Synthesis and properties of crown ether isocyanide silver(I) derivatives: X-ray structure of a self-assembled 22-membered diargentacycle

The crown ether isocyanide CNR (R = benzo-15-crown-5) reacts with silver(I) salts in the appropriate molar ratio to give [Ag(CNR)_n]X (n = 1, 2; X = CF₃SO₃, BF₄). X-ray diffraction studies of [Ag(CF₃SO₃)(CNR)] show the molecules associated in a dinuclear manner with an antiparallel orientation. The silver centers are tetracoordinated to the isocyanide and to three oxygens, one from the triflate anion and two from the second crown ether in the dimer. The molecular structure displays five cycles: the two 15-crown ether rings, two five-membered argentacycles and a 22-membered diargentacycle. The crown ether in these complexes is able to detect alkaline cations from M(CF₃SO₃) (M = Li, Na, K) by NMR in d₆-acetone solutions, and to distinguish Li⁺-Na⁺ from K⁺.     

A trigonal-prismatic Ag(I) complex and an octahedral Cu(II) complex incorporating with oxamide Ni(II) complex ligand: Syntheses, crystal structures and oxidative nuclease activities

A mononuclear macrocyclic complex Ni^IIL^3a (L^3a = dianion of 2,3-dioxo-5,6:13,14-dibenzo-9,10-cyclohexyl-7,12-bis(methoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene), which shows high DNA cleavage activity in the presence of H₂O₂, was reported in our previous work. Considering that many systems for natural enzyme-mediated DNA cleavage contain two or more metal active sites, two new trinuclear complexes [Cu(NiL^3a)₂(dca)₂]·2CH₃OH (abbreviated as Cu(NiL^3a)₂) and [Ag(NiL^3a)₂(NO₃)]·2CH₃OH·0.5H₂O (abbreviated as Ag(NiL^3a)₂) were synthesized in this work, where dca is the dicyanamide. The complexes were structurally characterized by single crystal X-ray analysis. The central Cu(II) or Ag(I) atom is linked to two [NiL^3a] ligands by oxamido bridges forming a trinuclear structure. In Cu(NiL^3a)₂, the central Cu(II) ion is in an octahedral coordination geometry. Whereas in Ag(NiL^3a)₂, the central Ag(I) ion is in a rarely reported trigonal-prismatic coordination geometry. The DNA cleavage behavior of the complexes in the presence of H₂O₂ was studied in detail. Comparing with the NiL^3a, the trinuclear complex Ag(NiL^3a)₂ nearly has no ability to cleave DNA, whereas Cu(NiL^3a)₂ is a much better DNA cleavage agent. Cu(NiL^3a)₂ can efficiently convert supercoiled DNA to nicked DNA with a rate constant of 0.074 ± 0.002 min⁻¹ when 40 μM Cu(NiL^3a)₂ and 0.6 mM H₂O₂ are used. The cleavage mechanism between the complex Cu(NiL^3a)₂ and plasmid DNA is likely to involve singlet oxygen as reactive oxygen species. Circular dichroism (CD) and fluorescence spectroscopy indicate that both Cu(NiL^3a)₂ and NiL^3a bind to DNA by a groove binding mode, and the binding between Cu(NiL^3a)₂ and DNA is much stronger than that between NiL^3a and DNA. The present results may provide some information for the design of efficient multinuclear artificial nucleases.     

细裂银叶菊叶的组织培养繁殖研究

以细裂银叶菊叶片为材料,进行愈伤组织的诱导、分化培养及生根诱导培养。结果表明：叶片愈伤组织的诱导以MS 2,4-D2mgL^-1 BA1mgL^-1 NAA0．1mgL^-1。培养基较好：分化培养以MStBA0．5mgL^-1 NAA0．1mgL^-1为好：生根诱导以1／2MS NAA0．01mgL^-4效果最好。     

鲢鱼骨骼肌肌球蛋白重链基因的cDNA克隆与表达

肌球蛋白分子含有2个约200kD的重链亚基和4个约20kD的轻链亚基,重链亚基由球状的头部(S1)和α-双螺旋的杆部(Rod)组成1。在鱼类肌肉蛋白质的组成中,肌球蛋白约占肌原纤维蛋白的50%以上,并且其基因在生物进化过程中的变异性很大,以致肌原纤维蛋白性质的变化主要是由肌球蛋白的变化引起的2。       

Silver oxynitrate – an efficacious compound for the prevention and eradication of dual-species biofilms

Preventing and eradicating biofilms remains a challenge in clinical and industrial settings. Recently, the present authors demonstrated that silver oxynitrate (Ag₇NO₁₁) prevented and eradicated single-species planktonic and biofilm populations of numerous microbes at lower concentrations than other silver (Ag) compounds. Here, the antimicrobial and anti-biofilm efficacy of Ag₇NO₁₁ is elaborated by testing its in vitro activity against combinations of dual-species, planktonic and biofilm populations of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. As further evidence emerges that multispecies bacterial communities are more common in the environment than their single-species counterparts, this study reinforces the diverse applicability of the minimal biofilm eradication concentration (MBEC?) assay for testing antimicrobial compounds against biofilms. Furthermore, this study demonstrated that Ag₇NO₁₁ had enhanced antimicrobial and anti-biofilm activity compared to copper sulfate (CuSO₄) and silver nitrate (AgNO₃) against the tested bacterial species.     

