Probing Pb cation via the iridium based phosphorescent dye

We demonstrate the concept of Pb²⁺ cation sensing using the emissive Ir(III) complex (1) based on the associated decrease of room-temperature phosphorescence upon forming the 1:1 adduct 1-Pb²⁺. Complex 1 bears two cyclometalated N-phenyl pyrazoles with pyrazoles residing at the mutual trans dispositions as well as one 3,5-di(pyridyl) pyrazolate chelate. X-ray structural analyses on the adduct 1-Pb²⁺ confirm the key function of 3,5-di(pyridyl) pyrazolate as it forms chelate interaction with the metal analytes, while quenching of phosphorescent emission is probably due to the Pb²⁺ induced perturbation, which increases the intersystem crossing to another lower-lying triplet state for the host chromophore via an enhanced spin–orbit coupling.     

Cation binding to biomolecules

The binding of Zn²⁺ to the purine and pyrimidine bases of the nucleic acids was studied by SCFab initio (pseudopotential) computations. The order of affinity of the bases is guanine cytosine > adenine uracil. Many geometrical features of the binding are similar to those observed previously in the interaction of the bases with Na⁺. A new feature is the possibility of chelation by Zn²⁺ between N₇ and the rotated NH₂ group of adenine.     

A chemosensor showing discriminating fluorescent response for highly selective and nanomolar detection of Cu and Zn and its application in molecular logic gate

A fluorescent based receptor (4Z)-4-(4-diethylamino)-2-hydroxybenzylidene amino)-1,2dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (receptor 3) was developed for the highly selective and sensitive detection of Cu²⁺ and Zn²⁺ in semi-aqueous system. The fluorescence of receptor 3 was enhanced and quenched, respectively, with the addition of Zn²⁺ and Cu²⁺ ions over other surveyed cations. The receptor formed host-guest complexes in 1:1 stoichiometry with the detection limit of 5 nM and 15 nM for Cu²⁺ and Zn²⁺ ions, respectively. Further, we have effectively utilized the two metal ions (Cu²⁺ and Zn²⁺) as chemical inputs for the manufacture of INHIBIT type logic gate at molecular level using the fluorescence responses of receptor 3 at 450 nm.     

Thermal investigations of nitrate-hydrates and deuterates of Ca2+, Cd2+ and Mg2+

DTA and DSC were used to study the thermal behaviour of Ca(NO₃)₂·4H₂O, Cd(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O and their deuterated analogues. Evidence was found concerning the process of melting of the initial hydrates and deuterates, followed by a one-stage dehydration of the melt to vield the respective anhydrous salt. T _m, ΔH _m ^o , ΔS _m ^o and ΔH _deh ^o were determined and the ΔH _f ^o values for the investigated hydrates were calculated from the ΔH _deh ^o data.

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Zusammenfassung DTA und DSC wurden zur Untersuchung des thermischen Verhaltens von Ca(NO₃)₂·4H₂O, Cd(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O und ihrer deuterierten Analoge eingesetzt. Man fand Aussagen bezüglich des Schmelzvorganges der Ausgangshydrate und Deuterate, gefolgt von einer Einschritt-Dehydratation der Schmelze unter Bildung der entsprechenden wasserfreien Salze. T _m, ΔH _m ^o , ΔS _m ^o und ΔH _deh ^o wurden ermittelt und die ΔH _f ^o Werte für die untersuchten Hydrate wurden anhand der ΔH _deh ^o berechnet.

     

Comparison of Ca2+ and Mg2+ binding to calmodulin. An enthalpy,entropy, and gibbs free energy analysis

A consistent set of G _B , H _B , and S _B parameters have been determined from ion specific electrode, calorimetric, and spectrophotometric studies for the binding of Ca²⁺ and Mg²⁺ to bovine calmodulin at pH=7.0 and an ionic strength I of 0.113M. A non-linear least squares analysis of calcium specific ion electrode data yields, on a molar basis, four calcium dissociation constants: 10^–7 for the first site, 10^–5 for the fourth site, and two constants between these values. Both calorimetric experiments and an indicator method provide evidence that Mg²⁺ binds to calmodulin, probably at the same sites as Ca²⁺, but with affinities about 100 times smaller: 4×10^–5 for the first site and 2×10^–3 for the fourth. Calorimetric titrations on Ca²⁺ binding to calmodulin in three buffers are consistent with 0.46 protons released upon binding at all four sites and yield an average H _B per site of 5.6 and 7.9 kJ-mol^–1 for Ca²⁺ and Mg²⁺, respectively. The entropy of the system increases by 524 and 361 J-K^–1-mol^–1 when Ca²⁺ and Mg²⁺, respectively, bind to four sites on calmodulin, i.e., the selectivity of calmodulin for Ca²⁺ is primarily derived from entropy effects. Further analysis based on elimination of the entropy term for the metal ions demonstrates that calmodulin bound to Ca²⁺ has a larger entropy than the unbound calmodulin; the opposite is true for calmodulin bound to Mg²⁺. These analyses are consistent with the hypothesis that Ca²⁺ forms tight complexes at all sites on calmodulin and that release of waters of hydration upon binding is the source of the increase of entropy in the system.     

