Study the effects of metallic ions on the combination of DNA and histones with molecular combing technique

The effects of monovalent (Na^ , K^ ) and divalent (Mg^2 , Ca^2 , Mn^2 ) ions on the interaction between DNA and histone are studied using the molecular combing technique. λ-DNA molecules and DNA-histone complexes incubated with metal cations (Na^ , K^ , Mg^2 , Ca^2 , Mn^2 ) are stretched on hydrophobic surfaces, and directly observed by fluorescence microscopy. The results indicate that when these cations are added into the DNA solution, the fluorescence intensities of the stained DNA are reduced differently. The monovalent cations (Na^ , K^ ) inhibit binding of histone to DNA. The divalent cations (Mg^2 , Ca^2 , Mn^2 ) enhance significantly the binding of histone to DNA and the binding of the DNA-histone complex to the hydrophobic surface. Mn^2 also induces condensation and aggregation of the DNA- histone complex.     

Monitoring the binding of metal cations and histones to DNA in real time using fluorescence assays

The binding of cations (Na +,K +,Mg 2+,Ca 2+,Mn 2+) and histones to DNA can be studied using fluorescence assays.Here,we measured the fluorescence intensity and fluorescence anisotropy of DNA and DNA-histone complexes in the presence of cations.We demonstrate that when different cations are added into a DNA solution,the fluorescence intensities of the stained DNA are reduced by different amounts.Compared with divalent cations,monovalent cations had a weaker effect on fluorescence intensity and fluorescence anisotropy.Divalent (Mn 2+,Mg 2+,Ca 2+) cations markedly enhanced the fluorescence anisotropy of DNA.The binding modes of monovalent and divalent cations to DNA may be different.Divalent cations can change the structure of DNA molecules,or promote the assembly of DNA strands.The addition of histones causes DNA condensation,which mostly occurs during the first few seconds.Cation binding to DNA is abrupt,and is much faster than that of histones.     

Study of the interaction of DNA and histones by spin-stretching and droplet evaporation

Molecular combing is a powerful and simple method for aligning DNA molecules onto a surface. Using this technique combined with fluorescence microscopy, DNA-histone complexes are stretched on a hydrophobic polymethyl methacrylate (PMMA) surface and observed directly. We have developed a new method to stretch single DNA-histone complexes, termed spin-stretching. The results show that the histones markedly enhance DNA binding to the PMMA surface. DNA winds around the histones and therefore decreases in length. The number of histones that bind to each DNA molecule is found to correlate with the histone concentration. The combed DNA-histone complexes are found to depend on two factors: the binding force on the surface and the centrifugal force at its local position. Na+ ions should compete with histones for binding to DNA; however, the observed competitive binding effect of Na+ ions at low concentrations was negligible.     

Interaction of Divalent Metal Ions with the Adenosine Triphosphate Measured Using Nuclear Magnetic Resonance

Theinteractionofadenosinetriphosphatewithdivalentmetalionsisimportantinbiochemicalfunctions.TheintracellularfreeMg2 canbeestimated[1]byseparatingtheα-andβ-phosphatepeaksoftheATPNMR31PspectrumandbyknowingtheMgATPdissociationconstant.TheneedfordivalentmetalionsforallenzymaticreactionsinvolvingATPiswellknown,buttheroleofthemetalionsisnotclear[2].ThisstudywasconductedtoobtaininformationconcerningchangesinthestructureofadenosinetriphosphatecausedbyinteractionwithdivalentmetalionsMg2 ,Ca2 ,…     

基于色氨酸的生物受体合成与阳离子识别研究

以胺羧配体EDTA、DTPA作为二价模板框架,利用简便方法设计合成了以色氨酸为核心识别单元、含有苯丙氨酸的开链式结构生物受体,并利用荧光光谱和质谱等技术研究了受体与碱土金属离子(Ca2+、Ba2+、Mg2+)和过渡金属离子(Cu2+、Fe2+、Co2+、Ni2+、Mn2+、Zn2+、Cd2+)以及碱金属离子(Li+、Na+、K+)之间的相互作用.结果发现,在水溶液中金属离子与吲哚环之间存在相互作用,这两个受体对多种具有重要生物学和环境保护意义的金属离子有着良好的选择性识别作用.     

