Factors governing the substitution of La3+ for Ca2+ and Mg2+ in metalloproteins: a DFT/CDM study

Trivalent lanthanide cations are extensively being used in biochemical experiments to probe various dication-binding sites in proteins; however, the factors governing the binding specificity of lanthanide cations for these binding sites remain unclear. Hence, we have performed systematic studies to evaluate the interactions between La3+ and model Ca2+ - and Mg2+ -binding sites using density functional theory combined with continuum dielectric methods. The calculations reveal the key factors and corresponding physical bases favoring the substitution of trivalent lanthanides for divalent Ca2+ and Mg2+ in holoproteins. Replacing Ca2+ or Mg2+ with La3+ is facilitated by (1) minimizing the solvent exposure and the flexibility of the metal-binding cavity, (2) freeing both carboxylate oxygen atoms of Asp/Glu side chains in the metal-binding site so that they could bind bidentately to La3+, (3) maximizing the number of metal-bound carboxylate groups in buried sites, but minimizing the number of metal-bound carboxylate groups in solvent-exposed sites, and (4) including an Asn/Gln side chain for sites lined with four Asp/Glu side chains. In proteins bound to both Mg2+ and Ca2+, La3+ would prefer to replace Ca2+, as compared to Mg2+. A second Mg2+-binding site with a net positive charge would hamper the Mg2+ --> La3+ exchange, as compared to the respective mononuclear site, although the La3+ substitution of the first native metal is more favorable than the second one. The findings of this work are in accord with available experimental data.     

Effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) and water coordination on the structure of glycine and zwitterionic glycine

Interactions between metal ions and amino acids are common both in solution and in the gas phase. Here, the effect of metal ions and water on the structure of glycine is examined. The effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) and water on structures of Gly.Mn+(H2O)m and GlyZwitt.Mn+(H2O)m (m = 0, 2, 5) complexes have been determined theoretically by employing the hybrid B3LYP exchange-correlation functional and using extended basis sets. Selected calculations were carried out also by means of CBS-QB3 model chemistry. The interaction enthalpies, entropies, and Gibbs energies of eight complexes Gly.Mn+ (Mn+ = Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) were determined at the B3LYP density functional level of theory. The computed Gibbs energies DeltaG degrees are negative and span a rather broad energy interval (from -90 to -1100 kJ mol(-1)), meaning that the ions studied form strong complexes. The largest interaction Gibbs energy (-1076 kJ mol(-1)) was computed for the NiGly2+ complex. Calculations of the molecular structure and relative stability of the Gly.Mn+(H2O)m and GlyZwitt.Mn+(H2O)m (Mn+ = Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+; m = 0, 2, and 5) systems indicate that in the complexes with monovalent metal cations the most stable species are the NO coordinated metal cations in non-zwitterionic glycine. Divalent cations Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+ prefer coordination via the OO bifurcated bonds of the zwitterionic glycine. Stepwise addition of two and five water molecules leads to considerable changes in the relative stability of the hydrated species. Addition of two water molecules at the metal ion in both Gly.Mn+ and GlyZwitt.Mn+ complexes reduces the relative stability of metallic complexes of glycine. For Mn+ = Li+ or Na+, the addition of five water molecules does not change the relative order of stability. In the Gly.K+ complex, the solvation shell of water molecules around K+ ion has, because of the larger size of the potassium cation, a different structure with a reduced number of hydrogen-bonded contacts. This results in a net preference (by 10.3 kJ mol(-1)) of the GlyZwitt.K+H2O5 system. Addition of five water molecules to the glycine complexes containing divalent cations Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+ results in a net preference for non-zwitterionic glycine species. The computed relative Gibbs energies are quite high (-10 to -38 kJ mol(-1)), and the NO coordination is preferred in the Gly.Mn+(H2O)5 (Mn+ = Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) complexes over the OO coordination.     

