Voltammetric Sensing of Soybean Agglutinin Using an Electrode Modified with Electron-transfer,Carbohydrate-mimetic/Cross-linker-peptide-collagen Film

We constructed an electrochemical sensor based on an electrode modified with electron-transfer, carbohydrate-mimetic peptides on collagen film. The peptide consisted of Ac-Y₄C combined with soybean agglutinin (SBA). To evaluate the binding between SBA and the peptide, we prepared Ac-Y₄CA_n (3-6) containing oligoalanine as a cross-linker. When SBA and Y₄C on the electrode were incubated, the peak was decreased by the SBA uptake of the peptide. The change in the peak current using Ac-Y₄CA₆ was the greatest of the four peptides. The calibration curve was linear and ranged from 4.0×10⁻¹⁴ to 1.2×10⁻¹² M with a detection limit of 1.3×10⁻¹⁴ M.     

Design of an electroactive peptide probe for sensing of a protein

We designed a new electroactive peptide probe that has a molecular recognition function for the sensing of a protein. Ovalbumin (OVA) was the model protein, and when RNRCKGTDVQAW interacted with OVA, it conjugated with a tyrosine-rich peptide (Y₄C). This peptide is electroactive, has a high degree of biocompatibility, and offers the possibility of gene expression. To measure the effect of a number of the tyrosine residues, voltammetric measurements were conducted using a series of tyrosine-rich peptides (Y_nC, n = 3–7) with sensitivities that ranged from 10⁻⁹ to 10⁻⁸ M. The electrode response of Y₅C was the maximum value in the series. However, the peak current did not increase when the number of tyrosine residues was increased in a linear fashion. This may have been due to the micelles that are formed by a tyrosine-rich surfactant peptide. Thus, Y₄C was suitable as an electroactive label for the construction of the peptide probe. The electrode response of Y₄CRNRCKGTDVQAW obtained by a glassy carbon electrode was 100-fold that of tyrosine alone. The measurement of OVA via the peptide probe resulted in a detection on the order of 10⁻¹² M. In contrast, the sensitivity of OVA using RCKGTDVQAWY₄C probe was at the 10⁻¹¹ M level, because the hydrophobic moiety gave it a molecular recognition function. The recoveries of the OVA using Y₄CRNRCKGTDVQAW in a solution containing fetal bovine serum ranged between 98 and 101%. Consequently, the combination of a specific peptide and an electroactive element could be a powerful probe for the sensing of proteins.     

Boosting Na+ Storage Ability of Bimetallic MoxW1−xSe2 with Expanded Interlayers

In spite of the valuable advancements in the fabrication of transition-metal selenides (TMSs)-based hybrid structures, only single-metal selenides have been obtained through most of the present methods. Herein, a facile room-temperature self-polymerization and subsequent selenization strategy is proposed for the synthesis of bimetallic Mo_xW_1−xSe₂ nanosheets with expanded interlayers decorated with N-doped carbon-matrix assembled flowerlike hierarchical microspheres (Mo_xW_1−xSe₂/NC). Depending on the excellent coordination ability of dopamine with metal ions, self-formed flowerlike single precursors are harvested. The unique hybrid architecture benefits the penetration of the electrolyte, accelerates Na⁺ insertion/extraction kinetics, enhances electron-transfer ability, and alleviates the volume expansion and aggregation during cycling processes. Therefore, the bimetallic Mo_xW_1−xSe₂/NC electrode delivers high reversible capacities of 264 mA h g⁻¹ at 1 A g⁻¹ for 700 cycles, 204.4 mA h g⁻¹ at 4 A g⁻¹ for 1400 cycles, and 153.3 mA h g⁻¹ at 8 A g⁻¹ for 2000 cycles, as well as an excellent rate capability up to 10 A g⁻¹ with a capacity of 188.9 mA h g⁻¹. Our study offers an effective strategy to boost sodium storage performance through elaborate structural engineering.     

