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141.
To understand nitrous oxide (N2O) emissions from terrestrial ecosystems it is necessary to understand the processes leading to N2O production. Here, for the first time, results are presented which identify in situ the processes of N2O production in a temperate grassland soil. A small portion of the nitrogen (N) applied in the summer to the grassland soil was rapidly transported below the main rooting zone (>20 cm) and resulted in large N2O productions at depths of 20-50 cm. Preferential pathways must have been responsible for this movement because the soil conditions were not conducive to leaching by piston flow. The N2O was entirely produced by nitrate (NO3−) reduction which was surprising because the bulk soil was aerobic. Therefore, reduction processes can operate during times of the year when it is least expected and cause large N2O concentrations deep in the soil profile. 相似文献
142.
Nancy I. LópezAmy T. Austin Osvaldo E. SalaBeatriz S. Méndez 《Soil biology & biochemistry》2003,35(12):1609-1613
We studied controls on nitrification in an undisturbed water-limited ecosystem by inhibiting autotrophic nitrifying bacteria in soils with varying levels of vegetative cover. The activity of nitrifying bacteria was disrupted using nitrapyrin, 2-chloro-6-(trichloromethyl)-pyridine, under field conditions in three microenvironments (underneath shrubs, next to grasses and in bare soil). Ammonia-oxidising bacteria were detected by PCR analysis of DNA in soils. The inhibition of nitrification changed the concentrations of NO3− and NH4+ in the soil, while the microenvironment was most important in determining the response of bacteria to the inhibitor. Nitrapyrin application resulted in a significant (p<0.05) reduction in soil NO3− concentration (39%) and a significant increase (p<0.001) in soil NH4+ concentration (41%). Untreated bare-soil microenvironments had the lowest concentrations of NH4+ (1.57 μg/g of dry soil) and NO3− (0.49 μg/g of dry soil) when compared to the other microenvironments, and showed the highest impacts of nitrification inhibition. For example, NH4+ concentrations increased 288% and NO3− concentrations decreased 60% in inhibited bare-soil microenvironments. In contrast, untreated microenvironments underneath shrubs had the highest levels of NH4+ (10.01 μg/g of dry soil) and NO3− (0.69 μg/g of dry soil), but showed no significant effects of inhibition of nitrification on soil nitrogen concentrations. 相似文献
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145.
The Kunitz-type protease inhibitors are the best-characterized family of serine protease inhibitors, probably due to their abundance in several organisms. These inhibitors consist of a chain of ~60 amino acid residues stabilized by three disulfide bridges, and was first observed in the bovine pancreatic trypsin inhibitor (BPTI)-like protease inhibitors, which strongly inhibit trypsin and chymotrypsin. In this review we present the protease inhibitors (PIs) described to date from marine venomous animals, such as from sea anemone extracts and Conus venom, as well as their counterparts in terrestrial venomous animals, such as snakes, scorpions, spiders, Anurans, and Hymenopterans. More emphasis was given to the Kunitz-type inhibitors, once they are found in all these organisms. Their biological sources, specificity against different proteases, and other molecular blanks (being also K+ channel blockers) are presented, followed by their molecular diversity. Whereas sea anemone, snakes and other venomous animals present mainly Kunitz-type inhibitors, PIs from Anurans present the major variety in structure length and number of Cys residues, with at least six distinguishable classes. A representative alignment of PIs from these venomous animals shows that, despite eventual differences in Cys assignment, the key-residues for the protease inhibitory activity in all of them occupy similar positions in primary sequence. The key-residues for the K+ channel blocking activity was also compared. 相似文献
146.
大白菜开花基因 LFY的克隆及dsRNA抑制载体的构建 总被引:2,自引:0,他引:2
以中国大白菜花蕾为材料,通过RT-PCR方法,参照GeneBank公布的序列克隆了Leafy(简称LFY)基因片段,测序分析结果表明,该基因与国外已经报道的序列具有94%的同源性。将此序列以相反方向插入到植物表达载体pROK2 35S启动子之间,并在2反向重复片段之间插入小麦乙酰辅酶A羧化酶的第20内舍子,从而构建了dsRNA抑制双元载体,该载体的构建为通过农杆菌介导转化大白菜进而解决早春扣反季栽培大白菜的先期抽薹问题创造了条件。 相似文献
147.
