A simplified radioimmunoassay for triiodothyronine (T3) using pre-incubated labelled antigen and antibody

We discribe the development of a simplified radioimmunoassay for triiodothyronine (T₃) using pre-incubated labelled T₃ and antibody. The assay is carried out by adding 50 l of standard or sample to 0.4 ml of pre-incubated reagent dispensed in assay tubes. The reaction is allowed to proceed for about four hours and the antigen-antibody complex precipitated by the addition of 1 cm³ of 22% polyethylene glycol solution. Due to the high dissociation constant of T₃-antibody complex at 37° C (2.83·10^–4 S^–1), the labelled antigen-antibody complex dissociates and thereby the unlabelled antigen binds with the antibody. With a four hour incubation the sensitivity of this assay is comparable to an assay done by the equilibrium method using the same antibody. Sixty serum samples were analyzed using this method and compared with the equilibrium assay (Y=0.94x+0.046 ng/cm³, r=0.98).     

A single reagent thyroxine radioimmunoassay

An homogenous radioimmunoassay of thyroxine using labelled antigen antibody complex as a single reagent is described. Variation of dose response curve slope with assay incubation time has been studied at two different antisera concentrations. The dissociation constant of the complex was found to be 3.5·10⁻⁴ s⁻¹. The assay involves only three pipettings and requires 45 minutes incubation at 37 °C and 10 μl of serum. Though the assay is essentially a nonequilibrium type, apparent increase in sample values, due to the drift of dose response curve for 45 minutes delay was less than 7.5%. Within and between assay variations were both less than 5% c. v. Assay has been validated by recovery experiments. Analysis of 40 serum samples by the proposed method and by an equilibrium assay gave similar values; r=0.957, Y=0.955X+0.478.     

Selective Detection of Methomyl Pesticide by a Catalytic Chemosensing Assay

The catalytic chemosensing assay (CCA), a new indicator displacement assay, was developed for selective detection of methomyl, a highly toxic pesticide. Trimetallic complex {[Fe^II(dmbpy)(CN)₄]-[Pt^II(DMSO)Cl]₂-[Ru^II(bpy)₂(CN)₂]} ( 1 ; dmbpy=4,4′-dimethyl-2,2′-bipyridine, bpy=2,2′-bipyridine) was synthesized as a task-specific catalyst to initially reduce and degrade methomyl to CH₃SH/CH₃NH₂/CH₃CN/CO₂. The thus-produced CH₃SH interacts with the trimetallic complex to displace the cis-[Ru^II(bpy)₂(CN)₂] luminophore for monitoring. Other pesticides, including organophosphates and similar carbamate pesticides, remained intact under the same catalytic conditions; a selective sensing signal is only activated when 1 recognizes methomyl. Furthermore, 1 can be applied to detect methomyl in real water samples. In the luminescent mode of the assay, the method detection limit (MDL) of 1 for methomyl (LD₅₀=17 mg kg⁻¹) was 1.12 mg L⁻¹.     

A solid phase radioimmunoassay for triiodothyronine using antibody-immobilized serum albumin microspheres

A solid phase radioimmunoassay for triiodothyronine (T₃) has been developed using antibody-immobilized serum albumin microspheres. Antibody albumin microspheres were prepared using a spinning disc aerosol generator. The low density of the antibody-albumin microspheres gives greater mobility for the particles there by ensuring better kinetics to the antigen-antibody reaction. The assay has a single incubation of one hour at 37° C and the separation of the antigen-antibody complex is accomplished by centrifugation. The sensitivity of this assay is 0.3 ng/cm³ and has a range of 0.3–4 ng/cm³.     

