A discrete self-assembled metal array in artificial DNA

DNA has a structural basis to array functionalized building blocks. Here we report the synthesis of a series of artificial oligonucleotides, d(5'-GH(n)C-3') (n = 1 to 5), with hydroxypyridone nucleobases (H) as flat bidentate ligands. Right-handed double helices of the oligonucleotides, nCu2+.d(5'-GH(n)C-3')2 (n = 1 to 5), were quantitatively formed through copper ion (Cu2+)-mediated alternative base pairing (H-Cu2+-H), where the Cu2+ ions incorporated into each complex were aligned along the helix axes inside the duplexes with the Cu2+-Cu2+ distance of 3.7 +/- 0.1 angstroms. The Cu2+ ions were coupled ferromagnetically with one another through unpaired d electrons to form magnetic chains.     

Discrete atom imaging of one-dimensional crystals formed within single-walled carbon nanotubes

The complete crystallography of a one-dimensional crystal of potassium iodide encapsulated within a 1.6-nanometer-diameter single-walled carbon nanotube has been determined with high-resolution transmission electron microscopy. Individual atoms of potassium and iodine within the crystal were identified from a phase image that was reconstructed with a modified focal series restoration approach. The lattice spacings within the crystal are substantially different from those in bulk potassium iodide. This is attributed to the reduced coordination of the surface atoms of the crystal and the close proximity of the van der Waals surface of the confining nanotube.     

有机肥中重金属对菜田土壤微生物群落代谢的影响

基于慈溪掌起镇的蔬菜施肥试验,结合常规理化分析和Micro RESPTM方法,在2年4次施肥后,分析不施肥(CK)、重金属达标商品有机肥(T1)和Pb-As-Cu-Zn添加有机肥(T2)施用土壤的基本理化性质、重金属累积以及微生物群落代谢特征,探讨重金属对施用有机肥土壤微生物群落代谢特征的影响。结果表明,T1和T2显著提高了旱地蔬菜轮作土壤有机质和部分养分含量,且二者无显著差异。但从重金属含量上看,T2土壤Cu、Zn全量以及有效态Cu、Zn、As含量显著高于T1和CK土壤。基于Micro RESPTM的微生物群落代谢特征分析指出,与CK相比,T1显著促进了土壤基础呼吸作用和微生物代谢功能多样性,T2却无类似的促进效果,可见T2土壤Cu、Zn和有效态As含量的大幅增加削弱了有机肥中有机质等养分对土壤微生物的促进作用。主成分和聚类分析进一步表明,T1与T2土壤的微生物群落水平生理指纹图谱(CLPP)存在明显差异,T2土壤中重金属及其有效性的增加诱导柠檬酸、苹果酸和草酸等羧酸代谢利用增强。综上,畜禽粪便有机肥对菜田土壤微生物群落代谢的作用同时受到有机肥本身及其残留重金属的影响,有机肥中过高的重金属残留会改变有机肥养分对土壤微生物代谢的影响。