以金纳米粒子为探针研究二价金属离子与脂质双层膜的相互作用

采用一步法制备了二1-联十六烷醇磷酸氢酯(DHP)脂质双层膜保护的金纳米粒子,并以此为探针用紫外-可见吸收光谱法研究了二价金属离子Ca2+和Mg2+与金纳米粒子表面支撑的DHP双层膜之间的相互作用.结果表明,Ca2+和Mg2+能够促使DHP双层膜发生聚集、融合和倒塌,并且Ca2+的作用要强于Mg2+.     

用空气直接氧化游离二价锰离子制备高纯四氧化三锰

一定温度下,根据锰离子浓度变化严格控制溶液pH的条件下,研究了用空气直接氧化游离二价锰制备高纯四氧化三锰的新方法. 结果表明,碱式硫酸锰的氧化速度比氢氧化锰慢,碱式硫酸锰的包裹夹带是造成四氧化三锰产品中硫含量高的根本原因. 该法与用空气直接氧化锰的水解物制备四氧化三锰的方法相比较,前者能大幅度降低四氧化三锰产品中的钙、镁和硫含量,部分解决了锰盐氧化法制备四氧化三锰过程中钙、镁和硫分离的难题.     

面向生物医用的镁合金成分及凝固组织研究

通过对镁合金铸锭后显微组织的观察,结合SEM能谱分析,研究了Ca,Mn元素对镁合金组织的影响.研究发现,Mg-2.0Mn的显微组织是由基体组织(α-Mg)和点状析出的组织(α-Mn)组成;Mg-0.5Ca的显微组织是由(α-Mg)基体组织和非平衡结晶形成的Mg2Ca相组成.Ca,Mn对镁合金的组织均有细化作用,当同时加入Ca,Mn合金元素时,镁合金的显微组织会更加细小,晶粒趋于均匀圆整,同时第二相颗粒减少.其原因是:Ca提高了Mn与镁合金的润湿性,提高了Mn的溶解与扩散能力,温度降低Mn原子从合金中析出,为合金凝固提供了大量的晶核.     

多种金属离子对白蜡虫碱性磷酸酶活性的影响

研究了多种金属离子对白蜡虫碱性磷酸酶活性的影响。结果表明：Li^ ,Na^ ,K^ 对酶活力没有影响，Ca^2 ，Mg^2 ,Ba^2 ,Mn^2 ,Co^2 有激活作用；而Zn^2 ,Cu^2 ,Cd^2 ,Pb^2 有抑制作用，Ca^2 是有效的激活剂，表现为非竞争性激活效应，Cu^2 为有效的抑制剂，表现为非竞争性抑制效应，酶液经EDTA透析处理后活力完全丧失，失活的酶可用加入Zn^2 和Ca^2 复活。     

Ca_8Mg(SiO_4)_4Cl_2:Eu~(2+),Mn~(2+)绿色荧光粉的光谱性质

在还原气氛下采用高温固相反应法合成了白光LED用绿色荧光粉Ca8Mg(SiO4)4Cl2:Eu2 ,Mn2 .在荧光粉的制备过程中,加入过量的CaCl2有利于提高荧光粉的发射强度.从实验结果可以看出,在Ca8Mg(SiO4)4Cl2基质中Eu2 -Mn2 间存在着能量传递,Mn2 的发射是来源于Eu2 的能量传递,能量传递的方式可能是共振传递.     

