苦草生长对沉积物中磷迁移转化的影响

构建了不同营养盐负荷的沉积物环境\"水-苦草-沉积物\"生态系统,监测分析了沉积物中总磷(TP)、生物可获得磷及其环境因子的垂直分布及变化,以苦草为例,研究了沉水植物生长对沉积物中磷迁移转化的影响,结果表明:生长期的苦草通过改变沉积物环境因子或自身的生理活动,直接或间接地对沉积物中不同形态磷的迁移转化产生了影响,并随着深度的增加而出现不同的变化。具体表现在,低(L)、中(M)、高(H)营养负荷的沉积物总磷(TP),相对于初始值均有不同程度的下降,但苦草组下降的幅度大,分别比对照组多下降了11.63、18.50和46.25 mg/kg;在垂直方向上均表现出随深度的增加TP呈减少趋势,苦草对沉积物影响的深度随根系的活动范围变化而变化,根系增长最长(比试验初始增加了9.2 cm)的低营养负荷苦草组(LV),可影响到6 cm以下的沉积物;中营养负荷苦草组(MV)、高营养负荷苦草组(HV)根系增加不明显(分别为2.60和2.10 cm),影响深度主要在6 cm以内;检验发现,苦草组与对照组差异显著(P0.05)。交换态磷(Ex-P)、铝磷(Al-P)随深度增加而升高,苦草组小于对照组;铁磷(Fe-P),随深度的增加而降低,苦草组大于对照组,其中,在L、M、H中,苦草组的Ex-P分别比对照组下降了0.065、0.215和1.483 mg/kg,Al-P分别为1.198、2.040和2.390 mg/kg;LV中苦草的影响深度可达到10 cm的深,而MV、HV中主要集中在6 cm以内;苦草组中的Fe-P分别比对照组高8.135、16.689和8.598 mg/kg,在垂直方向上的变化幅度亦大于对照组。检验发现,L中苦草组Ex-P与对照组有极显著差异(P0.01),M、H苦草组与对照组无显著差异(P0.05);L、M、H中Al-P、FeP苦草组与对照组均无显著差异(P0.05)。     

连续提取和液体磷核磁共振表征太湖梅梁湾沉积物中磷的剖面分布

应用连续提取法(SMT)和液体磷核磁共振(³¹PNMR)技术研究了太湖北部梅梁湾沉积物中磷形态和组成的剖面变化。结果表明,铁/铝磷是沉积物中磷的主要形态,约占总磷含量的44.0-54.6%。总磷、无机磷、有机磷和铁/铝磷含量均随沉积深度增加呈降低趋势,至18cm以下略有增加,而钙磷却在柱样下部随沉积深度增加呈累积趋势。³¹PNMR显示,沉积物磷主要由正磷酸盐(72.0-99.2%)和磷酸单酯(0.8-25.9%)构成,磷酸二酯、膦酸盐和焦磷酸盐的相对含量非常低,分别为1.0%、0.4-1.0%和 0.1%。正磷酸盐含量在沉积物表层9cm内减少了65%,9cm以下波动变化,但总体呈降低趋势。这些特征表明沉积物中磷对梅梁湾上覆水体具有强烈的释放潜力,是太湖富营养化发生的重要因素。     

纳米银在水-沉积物中的迁移机制研究

为研究纳米银(Ag NPs)在水体中的迁移、水-沉积物中的分配及转化机制,采用武汉东湖湖水及沉积物开展模拟实验,以硝酸银(Ag NO3)为参照,研究了Ag NPs和聚乙烯吡咯烷酮包裹纳米银[Poly(vinylpyrrolidone)-coated silver nanoparticles(PVP-Ag NPs)]在上覆水中的沉降、在沉积物中的迁移和形态分布、以及扰动释放过程。结果表明,上覆水银初始浓度均为75 mg/L的Ag NO3、Ag NPs及PVP-Ag NPs在120h后分别为0.086、0.957和2.770 mg/L,显示纳米银和硝酸银进入水体后120h内大部分沉入沉积物中,且经过包裹的纳米银比未包裹的纳米银在水中停留时间稍长;60d后三种银均主要分布在表层沉积物中,Ag NO3体系银含量随深度的增加而逐渐降低,Ag NPs和PVP-Ag NPs体系银在2 cm以上随深度的增加而增高,随后逐渐降低,表明纳米银比硝酸银具有更强的迁移能力。此外,PVP-Ag NPs在2—3 cm层中的银含量占总量的24.6%,而Ag NPs在同一层中含量仅为2.6%,说明前者的迁移能力更强。在沉积物中,硫化物和有机物是银的主要结合相。释放实验结果表明,沉积物中纳米银的释放量远小于硝酸银的释放量,表明纳米银一旦与沉积物结合就难以再次释放。以上实验结果为评价纳米银的生态安全提供了科学依据。     