Study of the ν4-2ν8 Fermi resonance in heavy isotopic species of CH3CN by the Modified Winther Method

The Modified Winther Method is used to calculate the Fermi coupling constant W for the resonance between ν₄ and 2ν₈ vibrational levels in four heavy isotopic species (¹³C, ¹⁵N) of gaseous CH₃CN. The change of isotopic mass is used as a frequency scanning variable. Reliable values of W (5.41 cm⁻¹)and of the anharmonicity of 2ν⁰₈ (−12.5 cm⁻¹) are obtained.     

EDL structure and peculiarities of ferricyanide cyclic voltammetry for silver deposits on gold

The evolution of electrochemical characteristics of a gold electrode upon the deposition of one and more atomic silver layers was studied by means of cyclic voltammetry and the method of potential temperature jump induced by the laser irradiation. Characteristics of the electric double layer on Ag monolayer are determined to be close to those of a massive silver electrode. Meanwhile, the electron-transfer parameters for the model redox system Fe(CN)₆^{3 −/4 −} correspond to a gold electrode. The silver beyond the first atomic layer in multilayer deposits was shown to transform into Ag hexacyanoferrate (II) due to the spontaneous chemical reaction with K₃Fe(CN)₆ from the solution. For the Fe(CN)₆^{3 −/4 −} redox system, the difference between oxidation and reduction peak potentials on a cyclic voltammogram increases with the growth of the silver layers number. This effect results from the corresponding increase in the ohmic resistance of the silver hexacyanoferrate (II) film and is not attributed to the changes in the electron-transfer kinetics.     

Carbon-Based Electron Buffer Layer on ZnOx−Fe5C2−Fe3O4 Boosts Ethanol Synthesis from CO2 Hydrogenation

The conversion of CO₂ into ethanol with renewable H₂ has attracted tremendous attention due to its integrated functions of carbon elimination and chemical synthesis, but remains challenging. The electronic properties of a catalyst are essential to determine the adsorption strength and configuration of the key intermediates, therefore altering the reaction network for targeted synthesis. Herein, we describe a catalytic system in which a carbon buffer layer is employed to tailor the electronic properties of the ternary ZnO_x−Fe₅C₂−Fe₃O₄, in which the electron-transfer pathway (ZnO_x→Fe species or carbon layer) ensures the appropriate adsorption strength of −CO* on the catalytic interface, facilitating C−C coupling between −CH_x* and −CO* for ethanol synthesis. Benefiting from this unique electron-transfer buffering effect, an extremely high ethanol yield of 366.6 g_EtOH kg_cat⁻¹ h⁻¹ (with CO of 10 vol % co-feeding) is achieved from CO₂ hydrogenation. This work provides a powerful electronic modulation strategy for catalyst design in terms of highly oriented synthesis.     

Atmospheric chemistry of acetone: Kinetic study of the CH3C(O)CH2O2+NO/NO2 reactions and decomposition of CH3C(O)CH2O2NO2

Pulse radiolysis was used to study the kinetics of the reactions of CH₃C(O)CH₂O₂ radicals with NO and NO₂ at 295 K. By monitoring the rate of formation and decay of NO₂ using its absorption at 400 and 450 nm the rate constants k(CH₃C(O)CH₂O₂+NO)=(8±2)×10⁻¹² and k(CH₃C(O)CH₂O₂+NO₂)=(6.4±0.6)×10⁻¹² cm³ molecule⁻¹ s⁻¹ were determined. Long path length Fourier transform infrared spectrometers were used to investigate the IR spectrum and thermal stability of the peroxynitrate, CH₃C(O)CH₂O₂NO₂. A value of k₋₆≈3 s⁻¹ was determined for the rate of thermal decomposition of CH₃C(O)CH₂O₂NO₂ in 700 torr total pressure of O₂ diluent at 295 K. When combined with lower temperature studies (250–275 K) a decomposition rate of k₋₆=1.9×10¹⁶ exp (−10830/T) s⁻¹ is determined. Density functional theory was used to calculate the IR spectrum of CH₃C(O)CH₂O₂NO₂. Finally, the rate constants for reactions of the CH₃C(O)CH₂ radical with NO and NO₂ were determined to be k(CH₃C(O)CH₂+NO)=(2.6±0.3)×10⁻¹¹ and k(CH₃C(O)CH₂+NO₂)=(1.6±0.4)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The results are discussed in the context of the atmospheric chemistry of acetone and the long range atmospheric transport of NO_x. © John Wiley & Sons, Inc. Int J Chem Kinet: 30: 475–489, 1998     