Hydroxylation of 4‐Amino‐5‐hydroxynaphthalene‐2,7‐disulfonic Acid Monosodium Salt Catalysed by Horseradish Peroxidase and Hydrogen Peroxide: Computation of Kinetic Parameters Including Its Application to Crude Plant Extracts

The new spectrophotometric assay method for the quantification of peroxidase activity uses 4‐amino‐5‐hydroxynaphthalene‐2,7‐disulfonicacid monosodium salt (AHNDSA) as chromogenic co‐substrate. The method is based on hydroxylation of AHNDSA in presence of H₂O₂/peroxidase forming quinone, having λ_max = 460 nm in the acetate buffer (pH = 4.0) at 30 °C. The linearity of H₂O₂ by kinetic method was 10–332 µM and for peroxidase by kinetic and fixed time methods were 1.18–18.92 and 1.18–9.46 nM, respectively. Catalytic efficiency and catalytic power for peroxidase assay were 7.965 × 10⁴ M^?1min^?1 and 3.76 × 10^?4 min^?1, respectively. From the plot of d(1/A_o) vs d(1/V_o) and d(1/H_o) vs d(1/V_o), the apparent Michaelis‐Menten constants for H₂O₂ and AHNDSA were K = 68 and K = 275 µM, respectively. The method was tested with some plant extracts and also compared with guaiacol/peroxidase system. Except Boerhavia diffusa, all other tested plant samples showed highest peroxidase activity. The proposed method is a rapid and convenient method to determine peroxidase activity by spectrophotometer. This method for the first time reports peroxidase activity in Lantana camara and Oplismenus compositus plants. Kinetic results showed that AHNDSA/peroxidase system can be better hydrogen donor for peroxidase assay than guaiacol system.     

Equilibrium Structure of Beryllium Dibromide from Combined Gas Electron Diffraction and Vibrational Spectroscopy Analysis

The molecular structure of BeBr₂ has been investigated by gas-phase electron diffraction at the temperature 800(10) K. The conventional analysis yielded the following values: r _g(Be–Br) = 1.944(6)Å, l(Be–Br) = 0.068(4)Å, r _g(Br–Br) = 3.848(8)Å, l(Br–Br) = 0.109(3)Å, k(Be–Br) = 1.1(1.1) × 10^–5 ų, (Br–Br) = 2.1(1.0) × 10^–5 ų. Three models of nuclear dynamics were used to simulate the conventional analysis values—infinitesimal vibrations and two models, which take into account the kinematic and dynamic anharmonicity of the bending vibration. All models give similar values of bond angle, amplitudes, and shrinkage, excluding the harmonic model, which yields too low value l(Br–Br). The equilibrium bond distance r _e(Be–Br) = 1.932(11) Å was estimated, taking into account the anharmonicity corrections for stretching and bending vibrations and centrifugal distortion.     

Nonvalent interactions in the crystal structures of (Et4N)2[Mo3S7Br6] and (Et4N)(H9O4)[Mo3S7Cl6] clusters

Crystal structures of (Et₄N)₂[Mo₃S₇Br₆] (I) and (Et₄N)(H₉O₄)[Mo₃S₇Cl₆] (II) clusters belonging to the class of Mo₃S ₇ ⁴⁺ were determined by X-ray diffraction analysis. Crystals I are orthorhombic a=19.106(3), b=12.930(2), c=29.887(5) Å, V=7383(2) ų, space group Pbca, Z=8, d_calc=2.253 g/cm³, R(F)=0.0402, wR(F²)=0.0587 for 2493 F_hkl>4σ. Crystals II are monoclinic, a=17.106(3), b=18.882(4), c=11.006(2), Å, β=126.13(3)°, V=2871.2(9) ų, space group Cc, Z=4, d_calc=2.147 g/cm³, R(F)=0.0181, wR(F²)=0.0445 for 2307 F_hkl>4σ. Structure I has an anion dimer with 3S_ax…Cl=3.258(4)–3.404(4) Å; the dimer is similar to that observed in the structures of A₂[M₃X₇Hal₆], A=Ph₄P⁺, Ph₃EtP⁺, and PPN⁺. In structure II, infinite chains of anions bonded by 3S_ax…Cl contacts of 3.183(3)–3.394(3) Å were found. A similar phenomenon was established earlier for the structure of (Et₄N)(H₉O₄)[Mo₃S₇Br₆] (III), which is not isostructural to II. Compounds II and III also differ in the structure of the H₉O₄ ⁺ cation: infinite helix in II and pyramid in III.     

