气温较低的秋冬季节,其余3种植物叶片气孔密度大PAHs含量高。叶面宽长比、气孔长宽比均与叶片PAHs含量呈极显著正相关,而叶面积与PAHs含量呈极显著负相关。表明叶面结构是影响叶片PAHs含量的重要因素。研究结果可为城市绿化树种合理选择与配置提供科学依据。     

Arginine deprivation and tumour cell death: Arginase and its inhibition

Arginase treatment of cell cultures reduced arginine in the medium to ~ micromolar levels within 5–30 min, and proved as effective as arginine-free medium (AFM) prepared by formulation. The enzyme was heat stable and as active at pH 7.2 as at pH 9.9. It persisted in culture for at least 3 days with only a small diminution in its speed of action, and still actively destroyed arginine after 6 days, since arginine supplementation failed to rescue viable cells.Addition of L-norvaline, an inhibitor of arginase, rescued cells from arginase-induced deprivation. Its efficacy at low concentrations was short-lived (probably < 1 day), while at higher concentrations it did not appear to inhibit completely the enzyme. However, L-norvaline at these same levels also slowed the growth of positive non-enzyme treated controls receiving the normal arginine levels. Thus the difference in this growth indicated that arginase was more inhibitory than cursory examination of initial kinetic data suggested. It also agreed with the inhibition of arginase in the ornithine assay used to measure biochemically enzyme activity. We conclude that norvaline partially but not completely antagonises arginase activity, which allows cell rescue in a dose-dependent manner between 0.4 and 4 mM, but cannot be used above about 2 mM without exhibiting a general non-specific interference of cell growth of its own, although no evidence of cell toxicity was observed in either AFM or arginine-containing medium. L-ornithine, the product of arginase that inhibits the enzyme by a feedback mechanism, had no inhibitory effect on arginase over a similar concentration range.     

Low activity of amine-oxidases and accumulation of conjugated polyamines in disfavour of organogenic programs in Chrysanthemum leaf disc explants

Foliar discs (8 mm diameter) from expanding leaves of the middle part of vegetative shoots of Chrysanthemum morifolium Ramat raised in vitro were induced to form directly on specific media in vitro either roots or vegetative buds, or callus. The budding programme, on its specific medium, was deviated to callus formation by the addition of 2 mM β-OH-E (β-OH-ethyldrazine, an inhibitor of diamine oxidase). Conversely vegetative buds instead of callus were formed on the callus medium in the presence of 2 mM DFMO (difluoromethylornithine, an inhibitor of ornithine decarboxylase). Callus formation was characterized by high accumulation of free and particularly conjugated polyamines (PA), very low or undetectable activities of diamine- and polyamine oxidases, and transglutaminase. DFMO-deviation of callus initiation in favour of bud formation lowered the accumulation of PA and increased the activity of amine-oxidases. The high catabolism of PA in the organogenic (rooting, budding) programs was questioned as to its role in developmental processes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Catabolic metabolism in Trypanosoma cruzi

Culture, blood and intracellular forms of Trypanosoma cruzi have a high rate of endogenous oxygen uptake and probably utilize amino acids and carbohydrates as their exogenous energy sources. It is likely that triglyceride is the main energy reserve. Oxidation of carbohydrate by all forms is probably via a glycolytic sequence and a complete tricarboxylic acid cycle. These data suggest that the substrates utilized and catabolic pathways present in mammalian forms of T. cruzi are similar to those of culture forms of the organism and are quite distinct from those of the bloodstream forms of African trypanosomes.     

Cytochrome P450s in flavonoid metabolism

In this review, cytochrome P450s characterized at the molecular level catalyzing aromatic hydroxylations, aliphatic hydroxylations and skeleton formation in the flavonoid metabolism are surveyed. They are involved in the biosynthesis of anthocyanin pigments and condensed tannin (CYP75, flavonoid 3′,5′-hydroxylase and 3′-hydroxylase), flavones [CYP93B, (2S)-flavanone 2-hydroxylase and flavone synthase II], and leguminous isoflavonoid phytoalexins [CYP71D9, flavonoid 6-hydroxylase; CYP81E, isoflavone 2′-hydroxylase and 3′-hydroxylase; CYP93A, 3,9-dihydroxypterocarpan 6a-hydroxylase; CYP93C, 2-hydroxyisoflavanone synthase (IFS)]. Other P450s of the flavonoid metabolism include methylenedioxy bridge forming enzyme, cyclases producing glyceollins, flavonol 6-hydroxylase and 8-dimethylallylnaringenin 2′-hydroxylase. Mechanistic studies on the unusual aryl migration by CYP93C, regulation of IFS expression in plant organs and its biotechnological applications are introduced, and flavonoid metabolisms by non-plant P450s are also briefly discussed.     