The liquidlike ordering of lipid A-diphosphate colloidal crystals: the influence of Ca2+, Mg2+, Na+, and K+ on the ordering of colloidal suspensions of lipid A-diphosphate in aqueous solutions

A comprehensive study was performed on electrostatically stabilized aqueous dispersion of lipid A-diphosphate in the presence of bound Ca2+, Mg2+, K+, and Na+ ions at low ionic strength (0.10-10.0-mM NaCl, 25 degrees C) over a range of volume fraction of 1.0 x 10(-4)< or =phi< or =4.95 x 10(-4). These suspensions were characterized by light scattering (LS), quasielastic light scattering, small-angle x-ray scattering, transmission electron microscopy, scanning electron microscopy, conductivity measurements, and acid-base titrations. LS and electron microscopy yielded similar values for particle sizes, particle size distributions, and polydispersity. The measured static structure factor, S(Q), of lipid A-diphosphate was seen to be heavily dependent on the nature and concentration of the counterions, e.g., Ca2+ at 5.0 nM, Mg2+ at 15.0 microM, and K+ at 100.0 microM (25 degrees C). The magnitude and position of the S(Q) peaks depend not only on the divalent ion concentration (Ca2+ and Mg2+) but also on the order of addition of the counterions to the lipid A-diphosphate suspension in the presence of 0.1-microM NaCl. Significant changes in the rms radii of gyration (R2G) 1/2 of the lipid A-diphosphate particles were observed in the presence of Ca2+ (24.8+/-0.8 nm), Mg2+ (28.5+/-0.7 nm), and K+ (25.2+/-0.6 nm), whereas the Na+ salt (29.1+/-0.8 nm) has a value similar to the one found for the de-ionized lipid A-diphosphate suspensions (29.2+/-0.8 nm). Effective particle charges were determined by fits of the integral equation calculations of the polydisperse static structure factor, S(Q), to the light-scattering data and they were found to be in the range of Z*=700-750 for the lipid A-diphosphate salts under investigation. The light-scattering data indicated that only a small fraction of the ionizable surface sites (phosphate) of the lipid A-diphosphate was partly dissociated (approximately 30%). It was also discovered that a given amount of Ca2+ (1.0-5.0 nM) or K+ (100 microM) influenced the structure much more than Na+ (0.1-10.0-mM NaCl) or Mg2+ (50 microM). By comparing the heights and positions of the structure factor peaks S(Q) for lipid A-diphosphate-Na+ and lipid A-diphosphate-Ca2+, it was concluded that the structure factor does not depend simply on ionic strength but more importantly on the internal structural arrangements of the lipid A-diphosphate assembly in the presence of the bound cations. The liquidlike interactions revealed a considerable degree of ordering in solution accounting for the primary S(Q) peak and also the secondary minimum at large particle separation. The ordering of lipid A-diphosphate-Ca2+ colloidal crystals in suspension showed six to seven discrete diffraction peaks and revealed a face-centered-cubic (fcc) lattice type (a=56.3 nm) at a volume fraction of 3.2 x 10(-4)< or =phi< or =3.9 x 10(-4). The K+ salt also exhibited a fcc lattice (a=55.92 nm) at the same volume fractions, but reveals a different peak intensity distribution, as seen for the lipid A-diphosphate-Ca2+ salt. However, the Mg2+ and the Na+ salts of lipid A-diphosphate showed body-centered-cubic (bcc) lattices with a=45.50 nm and a=41.50 nm, respectively (3.2 x 10(-4)< or =phi< or =3.9 x 10(-4)), displaying the same intensity distribution with the exception of the (220) diffraction peaks, which differ in intensity for both salts of lipid A-diphosphate.     

高锰酸钾-鲁米诺反应体系中碱土金属离子Mg2+,Ca2+,Sr2+,Ba2+化学发光行为研究

将被认为没有化学发光活性的第二主族(碱土金属)离子Mg^2 ,Ca^2 ,Sr^2 ,Ba^2 溶液注入到已充分反应的高锰酸钾与鲁米诺混合液中时,又发生了新的化学发光反应,并检测到强的化学发光信号．在对有关反应的动力学性质、化学发光光谱、紫外可见光谱及其它一系列实验研究的基础上,提出了可能的化学发光反应机理．同时,优化了反应条件,评价了这一反应用于Mg^2 ,Ca^2 ,Sr^2 ,Ba^2 分析的可行性．     

Effects of Ca2+, Zn2+ and Cd2+ on uridine diphosphate-glucuronyltransferase and beta-glucuronidase activities in rat liver microsomes

