Some pitfalls in PAGE-LA-ICP-MS for quantitative elemental speciation of dissolved organic matter and metalomics

An experimental approach to evaluate the capabilities and limitations of polyacrylamide gel electrophoresis (PAGE) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for quantitative elemental speciation is presented. Two metalloproteins (superoxide dismutase, containing Cu and Zn, and thyroglobulin, containing I) with high binding affinity for metals, and metal-dissolved organic matter (DOM) complexes (from a compost leachate sample) which show different types of metal binding are studied. Iodine can be quantitatively detected in thyroglobulin after PAGE-LA-ICP-MS using either sodium dodecyl sulfate (SDS) PAGE or native PAGE. However, detection of Cu and Zn in superoxide dismutase after PAGE-LA-ICP-MS depends on the conditions of the PAGE method because possible metal losses can occur (either with SDS-PAGE or with native PAGE). The use of PAGE-LA-ICP-MS to study the contribution of DOM to the mobilization of metals from environmental samples is possible, but it depends also on the PAGE separation conditions owing to disequilibrium effects of metal-DOM complexes. Presented at the 4th International Conference on Trace Element Speciation in Biomedical, Nutritional and Environmental Sciences, 25–29 May 2008, Munich-Neuherberg, Germany.     

Preparation and characterization of monoliths covalently bonded chelating groups for capillary electrochromatographic separation of metal ions

In this work, a novel polymer-based monolithic column was prepared using an o-phthalaldehyde-l-phenylalanine Schiff base complex as the reactive center and a mixture of methanol and n-propanol as the porogen. The monolithic column was employed for the separation of a metal ion mixture including Pb(II), Mn(II), Cu(II), Ni(II), Cr(III), Fe(III) and Cr(VI). Tetrabutylammonium bromide (TBAB) was used as a mobile phase additive to enhance the separation efficiency of metal ions by EDTA precomplexation. Using a phosphate buffer (20 mM, pH 3.0), TBAB (10 mM), MeOH (15%, v/v), an applied voltage of −15 kV, and detection at 220 nm, the metal ion mixture was satisfactorily resolved. The average theoretical plate number was 17,900 plates/m. The separation was also carried out in the absence of TBAB, leading to dissimilar elution order and shorter retention time. The separation behavior of the monolithic column was also compared with that of the blank polymer. The unique properties of the monolithic column might be mediated by a combination of electrophoretic behavior and chromatographic retention involving hydrophobic and hydrophilic interactions, as well as ligand exchange.     

Synthesis, crystal structure, electrochemistry and studies on protein binding, antioxidant and biocidal activities of Ni(II) and Co(II) hydrazone complexes

Bivalent transition metal hydrazone complexes of the composition [Ni(L₁)₂] (1), [Co(L₁)₂] (2), [Ni(L₂)₂] (3) and [Co(L₂)₂] (4) have been synthesised from the reactions of [MCl₂(PPh₃)₂] (where M = Ni or Co) with hydrazones derived from 2-acetyl pyridine and carboxylic acid hydrazides of benzhydrazide (HL₁) or thiophene-2-carboxylic acid hydrazide (HL₂), respectively. Structure of the ligands HL₁ and HL₂ and their corresponding complexes with Ni(II) and Co(II) ions were proposed based on the elemental analysis, infrared and ¹H NMR spectral methods. Single crystal X-ray diffraction study of complex 1 revealed a distorted octahedral geometry around the metal ion provided by two units of the ligand. To explore the potential medicinal value of the new complexes, binding interaction of all the complexes with bovine serum albumin (BSA) was studied at normal physiological conditions using fluorescence and UV-Vis spectral techniques. The number of binding sites (n) and binding constant (K_a) were calculated according to the double logarithm regression equation. The results of synchronous fluorescence spectrum showed that binding of metal hydrazones with BSA induced conformational changes in BSA. The in vitro antioxidant and antimicrobial potentials of the new chelates were also carried out.     

金属串配合物[Cr3(dpa)4LL'](dpa=dipyridylamide; L,L'=Cl,BF4, CCPh)的Cr-Cr成键特性

采用密度泛函理论UBP86方法计算了Cr₃(dpa)₄Cl₂ (1)、Cr₃(dpa)₄(BF₄)₂ (2)、Cr₃(dpa)₄Cl(BF₄) (3)、Cr₃(dpa)₄(CCPh)₂ (4)和Cr₃(dpa)₄Cl(CCPh) (5)金属串配合物的结构, 并对配合物的构型、Cr—Cr键的本质以及轴向配体对Cr—Cr键的影响进行了研究. 结果表明: (1) Cr—Cr平均键长较长的配合物趋于形成对称构型, 较短时趋于形成非对称构型. 最稳定的五重态的Cr—Cr平均键长最长, 故优化时趋于形成对称构型; 七重态的Cr—Cr平均键长最短, 趋于形成非对称构型; (2) 五重态的Cr₃⁶⁺金属链均存在三中心三电子σ键, 含弱σ给电子轴向配体BF₄^-的2和3的Cr—Cr短键还具有弱的π相互作用. 七重态下, 对称构型的4中仅有三中心三电子σ键, 而非对称构型的1-3、5的Cr—Cr短键为三重键, 非对称构型仍具有Cr₃⁶⁺链的σ离域作用, 仍具有分子导线的潜在应用; (3) 轴向配体L与Cr的作用主要表现为n_L→4_sCr或n_L→3_dz²Cr离域, 较强的σ给电子配体CCPh^-还存在σ_C—C→4_sCr离域. Cr与L的结合强度为2＜3＜1＜5＜4, CCPh^-与Cr的结合最强, 使Cr—Cr键减弱、Cr—Cr距离增长, 故4的各自旋重态均为对称构型.     