Studies On Rare-Earth Complexes with Crown Ethers. Part XXV. Synthesis,characterization, and structure of the complexes of lanthanide nitrates with 13-crown-4

The lanthanide nitrate complexes with 13-crown-4(13-C-4) have been prepared in AcOEt. These new complexes with the general formula Ln(NO₃)₃.(13-c-4) (Ln = La–Nd, Sm–Lu) have been characterized by means of elemental analysis, IR and ¹H-NMR spectra, conductivity measurements, and TG-DTA techniques. The crystal and molecular structure of Nd(No₃)₃. (13-c-4) has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group P2₁/a with Z = 8. Lattice parameters are a = 15.393(1), b = 12.578(1), c = 19.279(2) Å, β = 113.05(1)°, V = 3435 ų, D_c = 2.01 g cm^?3, μ = 31.0 cm^?1 (Mok₂), F(000) = 2056. The structure was solved by Patterson and Fourier techniques and refined by least-squares to a final conventional R value of 0.032 for 5218 independent reflections with I ? 3σ(I). There are two independent Nd(No₃)₃ · (13-C-4) monomers in one asymmetrical unit. The coordination numbers are ten in these two independent monomers.     

On-chip integrated hydrolysis, fluorescent labeling, and electrophoretic separation utilized for acetylcholinesterase assay

A sensitive on-chip acetylcholinesterase (AChE) assay that serves as a basis for the development of a fully integrated on-chip AChE-inhibitor detection assay is presented. The sequential steps required for the on-chip analysis process were integrated into a microchip. Transport and mixing of the reagents occurred by a combination of electroosmosis and electrophoresis using computer-controlled electrokinetic transport. AChE-catalyzed hydrolysis of acetylthiocholine to thiocholine was determined by on-chip reaction of thiocholine with eosinmaleimide, and the resulting thioether was electrophoretically separated and detected by laser-induced fluorescence (LIF). Enzyme-substrate mixing and reaction by confluent flow of reagents was compared with electrophoretically mediated microanalysis (EMMA), based on injection of an enzyme plug, and the utilization of differences in electrophoretic mobility as a driving force for efficient mixing and reaction. Both methods yielded similar results, however the EMMA-plug technique is preferable. The EMMA-plug technique was optimized for length and pushing time of enzyme plug, length of dyes mixture plug, acetylthiocholine concentration, and detector location. Detection of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and paraoxon, two AChE inhibitors, was demonstrated by off-chip mixing of the inhibitor and AChE, followed by the on-chip AChE assay. Limit of detection of VX for 5.5 min incubation and of paraoxon for 8 min incubation was 4 × 10⁻¹⁰ and 4 × 10⁻⁷ M, respectively. Utilization of the AChE microchip assay for inhibition kinetics was demonstrated also by evaluation of the inhibitor-enzyme bimolecular reaction constant (k_i). The evaluated k_i values for VX and paraoxon for AChE from the electric eel were 3.5 × 10⁷ and 1.7 × 10⁵ M⁻¹ min⁻¹, respectively, conforming well to reported values obtained by bulk methods.     

Stimuli‐responsive 4‐acryloylmorpholine/4‐acryloylpiperidine copolymers via nitroxide mediated polymerization

4‐acryloylmorpholine/4‐acryloylpiperidine statistical copolymers were synthesized by nitroxide mediated polymerization (NMP) with BlocBuilder unimolecular initiator in dimethylformamide solution at 120 °C. The copolymers had narrow molecular weight distributions (dispersity ? = 1.25–1.35, number average molecular weights M _n = 8.5–13.7 kg mol^?1). The copolymer microstructure was essentially statistical (reactivity ratios r _4AP = 0.81 ± 0.73, r _4AM = 0.73 ± 0.68 based on non‐linear fitting of the Mayo‐Lewis equation). Cloud point temperatures (CPT) in aqueous media were tuned from 11 °C to 92 °C, merely by adjusting the initial monomer composition. Using NMP permitted sharper control of the CPT transitions, compared to the similar copolymer made using conventional radical polymerization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2160–2170     

