Pattern recognition of proteins based on an array of functionalized porphyrins

A practical protein-detecting array is desirable for its potential application in proteomics, medical diagnostics, and pathogen detection. Here, we report a novel protein-detecting array based on porphyrins containing peripheral amino acids as protein surface receptors. The array of porphyrin receptors showed a unique pattern of fluorescence change upon interaction with certain protein samples. Both metal and nonmetal-containing proteins and mixtures of proteins gave distinct patterns, allowing their unambiguous identification. The composite pattern for each sample was subjected to principal component analysis (PCA) to generate a clustering map for more practical visualization. Increasing the number of porphyrin receptors from eight to sixteen gave improved resolution, suggesting that this array is expandable to give satisfactory resolution for any given sample system by carefully maximizing the chemical diversity of the receptors.     

Detection, characterization and identification of phenolic acids in Danshen using high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry

By using HPLC-diode array detection-electrospray ion trap tandem mass spectrometry (HPLC-DAD-ESI-MS(n)) in negative ion mode, we have analyzed the fragmentation pathways of 11 phenolic acids which were isolated from Danshen. Then the extract of Danshen was analyzed, and a total of 42 phenolic acids, including sixteen new minor constituents, were identified or tentatively identified for the first time. A new solid-phase extraction (SPE) method, new HPLC separation method, new liquid chromatography (LC)-MS and LC-MS(n) (n=3-5) data and proposed fragmentation pathways, LC retention time for phenolic acids are reported.     

m × n] metal ion arrays templated by coordination cages

Three-dimensional m × n arrays of metal ion clusters can be assembled as aromatic stacks of planar polynuclear metal complexes within columnar coordination cages. The polynuclear complexes and cage height program the final array structures of the metal ion clusters. Cyclic trinuclear Au(I) complexes (m = 3) assembled into trigonal prismatic arrays (n = 1-3) within the cages and the array structures were clearly shown by X-ray crystallographic analysis. A silver-sandwiched hetero-Au(3)-Ag-Au(3) cluster was also prepared by treating a hexanuclear Au(3)-Au(3) cluster with Ag(I) ion.     

Carbon Quantum Dots Based Chemosensor Array for Monitoring Multiple Metal Ions

The simultaneous identification of multiple metal ions in water has attracted enormous research interest in the past few decades. We herein describe a novel method for multiple metal ion detection using a carbon quantum dots (CQDs)-based chemosensor array and the CQDs are functionalized with different amino acids (glutamine, histidine, arginine, lysine and proline), which act as sensing elements in the sensor array. Eleven metal ions are successfully identified by the designed chemosensor array, with 100% classification accuracy. Importantly, the proposed method allowed the quantitative prediction of the concentration of individual metal ions in the mixture with the aid of a support vector machine (SVM). The sensor array also enables the qualitative detection of unknown metal ions under the interference of tap water and local river water. Thus, the strategy provides a novel high-throughput approach for the identification of various analytes in complex systems.     

A polyelectrolyte bearing metal ion receptors and electrostatic functionality for layer-by-layer self-assembly

A polyelectrolyte (BiPE) containing bipyridine ligands as metal ion receptors and quaternary ammonium groups is described, which can be assembled via electrostatic interactions or metal ion coordination. Electrostatic layer-by-layer self-assembly of BiPE with sodium poly(styrene sulfonate) (PSS) as oppositely charged component results in striated multilayers. The BiPE/PSS multilayers can reversibly bind and release transition metal ions including Fe(II), Ni(II), and Zn(II). Formation of 2-D arrays of metallo-units is achieved by μ-contact stamping transition metal salts onto the BiPE/PSS interface. Also, multilayers of BiPE are readily assembled through metal ion coordination. Due to the reversible nature of metal ion coordination, exposure of the multilayers to EDTA causes instant disassembly of the layer, a property needed to implement stimulus triggered release functions. The importance of metal ion coordination for multilayer formation is demonstrated by force-distance curves measured with AFM.     

Metal salen complexes incorporating triphenoxymethanes: efficient, size selective anion binding by phenolic donors with a visual report

A metal salen complex has been designed to orientate four phenol groups into a tetrahedral array that tightly binds fluoride ion though four OH...F hydrogen bonding interactions.     