The effect of various metals on uridine diphosphate (UDP)-glucuronyltransferase and beta-glucuronidase activities in rat liver microsomes was investigated. The presence of Mn2+, Cd2+, Zn2+, V5+, Ni2+, Co2+, Cu+ or Ca2+ (20 microM) in the enzyme reaction mixture did not cause a significant alteration of UDP-glucuronyltransferase activity in hepatic microsomes. Of these metals, Zn2+ and Cd2+ (20 microM) caused a remarkable increase in hepatic microsomal beta-glucuronidase activity. Appreciable effects of Zn2+ and Cd2+ on beta-glucuronidase activity were seen at 5.0 microM, and the effects were saturated at 50 microM. Ca2+ (5.0-50 microM) and/or the Ca2(+)-binding protein regucalcin (2.0 microM) did not have an appreciable effect on UDP-glucuronyltransferase and beta-glucuronidase activities in hepatic microsomes. Thus, Zn2+ and Cd2+ uniquely increased beta-glucuronidase activity. The Zn2(+)- and Cd2(+)-induced increase in beta-glucuronidase activity was completely reversed by the presence of an SH group-protecting reagent (dithiothreitol). The response of the microsomal enzyme to Zn2+ and Cd2+ (20 microM) was no longer seen after treatment with 0.2% Triton X-100 [polyoxyethylene(10)octylphenyl ether], indicating that the stimulation by these metals is dependent on membrane association. The present study suggests that, of various metals tested, Zn2+ and Cd2+ can uniquely increase hepatic microsomal beta-glucuronidase activity and that their effect is based on binding to membranous SH groups, beside the enzyme protein.     

土壤颗粒表面电场作用下固-液界面Mg2+-K+与Ca2+-K+交换动力学的比较研究

通过恒流法研究了不同表面电场作用下Mg2+、Ca2+吸附动力学. 结果发现: (1)实验初期阶段是强静电力作用下的零级动力学过程和一定反应时间后的弱静电力作用下的一级动力学过程, 且零级速率过程和一级速率过程之间存在明显的转折点; (2)不同电解质构成中Ca2+的吸附速率明显快于Mg2+的, 平衡吸附量也大于Mg2+的, 且Ca2+在土壤颗粒表面的覆盖度比Mg2+在土壤颗粒表面的覆盖度高; (3)离子的相对有效电荷系数与土壤颗粒表面电场作用的不同是各体系中Ca2+、Mg2+吸附动力学有差别的根本原因; (4)根据离子吸附的理论模型可以分别计算出速率系数、平衡吸附量、离子在土壤颗粒表面的覆盖度以及固定液的体积, 这些参数可以定量评估土壤颗粒表面电场对离子吸附动力学的影响.     

Simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ by using second-derivative spectrophotometry method

A new method of simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ is proposed here by using the second-derivative spectrophotometry method. In pH=10.35 Borax-NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal-porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0-0.60, 0-0.60, 0-0.40, 0-0.80 and 0-0.48 μg mL(-1) for Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+, respectively. The molar absorptivity of these color systems were 1.38×10(5), 1.01×10(5), 3.24×10(5), 1.07×10(5) and 1.29×10(5)Lmol(-1)cm(-1). The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results.     

Activation of hepatic microsomal Ca2+-adenosine triphosphatase by calcium-binding protein regucalcin

The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on Ca2+-adenosine triphosphatase (ATPase) activity in hepatic microsomes was investigated. Mg2+-ATPase activity was clearly increased by the presence of 50 microM Ca2+. Regucalcin (1.0-4.0 microM) caused a remarkable elevation (about 3-fold) of Ca2+-ATPase activity. Also, Mg2+-ATPase activity was increased (about 1.6-fold) by the presence of regucalcin (2.0 and 4.0 microM). Guanosine-5'-O-(3-thiotriphosphate) (GTPrs; 10(-5) and 10(-4) M) and nicotinamide adenine dinucleotide phosphate oxidized form (NADP+; 10(-5) to 10(-3) M) or reduced form (NADPH; 10(-4) and 10(-3) M) significantly increased Ca2+-ATPase activity. These increases were not enhanced by the presence of regucalcin (2.0 microM). Of various metal ions, a comparatively low concentration of V5+ (10(-5) M) or Cd2+ (10(-6) M) significantly increased Ca2+-ATPase activity, while Hg2+, Zn2+, Cu2+ and Mn2+ did not have such an effect. Regucalcin (2.0 microM) did not enhance the effect of V5+ and Cd2+ on Ca2+-ATPase activity. The present finding, that regucalcin activates hepatic microsomal Ca2+-ATPase, suggests a cell physiological role of regucalcin as an activator in the microsomal Ca2+-pump activity. This action of regucalcin may not be influenced by other regulators.     