筑坝河流磷素的迁移转化及其富营养化特征

人类活动过量营养物质输入是导致河流富营养化的主要原因,而河道过度的人为调控则进一步复杂化了河流的营养状态变化。闸坝是河流人为调控的重要工程措施之一,提高水资源利用效率的同时严重干扰了河流自然的生物地球化学循环,产生诸多负面生态环境效应。磷素的迁移转化对河流的营养限制作用受到越来越多的关注,国内外已有研究在筑坝河流磷的富营养化特征方面,已经取得了较为深刻的认识:水库闸坝建设滞留大量磷素,导致河流水体磷含量升高、营养物质比例变化,沉积物储存过量磷素形成的内源释放威胁,以及进一步浮游植物和有害藻类的生长响应等,使得筑坝河流的富营养化生态风险升高;在此基础上,也提出了根据降雨分配和闸控库区储水,合理设置闸坝泄流方式,以改善筑坝河流富营养化生态风险的重要管理思路。对于闸坝调控作用与水体富营养化的定量关系还有待进一步的探讨,而且随着河流资源开发和人为调控力度的增强,河流闸坝建设所产生的系列生态环境问题日益严峻,对此提出还需要系统研究的方向:闸坝调控作用下河流磷素的富营养化机制及其与氮、碳等元素的耦合作用,筑坝河流沉积物内源污染的综合管理,以及闸控景观河流的生态建设和修复等。     

土壤环境中微塑料污染及迁移转化规律研究进展

作为一种新兴的污染物,微塑料在水和土壤生态系统中普遍存在,并成为了近年来环境污染研究的热点之一.目前研究主要集中在海洋和淡水生态系统中微塑料的检测、赋存、表征和毒理学等方面,但与水生态系统相比,对土壤生态系统中微塑料的生态效应的了解还很有限.为此,论文综述了土壤环境中微塑料的来源、丰度及分布特征、微塑料对土壤结构和生物...     

核磁共振技术在微生物代谢研究中的应用

介绍了核磁共振的种类,并结合具体实例阐述了核磁共振技术在微生物代谢研究领域的应用。主要包括在代谢工程、环境保护及生态学研究、以及人与动物健康几个方面的应用。     

镉在土壤-香根草系统中的迁移及转化特征

以无植物组处理为对照,采用盆栽试验方式探讨不同Cd浓度胁迫条件下香根草根际土壤中重金属Cd的积累、迁移及转化特征。土壤Cd处理设4个浓度梯度,分别为0、2、20、80 mg/kg土壤干重。结果表明:(1)香根草可以显著降低土壤中生物有效态Cd和总Cd含量。(2)香根草各部分Cd积累量随处理浓度的增加和处理时间的延长而增加,90 d时80 mg/kg处理组地上部分和根的Cd积累量分别高达180.42 mg/kg和241.54 mg/kg。(3)各浓度Cd处理下,富集系数随着Cd处理浓度的增加而显著降低,随处理时间的延长而升高。(4)香根草地上部分Cd含量小于根部,各处理转移系数均小于1。随着处理时间的延长,中低浓度处理组的转移系数稍有降低,高浓度处理组的转移系数则显著上升。(5)种植香根草使其根际土中残渣态的Cd转化为生物有效态Cd,提高Cd清除效率。研究结果表明,香根草能够有效地吸收土壤中的Cd,降低土壤中总Cd含量,提高土壤安全性,可作为Cd污染地区植物修复的备选物种。     

二维核磁共振谱在多糖结构研究中的应用

二维核磁共振谱（2D NMR）是获取多糖结构信息,尤其是在多糖序列分析方面的有力工具。本文重点介绍了在多糖结构解析中常用的几种2D NMR谱以及2D NMR解析多糖结构的方法。     

核磁共振技术在药物检测中的应用进展CSCD

核磁共振(nuclear magnetic resonance, NMR)技术已发展成为新化合物结构鉴定和天然产物药物分析不可缺少的工具。因其具有非破坏性和无侵入性等特点,广泛应用于药物领域,从合成产物的表征到生物系统分子结构和构象的测定以及分析分子间相互作用等研究都离不开这个工具。核磁共振能提供丰富且精确的结构信息,如拉莫尔频率、化学位移、自旋-自旋偶合、偶极偶合和弛豫时间等参数,成为结构解析的“金标准”。本文总结了核磁共振技术在药物发现、药物相互作用、药物代谢组学以及固态核磁共振技术在固态药物分析中的应用进展。     