Elucidating the Mechanism of Simultaneous Activation of CH4 and CO2 Mediated by Single Group 10 Metal Anions in Gas Phase

Quantum chemistry calculations predict that besides the reported single metal anion Pt⁻, Ni⁻ can also mediate the co-conversion of CO₂ and CH₄ to form [CH₃−M(CO₂)−H]^– complex, followed by transformation to C−C coupling product [H₃CCOO−M−H]⁻ ( A ), hydrogenation products [H₃C−M−OCOH]⁻ ( B ) and [H₃C−M−COOH]⁻. For Pd⁻, a fourth product channel leading to PdCO₂⁻…CH₄ becomes more competitive. For Ni⁻, the feed order must be CO₂ first, as the weaker donor-acceptor interaction between Ni⁻ and CH₄ increases the C−H activation barrier, which is reduced by [Ni−CO₂]⁻. For Ni⁻/Pt⁻, the highly exothermic products A and B are similarly stable with submerged barrier that favors B . The smaller barrier difference between A and B for Ni⁻ suggests the C−C coupling product is more competitive in the presence of Ni⁻ than Pt⁻. The charge redistribution from M⁻ is the driving force for product B channel. This study adds our understanding of single atomic anions to activate CH₄ and CO₂ simultaneously.     

Reaction of [Fe4(μ3-CCH3)(CO)12]− with alkynes: Ethylidyne-alkyne coupling on a tetranuclear iron cluster anion

The [Fe₄(μ₄-η³-C(CH₃)C(R)C(R′)(μ-CO)₂(CO)₉]⁻ cluster anions have been obtained by the reaction of the Fe₄(μ₃-CCH₃)(CO)₁₂⁻ anion with RCCR alkynes in boiling 3-pentanone. In the cases in which R = R′ = C₆H₅ or CH₃, and R = H, R′ = C₆H₅ or t-Bu, only one isomer has been detected. In the case in which R = CH₃, and R′ = C₆H₅, two isomers with the C(CH₃)C(C₆H₅)C(CH₃) and C(CH₃)C(CH₃)C(C₆H₅) fragments have been identified.     

The anharmonic force constant K234 of CH3CN in different phases,solvents and complexes with Lewis acids

The Fermi coupling coefficient W and the anharmonic force constant K₂₃₄ of CH₃CN have been determined from i.r. and Raman studies of the v₂—v₃+v₄ Fermi doublet in liquid and gaseous phases, solutions in inert, basic and acidic solvents and in crystalline complexes with Lewis acids. The values of these parameters have been calculated by a modification of the Winther method. This method is also applied to gas phase data of the isotopic speices ¹³CH₃CN, CH₃ ¹³CN and CH₃C¹⁵N. Values of W are approximately 13±1 cm⁻¹ except for basic and inert solvents where they are approximately 18 cm⁻¹.     