The crystal and molecular structure of tetraethylammonium hydrotris(3,5-dimethylpyrazolyl)boratotricarbonylmolybdenum(0), [NEt4][Mo(CO)3HB(C5H7N2)3]

The crystal and molecular structure of tetraethylammonium hydrotris(3,5-dimethylpyrazolyl)boratotricarbonylmolybdenum(0), [N(C₂H₅)₄][Mo(CO)_3^? HB(3,5-Me₂pz)₃] has been determined from intensity data collected using counter methods. The salt crystallizes in space group Pna2₁ with parameters a = 18.038(6), b = 9.956(3), c = 16.881(3) Å, V = 3031.4(20) ų, Z = 4, d_calc = 1.33 g/ml and d_obs = 1.33 g/ml. Final convergence yielded a conventional R = 0.042 and a “goodness of fit” of 2.07. The steric pocket formed by the 3-methyl hydrogens of the pyrazolyl moiety is discussed.     

Solid Solution Formation between Vanadium(V) and ­Tungs­ten(V) Oxide Phosphate

The solid solutions (V_1–xW_x)OPO₄ with β‐VOPO₄ structure type (0.0 ≤ x ≤ 0.01) and α_II‐VOPO₄ structure type (0.04 ≤ x ≤ 0.26) were obtained from mixtures of V^VOPO₄ and W^VOPO₄ by conventional solid state reactions and by solution combustion synthesis. Single crystals of up to 3 mm edge length were obtained by chemical vapor transport (CVT) (800 → 700 °C, Cl₂ as a transporting agent). Single crystal structure refinements of crystals at x = 0.10 [a = 6.0503(2) Å, c = 4.3618(4) Å, R₁ = 0.021, wR₂ = 0.058, 21 parameters, 344 independent reflections] and x = 0.26 [a = 6.0979(2) Å, c = 4.2995(1) Å, R₁ = 0.030, wR₂ = 0.081, 21 parameters, 346 independent reflections] confirm the α_II‐VOPO₄ structure type (P4/n, Z = 2) with mixed occupancy V/W for the metal site. Due to the specific redox behavior of W⁵⁺ and V⁵⁺, solid solutions (V_1–xW_x)OPO₄ should be formulated as (V^IV_xV^V_1–2xW^VI_x)OPO₄. The valence states of vanadium and tungsten are confirmed by XPS measurements. V⁴⁺ with d¹ configuration was identified by EPR spectroscopy and magnetic measurements. Electronic spectra of the solid solutions show the IVCT(V⁴⁺ → V⁵⁺) and the LMCT(O^2– → V⁵⁺). (V_0.74W_0.26)OPO₄ powders exhibit semi‐conducting behavior (E_g = 0.7 eV).     

Single-crystal growth and crystal structure refinement of CuAlO2

Single crystals of the delafossite-type compound CuAlO₂ were grown from Al₂O₃Cu₂O melt by a slow-cooling method from 1200°C. Three types were found in as-grown crystals (single crystals, short-columnar twin crystals with concave angles, and laminar twin crystals). The twinning form is similar to the spinel-type twin. CuAlO₂ is rhombohedral, $\text{R}\text{3}\text{m, a = 2.8604(7), c = 16.953(5)}\text{A}\text{?}$, Z = 3, Dx = 5.12 g/cm³ and Dm = 5.06 g/cm³. The crystal structure of CuAlO₂ was analyzed by means of single-crystal X-ray diffraction with a conventional R value = 0.038. The value of the U₁₁ component of the thermal parameter of Cu⁺ was twice as large as U₃₃.     

Magnetic studies of vanadyl(IV) tartrate dimers

Temperature-dependent magnetic susceptibility data have been collected for solid sodium salts of the binuclearvanadyl(IV) complexes [(VO)₂(d-tart)₂]^4?, [(VO)₂(dl-tart)₂]^4?, [(VO)₂(dl-mmt)₂]^4?,and [(VO)₂(dl-dmt)₂]^4?. (“tart” = tartrate(4?), “mmt” = monomethyl-tartrate(4?), “dmt” = dimethyltartrate(4?).) Ferromagnetic intradimer- and antiferromagnetic interdimer exchange is found; however, both interactions are small and similar in magnitude and reliable exchange constants cannot be extracted. The intradimer interaction probably occurs by a superexchange mechanism.     