核磁共振技术及其在生命科学中的应用

核磁共振（NMR）是一种不破坏样品的无损伤分析技术,是分子结构分析不可或缺的手段。随着新技术、新方法的不断发展,其研究领域和应用范围已扩展到了几乎所有的自然科学领域。本文简要介绍了核磁共振波谱技术的基本原理、多维NMR以及在结构鉴定、构象分析、医学临床检测、蛋白质组学、代谢组学等方面的应用。同时,本文还就№技术的发展前景提出了一些看法。     

Application of 31P nuclear magnetic resonance technology in the study of phosphorus fractions and their translocation and transformation in sediments: a review

Phosphorus (P) release from sediments is one of the most important causes of lake eutrophication, while the activity of P is determined by P chemical form. Due to its advantages in improving our knowledge about the P fractions in environmental samples, the 31P nuclear magnetic resonance (31P NMR) technology has received extensive attention. This paper summarized the current studies on the characterization, translocation, and transformation of P fractions in sediments by using this technology, and described the technical principles, classification, analytical procedures, and specific application fields of this technology. At present, the researches of sediment P by using 31P NMR technology were focused on the characterization of different P forms, the effects of microbes on the P translocation and transformation, and the quantitative analysis of different P fractions. The studies on the P-extracting agents and extraction methods were the hot topics as well. The potential issues and research trends about the application of 31P NMR technology in environmental samples were also discussed.     

31P nuclear magnetic resonance study of enzymatically phosphorylated glycophorin A

Glycophorin A was phosphorylated using protein kinases and the new protein was investigated using³¹P NMR spectroscopy. Most of these ～30 moles of phosphate were found to be attached to Ser and Thr. Some of these phosphate residues appear to be affected by the carbohydrate residues present. The phosphorylated protein appears to be in a severe state of aggregation, with the degree of aggregationpH-dependent.     

A quantitative study of organic phosphate-amine interaction by 31P nuclear magnetic resonance

Interactions between the phosphate group of 4-deoxypyridoxine 5′-phosphate and different protonated amines were quantitatively measured by means of {³¹P}-¹H nuclear magnetic double resonance technique combined with pD titration. An interaction of the phosphate group with added amine resulted in a measurable difference in the ³¹P chemical shift of these phosphate-containing samples with and without amine [Δδ(³¹P)]. Basic amino acids and biogenic amines had significant measurable Δδ(³¹P) values. No interactions were observed for acidic or neutral α, β and γ-amino acids.     

Intracellular pH in Dictyostelium discoideum: a 31P nuclear magnetic resonance study

We have used phosphorus-31 nuclear magnetic resonance to determine intracellular pH in the cellular slime mold Dictyostelium discoideum. We devised an air-lift circulator to maintain the dense cell suspensions in a well-oxygenated and well-stirred state while causing minimal perturbation to the sample flowing through the detector coils. Cells continued to develop normally in this set-up. Spectra acquired under these conditions typically show two peaks in the inorganic phosphate region corresponding to pH values of 7.16 +/- 0.03 and 6.48 +/- 0.02. These peaks are believed to represent the mitochondrial and cytosolic compartments respectively, based on a comparison of these values with published data and the collapse of the two compartments upon addition of the mitochondrial uncoupler carbonyl cyanide 4-(trifluoromethoxy)-phenylhydrazone. Dictyostelium cells show a remarkable degree of intracellular pH homeostasis. Both mitochondrial and cytosolic pH remained unchanged as extracellular pH was varied from 4.3 to 8.1. There was also no apparent change in the pH of either compartment after up to 13.5 hours' development in suspension.     

Use of 31P nuclear magnetic resonance spectroscopy and electron microscopy to study phosphorus metabolism of microorganisms from wastewaters

We used 31P nuclear magentic resonance to study the transfer of phosphorus between Pis and polyphosphates in microorganisms involved in wastewater treatment. We showed that the transfer process is reversible and of the first order in accordance with the polyphosphate concentration. The presence of nitrates in the anoxic phase led to results similar to those obtained during the aerobic phase. (Anoxic implies absence of oxygen but presence of nitrate, whereas anaerobic implies absence of oxygen and nitrate. In bacteriology, the term anoxic is not common, and the term anaerobic implies absence of oxygen and includes the conditions under which nitrate is present.) We observed that carbon dioxide lowers the pH, which entails a hydrolysis of polyphosphates, and helium seems to stop the evolution of the cells. Further, 2,4-dinitrophenol decouples the oxidative phosphorylation and brings about a decrease in the polyphosphate pool.     

