Study of Factors Affecting the Performance of Voltammetric Copper Sensors Based on Gly‐Gly‐His Modified Glassy Carbon and Gold Electrodes

This paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly‐Gly‐His for the detection of copper ions. Gly‐Gly‐His is attached to a glassy carbon (GC) surface modified with 4‐carboxyphenyl moieties or a gold surface modified with 3‐mercaptopropionic acid by the reaction of the N‐terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X‐ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly‐Gly‐His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7–9. Interference studies and investigations of stability of the Gly‐Gly‐His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self‐assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure.     

Synthesis and thermodynamic properties of a metal-organic framework: [LaCu6(μ-OH)3(Gly)6im6](ClO4)6

A metal-organic complex, which has the potential property of absorbing gases, [LaCu₆(μ-OH)₃(Gly)₆im₆](ClO₄)₆ was synthesized through the self-assembly of La³⁺, Cu²⁺, glycine (Gly) and imidazole (Im) in aqueous solution and characterized by IR, element analysis and powder XRD. The molar heat capacity, C_p,m, was measured from T = 80 to 390 K with an automated adiabatic calorimeter. The thermodynamic functions [H_T − H_298.15] and [S_T − S_298.15] were derived from the heat capacity data with temperature interval of 5 K. The thermal stability of the complex was investigated by differential scanning calorimetry (DSC).     

Reply to “Comment on Aromatic‐Backbone Interactions in Model α‐Helical Peptides”

In response to Van Mourik's comments on our paper (J Comput Chem 2007, 28, 1208.) we present an extended version of our rotation method. We also prove that intramolecular interaction energies as well the basis set superposition errors calculated with our rotation method are comparable with those obtained by the counterpoise method of Boys and Bernardi (Mol Phys 1970, 19, 533). In intramolecular interaction energy calculations, if the interacting groups are in proximity, our rotation method is recommended to avoid artificial interactions, which can be induced by fragmentation. © 2007 Wiley Periodicals, Inc.J Comput Chem, 2008     

Role of gemini surfactants (m‐s‐m type; m = 16, s = 4–6) on the reaction of [Zn(II)‐Gly‐Phe]+ with ninhydrin

In the present paper, reaction of zinc‐glycylphenylalanine ([Zn(II)‐Gly‐Phe]⁺) with ninhydrin has been investigated in gemini (m‐s‐m type; m = 16, s = 4–6) surfactants at temperature (70 °C) and pH (5.0). Monitoring the appearance of product at 400 nm was used to follow the kinetics, spectrophotometrically. The order of the reaction with respect to [Zn(II)‐Gly‐Phe]⁺ was unity while with respect to [ninhydrin] was fractional. The reaction constants involved in the mechanism were obtained. In addition to the rate constant (k_Ψ) increase and leveling‐off regions are observed with the geminis, just like as seen with conventional surfactant hexadecyltrimethylammonium bromide (CTAB), the former produced a third region of increasing k_Ψ at higher concentrations. A close agreement between observed and calculated rate constants was found under varying experimental conditions. A suitable mechanism consistent with the experimental findings has been proposed. Copyright © 2014 John Wiley & Sons, Ltd.     

Low-temperature heat capacity and standard enthalpy of formation of neodymium glycine perchlorate complex [Nd2(Gly)6(H2O)4](ClO4)6·5H2O

Rare-earth perchlorate complex coordinated with glycine [Nd₂(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O was synthesized and its structure was characterized by using thermogravimetric analysis (TG), differential thermal analysis (DTA), chemical analysis and elementary analysis. Its purity was 99.90%. Heat capacity measurement was carried out with a high-precision fully-automatic adiabatic calorimeter over the temperature range from 78 to 369 K. A solid-solid phase transformation peak was observed at 256.97 K, with the enthalpy and entropy of the phase transformation process are 4.438 kJ mol⁻¹ and 17.270 J K⁻¹ mol⁻¹, respectively. There is a big dehydrated peak appears at 330 K, its decomposition temperature, decomposition enthalpy and entropy are 320.606 K, 41.364 kJ mol⁻¹ and 129.018 J K⁻¹ mol⁻¹, respectively. The polynomial equations of heat capacity of this compound in different temperature ranges have been fitted. The standard enthalpy of formation was determined to be −8023.002 kJ mol⁻¹ with isoperibol reaction calorimeter at 298.15 K.     