赤楠叶二氯甲烷部位、乙酸乙酯部位抗氧化活性的比较研究

通过测定1,1-二苯基-2-苦基肼(1,1-Diphenyl-2-picrylhydrazyl,DPPH)自由基清除率、还原力、金属离子对其抗氧化活性的影响及总酚质量分数等比较赤楠叶二氯甲烷部位、乙酸乙酯部位的抗氧化活性。结果表明:赤楠叶二氯甲烷部位、乙酸乙酯部位清除DPPH的EC50为0.63、0.10 mg/m L;还原力的EC50分别为0.87、0.09 mg/m L。除Al~(3+)、Fe~(3+)外,K~+、Na~+、Mn~(2+)、Mg~(2+)、Cu~(2+)、Zn~(2+)、Ca~(2+)等金属离子对赤楠叶乙酸乙酯部位的DPPH清除作用为抑制作用;除Cu~(2+)、Ca~(2+)外,K~+、Na~+、Mn~(2+)、Mg~(2+)、Al~(3+)、Zn~(2+)、Fe~(3+)等金属离子对赤楠叶二氯甲烷部位的DPPH清除能力有促进作用。赤楠叶二氯甲烷部位、乙酸乙酯部位的总酚质量分数分别为9.23%与59.17%。可见,赤楠叶乙酸乙酯部位具有较强的抗氧化活性与总酚含量,但其抗氧化活性较易受金属离子的拮抗作用。     

用于细胞内自由［Ca~（2＋）］测定的新萤光试剂Fura－2AM的合成、性能及应用研究

用于细胞内自由［Ｃａ２＋］生理作用规律研究的新强萤光试剂Ｆｕｒａ－２ＡＭ已由十七步合成成功。与过去广泛使用的该类试剂相比，其萤光强度高几十倍，对［Ｃａ２＋］亲和力稍弱，对镁和其它二价离子的选择性更好，特别是结合［Ｃａ２＋］后波长发生移动。这些优点使它成为目前最重要的特别是测定单细胞中［Ｃａ２＋］的萤光试剂之一。     

非金属夹杂物对弹簧钢局部腐蚀的影响

Certain inclusions in high-strength 60Si2Mn–Cr spring steel result in poor resistance to localized corrosion. In this work, to study the effect of inclusions on the localized corrosion behavior of spring steel, accelerated corrosion tests were performed by immersing spring steel in 3wt% FeCl₃ solution for different times. The results show that severe corrosion occurred in areas of clustered CaS inclusions. Sulfide inclusions containing Ca and Mg induced the strongest localized corrosion susceptibility. For the case of (Ca,Mn,Mg)S inclusions, the ability to induce localized corrosion susceptibility is ranked as follows: MgS > CaS > MnS. Moreover, CaS, (Ca,Mn)S, and (Ca,Mn,Mg)S inclusions were mainly responsible for inducing environmental embrittlement.     

EFFECT OF METAL IONS ON THE LACCASE ACTIVITY

The effects of five metal ions(Fe2+、Ca2+、Mg2+、Mn2+、Cu2+) on ABTS oxidation catalyzed by laccase were studied under condition of pH=4.5 by spectrophotometer. The results show that Fe2+ ion has obvious effect on the activity and the nature of inhibition is competitive type. It is found that the inhibition is realized through the reduction ofABTS.by Fe2+ ion. Other metal ions have slight influence on laccase activity.     

微波消解-火焰原子吸收法测定傣药铁刀木叶中5种金属元素

采用微波密闭消解系统对傣药铁刀木(Cassia siamea)叶进行消解,在最佳工作条件下使用火焰原子吸收分光光度计,并用标准曲线法测定铁刀木叶中钙、铜、锰、钠、镁5种金属元素的含量.实验表明,5种金属元素的含量有所不同,钙的含量最高,铜的含量最低.方法检出限均小于0.003 5μg/mL,加标回收率在96.28%～102.8%之间,相对偏差RSD≤2.13%,结果表明实验准确度和精密度符合实验要求,也为傣药铁刀木叶的有效成分研究提供一定的科学依据.     

