The solvation effect on the rattling behaviour of the hydrated excess proton in water.

The solvation effect on the kinetic rattling behaviour of the hydrated excess proton H(aq) in water is theoretically modeled by using density functional theory (DFT) and the quantum chemical cluster model (CM). To test the solvation effects on the proton morphology and rattling kinetics, different solvation models for the proton are constructed based on the gas phase (GP) Zundel cation, which include the gas phase-polarizable continuum model (GP-PCM), the gas phase-supermolecule model (GP-SM), and the gas phase-supermolecule-polarizable continuum model (GP-SM-PCM). These solvation models consider either one or both of the short- and long-range solute-solvent interactions.

Density functional theory studies on the solvent effects in Al(HO) water-exchange reactions: the number and arrangement of outer-sphere water molecules.

Density functional theory (DFT) calculations combined with cluster models are performed at the B3LYP/6-311+G(d,p) level for investigating the solvent effects in Al(HO) water-exchange reactions. A "One-by-one" method is proposed to obtain the most representative number and arrangement of explicit HOs in the second hydration sphere. First, all the possible ways to locate one explicit HO in second sphere (N' = 1) based on the gas phase structure (N' = 0) are examined, and the optimal pathway (with the lowest energy barrier) for N' = 1 is determined.

[Study on the Effects of Different Ferron System, Ferron Solubility, Experimental Temperature and Other Factors for the Accurate Determination of Mononuclear Aluminum Concentration in Aqueous Solution].

Ferron colorimetric method has been widely used in aluminum speciation analysis. However, some important factors that may affect the accurate determination of mononuclear Al concentration have not been studied yet. Using molar absorption coefficient ε as a key indicator, the critical issues in Al-Ferron coloring reaction system have been investigated experimentally in this paper, including different Ferron system, Ferron solubility, experimental temperature, ionic strength and the reference system.

Deriving TC50 values of nanoparticles from electrochemical monitoring of lactate dehydrogenase activity indirectly.

Nanotoxicity assessment methods for nanoparticles (NPs) such as carbon nanotubes (CNTs), nano-Al(2)O(3), and tridecameric aluminum polycation or nanopolynuclear (nano-Al(13)), particularly lactate dehydrogenase (LDH) assays are reviewed. Our researches on electrochemically monitoring the variations of LDH activity indirectly in the presence of multiwalled carbon nanotubes (MWCNTs), nano-Al(13), and nano-Al(2)O(3) separately to derive toxic concentrations of NPs altering LDH activity by 50% (TC(50)) values are discussed. TC(50) values indicated that the toxicity order was Al (III)> MWCNTs > nano-Al(13) > nano-Al(2)O(3).

Effect of monovalent cations (Li+, Na+, K+, Cs+) on self-assembly of thiol-modified double-stranded and single-stranded DNA on gold electrode.

In this article we investigate the effect of monovalent cations (Li(+), Na(+), K(+), Cs(+)) on self-assembly of thiol-modified double-stranded DNA (ds-DNA) and single-stranded DNA (ss-DNA) on gold electrodes. Electrochemical characteristics (surface coverage, ion penetration and charge transfer) of ds-DNA and ss-DNA self-assembled monolayers (SAMs) formed with different monovalent cations are inspected based on six important interfacial parameters including surface coverage (Γ(m)), interfacial capacitance (C), phase angle (Φ(1 Hz)), ion transfer resistance (R(it)*), current density difference (Δj) and charge transfer resistance (R(ct)) from chronocoulometry (CC), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Three sections are included: (1) Investigation of the relationships of parameters (Γ(m), C, Φ(1 Hz), R(it)*, Δj and R(ct)) for ds-DNA-SAMs and ss-DNA-SAMs with cation types and concentrations; (2) confirmation and explanation of our experimental results combined with our recently proposed simple DNA model and literature reports; (3) exploration of the mechanism for the orders of monovalent cations (Li(+), Na(+), K(+), Cs(+)) on availing the adsorption of ds-DNA and ss-DNA molecules on gold based on their physicochemical parameters (ion size, solvation free energy and enthalpy, ion-water bond length and water exchange rate) and possible binding modes with DNA molecules.