一步热解法制备Cu/Fe双金属生物炭复合材料及其高效吸附Pb2+性能

使用一步热解法制备了 Cu/Fe双金属生物炭复合材料(BC@Cu/Fe-X,X=3、5、10)和 Fe生物炭复合材料(BC@Fe)。考察了Cu掺杂量对BC@Cu/Fe-X吸附Pb²⁺的影响,确定最佳掺杂比例。结果显示BC@Cu/Fe-5吸附Pb²⁺性能最好。考察了吸附时间、Pb²⁺浓度、pH、背景离子、空气中老化等实验条件对 BC@Cu/Fe-5 吸附 Pb²⁺的影响。通过动力学、热力学数据拟合分析了BC@Cu/Fe-5吸附Pb²⁺的行为,利用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FTIR)等表征手段解析了BC@Cu/Fe-5吸附Pb²⁺前后特征峰变化。BC@Cu/Fe-5吸附Pb²⁺的机理如下：大约42%的Pb²⁺被还原为Pb⁰,33%的Pb²⁺形成PbO/Pb(OH)₂,25%的Pb²⁺与O—H、C—O、C=O、COO、Fe—O等官能团形成配合物。Cu掺杂可以提高Fe还原Pb²⁺的能力。     

Safranal Induces Vasorelaxation by Inhibiting Ca2+ Influx and Na+/Ca2+ Exchanger in Isolated Rat Aortic Rings

Introduction: Safranal, which endows saffron its unique aroma, causes vasodilatation and has a hypotensive effect in animal studies, but the mechanisms of these effects are unknown. In this study, we investigated the mechanisms of safranal vasodilation. Methods: Isolated rat endothelium-intact or -denuded aortic rings were precontracted with phenylephrine and then relaxed with safranal. To further assess the involvement of nitric oxide, prostaglandins, guanylate cyclase, and phospholipase A₂ in safranal-induced vasodilation, aortic rings were preincubated with L-NAME, indomethacin, methylene blue, or quinacrine, respectively, then precontracted with phenylephrine, and safranal concentration–response curves were established. To explore the effects of safranal on Ca²⁺ influx, phenylephrine and CaCl₂ concentration–response curves were established in the presence of safranal. Furthermore, the effect of safranal on aortic rings in the presence of ouabain, a Na⁺-K⁺ ATPase inhibitor, was studied to explore the contribution of Na⁺/Ca²⁺ exchanger to this vasodilation. Results: Safranal caused vasodilation in endothelium-intact and endothelium-denuded aortic rings. The vasodilation was not eliminated by pretreatment with L-NAME, indomethacin, methylene blue, or quinacrine, indicating the lack of a role for NO/cGMP. Safranal significantly inhibited the maximum contractions induced by phenylephrine, or by CaCl₂ in Ca²⁺-free depolarizing buffer. Safranal also relaxed contractions induced by ouabain, but pretreatment with safranal totally abolished the development of ouabain contractions. Discussion/Conclusion: Inhibition of Na⁺-K⁺ ATPase by ouabain leads to the accumulation of Na⁺ intracellularly, forcing the Na⁺/Ca²⁺ exchanger to work in reverse mode, thus causing a contraction. Inhibition of the development of this contraction by preincubation with safranal indicates that safranal inhibited the Na⁺/Ca²⁺ exchanger. We conclude that safranal vasodilation is mediated by the inhibition of calcium influx from extracellular space through L-type Ca²⁺ channels and by the inhibition of the Na⁺/Ca²⁺ exchanger.     

