A Structural and Calorimetric Study on the Interaction Between Jack Bean Urease and Cyanide Ion

The cyanide ion was studied as an effecter of Jack bean urease at 300 K in 30 mmol⋅L⁻¹ Tris buffer, pH=7. The inhibition was investigated by isothermal titration calorimetry (ITC). The extended solvation model was used for CN⁻+JBU interaction over the whole range of CN⁻ concentrations. The binding parameters recovered from the solvation model were attributed to the interaction with cyanide ion. It was found that cyanide ion acted as a noncooperative inhibitor of urease, and there is a set of 12 identical and independent binding sites for CN⁻ ions. The dissociation equilibrium constant is 749.99 μmol⋅L⁻¹. The molar enthalpy of binding is ΔH=−13.60 kJ⋅mol⁻¹.     

Selective separation and determination of primidone in pharmaceutical and human serum samples using molecular imprinted polymer-electrospray ionization ion mobility spectrometry (MIP-ESI-IMS)

Application of electrospray ionization ion mobility spectrometry (ESI-IMS) as the detection technique for separation method based on molecular imprinted polymer (MIP) was investigated and evaluated. The method is exhaustively validated, including sensitivity, selectivity, recovery, reproducibility, and column capacity. The linear dynamic range of 0.02-2.00 μg mL⁻¹ was obtained for primidone analysis with ESI-IMS. The recovery of drug analyzed was calculated to be above 90% and the relative standard deviation (RSD), was below 3% for all experiments. Various real samples were analyzed with the coupled techniques, and the results obtained revealed the efficient clean-up of the samples using MIP separation before the analysis by ESI-IMS as a detection technique.     

A high performance method for thermodynamic study on the binding of copper ion and glycine with Alzheimer’s amyloid β peptide

The interaction of Cu²⁺ to the first 16 residues of the Alzheimer’s amyloid β peptide, Aβ(1–16) was studied by isothermal titration calorimetry at pH 7.2 and 37°C in aqueous solution. The Gholamreza Rezaei Behbehani (GRB) solvation model was used to reproduce the enthalpies of interactions of Aβ(1–16) with glycine, Gly+Aβ(1–16), and Cu²⁺ ions, Cu²⁺ +Aβ(1–16), over the whole range of Cu2+ concentrations. The binding parameters recovered from the solvation model were attributed to the structural change of Aβ(1–16) due to the glycine and Cu²⁺ interactions. It was found that there is a set of two identical binding sites for Cu²⁺ ions. p=2 indicates that the binding has positive cooperativity in the two binding sites. Aβ(1–16) structure is destabilized greatly as a result of binding to Cu²⁺ ions.     

Spectroscopic observation and structure of CS2 dimer

Infrared spectra of the CS(2) dimer are observed in the region of the CS(2) ν(3) fundamental band (～1535 cm(-1)) using a tunable diode laser spectrometer. The weakly bound complex is formed in a pulsed supersonic slit-jet expansion of a dilute gas mixture of carbon disulfide in helium. Contrary to the planar slipped-parallel geometry previously observed for (CO(2))(2), (N(2)O)(2), and (OCS)(2), the CS(2) dimer exhibits a cross-shaped structure with D(2d) symmetry. Two bands were observed and analyzed: the fundamental (C-S asymmetric stretch) and a combination involving this mode plus an intermolecular vibration. In both cases, the rotational structure corresponds to a perpendicular (ΔK = ±1) band of a symmetric rotor molecule. The intermolecular center of mass separation (C-C distance) is determined to be 3.539(7) A?. Thanks to symmetry, this is the only parameter required to characterize the structure, if the monomer geometry is assumed to remain unchanged in the dimer. From the band centers of the fundamental and combination band an intermolecular frequency of 10.96 cm(-1) is obtained, which we assign as the torsional bending mode. This constitutes the first high resolution spectroscopic investigation of CS(2) dimer.     

Reduced Graphene Oxide|Carbon Ceramic Electrode Modified with CdS‐Hemoglobin as a Sensitive Hydrogen Peroxide Biosensor

A sensitive hydrogen peroxide (H₂O₂) biosensor was developed based on a reduced graphene oxide|carbon ceramic electrode (RGO|CCE) modified with cadmium sulfide‐hemoglobin (CdS‐Hb). The electron transfer kinetics of Hb were promoted due to the synergetic function of RGO and CdS nanoparticles. The transfer coefficient (α) and the heterogeneous electron transfer rate constant (k_s) were calculated to be 0.54 and 2.6 s^?1, respectively, indicating a great facilitation achieved in the electron transfer between Hb and the electrode surface. The biosensor showed a good linear response to the reduction of H₂O₂ over the concentration range of 2–240 µM with a detection limit of 0.24 µM (S/N=3) and a sensitivity of 1.056 µA µM^?1 cm^?2. The high surface coverage of the CdS‐Hb modified RGO|CCE (1.04×10^?8 mol cm^?2) and a smaller value of the apparent Michaelis? Menten constant (0.24 mM) confirmed excellent loading of Hb and high affinity of the biosensor for hydrogen peroxide.     