离子色谱法测定尿液中的C2O42-、Ca2+、Mg2+

利用离子色谱法测定尿液中的草酸根、钙、镁离子：测定草酸根时，先在尿液中加入氯化钙使之转化成草酸钙沉淀，分离后用盐酸溶解草酸钙沉淀，然后进行测定测定钙、镁离子时，在酸性尿液中加入氧化剂过硫酸钾，在微沸状态下氧化尿液中的有机物，从而避免对色谱柱的污染：草酸根、钙、镁离子的回收率分别为108．3％～109．7％、94．9％～100．7％、97．2％～97.4％，相对标准偏差分别为2．4％、2.5％、3．1％。     

Selective 226Ra2+ ionophores provided by self-assembly of guanosine and isoguanosine derivatives

The self-assembled guanosine (G 1)-based hexadecamers and isoguanosine (isoG 2)-based decamers are excellent 226Ra2+ selective ionophores even in the presence of excess alkali (Na+, K+, Rb+, and Cs+) and alkaline earth (Mg2+, Ca2+, Sr2+, and Ba2+) cations over the pH range 3-11. G 1 requires additional picrate anions to provide a neutral assembly, whereas the isoG 2 assembly extracts 226Ra2+ cations without any such additives. Both G 1-picrate and isoG 2 assemblies show 226Ra2+ extraction even at a 0.35 x 10(6) fold excess of Na+, K+, Rb+, Cs+, Mg2+, or Ca2+ (10(-2) M) to 226Ra2+ (2.9 x 10(-8) M) and at a 100-fold salt to ionophore excess. In the case of the G 1-picrate assembly, more competition was observed from Sr2+ and Ba2+, as extraction of 226Ra2+ ceased at an M2+/226Ra2+ ratio of 10(6) and 10(4), respectively. With the isoG 2 assembly, 226Ra2+ extraction also occurred at a Sr2+/226Ra2+ ratio of 10(6) but ceased at a 10(6) excess of Ba2+. The results clearly demonstrate the power of molecular self-assembly for the construction of highly selective ionophores.     

Modeling of ionic equilibria of trace metals (Cu2+, Zn2+, Cd2+) in concentrated aqueous electrolyte solutions at 25 degrees C

This work presents a model of activity coefficients and a database for ionic equilibria of Cu2+, Zn2+, and Cd2+ in (H+, Na+, K+, Mg2+, Ca2+)(OH-, Cl-, NO-3, ClO-4, HSO-4, SO2-(4), HCO-3, CO(2-)3) aqueous media valid up to 6-12 m ionic strength. The activity coefficient of a dissolved species is represented by empirical equation [Formula: see text] , where Agamma is Debye-Hückel constant (1.17 at 25 degrees C), gammai and zi are activity coefficient and charge of a dissolved species i, I is molal ionic strength, bij is model parameter, and mj is molal concentration of dissolved species. The model is applicable to the modeling of ionic equilibria, as well as to simulation of solubility of salts in mixed electrolyte solutions.     

Stability constants and thermodynamic parameters of Mn2+, Co2+, Ni2+ Cu2+, Zn2+, Cd2+, UO2(2+), Th4+, Ce3+ and Pr3+-complexes with some Schiff base hydrazones containing the pyrimidine moiety

Proton-ligand dissociation and metal-ligand formation constants of 2-amino-4-chloro-6-[alpha-(phenyl)ethylidenehydrazino]pyrimidine; (AHP) and its p-chloro (ClAHP) and p-methoxy (OMeAHP) derivatives (Str.I&II) with Mn2+, Co2+ Ni2+, Cu2+, Zn2+, Cd2+, UO2(2+), Th4+, Ce3+ and Pr3+ ions have been evaluated potentiometrically in 75% (v/v) dioxane-water and 0.1 mol dm(-3) KNO3. The thermodynamic functions (deltaG, deltaH and deltaS) for the complexation of OMeAHP were evaluated and discussed. The effect of the temperature, dielectric constant of the solvents, mole fraction of dioxane and ionic strength of the medium on the stability of Pr3+-complexes show that the stability of the chelates increases by increasing both the electron repelling property of the substituents and the organic solvent content, and by decreasing the temperature, the ionic strength and the dielectric constant of the medium.     