Manganese(II)-containing MRI contrast agent employing a neutral and non-macrocyclic ligand

The ligand N,N'-bis(2-pyridylmethyl)-bis(ethylacetate)-1,2-ethanediamine (debpn) coordinates divalent transition metal ions in either a pentadentate or hexadentate fashion. The coordination number correlates with the ionic radius of the metal ion, with larger cations being heptacoordinate as assessed by solid-state analysis. With Mn(II), the debpn ligand is hexadentate and remains bound to the oxophilic metal ion, even when dissolved in water. The ligand's incomplete coordination of the manganous ion allows water molecules to coordinate to the metal center. These two properties, coupled with the high paramagnetism associated with the S = 5/2 metal center, enable [Mn(debpn)(H(2)O)](ClO(4))(2) to serve as a stable and effective magnetic resonance imaging contrast agent despite the ligand's lack of both a macrocyclic component and an anionic charge.     

Recognition of adulteration of Italian wines by thin-film multisensor array and artificial neural networks

The paper reports the use of a chemoresistive multisensor array for recognition of some adulterated Italian wines (two white, four red, two rosè) added with methanol, ethanol or other same-colour wine. A multisensor array constituted by four thin-film semiconducting metal oxide sensors, surface-activated by Pt, Au, Pd, Bi metal catalysts, has been used to generate the chemical pattern of the volatile compounds present in the wine samples. The responses of the multisensor array towards wines tested by headspace sampling have been evaluated. Multivariate analysis including principal component analysis (PCA) as well as back-propagation method trained artificial neural networks (ANNs) have been applied to analytical data generated from the multisensor array to identify both the adulteration of wines and to determine the added content of adulterant agent of methanol or ethanol up to 10 vol.%. The cross-validated ANNs provide the highest achieved percentage of correct classification of 93% and the highest achieved correlation coefficient of 0.997 and 0.921 for predicted-versus-true concentration of methanol and ethanol adulterant agent, respectively.     

Hinge sugar as a movable component of an excimer fluorescence sensor

[reaction: see text] The ring flip of a carbohydrate is employed for the tongs-like movable component of a metal ion sensor. A pair of separated pyrene groups attached to the carbohydrate component are placed side by side when it recognizes metal ions, affording excimer fluorescence. This novel molecular sensor is selective for Zn(2+) and Cd(2+).     

Colorimetric sensing of anions in water using ratiometric indicator-displacement assay

The analysis of anions in water presents a difficult challenge due to their low charge-to-radius ratio, and the ability to discriminate among similar anions often remains problematic. The use of a 3 × 6 ratiometric indicator-displacement assay (RIDA) array for the colorimetric detection and identification of ten anions in water is reported. The sensor array consists of different combinations of colorimetric indicators and metal cations. The colorimetric indicators chelate with metal cations, forming the color changes. Upon the addition of anions, anions compete with the indicator ligands according to solubility product constants (K_sp). The indicator–metal chelate compound changes color back dramatically when the competition of anions wins. The color changes of the RIDA array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis and hierarchical clustering analysis. No confusion or errors in classification by hierarchical clustering analysis were observed in 44 trials. The limit of detection was calculated approximately, and most limits of detections of anions are well below μM level using our RIDA array. The pH effect, temperature influence, interfering anions were also investigated, and the RIDA array shows the feasibility of real sample testing.     

Base‐Promoted Coupling of Carbon Dioxide,Amines, and Diaryliodonium Salts: A Phosgene‐ and Metal‐Free Route to O‐Aryl Carbamates

A phosgene‐ and metal‐free synthesis of O‐aryl carbamates is realized through a three‐component coupling of carbon dioxide, amines and diaryliodonium salts. The reaction only requires a base as the promoter, providing access to a diverse array of O‐aryl carbamates in moderate to high yields with excellent chemoselectivity.     

Selective retention of basic compounds by metal aquo‐ion affinity chromatography

A novel metal aquo‐ion affinity chromatography has been developed for the analysis of basic compounds using heat‐treated silica gel containing hydrated metal cations (metal aquo‐ions) as the packing material. The packing materials of the metal aquo‐ion affinity chromatography were prepared by the immobilization of a single metal component such as Fe(III), Al(III), Ag(I), and Ni(II) on silica gel followed by extensive heat treatment. The immobilized metals form aquo‐ions to present cation‐exchange ability for basic analytes and the cation‐exchange ability for basic analytes depends on pK_a of the immobilized metal species. In the present study, to evaluate the retention characteristics of metal aquo‐ion affinity chromatography, the on‐line solid‐phase extraction of drugs was investigated. Obtained data clearly evidence the selective retention capability of metal aquo‐ion affinity chromatography for basic analytes with sufficient capacity.     