希土化合物对离体巨噬细胞的影响

本文应用细胞培养法和单细胞阳离子测定系统研究了希土化合物以地巨噬细胞的影响，结果表明，在培养介质中ＳｍＣｌ３和Ｙｃｌ３的浓度大于１ｍｍｏｌ．ｄｍ＾－３时，有明显的细胞毒性，Ｙｃｌ３的细胞毒性大于ＳｍＣｌ３，ＳｍＣｌ３和ＹＣｌ３的细胞毒性明显大于Ｓｍ（Ａｌａ）３Ｃｌ３和Ｙ（Ａｌａ）２Ｃｌ３。希土化合物的作用使细胞（Ｃａ＾２＋ｉ）升高；毒性越大，Ｃａ＾２＋ｉ升高越甚。低浓度Ｓｍ＾３＋和Ｙ６３＋对细胞膜     

Study on the preparation and adsorption thermodynamics of chitosan microsphere resins

The aim of this research is to study the thermodynamic behavior of resins of chitosan microspheres (RCM) in adsorbing Cu²⁺, so that the theoretical basis of the application of RCM to eliminate metal ions in wastewater or fruit and vegetable juice can be obtained. First, RCM were prepared from chitosan as a raw material by using reverse phase suspension cross-linking polymerization, and some physicochemical properties of RCM were characterized. Second, the adsorption behavior of Cu²⁺ onto RCM was investigated by the batch method. The results show that the diameter of the microspheres was relatively uniform and the surface of microspheres was compacted with pores. The physical properties of the RCM were as follows: water content 51.982%, skeletal density 1.212 g · cm⁻³, pileup density 0.862 g·L⁻¹, porosity was in 0.554 and crosslinking degree was in 13.581%. The saturated adsorption capacity of RCM for Cu²⁺ was 0.993 mmol·g⁻¹. At the same time, the results also indicated that the adsorption of RCM for Cu²⁺ followed the Langmuir isotherm equation: C _e/Q = 11.614 + 1.0075C _e at 313 K and the adsorption appeared to be of the monomolecular type. The adsorption was found through thermodynamic study to be a spontaneous endothermic process of increased entropy. The adsorption potential decreased gradually as Cu²⁺ concentration increased at the same temperature and it increased as temperature increased at the same initial concentration of Cu²⁺. __________ Translated from Periodical of Ocean University of China, 2008, 38(1) (in Chinese)     

A squaraine-based chemosensor for Hg and Pb

A novel unsymmetrical cationic squaraine dye (USqH⁺), absorbing in the near-infrared region (600-850 nm), was synthesized by reacting a semi-squaric acid derivative 3-[4-(N,N-dioctylamino)phenyl]-4-hydroxycyclobutene-1,2-dione with the squarylium dye, bis(3-methylbenzothiazol-2-ylidene)squaraine. Addition of micromolar amounts of Hg²⁺ and Pb²⁺ to solutions of USqH⁺ in dichloromethane brings about significant changes in its absorption spectrum, resulting in a change in colour of the solution from green to pink. The absorption spectrum of the dye is relatively insensitive to other environmentally relevant metal ions, making it possible to visually detect Hg²⁺ and Pb²⁺ in the presence of other metal ions. Molecular modeling of the complexes at the density functional theory (DFT) and semiempirical PM3 levels strongly suggests that the oxygen atoms are the most likely choice for cation binding. The calculations also indicate a high affinity of Hg²⁺ and Pb²⁺ toward the formation of 2:1 complexes, which is in good agreement with the experimental results.     

Ion-dipole interactions of macrocyclic ethers using13C dipole-dipole relaxation time measurements. Part XI: The complexation of 1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane with Ca2+ in CD3OH

The association constants,K _a, of Ca²⁺ complexes with the nonequivalent binding site macrocycle,1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane, were determined in CD₃OH solution using¹³C dipole-dipole relaxation time,T ₁ ^DD , studies. The measurements ofT ₁ ^DD of the macrocyclic backbone for different stoichiometries (n:m) of complex formation were conducted under extreme narrowing experimental NMR conditions. The general equilibria given with 1/K _a[L ₀] ^n+m–1 = (1-nP) ⁿ (1-mP) ^m /P was used for identical cation and macrocyclic ether-ester concentrations in CD₃OH and the association constants found were comparatively small depending on the cyclic ether-ester segments. The logK _a values varied from 1.09 to 0.231 for 1 :1 and from 2.43 to 3.61 for 1 : 2 and from 2.29 to 4.24 for 2 : 1 ligand to cation complex stoichiometries.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

