塔里木河下游干旱胁迫下的胡杨叶绿素荧光特性研究

 结合塔里木河下游典型监测断面和地下水位埋深的监测数据,测量了不同地下水位处胡杨的叶绿素荧光参数、水势及土壤含水量,探讨了不同地下水位埋深条件下胡杨的叶绿素荧光特性。结果显示,随着地下水位埋深加大,胡杨受到的干旱胁迫加剧,胡杨叶片光适应下的实际光化学量子产量、电子传输速率和光化学猝灭、相对叶绿素含量普遍下降,且下降幅度随地下水位埋深加大而增加; 非光化学猝灭和调节性能量耗散量子产量随光合有效辐射增大而显著升高; 潜在最大光化学量子产量总体处于适宜状态,表明胡杨在地下水位埋深4~8 m左右时,尚能通过自身能力进行调节,光系统Ⅱ未发生不可逆转的因干旱胁迫造成的损伤。     

共振光猝灭法测定环境水样中痕量硒

在阿拉伯树胶(AG)存在下,0.14 mol/L硫酸介质中,硒(Ⅳ)与过量的I-反应生成I3-,加入乙酸钠后I3-与亚甲基蓝反应成离子缔合物,在波长288 nm处共振光猝灭,建立了共振光散射法测定痕量硒的方法.确定了碘化钾、亚甲基蓝、乙酸钠和增溶剂阿拉伯树胶溶液的浓度,在室温(20～30℃)下反应15 min,提高了体...     

比较基因组学分析弧菌属群体感应通路的分布与进化

群体感应是一种细菌细胞间的通讯过程, 细菌通过测量细胞外自诱导剂浓度从而感知群体细胞密度变化。群体感应使细菌能够在两种基因表达模式下转换: 在低细胞密度时有利于个体发展, 而在高细胞密度时则有利于群体发展。目前主要有7种群体感应通路, 分别以oligopeptides、AHL(Acylated Homoserine Lactones)、AI-2(Autoinducer-2)、CAI-1(Cholera Autoinducer-1)、PQS(Pseudomonas Quinolone Signal)、AI-3(Autoinducer-3)以及DSF(Diffusible Signal Factor)作为各群体感应通路的信号分子; 其中oligopeptides存在于革兰氏阳性细菌中, 其余6种信号分子存在于革兰氏阴性细菌中。弧菌是导致人类感染和水产品污染的主要病原菌, 传统的抗生素治疗弧菌感染具有很强的选择压力, 导致越来越多耐药弧菌出现。面对愈发严峻的弧菌耐药性问题, 目前群体感应淬灭被认为是治疗弧菌感染的重要替代手段之一, 因而有必要调查弧菌属细菌不同群体感应通路的分布情况, 为针对弧菌的群体感应淬灭剂研发提供重要参考信息。通过比较基因组学分析, 发现全基因组测序的46株弧菌存在AHL、AI-2以及CAI-1这3种信号分子通路, 其中5株弧菌均含有上述3种信号分子通路, 共有30株弧菌只含有AI-2和CAI-1两种信号分子通路; 而46株弧菌都不存在PQS、AI-3以及DSF群体感应通路。此外, 弧菌群体感应通路的分布与物种进化有关, 含有同种群体感应信号分子通路的弧菌, 其亲缘关系较近, 说明该通路的基因进化自它们的共同祖先。本研究表明开发针对弧菌的群体感应淬灭剂应以AI-2和CAI-1两种信号分子介导的通路作为靶点。     

Growth and survival of Halimione portulacoides stem cuttings in heavy metal contaminated soils

The halophytic shrub Halimione portulacoides demonstrates a high tolerance to heavy metal contamination and a capacity for accumulating metals within its tissues. On the Iberian Peninsula, this species has colonized habitats with high levels of metal pollution. The aim of this study is to analyze the response of H. portulacoides stem cuttings to this pollution. Growth, photosynthesis and metal uptake were examined in H. portulacoides through an experiment in which stem cuttings were replanted in metal-contaminated soil. This condition decreased growth and lowered both photosynthetic rate and stomatal conductance. Reduced photosynthetic performance was largely due to the reduced concentration of photosynthetic pigments. Despite these responses, there was some important evidence suggesting the phytoremediatory potential of Halimione stem cuttings. The results of our study indicate that this salt-marsh shrub may represent a biotool of value in the restoration of polluted areas.     