中药成分五味子甲素及其金属离子复合物与血清白蛋白相互作用的研究

在模拟人体生理条件下,采用紫外光谱法、荧光光谱法和同步荧光光谱法研究五味子甲素及其金属离子复合物与血清白蛋白(SA)的结合作用。结果表明:五味子甲素与金属离子形成1∶1复合物;五味子甲素对SA的荧光猝灭机制为静态猝灭和非辐射能量转移;五味子甲素与牛血清白蛋白(BSA)和人血清白蛋白(HSA)的结合常数K、结合位点数n、结合距离r分别为3.58×104L·mol-1和6.42×103L·mol-1、0.944和0.993、2.18nm和1.63nm,其作用力以氢键和范德华力为主。同步荧光光谱法的结果表明:结合位点靠近色氨酸,并使色氨酸的疏水性减弱。共存金属离子对五味子甲素与SA的相互作用有一定的影响。     

Ternary complexes in analytical chemistry

Reactions between a complex AB and a third component C do not always proceed by a displacement mechanism governed by the energy difference of the chemical bonds A-B and A-C. The third component often becomes part of the complex, forming a mixed co-ordination sphere or ternary complex. The properties of this ternary complex ABC are not additive functions of the properties of AB and AC. Such reactions are important in many methods in analytical chemistry, particularly in photometric analysis, extractive separation, masking, etc. The general properties of the four basic types of ternary complex are reviewed and examples given. The four types comprise the systems (a) metal ion, electronegative ligand, organic base, (b) one metal ion, two different electronegative ligands, (c) ternary heteropoly acids, and (d) two different metal ions, one ligand.     

Formation of multimeric steroid metal adducts and implications for isomer mixture separation by traveling wave ion mobility spectrometry

Steroid analysis is essential to the fields of medicine and forensics, but such analyses can present some complex analytical challenges. While chromatographic methods require long acquisition times and often provide incomplete separation, ion mobility spectrometry (IMS) as coupled to mass spectrometry (MS) has demonstrated significant promise for the separation of steroids, particularly in concert with metal adduction and multimerization. In this study, traveling wave ion mobility spectrometry (TWIMS) was employed to separate multimer steroid metal adducts of isomers in mixtures. The results show the ability to separate steroid isomers with a decrease in resolution compared with single component standards because of the formation of heteromultimers. Additionally, ion‐neutral collision cross sections (CCS) of the species studied were measured in the mixtures and compared with CCSs obtained in single component standards. Good agreement between these values suggests that the CCS may aid in identification of unknowns. Furthermore, a complex mixture composed of five sets of steroid isomers were analyzed, and distinct features for each steroid component were identified. This study further demonstrated the potential of TWIMS‐MS methods for the rapid and isomer‐specific study of steroids in biological samples for use either in tandem with or without chromatographic separation.     

Structures and energetics of complexation of metal ions with ammonia,water, and benzene: A computational study

Quantum chemical calculations have been performed at CCSD(T)/def2‐TZVP level to investigate the strength and nature of interactions of ammonia (NH₃), water (H₂O), and benzene (C₆H₆) with various metal ions and validated with the available experimental results. For all the considered metal ions, a preference for C₆H₆ is observed for dicationic ions whereas the monocationic ions prefer to bind with NH₃. Density Functional Theory–Symmetry Adapted Perturbation Theory (DFT‐SAPT) analysis has been employed at PBE0AC/def2‐TZVP level on these complexes (closed shell), to understand the various energy terms contributing to binding energy (BE). The DFT‐SAPT result shows that for the metal ion complexes with H₂O electrostatic component is the major contributor to the BE whereas, for C₆H₆ complexes polarization component is dominant, except in the case of alkali metal ion complexes. However, in case of NH₃ complexes, electrostatic component is dominant for s‐block metal ions, whereas, for the d and p‐block metal ion complexes both electrostatic and polarization components are important. The geometry (M⁺–N and M⁺–O distance for NH₃ and H₂O complexes respectively, and cation–π distance for C₆H₆ complexes) for the alkali and alkaline earth metal ion complexes increases down the group. Natural population analysis performed on NH₃, H₂O, and C₆H₆ complexes shows that the charge transfer to metal ions is higher in case of C₆H₆ complexes. © 2016 Wiley Periodicals, Inc.     