Phosphorothioate analogues of 5-phosphoribosyl 1-diphosphate: 31P nuclear magnetic resonance study

31P nuclear magnetic resonance (NMR) has been used to study the 1-phosphorothioate analogues of 5-phosphoribosyl 1-diphosphate (P-Rib-PP). Comparison of the proton-decoupled spectra of 5-phosphoribosyl 1-O-(2-thiodiphosphate) (P-Rib-PP beta S) and the SP diastereomer of 5-phosphoribosyl 1-O-(1-thiodiphosphate) (P-Rib-PP alpha S) with the parent molecule revealed a characteristic large downfield chemical shift change for the resonance signal associated with the thiophosphate group (delta delta approximately 40-50 ppm) and an increase in the magnitude of the phosphate-thiophosphate spin-spin coupling constant (delta J alpha beta approximately 10 Hz). Both these changes are consistent with the observed effects of sulfur substitution on the behavior of the adenosine nucleotides, particularly ADP [Jaffe, E. K., & Cohn, M. (1978) Biochemistry 17, 652-657]. High-field 31P NMR has also been used to demonstrate the diastereomeric purity of P-Rib-PP alpha S (Sp diastereomer) and the greater lability of this analogue when compared with both P-Rib-PP beta S and P-Rib-PP. Sulfur substitution was found to cause a large decrease in the apparent pKa associated with the thiophosphate moiety of P-Rib-PP beta S (delta pKa approximately 1.4 units) and also to enhance the sensitivity of the thiophosphate chemical shift to protonation and, in particular, to Mg2+ binding, compared with P-Rib-PP. The potential application of the phosphorothioate analogues as probes of the reactions catalyzed by the phosphoribosyltransferase enzymes is discussed.     

31P nuclear magnetic resonance study of growth and dimorphic transition in Candida albicans

A 31P NMR study of the fungal pathogen Candida albicans was carried out. Yeast-form cells at different phases of growth, as well as germ tubes and hyphae were examined. In all cases, the NMR spectra showed well separated resonance peaks arising from phosphorus-containing metabolites, the most prominent being attributable to inorganic phosphate (Pi) polyphosphates, sugar phosphates and mononucleotides, NAD, ADP and ATP. Relevant signals were also detected in the phosphodiester region. The intensity of most signals, as measured relative to that of Pi, was clearly modulated both at the different phases of growth and during yeast-to-mycelium conversion, suggesting significant changes in the intracellular concentration of the corresponding metabolites. In particular, the intensity of the polyphosphate signal was high in exponentially growing, yeast-form cells, then progressively declined in the stationary phase, was very low in germ tubes and, finally, undetectable in hyphae. NMR spectral analysis of the Pi region showed that from early-stationary phase, Pi was present in two different cellular compartments, probably corresponding to the cytoplasm and the vacuole. From the chemical shift of Pi, the pH values of these two compartments could be evaluated. The cytoplasmic pH was generally slightly lower than neutrality (6.7-6.8), whereas the vacuolar pH was always markedly more acidic.     

Use of 31P nuclear magnetic resonance spectroscopy and electron microscopy to study phosphorus metabolism of microorganisms from wastewaters.

We used 31P nuclear magentic resonance to study the transfer of phosphorus between Pis and polyphosphates in microorganisms involved in wastewater treatment. We showed that the transfer process is reversible and of the first order in accordance with the polyphosphate concentration. The presence of nitrates in the anoxic phase led to results similar to those obtained during the aerobic phase. (Anoxic implies absence of oxygen but presence of nitrate, whereas anaerobic implies absence of oxygen and nitrate. In bacteriology, the term anoxic is not common, and the term anaerobic implies absence of oxygen and includes the conditions under which nitrate is present.) We observed that carbon dioxide lowers the pH, which entails a hydrolysis of polyphosphates, and helium seems to stop the evolution of the cells. Further, 2,4-dinitrophenol decouples the oxidative phosphorylation and brings about a decrease in the polyphosphate pool.     

Study of in vivo cellular metabolism by phosphorus 31 nuclear magnetic resonance

Phosphorus-31 nuclear magnetic resonance spectroscopy has been recently increasingly used to study cellular metabolism in a manner respecting the cell integrity. Intrinsic advantages of the phosphorus nucleus for in vivo NMR studies are discussed in this review together with some selected applications. A particular emphasis is layed on metabolite identification and quantitation (relative and absolute concentrations), the measurement of intracellular pH and the problem of cellular compartmentation. The determination of metabolite fluxes under normal and abnormal biological and physiological conditions, and the in vivo direct measurement by saturation transfer techniques of kinetic parameters for enzymatic reactions at equilibrium, are illustrated by several examples taken from the available literature and work carried out in this laboratory. Whenever possible, and appropriate, the NMR approach has been compared with other more classical techniques of investigation. The future and the potentialities of phosphorus-31 NMR study of intact biological systems, the clinical applications and the foreseeable interfacing with imaging techniques are evaluated. The concept of "functional imaging" versus "anatomic imaging" is proposed to illustrate the impact of this new technology in the understanding of cellular mechanisms, not only in the intact cell but also in whole tissues or organs after excision or in living animals and human.