Dual-mode semisquaraine-based sensor for selective detection of Hg2+ in a micellar medium

[reaction: see text] A novel chemosensor based on semisquaraine dye (SSQ) for selective detection of Hg2+ is described. SSQ is obtained in quantitative yields from the reaction between squaric acid and 6-ethoxy-2-quinaldinium iodide. SSQ in combination with surfactant shows a dual chromogenic and fluorogenic response selectively toward Hg2+ as compared to Li+, Na+, K+, Ag+, Ca2+, Mg2+, Zn2+, Pb2+, Cd2+, Cu2+, and Fe3+ due to the soft acid nature and size of the mercuric ion.     

Fluorescence sensing and binding behavior of aminobenzenesulfonamidoquinolino-beta-cyclodextrin to Zn2+

A water-soluble fluorescent zinc sensor which binds strongly to Zn2+ (log K = 12.4) was successfully synthesized under physiological conditions. This sensor exhibits a good fluorescence response to Zn2+ over a wide pH range in water. Under the same conditions, several metal ions commonly present in a physiological environment, such as Na+, K+, Ca2+, Mg2+, Mn2+, Fe2+, and Co2+, showed little interference to the fluorescence response to Zn2+. [structure: see text]     

基于新的亚胺蒽醌生色离子载体的选择性碱土金属离子传感

基于亚胺蒽醌衍生的冠醚,合成得到一对新的生色离子载体1和2,其中化合物1显示对于 Ba2+ 和Ca2+离子的选择性生色传感,而2 则对Mg2+显示出高选择性与高灵敏性的“肉眼”识别性能。     

Simultaneous uptake of Ni2+, NH4+ and PO4(3-) by amorphous CaO-Al2O3-SiO2 compounds

Simultaneous uptake of Ni2+, NH4+, and PO4(3-) by amorphous CaO-Al2O3-SiO2 (C-A-S) compounds was investigated using batch and column methods. Fifteen different C-A-S samples with systematically varied chemical compositions were prepared by coprecipitation from ethanol-water solutions containing Ca(NO3)2.4H2O, Al(NO3)3.9H2O, and Si(OC2H5)4, using NH4OH as the precipitating agent. The resulting precipitates were dried and heated at various temperatures to produce the C-A-S samples, which were then characterized by XRD, FTIR, solid state MAS NMR, DTA-TG, and N2 adsorption. All the C-A-S samples prepared at 600-900 degrees C were amorphous, apart from the CaO-rich samples. Simultaneous uptake of Ni2+, NH4+, and PO4(3-) was determined by a batch method using a solution with an initial concentration of 2 mM. In these experiments, the uptake abilities of the C-A-S samples for Ni2+ and PO4(3-) were high, but were relatively low for NH4+. The uptake abilities for Ni2+ and PO4(3-) increased but that for NH4+ decreased as the silica content in the C-A-S decreased, suggesting that similar uptake mechanisms (ion substitution and/or precipitation) are operating for Ni2+ and PO4(3-), but the uptake mechanism for NH4+ is different (physical adsorption). The column experiments indicate that the order of uptake ability of C-A-S for the three ions is NH4+ < PO4(3-) < Ni2+. Although the silica content of the C-A-S does not have the expected influence on the uptake of these three ions, for NH4+ it plays an important role in the formation of the amorphous phase and also in the suppression of Ca2+ and/or Al3+ release from the C-A-S during the uptake experiments. The optimum uptake properties of the C-A-S can thus be controlled by adjusting the chemical compositions and heating conditions under which the samples are prepared.     