The nitric oxide adsorption on gold neutral,cation, and anion atoms: A comparative ab initio MRCI—MRPT2 studies

The Au^ν + NO(²Π) → AuNO^ν reaction, for ν = ?1, 0, +1, anion, neutral, and cation are calculated and predicted at multireference configuration interaction (MRCI) and multireference second order perturbation (MRPT2) levels of theory, in this way the main parameters: reaction path surfaces, total and adsorption energies, optimized geometries, and Mulliken charges distribution are presented and compared. The AuNO (X ¹A′) complex is created spontaneously with ?11.32 and ?13.14 kcal/mol adsorption energies with the MRCI and MRPT2 approaches, respectively. The AuNO bonding in the neutral gold nitrosyl complex has a covalent character and the nitric oxide (NO) molecule is not dissociated. The others excited states (a ³A″, b ³A′, and A ¹A″) do not present bonding. The gold nitrosyl cationic (X ²A′, A ²A″, and a ⁴A″) and anionic (X ²A″ and a ⁴A″) are bonding and present a dative covalent bond. The Mulliken analysis done for ionic species show that the binding is done through soft electrostatic interactions, due to that there is some charge transfer, delocalized onto the NO molecule for the AuNO^± ionic species whereas the AuNO (X ¹A′) neutral complex presents a little charge transfer. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Violet and greenish photoprotein obelin mutants for reporter applications in dual-color assay

Two kinds of Ca²⁺-regulated photoprotein obelin with altered color of bioluminescence were obtained by active-center amino acid substitution. The mutant W92F-H22E emits violet light (λ_max = 390 nm) and the mutant Y139F emits greenish light (λ _max = 498 nm), with small spectral overlap, both display high activity and stability and thus may be used as reporters. For demonstration, the mutants were applied in dual-color simultaneous immunoassay of two gonadotropic hormones—follicle-stimulating hormone and luteinizing hormone. Bioluminescence of the reporters was simultaneously triggered by single injection of Ca²⁺ solution, divided using band-pass optical filters and measured with a two-channel photometer. The sensitivity of simultaneous bioluminescence assay was close to that of a separate radioimmunoassay. Figure Two kinds of Ca²⁺-regulated photoprotein obelin with altered color of bioluminescence were obtained and applied in dual-color simultaneous immunoassay of two gonadotropic hormones.     

A Thermodynamic Study Between 18-Crown-6 with Mg2+, Ca2+, Sr2+and Ba2+ Cations in Water–Methanol and Water–Ethanol Binary Mixtures Using The Conductometric Method

The complexation reactions between Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations with the macrocyclic ligand, 18-Crown-6 (l8C6) in water–methanol (MeOH) binary systems as well as the complexation reactions between Ca²⁺ and Sr²⁺ cations with 18C6 in water–ethanol (EtOH) binary mixtures have been studied at different temperatures using conductometric method. The conductance data show that the stoichiometry of all the complexes is 1:1. It was found that the stability of 18C6 complexes with Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations is sensitive to solvent composition and in all cases, a non-linear behaviour was observed for the variation of log K _f of the complexes versus the composition of the mixed solvents. In some cases, the stability order is changed with changing the composition of the mixed solvents. The selectivity order of 18C6 for the metal cations in pure methanol is: Ba²⁺ > Sr²⁺ > Ca²⁺ > Mg²⁺. The values of thermodynamic parameters (Δ H _c ° and Δ S _c °) for formation of 18C6–Mg²⁺, 18C6–Ca²⁺, 18C6–Sr²⁺ and 18C6–Ba²⁺complexes were obtained from temperature dependence of the stability constants. The obtained results show that the values of (Δ H _c ° and Δ S _c °) for formation of these complexes are quite sensitive to the nature and composition of the mixed solvent, but they do not vary monotonically with the solvent composition.This revised version was published online in July 2005 with a corrected issue number.     

A highly selective visual and fluorescent sensor for Pb2+ and Zn2+ and crystal structure of Cu2+ complex based-on a novel single-armed Salamo-type bisoxime

A novel single-armed Salamo-type bisoximes (H₄L) has been designed and synthesised. An obvious colour change from yellow (H₄L) to pale pink (HL-Pb²⁺) which can be visually observed by the naked eye in visible light. H₄L can act as a fluorescent sensor for ratiometric recognition of Zn²⁺ with high selectivity and sensitivity. Crystallographic data of the [Cu(HL)(μ-OAc)Cu] reveals that the two Cu²⁺ ions are both penta-coordinated with square pyramidal geometries, and forms a 2D supramolecular plane structure by hydrogen bonding interactions.     