野生毛樱桃生长期矿质营养含量变化与果实生长的关系

研究了野生毛樱桃生长期果实生长与叶果中7种矿质营养元素(Cu,Zn,Fe,Mn．Ca,Mg,K)的含量变化及其相关关系。结果表明,果实中Cu,Zn,Fe,Mn,Ca,Mg元素含量与果实生长呈负相关,其中Zn,Mg元素达显著水平;叶片中Cu,Zn,Fe,Mn,K元素含量与果实生长呈负相关,其中K元素达显著水平．叶片中Ca,Mg元素与果实生长呈正相关,其中Ca元素达显著水平。果实中各营养元素(除K外)生长期变化相互间均达极显著正相关。叶片中Ca与Mg元素呈极显著正相关;Zn,K均与Ca,Mg元素呈极显著负相关;Cu与Ca元素呈显著负相关;K与Zn,Cu元素呈显著正相关;Zn与Cu,Mn元素均呈显著正相关。叶片和果实中矿质营养元素间相关性均不显著。     

Ca_8Mg(SiO_4)_4Cl_2:Ce~(3 ),Eu~(2 )的光致发光特性

对Ca8Mg（SiO4）4Cl2:Ce3 ,Eu2 系列荧光粉进行合成与测试,探讨Ca8Mg（SiO4）4Cl2：Ce3 ,Eu2 中Ce3和Eu2 之间的相互作用,初步判断Ca8Mg（SiO4）4Cl2：Ce3 ,Eu2 中Ce3 →Eu2 的能量传递主要是电偶极-偶极相互作用的结果.     

LTRPC7 is a Mg.ATP-regulated divalent cation channel required for cell viability

The molecular mechanisms that regulate basal or background entry of divalent cations into mammalian cells are poorly understood. Here we describe the cloning and functional characterization of a Ca2+- and Mg2+-permeable divalent cation channel, LTRPC7 (nomenclature compatible with that proposed in ref. 1), a new member of the LTRPC family of putative ion channels. Targeted deletion of LTRPC7 in DT-40 B cells was lethal, indicating that LTRPC7 has a fundamental and nonredundant role in cellular physiology. Electrophysiological analysis of HEK-293 cells overexpressing recombinant LTRPC7 showed large currents regulated by millimolar levels of intracellular Mg.ATP and Mg.GTP with the permeation properties of a voltage-independent divalent cation influx pathway. Analysis of several cultured cell types demonstrated small magnesium-nucleotide-regulated metal ion currents (MagNuM) with regulation and permeation properties essentially identical to the large currents observed in cells expressing recombinant LTRPC7. Our data indicate that LTRPC7, by virtue of its sensitivity to physiological Mg.ATP levels, may be involved in a fundamental process that adjusts plasma membrane divalent cation fluxes according to the metabolic state of the cell.     

湖南邵东地产黄花菜中微量元素的分析

本文采用火焰原子吸收分光光度法测定了湖南邵东地产黄花菜中的钙、镁、锌、铜、铁、锰、硒,铬、镉九种微量元素的含量,钙、镁、锌、铜、铁、锰、硒,铬、镉含量分别为4630.3841、250.310、27.352、4.931、165.304、13.732、0.2223、.1021、.520μg/g,含量大小是Ca>Mg>Fe>Zn>Mn>Cu>Cr>Cd>Se.结果表明钙含量最高,镁、锌、铜、铁、锰、铬、镉含量次之,硒含量最低.邵东地产黄花菜中含有较丰富的微量元素,有很大的开发价值.     

金属离子对纤维素碱性降解影响的初步研究

以纤维素二糖、微晶纤维素及脱脂棉作为纤维素模型物,分别考察K+、Mg2+和Ca2+对纤维素碱性降解性能的影响.结果表明:金属离子的种类、用量及反应时间均会影响纤维素的碱性降解.K+对纤维素碱性降解有促进作用,Mg2+和Ca2+则会抑制纤维素碱性降解反应;并且随着金属离子用量的增加及反应时间的延长,K+的促进作用及Mg2+、Ca2+的抑制作用愈加明显.