Zhongpeng Ding Feifei Li Lianghui Xie Minqing Gu Chunlei Li Chang Liu Chao Peng Wenbao Li 《Marine drugs》2022,20(12)
Phenylahistin is a naturally occurring marine product with a diketopiperazine structure that can bind to the colchicine site of microtubulin as a possible anticancer agent. To develop more potent microtubule inhibitors, novel phenylahistin derivatives were designed and synthesized based on the co-crystal complexes of phenylahistin derivatives and microtubulin. We established a focused library of imidazole-type molecules for the introduction of different groups to the C-ring and A-ring of phenylahistin. Structure–activity relationship studies indicated that appropriate hydrocarbon substituents and unsaturated alkenyl substituents at the 1-position of the imidazole group are important for improving the activity of such compounds. In addition, this study found that propylamine groups could maintain the activity of these compounds, as exemplified by compound 16d (IC50 = 5.38 nM, NCI-H460). Compound 15p (IC50 = 1.03 nM, NCI-H460) with an allyl group exhibited potent cytotoxic activity at the nanomolar level against human lung cancer cell lines. Immunofluorescence assay indicated that compound 15p could efficiently inhibited microtubule polymerization and induced a high expression of caspase-3. 15p also displayed good pharmacokinetic characteristics in vitro. Additionally, the growth of H22 transplanted tumors was significantly inhibited in BALB/c mice when 15p alone was administered at 4 mg/kg, and the tumor inhibition rate was as much as 65%. Importantly, the continuous administration of 15p resulted in a lower toxicity than that of docetaxel (10 mg/kg) and cyclophosphamide (20 mg/kg). Overall, the novel allyl-imidazole-diketopiperazine-type derivatives could be considered safe and effective potential agents for cancer treatment. 相似文献
148.
以1年生、2年生和5年生厚壁毛竹的秆、枝、叶为研究对象,对其主要化学组成进行分析;同时对竹粉和综纤维素进行稀硫酸处理,分析其糖及抑制物的浓度。结果表明:随着竹龄和部位的不同,厚壁毛竹的主要化学组成呈现一定的变异规律,叶片的灰分含量最高,秆部灰分含量最低,叶片的苯醇抽提物最高;1年生厚壁毛竹秆部的纤维素含量最高,不同竹龄的厚壁毛竹的综纤维素含量变化不大;5年生厚壁毛竹秆部的酸不溶木质素含量最高,而1年生厚壁毛竹叶片的含量最低;秆的各种糖浓度均大于枝,枝的糖浓度均大于叶;抑制物中乙酸的浓度最高,乙酰丙酸的浓度最低;竹粉中糖含量及抑制物浓度均比综纤维素高。 相似文献
149.
为评价不同类型病毒抑制剂在不同发病条件下对烟草花叶病的防控效果,选用2种生物制剂(AHO、宁南霉素)和2种化学农药(吗胍·乙酸铜、烯·羟·硫酸铜)进行田间药效试验.大田接种烟草花叶病毒(TMV)的试验表明,AHO和吗胍·乙酸铜对TMV的平均防效较高,分别为41.8%和39.8%,宁南霉素和烯·羟·硫酸铜对TMV的平均防效较低,分别为25.4%和14.5%;在自然发病状态下,AHO对TMV的平均防效为45.5%,宁南霉素的平均防效次之,为36.6%,而烯·羟·硫酸铜和吗胍·乙酸铜的平均防效则分别为28.7%和16.2%.AHO在不同带毒环境下防控烟草花叶病的效果都优于其他3种市售药物,表明其具有开发成为绿色抗烟草花叶病新型农药的潜力. 相似文献
150.