Insight into the structural characteristics of core-links and flat-aluminum tridecamers: a density functional theory study.

The structures of core-links Al(13) (C-Al(13)) and flat-Al(13) (F-Al(13)) complexes in aqueous solution have been investigated using density functional theory (DFT) at the level of B3LYP/6-31G(d). The present work focuses on the following three aspects: (1) C-Al(13)(9+) was optimized with the consideration of solvent effect and the (27)Al NMR chemical shifts using Hartree Fock GIAO and B3LYP GIAO methods were computed respectively; (2) the optimization of F-Al(13)(15+) was also performed and the (27)Al NMR chemical shifts were obtained using the same methods as above; (3) the structural parameters of a series of typical aluminum species (Al(3+), AlOH(2+), AlF(2+), Al(2)(4+), Al(6)(6+), K-Al(13)(7+), C-Al(13)(9+) and F-Al(13)(15+)) were compared.

Studies on the effect of electrode pretreatment on the coverage of self-assembled monolayers of dodecanethiol on gold by electrochemical reductive desorption determination.

This paper examines the effect of five major pretreatments on the surface coverage Γ(m) of dodecanethiol self-assembled monolayer on polycrystalline gold electrode (C(12)SH-SAMs-Au). It is based on the electrochemical reductive desorption in the alkaline solution by cyclic voltammetry (CV). The five different pretreatment methods include: aqua regia pretreatment, reductive annealed pretreatment, UV/O(3) pretreatment, piranha reagents pretreatment and simple polishing pretreatment, and then all above pretreatments following the same procedure of electrochemistry cleaning.

Density functional theory studies on the structures and water-exchange reactions of aqueous Al(III)-oxalate complexes.

The structures and water-exchange reactions of aqueous aluminum-oxalate complexes are investigated using density functional theory. The present work includes (1) The structures of Al(C(2)O(4))(H(2)O)(4)(+) and Al(C(2)O(4))(2)(H(2)O)(2)(-) were optimized at the level of B3LYP/6-311+G(d,p). The geometries obtained suggest that the Al-OH(2) bond lengths trans to C(2)O(4)(2-) ligand in Al(C(2)O(4))(H(2)O)(4)(+) are much longer than the Al-OH(2) bond lengths cis to C(2)O(4)(2-).

Exploration of the specific structural characteristics of thiol-modified single-stranded DNA self-assembled monolayers on gold by a simple model.

This paper proposed a simple hexagonal model to explore the specific structural characteristics of thiol-modified single-stranded DNA (ss-DNA) self-assembled monolayers (SAMs) on gold substrate. The calibrated gyration diameter d'(g)(d'(g)=rd(g)) was used to quantify the size of ss-DNA molecules on gold by introducing a calibrating factor r, where d(g) was ss-DNA gyration diameter in solution. Based on the model, the interfacial parameters of ss-DNA-SAMs on gold assembled under different ionic strength were obtained theoretically.

Multi-walled carbon nanotubes decrease lactate dehydrogenase activity in enzymatic reaction.

The oxidation of 1, 4-nicotinamide adenine dinucleotide (NADH) to β-nicotinamide adenine dinucleotide (NAD(+)) coupled with converting of pyruvic acid (PA) to lactate catalyzed by lactate dehydrogenase (LDH), NADH+PA+H(+)⇌LDHNAD(+)+Lactate, was widely adopted to quantify the cell's death, membrane infiltration and proliferation induced by potential toxins. The differential pulse voltammetry (DPV) cathodic signal of NAD(+) at a hanging mercury drop electrode (HMDE) showed LDH activity decreased with the elevating dosages of and the pre-contact time (t(c)) with multi-walled carbon nanotubes (MWCNTs). Comparison of kinetic rate constant of above enzymatic reaction (ER) was able to sensitively assay the adverse influence of MWCNTs.

Electrochemical studies on the permeable characteristics of thiol-modified double-stranded DNA self-assembled monolayers on gold.