Ag~+,Sr~(2+),Yb~(3+)双掺杂对Ca_3Co_4O_(9-δ)热电性能的影响

采用溶胶-凝胶和冷压方法,在Ca3Co4O9-δ体系中引入不同量的Ag~+,Sr~(2+)或Yb~(3+)离子制备了可在300~870 K下稳定存在且热电性能优良的陶瓷材料Ca_(3-x-y)Ag_xSr_yCo_4O_(9-δ),Ca_(3-x-z)Ag_xYb_zCo_4O_(9-δ)和Ca_(3-y-z)Sr_yYb_zCo_4O_(9-δ)(x,y,z=0.1,0.15,0.2).通过X射线衍射(XRD)、傅里叶变换红外光谱(IR)和扫描电子显微镜(SEM)等手段对产物进行表征.结果显示,所制备的样品纯度较高,晶粒均匀,晶粒间较致密,适量的Ag~+,Sr~(2+),Yb~(3+)离子取代Ca~(2+)离子固溶到晶体中使制备的双掺杂材料晶胞体积发生了变化,但并未引起晶体对称结构的变化.电阻率和Seebeck系数结果表明,双掺杂优化了样品载流子的浓度,使样品电阻率不断减小,并使Seebeck系数的值不断增大.经过计算可知,Seebeck系数随电子有效质量的增大而增大.热导率结果表明,双掺杂的样品热导率随掺杂元素的不同而变化,计算结果显示声子热导依然在样品中占据主体贡献,这与Ca_3Co_4O_(9-δ)单掺杂Ag~+,Sr~(2+)或Yb~(3+)的结果吻合.随着温度的升高,双掺杂样品Ca_(2.7)Ag_(0.2)Yb_(0.1)Co_4O_(9-δ)在870 K下热电优值(ZT)值达到最大(0.18).     

Studies on the Synthesis of bis(Benzo diaza 23-crown-7) and its Complexes with K+, Mg2+, Ca2+ and Ba2+ Perchlorates

A novel (E,E)-dioxime (H2L) containing a 23-membered macrocyclic ionophore was synthesized from the reaction of 2,3-(4-aminobenzo)-1,4,11,14,17-pentaoxa-6,22-dioxo-7,21-diaza-cyclotricosane-2-ene (5) prepared from 2,3-(4-nitrobenzo)-1,4,11,14,17-pentaoxa-6,22-dioxo-7,21-diazacyclotricosane-2-ene (4) and cyanogen di-N-oxide (6). H2L encapsulates and coordinates to alkaline earth metal cations via the oxygen atom to form complexes, H2L2MX (M = K+, Mg2+, Ca2+ and Ba2+; X = ClO4-). After the complexation with alkaline earth metal cations, 1H-NMR, 13C-NMR and IR data were obtained and a comparison of these spectral data is presented.     

DSB显著提高羧酸盐驱油体系抗钙镁离子能力的研究

测定了工业品级的天然混合长链烷基羧酸盐(SDC)以及与3-(N,N-二甲基十二烷基胺)-2-羟基-丙磺酸(DSB)复配驱油体系的界面张力(ITFmin), 分别得出其抗钙镁离子的能力为400和5000 mg/L. 选择试剂级十二烷基羧酸钠与DSB复配, 测定了不同配比溶液的表面张力值和临界胶束浓度cmc, 结合长链烷基脂肪酸与钙离子的溶度积Ksp, 分析了对不溶性长链烷基羧酸盐形成的影响. 根据现场驱油体系配方, 计算了两者在溶液中的摩尔配比为4:1时的十二烷基羧酸盐在胶束中的摩尔分数xm1为0.51, 相互作用参数βm值为-3.11, 反映了两者有较强的相互作用. 采用量子化学方法, 对由1个十二烷基羧酸分子、1个DSB分子及1个二价钙离子组成的模型复合物进行了能量计算和电荷分布计算, 得出在长链烷基羧酸盐和DSB两者混合胶束的界面层中存在负电荷空穴, 提出二价金属离子被络合的模型, 合理地解释了实验事实.     

Highly sensitive and selective chemosensor for Hg2+ based on the rhodamine fluorophore

A novel tren-based tripodal chemosensor 1 bearing a rhodamine and two tosyl groups was synthesized and its sensing behavior toward metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of a Hg2+ ion to a CH3CN solution of 1 gave a visual color change as well as significantly enhanced fluorescence, while other ions including Pb2+, Zn2+, Cu2+, Ca2+, Ba2+, Cd2+, Co2+, Mg2+, Ag+, Cs+, Li+, and Na+ induced no or much smaller color/spectral changes, which constituted a Hg2+-selective fluorescent chemosensor (OFF-ON).