Kinetics and products of propargyl (C3H3) radical self‐reactions and propargyl‐methyl cross‐combination reactions

Propargyl (HCC CH₂) and methyl radicals were produced through the 193‐nm excimer laser photolysis of mixtures of C₃H₃Cl/He and CH₃N₂CH₃/He, respectively. Gas chromatographic and mass spectrometric (GC/MS) product analyses were employed to characterize and quantify the major reaction products. The rate constants for propargyl radical self‐reactions and propargyl‐methyl cross‐combination reactions were determined through kinetic modeling and comparative rate determination methods. The major products of the propargyl radical combination reaction, at room temperature and total pressure of about 6.7 kPa (50 Torr) consisted of three C₆H₆ isomers with 1,5‐hexadiyne(CHC CH₂ CH₂ CCH, about 60%); 1,2‐hexadiene‐5yne (CH₂CC CH₂ CCH, about 25%); and a third isomer of C₆H₆ (∼15%), which has not yet been, with certainty, identified as being the major products. The rate constant determination in the propargyl‐methyl mixed radical system yielded a value of (4.0 ± 0.4) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ for propargyl radical combination reactions and a rate constant of (1.5 ± 0.3) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ for propargyl‐methyl cross‐combination reactions. The products of the methyl‐propargyl cross‐combination reactions were two isomers of C₄H₆, 1‐butyne (about 60%) and 1,2‐butadiene (about 40%). © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 118–124, 2000     

Communication: The insertion of silylene in C?H bonds; rate constant limits and the energy barrier

The technique of laser flash photolysis has been used to set limits on the rate constants for the bimolecular reactions of SiH₂ with methane (CH₄) and tetramethylsilane (SiMe₄) at both ambient and elevated temperatures (ca 600 K). These limits show that the energy barriers to insertion reactions of SiH₂ in the C H bonds of CH₄ are at least 45(±6) kJ mol⁻¹ and in the C H and/or Si C bonds of SiMe₄ are at least 23(±6) kJ mol⁻¹. The best thermochemical estimate of the activation energy for SiH₂+CH₄ is 59(±12) kJ mol⁻¹. Reasons for the greatly diminished reactivity of SiH₂ with C H as compared with Si H bonds are discussed. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 393–395, 1999     

Sensing lymphoma cells based on a cell-penetrating/apoptosis-inducing/electron-transfer peptide probe

To electrochemically sense lymphoma cells (U937), we fabricated a multifunctional peptide probe that consists of cell-penetrating/apoptosis-inducing/electron-transfer peptides. Electron-transfer peptides derive from cysteine residue combined with the C-terminals of four tyrosine residues (Y₄). A peptide whereby Y₄C is bound to the C-terminals of protegrin 1 (RGGRLCYCRRRFCVCVGR-NH₂) is known to be an apoptosis-inducing agent against U937 cells, and is referred to as a peptide-1 probe. An oxidation response of the peptide-1 probe has been observed due to a phenolic hydroxyl group, and this response is decreased by the uptake of the peptide probe into the cells. To improve the cell membrane permeability against U937 cells, the RGGR at the N-terminals of the peptide-1 probe was replaced by RRRR (peptide-2 probe). In contrast, RNRCKGTDVQAWY₄C (peptide-3 probe), which recognizes ovalbumin, was constructed as a control. Compared with the other probes, the change in the peak current of the peptide-2 probe was the greatest at low concentrations and occurred in a short amount of time. Therefore, the cell membrane permeability of the peptide-2 probe was increased based on the arginine residues and the apoptosis-inducing peptides. The peak current was linear and ranged from 100 to 1000 cells/ml. The relative standard deviation of 600 cells/ml was 5.0% (n = 5). Furthermore, the membrane permeability of the peptide probes was confirmed using fluorescent dye.     

Analysis of the ν2 :ν3 + ν4 Fermi resonance in CH3CN isotopic species in solution

Infrared bands due to ν₃ + ν₄, ν₂, ν₃ and ν₄ were recorded for the species CH₃CN, ¹³CH₃CN, CH₃¹³CN and CH₃C¹⁵N in the solvents carbon tetrachloride, chloroform, benzene, pyridine and dimethyl sulphoxide. Values of W₂₃₄ were extracted by the modified Winther method, which are slightly less, 11.2–11.9 cm⁻¹, than the value in the gas, 12.15 cm⁻¹. Relative intensity measurements of ν₃ + ν₄ and ν₂ in CCl₄ are compatible with an unperturbed intensity ratio, I_{ν3 + ν4}/ I_ν2 of ∼ 0.03. The fallibility of the infrared intensity method for determining W, and the need for precise frequency data in the Winther method, are stressed.     