In this article we studied the permeable characteristics of thiol-modified double-stranded DNA (ds-DNA) self-assembled monolayers (SAMs) on a gold substrate assembled under different NaCl concentrations by electrochemical methods. It was based on the inspection of five important parameters including interfacial capacitance (C), phase angle (Φ(1 Hz)), ions transfer resistance (R(it)*), current density difference (Δj) and electron transfer rate (k(et)) through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Three sections were included: (1) Investigation of the relationships of C, Φ(1 Hz), R(it)*, Δj and k(et) with NaCl concentrations and comparison with the reports from literature.

DFT study on the interaction between monomeric aluminium and chloride ion in aqueous solution.

The interaction of monomeric aluminium and chloride ion in aqueous solution is investigated by density functional theory (DFT) calculations. The computational results show that it is difficult for Cl(-) to enter the inner-coordination shell of aluminium complexes by replacing the bound water molecules, independent of pH and the concentration of Cl(-). However, pH and the concentration of Cl(-) might influence the conformations, bond lengths and natural charge populations of monomeric aluminium complexes to a given extent.

Density functional theory study on aqueous aluminum-fluoride complexes: exploration of the intrinsic relationship between water-exchange rate constants and structural parameters for monomer aluminum complexes.

Density functional theory (DFT) calculation is carried out to investigate the structures, (19)F and (27)Al NMR chemical shifts of aqueous Al-F complexes and their water-exchange reactions. The following investigations are performed in this paper: (1) the microscopic properties of typical aqueous Al-F complexes are obtained at the level of B3LYP/6-311+G**. Al-OH(2) bond lengths increase with F(-) replacing inner-sphere H(2)O progressively, indicating labilizing effect of F(-) ligand.

DFT study on the mechanism for the substitution of F(-) into Al(III) complexes in aqueous solution.

The mechanisms for the substitution of an aqua ligand with F(-) in monomeric Al complexes were studied with density functional theory (DFT). Typical mechanisms are modeled to determine the preferred substitution pathway according to the activation energy barriers. The present computational results are in favor of interchange associative (I(a)) mechanism for the substitution of F(-) into Al(H(2)O)(6)(3+), whereas interchange dissociative (I(d)) mechanism is preferred for the substitution into Al(H(2)O)(5)(OH)(2+), which is in agreement with the previous experimental findings.

A sensitive electrochemical approach for monitoring the effects of nano-Al2O3 on LDH activity by differential pulse voltammetry.

In this paper, a sensitive electrochemical approach for monitoring the effect of nano-Al(2)O(3) on lactate dehydrogenase (LDH) activity is established. It is based on the determination of reduction current of NAD(+) involved in enzyme promoting catalytic reaction of "pyruvate + NADH + H+ [see text]L D H lactate + NAD+" by differential pulse voltammetry (DPV). Various influencing factors including nano-type, nano-size, and adsorbed pollutant organics have been investigated.

Density functional investigation of the water exchange reaction on the gibbsite surface.

The water exchange reactions on the gibbsite surface have been investigated by density functional calculations (B3LYP/6-31G(d) level) combining the supermolecular model and PCM model in this paper, and the water exchange rate constants on the gibbsite surface have also been predicted. In the proposed reaction pathways, the clusters Al6(OH)18(H2O)6(0) and Al6(OH)12(H2O)12(6+) are used as the models of gibbsite surface and protonated gibbsite surface respectively to examine the effect of protonation of gibbsite surface on the water exchange rate constants. The activation energy barriers DeltaE(s) not equal to (aq) for Al6(OH)18(H2O)6(0) and Al6(OH)12(H2O)12(6+) are 28.

Density functional study of the water exchange reaction of the polyoxocation GeO4Al12(OH)24(H2O)12(8+) (K-GeAl12) in aqueous solution.