Electrochemistry of and Redox‐Induced Metal Release from Metallothioneins at a Nafion‐Coated Bismuth Film Electrode

Nafion‐coated bismuth film electrodes (NCBiFEs) were used to investigate the redox behavior of and metal release from rabbit liver metallothioneins (MTs) in an acetate buffer. Owing to the permselective exchange between positively charged MT molecules and cations in Nafion and the absence of detectable MT adsorption at bismuth surface, a diffusion‐controlled Nernstian redox wave of MTs (E_pc=?0.869 V) was observed for the first time. The Nernstian behavior of the diffusing MTs is in contrast to the voltammetric responses of MTs at thin mercury films or Nafion‐coated mercury film electrodes, which either result in the replacement of the metals originally present in MTs by mercury or lead to a noticeable MT adsorption. By avoiding these undesirable features, the NCBiFE provides an excellent milieu for voltammetric studies of different types of MTs and related isoforms, paving the way for studying the redox‐modulated metal transfer of MTs and understanding the biological role of MTs in heavy metal detoxification and essential metal regulations.     

Peculiarities in the Raman spectra of ZrB12 and LuB12 single crystals

We have measured Raman spectra of high-quality Zr^natB₁₂, Lu^natB₁₂ and Lu¹¹B₁₂ single crystals with high resolution, and the observed strong peaks are attributed to specific vibration modes. Besides, there are a number of additional Raman peaks in spectral ranges, where only Raman-inactive vibrations of the atomic arrangement are expected. Accordingly, it is assumed, that the investigated crystals contain intrinsic structural imperfections or distortions in sufficient concentration and efficiency to initiate the observed breaking of phonon selection rules. We suppose boron vacancies, boron isotope effects and displacements of the metal atoms to be reasons for such imperfections.     

Synthesis of uniform-sized bimetallic iron–nickel phosphide nanorods

We synthesized uniform-sized nanorods of iron–nickel phosphides from the thermal decomposition of metal–phosphine complexes. Uniform-sized (Fe_xNi_1−x)₂P nanorods (0x1) of various compositions were synthesized by thermal decomposition of Ni–trioctylphosphine (TOP) complex and Fe–TOP complex. By measuring magnetic properties, we found that blocking temperature and coercive field depend on Ni content in the nanorods. Both parameters were more sensitive to doping compared with bulk samples.     

官能化罗丹明基金属阳离子荧光探针

重金属离子对环境和生物体具有极强的生理毒性,故高选择性和高灵敏度的离子检测荧光探针的研究有着重要意义。荧光分子探针在表达分子间识别行为以及复杂的环境、生命体系的内状态信息方面具有优异的性能,已广泛深入的用于构建新型功能性探针分子。本文综述了近年来基于罗丹明的金属阳离子如Hg₂₊、Cu₂₊、Fe₃₊等荧光分子探针的研究进展,包括探针的结构特征、检测机理、检测水平,更重要的是其在环境检测、生物成像、分子器件等方面的新应用,并对荧光探针所面临的问题和发展前景做了分析。     

Silicene,a promising new 2D material

Silicene is emerging as a two-dimensional material with very attractive electronic properties for a wide range of applications; it is a particularly promising material for nano-electronics in silicon-based technology. Over the last decade, the existence and stability of silicene has been the subject of much debate. Theoretical studies were the first to predict a puckered honeycomb structure with electronic properties resembling those of graphene. Though these studies were for free-standing silicene, experimental fabrication of silicene has been achieved so far only through epitaxial growth on crystalline surfaces. Indeed, it was only in 2010 that researchers presented the first experimental evidence of the formation of silicene on Ag(1 1 0) and Ag(1 1 1), which has launched silicene in a similar way to graphene. This very active field has naturally led to the recent growth of silicene on Ir(1 1 1), ZrB₂(0 0 0 1) and Au(1 1 0) substrates. However, the electronic properties of epitaxially grown silicene on metal surfaces are influenced by the strong silicene–metal interactions. This has prompted experimental studies of the growth of multi-layer silicene, though the nature of its “silicene” structure remains questionable. Of course, like graphene, synthesizing free-standing silicene represents the ultimate challenge. A first step towards this has been reported recently through chemical exfoliation from calcium disilicide (CaSi₂). In this review, we discuss the experimental and theoretical studies of silicene performed to date. Special attention is given to different experimental studies of the electronic properties of silicene on metal substrates. New avenues for the growth of silicene on other substrates with different chemical characteristics are presented along with foreseeable applications such as nano-devices and novel batteries.     

Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

Hydrogen(H)-bond dynamics are involved in many elementary processes in chemistry and biology. Because of its fundamental importance, a variety of experimental and theoretical approaches have been employed to study the dynamics in gas, liquid, solid phases, and their interfaces. This review describes the recent progress of direct observation and control of H-bond dynamics in several model systems on a metal surface by using low-temperature scanning tunneling microscopy (STM). General aspects of H-bond dynamics and the experimental methods are briefly described in chapter 1 and 2. In the subsequent four chapters, I present direct observation of an H-bond exchange reaction within a single water dimer (chapter 3), a symmetric H bond (chapter 4) and H-atom relay reactions (chapter 5) within water–hydroxyl complexes, and an intramolecular H-atom transfer reaction (tautomerization) within a single porphycene molecule (chapter 6). These results provide novel microscopic insights into H-bond dynamics at the single-molecule level, and highlight significant impact on the process from quantum effects, namely tunneling and zero-point vibration, resulting from the small mass of H atom. Additionally, local environmental effect on H-bond dynamics is also examined by using atom/molecule manipulation with the STM.