High performance cathode-supported SOFC with perovskite anode operating in weakly humidified hydrogen and methane

A high performance cathode-supported solid oxide fuel cell (SOFC), suitable for operating in weakly humidified hydrogen and methane, has been developed. The SOFC is essentially made up by a YSZ/LSM composite supporting cathode, a thin YSZ film electrolyte, and a GDC-impregnated La_0.75Sr_0.25Cr_0.5Mn_0.5O₃ (LSCM) anode. A gas tight thin YSZ film (∼27 μm) was formed during the co-sintering of cathode/electrolyte bi-layer at 1200 °C. The cathode-supported SOFC developed in this study showed encouraging performance with maximum power density of 0.182, 0.419, 0.628 and 0.818 W cm⁻² in air/3% H₂O–97% H₂ (and 0.06, 0.158, 0.221 and 0.352 W cm⁻² in air/3% H₂O–97% CH₄) at 750, 800, 850 and 900 °C, respectively. Such performance is close to that of the cathode-supported cell (0.42 W cm⁻² vs. 0.455 W cm⁻² in humidified H₂ at 800 °C) developed by Yamahara et al. [Solid State Ionics 176 (2005) 451–456] with a Co-infiltrated supporting LSM-YSZ cathode, a (Sc₂O₃)_0.1(Y₂O₃)_0.01(ZrO₂)_0.89 (SYSZ) electrolyte of 15 μm in thickness and a SYSZ/Ni anode, indicating that the performance of the GDC-impregnated LSCM anode is comparable to that made of Ni cermet while stable in weakly humidified methane fuel.     

Absolute rate constants for F + CH3CHO and CH3CO + O2, relative rate study of CH3CO + NO,and the product distribution of the F + CH3CHO reaction

Using a pulse-radiolysis transient UV–VIS absorption system, rate constants for the reactions of F atoms with CH₃CHO (1) and CH₃CO radicals with O₂ (2) and NO (3) at 295 K and 1000 mbar total pressure of SF₆ was determined to be k₁=(1.4±0.2)×10⁻¹⁰, k₂=(4.4±0.7)×10⁻¹², and k₃=(2.4±0.7)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹. By monitoring the formation of CH₃C(O)O₂ radicals (λ>250nm) and NO₂ (λ=400.5nm) following radiolysis of SF₆/CH₃CHO/O₂ and SF₆/CH₃CHO/O₂/NO mixtures, respectively, it was deduced that reaction of F atoms with CH₃CHO gives (65±9)% CH₃CO and (35±9)% HC(O)CH₂ radicals. Finally, the data obtained here suggest that decomposition of HC(O)CH₂O radicals via C C bond scission occurs at a rate of <4.7×10⁵ s⁻¹. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 913–921, 1998     

Ab initio molecular orbital study on structures and energetics of CH3O−(H2O)n and CH3S−(H2O)n in gas phase

