The dragonfly has excellent flying capacity and its wings are typical 2-dimensional composite materials in micro-scale or nano-scale. The nanomechanical behavior of dragonfly membranous wings was investigated with a n...The dragonfly has excellent flying capacity and its wings are typical 2-dimensional composite materials in micro-scale or nano-scale. The nanomechanical behavior of dragonfly membranous wings was investigated with a nanoindenter. It was shown that the maxima of the reduced modulus and nanohardness of the in-vivo and fresh dragonfly wings are about at position of 0.7L, where L is the wing length. It was found that the reduced modulus and nanohardness of radius of the wings of dragonfly are large. The reduced modulus and nanohardness of Costa, Radius and Postal veins of the in-vivo dragonfly wings are larger than those of the fresh ones. The deformation, stress and strain under the uniform load were analyzed with finite element simulation software ANSYS. The deformation is little and the distribution trend of the strain is probably in agreement with that of the stress. It is shown that the main veins have better stabilities and load-bearing capacities. The understanding of dragonfly wings＇ nanomechanical properties would provide some references for improving some properties of 2-dimentional composite materials through the biomimetic designs. The realization of nanomechanical properties of dragonfly wings will provide inspirations for designing some new structures and materials of mechanical parts.展开更多
【目的】鉴定黄蜻幼虫肠道中具有除草活性的真菌,并分析其除草活性成分。【方法】通过形态学观察和分子生物学5.8S r DNA-ITS序列分析,明确菌株QTYC-51的分类地位。结合培养皿生物分析法测定菌株发酵液和单体化合物的除草活性,采用色谱...【目的】鉴定黄蜻幼虫肠道中具有除草活性的真菌,并分析其除草活性成分。【方法】通过形态学观察和分子生物学5.8S r DNA-ITS序列分析,明确菌株QTYC-51的分类地位。结合培养皿生物分析法测定菌株发酵液和单体化合物的除草活性,采用色谱方法从该菌乙酸乙酯粗提物中分离活性成分,并利用质谱和核磁共振谱鉴定活性物质。【结果】菌株QTYC-51被鉴定为拟盾壳霉属菌(Paraconiothyrium sp.),其发酵液对稗草和反枝苋幼根生长有较好的抑制作用,抑制率分别为76.9%和56.5%。从QTYC-51发酵产物中分离到5个单体化合物,分别为1,8-dihydroxyanthraquinone,1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione,hydroxyvertixanthone,globosuxanthone和1,3,6,8-tetrahydroxyanthraquinone。在供试浓度为100μg/m L时,化合物globosuxanthone对稗草和反枝苋幼根生长有明显的抑制作用,抑制率分别为94.1%和79.0%,与阳性对照2,4-二氯苯氧乙酸效果相当;化合物1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione具有较好的除草活性,对稗草和反枝苋幼根的生长抑制率分别为50.3%和58.6%。【结论】菌株QTYC-51具有开发为微生物源除草剂的潜能。展开更多
【目的】从黄蜻幼虫肠道中分离出具有除草活性的真菌,并在其代谢产物中寻找具有除草活性的先导化合物。【方法】采用涂布平板法对黄蜻幼虫肠道共生真菌进行分离,通过形态学观察和5.8S r RNA序列分析初步确定目标菌株QTYC01的分类地位。...【目的】从黄蜻幼虫肠道中分离出具有除草活性的真菌,并在其代谢产物中寻找具有除草活性的先导化合物。【方法】采用涂布平板法对黄蜻幼虫肠道共生真菌进行分离,通过形态学观察和5.8S r RNA序列分析初步确定目标菌株QTYC01的分类地位。利用离体的方法测定菌株发酵液及其乙酸乙酯提取物的除草活性以及粗提物对常见农作物的安全性;利用盆栽方法测定发酵液对稗草幼苗的活性。运用重结晶的方法对发酵产物进行分离、纯化,利用质谱和核磁共振谱分析鉴定出化合物的结构。【结果】菌株QTYC01被鉴定为Curvularia crepinii。离体活性测试发现QTYC01发酵液可显著抑制稗草和反枝苋幼根的生长,其抑制率分别可达95.0%和90.1%,并可使经喷施发酵液的稗草幼苗的受害率达到71.1%。发酵液的乙酸乙酯提取物对稗草和反枝苋幼根具有很好的抑制效果,在100μg/m L的浓度条件下,粗提物对稗草和反枝苋的抑制活性分别为56.8%和71.2%,且在该浓度条件下对一些常见农作物具有很好的安全性,其抑制率均低于32.6%。进一步从其乙酸乙酯提取物中分离得到化合物(5Z)-7-oxozeaenol,活性测试表明化合物具有较好的抑制反枝苋活性,其IC_(50)为4.8μg/m L。【结论】菌株QTYC01具有开发为新型微生物除草剂的潜力。展开更多
基金This work was supported by National Natural Science Foundation of China （Grant Nos. 30600131 and 50675087）, by the 8th key subject of Henan province and by Science and Technique Plan Project of Henan Tech- nology Department （Grant No. 162102310431）.
文摘The dragonfly has excellent flying capacity and its wings are typical 2-dimensional composite materials in micro-scale or nano-scale. The nanomechanical behavior of dragonfly membranous wings was investigated with a nanoindenter. It was shown that the maxima of the reduced modulus and nanohardness of the in-vivo and fresh dragonfly wings are about at position of 0.7L, where L is the wing length. It was found that the reduced modulus and nanohardness of radius of the wings of dragonfly are large. The reduced modulus and nanohardness of Costa, Radius and Postal veins of the in-vivo dragonfly wings are larger than those of the fresh ones. The deformation, stress and strain under the uniform load were analyzed with finite element simulation software ANSYS. The deformation is little and the distribution trend of the strain is probably in agreement with that of the stress. It is shown that the main veins have better stabilities and load-bearing capacities. The understanding of dragonfly wings＇ nanomechanical properties would provide some references for improving some properties of 2-dimentional composite materials through the biomimetic designs. The realization of nanomechanical properties of dragonfly wings will provide inspirations for designing some new structures and materials of mechanical parts.
文摘【目的】鉴定黄蜻幼虫肠道中具有除草活性的真菌,并分析其除草活性成分。【方法】通过形态学观察和分子生物学5.8S r DNA-ITS序列分析,明确菌株QTYC-51的分类地位。结合培养皿生物分析法测定菌株发酵液和单体化合物的除草活性,采用色谱方法从该菌乙酸乙酯粗提物中分离活性成分,并利用质谱和核磁共振谱鉴定活性物质。【结果】菌株QTYC-51被鉴定为拟盾壳霉属菌(Paraconiothyrium sp.),其发酵液对稗草和反枝苋幼根生长有较好的抑制作用,抑制率分别为76.9%和56.5%。从QTYC-51发酵产物中分离到5个单体化合物,分别为1,8-dihydroxyanthraquinone,1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione,hydroxyvertixanthone,globosuxanthone和1,3,6,8-tetrahydroxyanthraquinone。在供试浓度为100μg/m L时,化合物globosuxanthone对稗草和反枝苋幼根生长有明显的抑制作用,抑制率分别为94.1%和79.0%,与阳性对照2,4-二氯苯氧乙酸效果相当;化合物1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione具有较好的除草活性,对稗草和反枝苋幼根的生长抑制率分别为50.3%和58.6%。【结论】菌株QTYC-51具有开发为微生物源除草剂的潜能。