Synthesis,characterization, and bonding of indium clusters. Rb2In3, a zintl phase with layers of closo-indium octahedra

The Rb-In system contains only RbIn₄ (BaAl₄ type) and Rb₂In₃ in the 0–80 at.% In region. The structure of Rb₂In₃ consists of rubidium ions between layers of closo-In₆ clusters joined into sheets through exo bonds at four coplanar vertices (I4/mmm, a=6.8735 (4) Å, c=15.899 (1) Å, R(F)/R_w=3.2/3.5%). The phase is isostructural with Cs₂In₃ when a probable error in the earlier space group assignment is corrected. Rb₂In₃ is a poor conductor (P> 10³ μohm · cm) with a temperature-independent magnetic susceptibility of (0 ± 4) x 10^?6 emu/mol after core and orbital corrections. The corresponding Zintl phase (closed shell configuration) predicted on the basis of conventional electron counting for the cluster network is supported by extended-Hückel MO calculations. The structures of Rb₄In₆ and In₄Rb show a close, inverse relationship in the same space group.     

Efficient Fe(III)/Fe(II) cycling triggered by MoO2 in Fenton reaction for the degradation of dye molecules and the reduction of Cr(VI)

There is a relatively low efficiency of Fe(III)/Fe(II) conversion cycle and H₂O₂ decomposition (<30%) in conventional Fenton process, which further results in a low production efficiency of OH and seriously restricts the application of Fenton. Herein, we report that the commercial MoO₂ can be used as the cocatalyst in Fenton process to dramatically accelerate the oxidation of Lissamine rhodamine B (L-RhB), where the efficiency of Fe(III)/Fe(II) cycling is greatly enhanced in the Fenton reaction meanwhile. And the L-RhB solution could be degraded nearly 100% in 1 min in the MoO₂ cocatalytic Fenton system under the optimal reaction condition, which is apparently better than that of the conventional Fenton system (～50%). Different from the conventional Fenton reaction where the OH plays an important role in the oxidation process, it shows that ¹O₂ contributes most in the MoO₂ cocatalytic Fenton reaction. However, it is found that the exposed Mo⁴⁺ active sites on the surface of MoO₂ powders can greatly promote the rate-limiting step of Fe³⁺/Fe²⁺ cycle conversion, thus minimizing the dosage of H₂O₂ (0.400 mmol/L) and Fe²⁺ (0.105 mmol/L). Interestingly, the MoO₂ cocatalytic Fenton system also exhibits a good ability for reducing Cr(VI) ions, where the reduction ability for Cr(VI) reaches almost 100% within 2 h. In short, this work shows a new discovery for MoO₂ cocatalytic advanced oxidation processes (AOPs), which devotes a lot to the practical water remediation application.     

Peroxidase‐catalyzed electrochemical assay of hydrogen peroxide: A ping–pong mechanism

In view of the great importance of determination of hydrogen peroxide in many scientific fields and industrial applications and the attractive operational simplicity of potentiometric approach for the enzymatic assay, the kinetics of horseradish peroxidase–catalyzed electrochemical assay of H₂O₂ was studied in this work at 25°C. All kinetic characteristics were determined by the double reciprocal Lineweaver–Burk and (primary and secondary) double reciprocal Hanes–Woolf plots. The results confirmed that the reaction follows a ping–pong mechanism. The Michaelis–Menten constants for H₂O₂ and 4‐fluorophenol were K_m = 0.081 ± 0.001 mM and K^4‐FP_m = 0.185 ± 0.002 mM, respectively. The maximum rate was also estimated to be V_max = 0.182 ± 0.002 mM min^?1 (at 25 ± 0.05°C). © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 699–704, 2012     