Infrared spectra of ethylene clusters: (C2D4)2 and (C2D4)3

Spectra of ethylene dimers and trimers are studied in the ν(11) fundamental band region of C(2)D(4) (≈2200 cm(-1)) using a tuneable quantum cascade laser to probe a pulsed supersonic slit jet expansion. The dimer spectrum is that of a prolate symmetric top perpendicular band, with a distinctive appearance because the A rotational constant is almost exactly equal to six times the B constant. The analysis supports the previously determined cross-shaped dimer structure with D(2d) symmetry. An ethylene trimer has not previously been observed with rotational resolution. The spectrum is that of an oblate symmetric top parallel band. It leads to a proposed trimer structure which is barrel shaped and has C(3h) or C(3) symmetry, with the ethylene monomer C-C axes approximately aligned along the trimer symmetry axis.     

Development of a voltammetric procedure for assay of thebaine at a multi-walled carbon nanotubes electrode: quantification and electrochemical studies

The study of electrochemical behavior and determination of thebaine (THEB), an opiate alkaloid, is described on a multi-walled carbon nanotube (MWCNT) modified glassy carbon electrode by adsorptive stripping voltammetry and electrochemical impedance spectroscopy. The results indicated that MWCNT electrodes remarkably enhance electrocatalytic activity toward the oxidation of THEB in a wide pH range of 2.0–10.0, and it shows two irreversible and diffusion-controlled anodic peaks. Then, a sensitive, simple, and time-saving cyclic voltammetric procedure was developed for the analysis of THEB in human urine samples. Under optimized conditions, the oxidation peak has two linear dynamic ranges of 1.0–80.0 and 100.0–600.0 μM, with detection limit of 0.23 μM and a precision of <4% (relative standard deviation for eight analysis).     

Norm Transitive Semigroups on Operator Algebra

Let $\mathcal A $ be a semigroup of bounded linear operators on the Banach algebra $B(X)$ for a separable Banach space $X$ . We show the transitivity of $\mathcal A $ with the operator norm topology, implies hypercyclicity with the strong operator topology (SOT) while the converse may not be true. As a consequence, SOT-transitive semigroup of left multiplication operators on $B(X)$ is characterized.     

Wettability of calcite and mica modified by different long-chain fatty acids (C18 acids)

The effect of long-chain fatty acid adsorption on the wetting states of calcite and mica powders is investigated. The selected long-chain fatty acids are saturated or unsaturated aliphatic acids (stearic acid and oleic acid, respectively) and naphthenic acids with saturated or unsaturated aromatic rings (18-cyclohexyloctadecanoic acid and 18-phenoloctadecanoic acid, respectively). The amount of irreversibly adsorbed acid is determined by thermogravimetric analysis. The affinity of water and n-decane for these samples before and after modification is deduced from their adsorption isotherm and microcalorimetry. Thermodynamic analysis of surface pressure and spreading tension are performed based on adsorption isotherms. The enthalpy versus coverage curve for water adsorption and its comparison to liquefaction enthalpy is shown to be a meaningful method for characterizing the wettability of a surface. The naphthenic acid with unsaturated aromatic ring deeply modifies the calcite to an oil-wet state. The mica powder was not as strongly modified as calcite by these acid molecules.     

A cloud point extraction for spectrophotometric determination of ultra- trace antimony without chelating agent in environmental and biological samples

We report on a simple, sensitive and reliable method for the cloud point extraction of antimony (Sb) and its subsequent spectrophotometric detection. It is based on the color reaction of Sb (III) with iodide in acidic medium and subsequent micelle-mediated extraction of tetraiodoantimonate using a non-ionic surfactant in the absence of any chelating agent. The effects of reaction and extraction parameters were optimized. The calibration plot is linear in the range of 0.80–95?ng?mL^?1 of antimony in the sample solution, with a regression coefficient (r) of 0.9994 (for n?=?9). The detection limit (at SNR?=?3) is 0.23?ng?mL^?1, and the relative standard deviations at 10 and 70?ng?mL^?1 of antimony are 3.32 and 1.85?% (at n?=?8), respectively. The method compared favorably to other methods and was applied to determine antimony in seawater, anti-leishmania drug (glucantime), and human serum.