The water exchange reaction of the polyoxocation GeO(4)Al(12)(OH)(24)(H(2)O)(12)(8+) (K-GeAl(12)) in aqueous solution has been simulated by means of supermolecule density functional calculations. In the proposed dissociative pathway, the leaving water molecule in the first coordination sphere is dissociated from its coordinated aluminium, and via a transition state enters into the second coordination sphere. Our calculated results indicate that the polyoxocation K-GeAl(12) exchanges water in a dissociative way with a barrier height of 37.

Electrochemical and spectrometric studies of double-strand calf thymus gland DNA denatured by Al(III) at neutral pH.

The interaction between double-strand calf thymus gland DNA (ds-DNA) and Al(III) was studied by using differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE), Raman spectrometry and circular dichroism (CD) spectra. It was shown that at neutral pH ds-DNA did not produce any cathodic peak at the HMDE in the potential window from -550 to -2000 mV vs. SCE.

Electrochemical behavior of lactate dehydrogenase immobilized on "silica sol-gel/nanometre-sized tridecameric aluminum polycation" modified gold electrode and its application.

This paper reports the electrochemical behavior of lactate dehydrogenase (LDH) immobilized in the silica sol-gel film on gold electrode after adding nanometre-sized tridecameric aluminium polycation (nano-Al13, also called nanopolynuclear Al13) as a promoter. A pair of surface controlled quasi-reversible cyclic voltammetry peaks with the formal potential (E0') of 154 mV (vs. SCE) was found in the presence of nano-Al13.

Theoretical investigation of dehydration of aquated Al(OH)2+ species in aqueous solution.

Reaction pathways, solvent effects and energy barriers have been investigated for the dehydration processes of aquated Al(OH)(2)(+) species in aqueous solution by density functional calculations using a supermolecule model. The dehydration processes from Al(H(2)O)(4)(OH)(2)(+) to Al(H(2)O)(2)(OH)(2)(+) involve the water exchange on cis-Al(H(2)O)(4)(OH)(2)(+) and dehydration of the following intermediate pentacoordinate Al(H(2)O)(3)(OH)(2)(+). The calculated results indicate that cis-Al(H(2)O)(4)(OH)(2)(+) exchanges water in a dissociative way with an activation energy of 27.

Assessment of the accuracy of theoretical methods for calculating (27)Al nuclear magnetic resonance shielding tensors of aquated aluminum species.

Assessment of the accuracy of methods including 29 DFT methods and 2 ab initio wave function theory (WFT) methods for predicting (27)Al nuclear magnetic resonance shielding tensors of aquated Al(III) species was carried out. Among all of the tested methods, HF and MP2 methods give the best performance for the calculations of chemical shifts. Among all of the DFT methods with GIAO calculations, O3LYP and MPWKCIS1K are the most accurate models for calculations of chemical shifts, followed in order by BHandHLYP, B98, B97-1, mPW1PW91, PBE1PBE, and MPW1KCIS.

Density functional theory study of the aluminium(III) hydrolysis in aqueous solution.

Supermolecule density functional calculations were performed on the hydrolysis of aluminum(III) and prediction of pK(a) in aqueous solution. The optimization results showed that the most stable structures for the first, second and third hydrolysis products were hexacoordinate, hexacoordinate and pentacoordinate, respectively. The different coordination geometries could easily transform into each other due to the small energy gaps (within 2.

Theoretical investigation on the dimerization of the deprotonated aquo ion of Al(III) in water.

Reaction pathways, solvent effects and energy barriers have been investigated for the dimerization of the deprotonated aquo ion of Al(III) in aqueous solution by performing supramolecule density functional theory calculations. Two competing reaction pathways were investigated, sharing a common first step and third step, i.e.

Resonance Rayleigh scattering method for the recognition and determination of double-stranded DNA using amikacin.

In weakly acidic buffer medium, the interaction of amikacin with calf thymus DNA, yeast RNA and denatured DNA has been investigated by using resonance Rayleigh scattering (RRS) technique. The result shows that calf thymus DNA is capable of enhancing the RRS intensity of the amikacin, while yeast RNA and denatured DNA have very little enhancement effect. Based on the characteristics, a sensitive assay for detecting double-stranded DNA in the presence of denatured DNA and yeast RNA has been developed.