Three new mixed‐ligand copper(II) complexes containing glycyl‐l‐valine and N,N‐aromatic heterocyclic compounds: Synthesis,characterization, DNA interaction,cytotoxicity and antimicrobial activity

Three novel copper(II) complexes, [Cu(Gly‐l ‐Val)(HPBM)(H₂O)]·ClO₄·H₂O ( 1 ), [Cu(Gly‐l ‐Val)(TBZ)(H₂O)]·ClO₄ ( 2 ) and [Cu(Gly‐l ‐Val)(PBO)(H₂O)]·ClO₄ ( 3 ) (Gly‐l ‐Val = glycyl‐l ‐valine anion, HPBM = 5‐methyl‐2‐(2′‐pyridyl)benzimidazole, TBZ = 2‐(4′‐thiazolyl)benzimidazole, PBO = 2‐(2′‐pyridyl)benzoxazole), have been prepared and characterized with elemental analyses, conductivity measurements as well as various spectroscopic techniques. The interactions of these copper complexes with calf thymus DNA were explored using UV–visible, fluorescence, circular dichroism, thermal denaturation, viscosity and docking analyses methods. The experimental results showed that all three complexes could bind to DNA via an intercalative mode. Moreover, the cytotoxic effects were evaluated using the MTT method, and the antimicrobial activity of these complexes was tested against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The results showed that the activities are consistent with their DNA binding abilities, following the order of 1 > 2 > 3 .     

Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Synthesis, Crystal Structure and Biological Activity of a Novel Amino Acid Salt (HGly)_4[HPMo_(12)O_(40) ]_2·22H_2O

IntroductionIn the last few years there has been a rapidlygrowing number of reports in the literature ad-dressing the use of polyoxometalates as antiviraland anti- tumor agents[1— 4] . Polyoxometalates areexcellent molecular acceptors,a number of organicsubstrates containing N,S and O atoms are excel-lent molecular donors,by means of molecular as-semblies,they can form novel compounds at roomtemperature[5— 7] .As is known,amino acids are thebasic units of biological molecules and interactio…     

电色谱模式下四肽印迹整体柱分子识别机理的研究

本文采用原位聚合法制备了以四肽YPLG为模板的毛细管分子印迹整体柱,在毛细管电色谱模式下以模板分子和它的结构类似物YPGL为样品,对分子印迹聚合物的识别机理进行了研究。这两种四肽由于化学结构相似且等电点非常相近,普通的电色谱和毛细管电泳方法分离非常困难。但我们的实验表明,印迹整体柱对模板分子具有特异性识别能力,因此YPLG与YPGL之间的分离因子为1.73,分离度达3.72。实验中系统地研究了流动相中有机溶剂的含量、缓冲溶液的pH值、缓冲溶液的盐浓度以及柱温对四肽识别的影响。实验中我们观察到模板在印迹柱上具有非线性的Van’t Hoff行为,揭示可能存在多重保留机理。本研究结果表明,在毛细管电色谱模式下,分子印迹整体柱的分子识别主要决定于样品与印迹聚合物之间的氢键作用以及印迹孔穴的三维结构。     

Improving detection sensitivity of amino acids in thyroid tissues by using phthalic acid as a mobile phase additive in hydrophilic interaction chromatography-electrospray ionization-tandem mass spectrometry

In this work, 0.08 mmol L⁻¹ of phthalic acid was introduced as a mobile phase additive to quantify free amino acids (AAs) by hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray ionization tandem mass spectrometry (ESI-MS/MS). The addition of phthalic acid significantly increased the signal intensity of protonated AA ions, resulting from the decrease of the relative abundance of AA sodium adducts. Meanwhile, the chromatographic peak shapes of AAs were optimized. As a consequence, there was a noticeable increase in the sensitivity of detection for AAs. The limits of detection (LOD) and quantification (LOQ) of the AAs ranged from 0.0500 to 20.0 ng mL⁻¹ and from 0.100 to 50.0 ng mL⁻¹, respectively, which were 4–50 times lower compared to the values measured without the addition of phthalic acid. The enhanced detection and separation of AAs were obtained by merely adding phthalic acid to the mobile phase without changing other conditions. Eventually, this simple method was validated and successfully applied to the analysis of twenty-four kinds of free AAs in human thyroid carcinoma and para-carcinoma tissues, demonstrating a significant increase of most AAs in thyroid carcinoma tissues (p < 0.05).