Isolation of glucosinolates and the identification of o-(α-l-rhamnopyranosyloxy)benzylglucosinolate from Reseda odorata

A method has been developed for the quantitative isolation of glucosinolates by ion-exchange chromatography and high voltage electrophoresis avoiding strongly alkaline and acidic conditions. The compounds were identified by ¹H and ¹³C NMR spectroscopy and through the products arising from enzymatic, acid and alkaline hydrolysis. The method is well suited for the isolation and identification of glucosinolates containing aglucone parts which produce non-volatile compounds on enzymatic hydrolysis. The method has been used in the isolation and identification of 2-hydroxy-2-methylpropylglucosinolate from Reseda alba, 2-hydroxy-2-phenylethylglucosinolate from R. luteola and a new glucosinolate, o-(α-l-rhamnopyranosyloxy)benzylglucosinolate, occurring in R. odorata. The glucosinolate content in different parts of this plant has been determined and the metabolism of glucosinolates is briefly discussed.     

Plasmodium falciparum: interaction of shikimate analogues with antimalarial drugs

The shikimate pathway for aromatic biosynthesis presents a target for antimalarial drug development as this pathway is absent from animals. This study extends previous work on inhibitors of the shikimate pathway, by examining their interaction with the antimalarial drugs pyrimethamine and atovaquone. Combinations of atovaquone with several shikimate analogues exhibited synergistic effects. These findings highlight potential use of shikimate pathway inhibitors in combination therapy.     

Anaerobic degradation of ethylbenzene and other aromatic hydrocarbons by new denitrifying bacteria

Anaerobic degradation of alkylbenzenes with side chains longer than that of toluene was studied in freshwater mud samples in the presence of nitrate. Two new denitrifying strains, EbN1 and PbN1, were isolated on ethylbenzene and n-propylbenzene, respectively. For comparison, two further denitrifying strains, ToN1 and mXyN1, were isolated from the same mud with toluene and m-xylene, respectively. Sequencing of 16SrDNA revealed a close relationship of the new isolates to Thauera selenatis. The strains exhibited different specific capacities for degradation of alkylbenzenes. In addition to ethylbenzene, strain EbN1 utilized toluence, but not propylbenzene. In contrast, propylbenzene-degrading strain PbN1 did not grow on toluene, but was able to utilize ethylbenzene. Strain ToN1 used toluene as the only hydrocarbon substrate, whereas strain mXyN1 utilized both toluene and m-xylene. Measurement of the degradation balance demonstrated complete oxidation of ethylbenzene to CO₂ by strain EbN1. Further characteristic substrates of strains EbN1 and PbN1 were 1-phenylethanol and acetophenone. In contrast to the other isolates, strain mXyN1 did not grow on benzyl alcohol. Benzyl alcohol (also m-methylbenzyl alcohol) was even a specific inhibitor of toluene and m-xylene utilization by strain mXyN1. None of the strains was able to grow on any of the alkylbenzenes with oxygen as electron acceptor. However, polar aromatic compounds such as benzoate were utilized under both oxic and anoxic conditions. All four isolates grew anaerobically on crude oil. Gas chromatographic analysis of crude oil after growth of strain ToN1 revealed specific depletion of toluene.     

芘在土壤中的共代谢降解研究

高分子量多环芳烃（PAHs)的降解通常以共代谢方式进行,研究比较了高分子量多环芳烃代表种类芘作为唯一C源和能源的降解过程和有共代谢底物存在下的降解过程,结果表明,25d后前者中芘的降解率57％,而后者中芘的降解率为80％,且有共代谢底物存在下,芘在降解过程中关衰期缩短;水扬酸,邻苯二甲酸,琥珀酸钠能作为共代谢底物提高芘的降解率,琥珀酸钠效果最好,芘和低要子量多环芳烃之间也有共代谢关系,菲促进了芘的降解,但萘未出现同样的结果,此外,这阐明了共代谢原理和适宜作高分子量多环芳烃共代谢底物的物质。