Response of a copper(II) and iron(III) ion-selective electrode bielectrode array in saline media

A bielectrode array comprising a jalpaite membrane (i.e., Ag_1.5Cu_0.5S) copper(II) ion-selective electrode (ISE) and chalcogenide glass membrane (i.e., Fe_2.5(Se₆₀Ge₂₈Sb₁₂)_97.5) iron(III) ISE has been assembled by individually wiring each solid-state sensor into a single electrode body. Furthermore, a dual metal ion buffer calibration standard incorporating copper(II) and iron(III) coordinating ligands to regulate the levels of free copper(II) and iron(III) in the buffer has been developed to enable simultaneous calibration of the bielectrode ISE array. In this work, the bielectrode ISE array has been employed in the continuous flow analysis (CFA) of free copper(II) and iron(III) in seawater media. It is shown that the individual electrodes displayed Nernstian response in the metal ion buffer calibration standard over a wide dynamic range (viz., 10⁻¹⁵ to 10⁻⁵ M aCu²⁺ and 10⁻²¹ to 10⁻¹¹ M aFe³⁺), and the results of repetitive CFA analyses of free copper(II) and iron(III) in seawater are commensurate with the typical values found in coastal seawater samples. Clearly, the bielectrode ISE array may be used in the simultaneous analysis of free copper(II) and iron(III) in seawater without fear of cross-interference between the solid-state sensors.     

Four‐State Molecular Shuttling of [2]Rotaxanes in Response to Acid/Base and Alkali‐Metal Cation Stimuli

In this study, we synthesized [2]rotaxanes possessing three recognition sites—a dialkylammonium, an alkylarylamine, and a tetra(ethylene glycol) stations—in their dumbbell‐like axle component and dibenzo[24]crown‐8 (DB24C8) as their macrocyclic component. These [2]rotaxanes behaved as four‐state molecular shuttles: i) under acidic conditions, the DB24C8 unit encircled both the dialkylammonium and alkylarylammonium stations; ii) under neutral conditions, the dialkylammonium unit was the predominant station for the DB24C8 component; iii) under basic conditions, when both ammonium centers were deprotonated, the alkylarylamine unit became a suitable station for the DB24C8 component; and iv) under basic conditions in the presence of an alkali‐metal cation, the tetra(ethylene glycol) unit recognized the DB24C8 component through cooperative binding of the alkali‐metal ion. In addition, we observed that the [2]rotaxanes exhibited selective recognition for metal cations. These shuttling motions of the macrocyclic component proceeded reversibly.     

Empirical Multicomponent Equilibrium and Film-Pore Model for the Sorption of Copper,Cadmium and Zinc onto Bone Char

The adsorption of three metal ions onto bone char has been studied in both equilibrium and kinetic systems. An empirical Langmuir-type equation has been proposed to correlate the experimental equilibrium data for multicomponent systems. The sorption equilibrium of three metal ions, namely, cadmium (II) ion, zinc (II) ion and copper (II) ion in the three binary and one ternary systems is well correlated by the Langmuir-type equation. For the batch kinetic studies, a multicomponent film-pore diffusion model was developed by incorporating this empirical Langmuir-type equation into a single component film-pore diffusion model and was used to correlate the multicomponent batch kinetic data. The multicomponent film-pore diffusion model shows some deviation from the experimental data for the sorption of cadmium ions in Cd-Cu, Cd-Zn and Cd-Cu-Zn systems. However, overall this model gives a good correlation of the experimental data for three binary and one ternary systems.     

Gold surface plasmon crystal structure based‐on polystyrene template for biosensor application

In this communication, we assembled ordered polystyrene (PS) microsphere array as a template with the drop‐coating method, and the oxygen plasma was used to etch the template to adjust the spacing between the PS microspheres. Nano‐triangular gold array and silver nano‐pyramid array were obtained by ion beam sputtering to deposit precious metal gold and silver. We observed the surface morphology of Au and Au/Ag composite films by scanning electron microscope and characterized the films by X‐ray diffraction and ultraviolet/visible light spectrophotometer. The results show that the etching time of oxygen plasma has an obvious effect in adjusting the spacing between PSs and has a significant effect on the morphology of Au structure.