Silver nanoparticles （AgNPs） are widely used antimicrobial compounds; however, they may pose a threat to non-targeted bacteria in the environment. In this study high-throughput sequencing was used to investigate the...Silver nanoparticles （AgNPs） are widely used antimicrobial compounds; however, they may pose a threat to non-targeted bacteria in the environment. In this study high-throughput sequencing was used to investigate the effects of different concentrations of AgNPs （10, 50, and 100 mg kg-1） on soil microbial community structure during short-term （7 d） exposure. The amounts of Acidobacteria, Actinobacteria, Cyanobacteria, and Nitrospirae significantly decreased with increasing AgNP concentration; meanwhile, several other phyla （e.g., Proteobacteria and Planctomycetes） increased and dominated. Nitrosomonas europaea, a well-characterized ammonia- oxidizing bacterium, was used to study the sensitivity of bacteria to AgNPs and ionic silver （Ag＋）. Flow cytometry was used to monitor the toxicity of low （1 mg L-l）, middle （10 mg L-l）, and high concentrations （20 mg L-1） of AgNPs, as well as Ag＋ （1 mg L-1） released into the medium from 20 mg L-1 concentration of AgNPs, towards N. europaea. After 12 h of exposure, the survival rate of N. europaea treated with 1 mg L-1 Ag＋ was significantly lower than those treated with low （1 mg L-1） and middle concentrations （10 mg L-1） of AgNPs, but the survival rate in the treatment with high concentration （20 mg L-1） of AgNPs was much lower. Additionally, necrosis rates were higher in the treatment with 20 mg L-1 AgNPs. Electron microscopy showed that Ag＋ caused serious damage to the cell wall of N. europaea, disintegrated the nucleoids, and condensed next to the cell membrane; however, dissolved Ag＋ is only one of the antibacterial mechanisms of AgNPs.展开更多
Five new diacid amides of di-cholesteryl L-glycinates were designed and prepared.The compounds with linkers containing 0,1, 2,3,or 4 methylene units are denoted as 1,2,3,4,and 5,respectively.Their gelation behaviors i...Five new diacid amides of di-cholesteryl L-glycinates were designed and prepared.The compounds with linkers containing 0,1, 2,3,or 4 methylene units are denoted as 1,2,3,4,and 5,respectively.Their gelation behaviors in 25 solvents were tested as novel low-molecular-mass organic gelators(LMOGs).It was shown that the length of the linker connecting the two-cholesteryl residues in a gelator plays a crucial role in the gelation behavior of the compound.1 gels 11 of the 25 solvents tested at a concentration lower than 1.0%,while 2 gels 17 of the solvents tested.4 and 5,however,gel only 2 and 4 of them,respectively. SEM observation reveals that the lengths of the linkers and the identity of the solvents are the main factors affecting the structures of the aggregates in the gels.Experimentally,a clear linker effect on the microstructures of the gels was observed.As example,the aggregates of 1,2 and 3 in benzene or 1-heptanol adopt structures of thin fibers,rods or lamellas,respectively. Furthermore,it was found that the gelation and aggregation behaviors of 2,3,4,and 5 in DMSO showed an even-odd effect.展开更多
基金supported by the National Natural Science Foundation of China (No. 41430752)
文摘Silver nanoparticles （AgNPs） are widely used antimicrobial compounds; however, they may pose a threat to non-targeted bacteria in the environment. In this study high-throughput sequencing was used to investigate the effects of different concentrations of AgNPs （10, 50, and 100 mg kg-1） on soil microbial community structure during short-term （7 d） exposure. The amounts of Acidobacteria, Actinobacteria, Cyanobacteria, and Nitrospirae significantly decreased with increasing AgNP concentration; meanwhile, several other phyla （e.g., Proteobacteria and Planctomycetes） increased and dominated. Nitrosomonas europaea, a well-characterized ammonia- oxidizing bacterium, was used to study the sensitivity of bacteria to AgNPs and ionic silver （Ag＋）. Flow cytometry was used to monitor the toxicity of low （1 mg L-l）, middle （10 mg L-l）, and high concentrations （20 mg L-1） of AgNPs, as well as Ag＋ （1 mg L-1） released into the medium from 20 mg L-1 concentration of AgNPs, towards N. europaea. After 12 h of exposure, the survival rate of N. europaea treated with 1 mg L-1 Ag＋ was significantly lower than those treated with low （1 mg L-1） and middle concentrations （10 mg L-1） of AgNPs, but the survival rate in the treatment with high concentration （20 mg L-1） of AgNPs was much lower. Additionally, necrosis rates were higher in the treatment with 20 mg L-1 AgNPs. Electron microscopy showed that Ag＋ caused serious damage to the cell wall of N. europaea, disintegrated the nucleoids, and condensed next to the cell membrane; however, dissolved Ag＋ is only one of the antibacterial mechanisms of AgNPs.
基金supported by the Ministry of Science and Technology of China (2007AA03Z349)the National Natural Science Foundation of China (20773083, 20902055)
文摘Five new diacid amides of di-cholesteryl L-glycinates were designed and prepared.The compounds with linkers containing 0,1, 2,3,or 4 methylene units are denoted as 1,2,3,4,and 5,respectively.Their gelation behaviors in 25 solvents were tested as novel low-molecular-mass organic gelators(LMOGs).It was shown that the length of the linker connecting the two-cholesteryl residues in a gelator plays a crucial role in the gelation behavior of the compound.1 gels 11 of the 25 solvents tested at a concentration lower than 1.0%,while 2 gels 17 of the solvents tested.4 and 5,however,gel only 2 and 4 of them,respectively. SEM observation reveals that the lengths of the linkers and the identity of the solvents are the main factors affecting the structures of the aggregates in the gels.Experimentally,a clear linker effect on the microstructures of the gels was observed.As example,the aggregates of 1,2 and 3 in benzene or 1-heptanol adopt structures of thin fibers,rods or lamellas,respectively. Furthermore,it was found that the gelation and aggregation behaviors of 2,3,4,and 5 in DMSO showed an even-odd effect.