光照强度及栽培基质对秋海棠新品种‘宁明银’生长的影响

秋海棠是世界著名的观赏植物,不同种类和品种对栽培基质、光照、温度和湿度等生长环境条件的要求不同。‘宁明银’秋海棠是最近培育出的新品种,具有很高的观赏价值和市场潜力,但其栽培适宜条件还不清楚。为了摸索该品种的最佳栽培基质和光照条件,该研究利用四种光强(遮光45%、60%、75%、90%)和四种无土栽培基质(泥炭∶珍珠岩=1∶1;泥炭∶珍珠岩∶松树皮=1∶1∶1;腐叶土∶珍珠岩∶松树皮=1∶1∶1;玉米秆∶珍珠岩∶松树皮=1∶1∶1)在上海辰山植物园栽培大棚中开展盆栽试验,比较分析‘宁明银’秋海棠的生长表现。结果表明:在遮光45%条件下,腐叶土、珍珠岩、松树皮同等比例混合的栽培基质中,‘宁明银’秋海棠的叶片数、最大叶面积、地上部分鲜重与干重、地下部分干重均表现出最大值,且该条件下植株的相对含水量和根冠比最小,相对叶绿素含量也最高。因此,盆栽‘宁明银’秋海棠的最佳无土栽培条件为腐叶土、珍珠岩、松树皮等比例混合栽培基质和45%遮光,利用此条件可指导‘宁明银’秋海棠的商品化盆栽生产。     

鲢快速逃逸游泳行为研究

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Antioxidant,antibacterial and cytotoxic potential of silver nanoparticles synthesized using terpenes rich extract of Lantana camara L. leaves

Several attempts have been made for green synthesis of silver nanoparticles (AgNPs) using different plant extracts. Present study revealed that, antioxidant, antibacterial and cytotoxic AgNPs were synthesized using terpenes-rich extract (TRE) of environmentally notorious Lantana camara L. leaves. AgNPs were characterized by advanced techniques like UV–Visible and Infra red spectroscopy; XRD, SEM techniques as terpenes coated sphere shaped NPs with average diameter 425 nm. Further, on evaluation, AgNPs were found to exhibit dose – dependent antioxidant potential, good to moderate antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa; and toxicity on Brine shrimp (A. salinanauplii) with LD₅₀ value 514.50 µg/ml.     

白鹇种群分布与栖息地斑块特征的关系

为了解白鹇(Lophura nycthemera)种群分布与栖息地斑块特征之间的关系,于1998年9月至1999年8月在浙江省古田山国家自然保护区及其外围地区对白鹇种群进行调查.通过羽迹法调查并估计斑块内局部种群数量的相对大小,分析斑块内植被及景观特征对斑块占有及种群相对密度大小的影响.结果表明,斑块面积、总盖度、乔木层盖度和灌木层高度等对斑块内有无白鹇出现影响显著,斑块面积大、总盖度及乔木层盖度高、灌木层高度高的斑块内白鹇出现率高,斑块面积大则局部种群的相对密度也大,两者间呈极显著正线性相关.     

银狐气味对根田鼠繁殖和觅食的影响

在实验室条件下, 主要测定银狐的气味对根田鼠社会行为、觅食、繁殖特征及性激素水平的影响, 并探讨银狐气味使根田鼠产生繁殖迟滞的机制。结果表明, 银狐气味对82 %的配对根田鼠产生显著的繁殖迟滞, 对根田鼠一般动作、探究、自我修饰及婚配行为的频次具有显著的抑制作用( P < 0105) 。对各种行为累积时间的作用则产生明显的性别差异, 银狐气味可提高雄体及雌体一般动作及雌体亲密行为的累积时间; 对雄体自我修饰行为, 以及雌体攻击、探究及自我修饰行为的累积时间有显著的降低作用( P < 0105) 。雄体附睾精子计数、雌体卵巢指数及胚胎重量极显著地减低( P < 0101) , 相应地, 雌体血清孕酮显著地提高( P< 0101) 。