八肋游仆虫中心蛋白N端半分子Loop区首个氨基酸的作用

本文通过分子生物学方法将八肋游仆虫中心蛋白N端半分子loop区的首个氨基酸,天冬氨酸Asp37和Asp73,分别突变为带相反电荷的赖氨酸。使用铽敏化荧光、TNS疏水探针研究了八肋游仆虫中心蛋白N端半分子loop区的首个氨基酸的作用。结果表明：当中心蛋白loop Ⅰ区37位的天冬氨酸突变为赖氨酸后,loop Ⅰ丧失了金属离子结合能力,进而影响了中心蛋白依赖于金属离子的构象变化;而loop Ⅱ区73位的天冬氨酸突变为赖氨酸后仍保持金属离子结合能力,依赖于金属离子的构象变化减小。中心蛋白发挥大部分生物功能都依赖于金属离子,这就表明loop Ⅰ区37位的天冬氨酸在中心蛋白发挥生物功能时起着重要作用,是不可缺少的。在10 mmol·L^-1 Hepes、pH 7.4、20 mmol·L^-1 KCl条件下,八肋游仆虫中心蛋白N端半分子loop Ⅱ与金属离子Tb³⁺和Ca²⁺的结合常数分别为：K_Ⅱ(Tb³⁺)=(8.31±0.18)×10⁴ L·mol^-1和K_Ⅱ(Ca²⁺)=(0.94±0.12)×10² L·mol^-1,中心蛋白N端半分子的两个金属结合部位结合能力顺序为：Ⅰ>Ⅱ。     

八肋游仆虫中心蛋白N-端半分子与Tb3+，Ca2+的结合

用分子生物学方法表达、纯化了游仆虫中心蛋白及N-端半分子，用铽荧光探针法、离子竞争法研究了pH 7.4，0.01 mol· L^-1 Hepes条件下中心蛋白与铽、钙的结合性质。结果表明中心蛋白有4个铽结合部位，其中2个为高亲合结合部位、2个为低亲合结合部位。具有2个低亲合结合部位的中心蛋白半分子与铽结合的条件常数是(2.13±0.10)×10⁵ L·mol^-1，与钙结合的条件常数是(7.52±0.02)×10² L·mol^-1。     

The remarkable indifference of alkali metal cation binding constants to sidearm thioether and sulfoxide donors in azalariat ethers

The first example of a lariat ether containing a sulfur sidearm donor is reported here along with a comparison of cation binding strengths to Na⁺ and K⁺. The binding strength differs remarkably little from analogs completely lacking a sidearm donor group and similar results are observed for the novel sulfoxide analog.     

A confocal study of mechanism of 5-hydroxytryptamino induced intracellular calcium dynamics in cultured rat stomach fundus smooth muscle cells with a new Ca2+ indicator STDln-AM

A new fluorescent Ca²⁺ indicator STDln-AM for detecting [Ca²⁺], transients in cultured smooth muscle cells is presented. By making a comparison, the difference between STDln and fluo-3 is discussed in detail. Using the new Ca²⁺ indicator, the mechanism of 5-hydroxytryptamino (5-HT) induced intracellular calcium dynamics in stomach fundus smooth muscle cells (SFSMC) of rats is investigated. It is shown that in contrast with fluo-3, STDln is uniformly distributed in the cytosolic compartment but excluded from the nucleus, when it is transfected into cells. This feature makes it a real cytosol Ca²⁺ indicator and can reflect changes of cytosol [Ca²⁺] more accurately than that of fluo-3. In addition, STDln responds to the [Ca²⁺], transients more sensitive and faster than fluo-3. The results also show that, the L-type Ca²⁺ channel inhibitor Mn9202 and the PLC inhibitor Compound 48/80 can significantly inhibit the [Ca²⁺], elevation induced by 5-HT, while the PKC inhibitor D-Sphingosine can enhance the effect of 5-HT. The results suggest that 5-HT acts by the way of 5-HT₂ receptors on SFSMC, then through 5-HT₂ receptors coupled IP₃/Ca²⁺ and GC/PKC double signal transduction pathways to make Ca²⁺ release from intracellular Ca²⁺ stores and Ca²⁺ influx possibly through L-type calcium channels.