The purpose of this article was to calculate the structures and energetics of CH₃O⁻(H₂O)_n and CH₃S⁻(H₂O)_n in the gas phase; the maximum number of water molecules that can directly interact with the O of CH₃O⁻; and when n is larger, we asked how the CH₃O⁻ and CH₃S⁻ moiety of CH₃O⁻(H₂O)_n and CH₃S⁻(H₂O)_n changes and how we can reproduce experimental ΔH ⁰_{n−1, n}. Using the ab initio closed-shell self-consistent field method with the energy gradient technique, we carried out full geometry optimizations with the MP2/aug-cc-pVDZ for CH₃O⁻(H₂O)_n (n=0, 1, 2, 3) and the MP2/6–31+G(d,p) (for n=5, 6). The structures of CH₃S⁻(H₂O)_n (n=0, 1, 2, 3) were fully optimized using MP2/6–31++G(2d,2p). It is predicted that the CH₃O⁻(H₂O)₆ does not exist. We also performed vibrational analysis for all clusters [except CH₃O⁻(H₂O)₆] at the optimized structures to confirm that all vibrational frequencies are real. Those clusters have all real vibrational frequencies and correspond to equilibrium structures. The results show that the above maximum number of water molecules for CH₃O⁻ is five in the gas phase. For CH₃O⁻(H₂O)_n, when n becomes larger, the C—O bond length becomes longer, the C—H bond lengths become smaller, the HCO bond angles become smaller, the charge on the hydrogen of CH₃ becomes more positive, and these values of CH₃O⁻(H₂O)_n approach the corresponding values of CH₃OH with the n increment. The C—O bond length of CH₃O⁻(H₂O)₃ is longer than the C—O bond length of CH₃O⁻ in the gas phase by 0.044 Å at the MP2/aug-cc-pVDZ level of theory. The structure of the CH₃S⁻ moiety in CH₃S⁻(H₂O)_n does not change with the n increment. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1138–1144, 1999     

Reaction of CH3CHO with Y+: A density functional theoretical study

The reaction mechanism of the Y⁺ cation with CH₃CHO has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/ECP/6-311++G** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a CH₃CHO-metal complex followed by C-C, aldehyde C-H, methyl C-H and C-O activation. These reactions can lead to four different products (Y⁺CH₄ + CO, Y⁺CO + CH₄, Y⁺COCH₂ + H₂ and Y⁺O + C₂H₄). The minimum energy reaction path is found to involve the spin inversion in the different reaction steps, this potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.     

Protonation of γ-Butyrolactone and γ-Butyrolactam

Abstract : γ-Butyrolactone and γ-butyrolactam were reacted in the superacidic systems XF/MF₅ (X=H, D; M=As, Sb). Salts of the monoprotonated species of γ-butyrolactone were obtained in terms of [(CH₂)₃OCOH]⁺[AsF₆]⁻, [(CH₂)₃OCOH]⁺[SbF₆]⁻ and [(CH₂)₃OCOD]⁺[AsF₆]⁻ and the analogous lactam salts in terms of [(CH₂)₃NHCOH]⁺[AsF₆]⁻, [(CH₂)₃NHCOH]⁺[SbF₆]⁻ and [(CH₂)₃NDCOD]⁺[AsF₆]⁻. The salts were characterized by low temperature Raman and infrared spectroscopy and for both protonated hexafluoridoarsenates, [(CH₂)₃OCOH]⁺[AsF₆]⁻ and [(CH₂)₃NHCOH]⁺[AsF₆]⁻, single-crystal X-ray structure analyses were conducted. In addition to the experimental results, quantum chemical calculations were performed on the B3LYP/aug-cc-pVTZ level of theory. As in both crystal structures C⋅⋅⋅F contacts were observed, the nature of these contacts is discussed with Mapped Electrostatic Potential as a rate of strength.     

Exploring the Symmetry,Structure, and Self‐Assembly Mechanism of a Gigantic Seven‐Fold Symmetric {Pd84} Wheel

The symmetry, structure and formation mechanism of the structurally self‐complementary { Pd₈₄ } = [Pd₈₄O₄₂(PO₄)₄₂(CH₃CO₂)₂₈]⁷⁰⁻ wheel is explored. Not only does the symmetry give rise to a non‐closest packed structure, the mechanism of the wheel formation is proposed to depend on the delicate balance between reaction conditions. We achieve the resolution of gigantic polyoxopalladate species through electrophoresis and size‐exclusion chromatography, the latter has been used in conjunction with electrospray mass spectrometry to probe the formation of the ring, which was found to proceed by the stepwise aggregation of {Pd₆}⁻ = [Pd₆O₄(CH₃CO₂)₂(PO₄)₃Na_6−nH_n]⁻ building blocks. Furthermore, the higher‐order assembly of these clusters into hollow blackberry structures of around 50 nm has been observed using dynamic and static light scattering.