合浦珠母贝基质蛋白KRMP-3对二价金属离子选择性的研究

用大肠杆菌表达含有GST标签的基质蛋白KRMP-3。利用圆二色谱(Circular Dichroism, CD)研究不同浓度钙离子和镁离子对基质蛋白 KRMP-3二级结构的影响。结果表明,钙离子对其二级结构的变化远大于镁离子;同时,采用荧光淬灭法研究 KRMP-3对钙,镁,锶,钡等二价金属离子的选择性,结果表明, KRMP-3对钙离子有特异性选择性,钙离子与KRMP-3的结合常数K约为103 L/mol,结合位点数 n 近似为1,表明 KRMP-3与钙离子的结合能力适中,推测基质蛋白 KRMP-3对合浦珠母贝( Pinctada fucata)棱柱层形成起到促进作用。     

Implementation schemes for avoiding artifact discontinuities in simulated annealing

The simulated annealing algorithm has been applied successfully to conditional simulation of categorical variables (e.g., rock or facies units) with the objective of improving the match between measured and modeled spatial variability. In some implementation schemes, however, spurious features termed “artifact discontinuities” may occur near conditioning data, especially during the “zero- temperature” case referred to as simulated quenching. This paper shows that artifact discontinuities can be avoided by considering the anisotropy of the spatial variability model, reducing the number of lag vectors used in the objective function, and providing a rudimentary initial configuration. Results from several test cases suggest that the artifact discontinuities might be caused by overly precise fitting of measured to modeled spatial variability.     

Observations concerning the nature of maceral fluorescence alteration with time

Distinctive features of the alteration of maceral fluorescence intensity with upon blue-light or UV excitation are related to the level of organic maturation. Alteration has been measured in different media; the results demonstrate clearly that the negative component of the alteration phenomenon is due to photochemical oxidation. Highly weathered bituminous coals do not display negative alteration because the potential for oxidation quenching has been reduced. The positive component of alteration is thought to be due to the creation of additional absorption centers and increased molecular rigidity as a result of photochemical oxidation and the enhancement of cross-linking among mobile phase and network molecules.     

Determination of Hg and MeHg complexation with dissolved organic matter by fluorescence quenching titration

In natural waters inorganic mercury （Hg） and methylmercury （MeHg） are complexed with a variety of inorganic and organic ligands, such as OH^-, Cl^-, sulfide, thiols, and dissolved organic matter （DOM）. The bioavailability and toxicity of Hg and MeHg are related to their speciation, instead of their total concentrations. Among these species, Hg-DOM and MeHg-DOM complexes are the least known, due to the complexity and site-specificity of DOM in natural waters. Here we report the complexation between DOM and Hg or MeHg using fluorescence spectroscopy. The Suwannee River fulvic acid, peat humic acid, amino acid typotophan, and natural organic matter from the Suwannee River, Nordic River, and Delta Marsh were studied at their respective excitation/emission maxima,     

Isolation and characterization of AHL-degrading bacteria from fish and pond sediment

Quorum sensing (QS) disruption is considered as a potential alternative strategy to combat bacterial diseases in aquaculture. In this study, we isolated and identified bacteria degrading QS molecules from pond sediment and fish intestine. A total of 132 strains were obtained in the enrichment culture, of which two strains were identified as Enterobacter sp. f003 and Staphylococcus sp. sw120, being isolated from the fish intestine and pond sediment, respectively. We found that strains f003 and sw120 could degrade acyl-homoserine lactones (AHLs) and cause no hemolysis of sheep red blood cells. The AHL lactonase (aiiA) homologous gene in the two strains was detected in PCR amplification and the high-degrading activity to N-hexanoyl-L-homoserine lactone (C6-HSL) and AHLs secreted from pathogenic Aeromonas hydrophila was assessed. Meanwhile, the artificial infection of cyprinid Carassius auratus gibelio with intraperitoneal injection showed that the two strains were avirulent. Therefore, the obtained indigenous bacteria are candidate probiotics against pathogenic A. hydrophila in aquaculture.     

基于荧光猝灭原理的溶解氧分析仪的研制及其应用

研制出一种对溶解氧敏感的传感膜,其荧光材料主要是邻菲咯啉钌。由光源发出的中心波长为465 nm的强光照射到铺有该络合物的膜片上,激发出中心波长为620 nm的荧光,水体中的溶解氧会对激发出的荧光产生猝灭效应,猝灭程度与溶解氧的质量浓度之间存在线性关系。该膜片在无氧水中的荧光强度是空气饱和水中的20倍,变化较为明显。对比检测荧光信号在待测水体中猝灭前后的强度,即可测出水体中溶解氧的质量浓度。基于这一原理和荧光测量技术研制了光学溶解氧分析仪,利用该仪器对6处不同水域的天然水体进行测试,所得测试结果与国标碘量法的测试结果之间不存在显著性差异,误差≤2%,响应时间<1 min。在海水中30 m深处进行36h稳定性考察,所得溶解氧质量浓度数值平均偏差小于0.2 mg.L-1,证实仪器可适应较为恶劣的环境,且稳定性较好。