Molecular and crystal structure of Bis(η5-cyclopentadienyl)titanium(IV) Dibromide,Ti(η5-C5H5)2Br2

The crystal and molecular structure of Bis(η⁵-cyclopentadienyl)titanium(IV) dibromide, Ti(η⁵?C₅H₅)₂Br₂, has been investigated by an X-ray structure determination. Crystal data: triclinic, a = 7.872(5), b = 11.807(5), c = 12.310(3) Å, α = 107.62(3), β = 100.83(4), γ = 90.69(4)°, V = 1 068(14) ų, T = 293, space group P1 , Z = 4 (there are two crystallographically independent molecules in the asymmetric unit cell and their conformations are similar). Final R and R_w values are 0.068 and 0.073, respectively. The structural results are compared to those for similar type molecules.     

Beiträge zum thermischen Verhalten und zur Kristallchemie von wasserfreien Phosphaten. XV. Darstellung,Kristallstruktur und Eigenschaften von Kupfer(II)-ultraphosphat CuP4O11 (≙ Cu2P8O22)

Synthesis, Crystal Structure, and Properties of Copper(II) Ultraphosphate CuP₄O₁₁ CuP₄O₁₁ was synthesised from Cu₂P₄O₁₂ and P₄O₁₀ (500°C, sealed silica ampoules) using iodine and a few mg of CuP₂ or phosphorus as mineraliser. Chemical transport reactions in a temperature gradient 600 → 500°C led to the formation of well developed, colourless, transparent crystals with edge-lengths up to 5 mm (deposition rate m ≈? 2 mg/h). The crystal structure of copper(II) ultraphosphate (C1 ; Z = 8; a = 13.084(3) Å, b = 13.024(2) Å, c = 10.533(2) Å, α = 89.28(2)°, β = 118.42(2)°, γ = 90.30(2)°) has been determined and refined from X-ray data obtained from a pseudo-merohedrally twinned crystal (twin element two-fold rotation axis // b; volume ratio: 17/3; 3063 independent reflections with 2θ ? 53.4°; 291 variables; conventional residual (based on F) R1 = 0.038, wR2 = 0.101 (based on F²), GooF = 1.10). The crystal structure of CuP₄O₁₁ is built from four crystallographically independent ten-membered polyphosphate rings of very similar conformation. These rings are linked to form two-dimensional nets parallel (?2 0 1) planes. There is a close topological relationship between these nets and those formed in polyphosphides CdP₄ and CuP₂. Copper on two crystallographic sites (Cu₂P₈O₂₂) is coordinated by oxygen thus forming elongated [CuO₆] octahedra (d_eq(Cu? O) ≈? 1.96 Å; d_ax(Cu? O) ≈? 2.34 Å). The crystal g-tensor of CuP₄O₁₁ has been determined from powder samples to g₁ = 2.09, g₂ = 2.24, g₃ = 2.36. These values are in good agreement with molecular g-values from calculations within the framework of the angular overlap model on the two independent CuO₆ octahedra (Cu²⁺(1): g_x = 2.09, g_y = 2.10, g_z = 2.52; Cu²⁺(2): g_x = 2.08, g_y = 2.11, g_z = 2.52) assuming exchange coupling. The observed broad absorption band (7000 cm^?1 to 13000 cm^?1) from powder reflectance measurements (4000–28000 cm^?1) and the bulk magnetic susceptibility of μ_exp = 1.99 μ_B is also reproduced nicely by this calculations.     

An aptamer-based colorimetric assay for chloramphenicol using a polymeric HRP-antibody conjugate for signal amplification

We describe an aptamer-based colorimetric assay for chloramphenicol (CAP) based on the ability of anti-single-stranded DNA antibody (anti-ssDNA Ab) to recognize ssDNA, and the catalytic ability of PowerVision (PV), which is a polymeric conjugate of horseradish peroxidase and antibody with a high enzyme-to-antibody ratio. The complementary DNA of the aptamer (cDNA) was immobilized on magnetic gold nanoparticles (Fe₃O₄@Au) and used as a capture probe (AuMNPs-cDNA). The ssDNA Ab and PV were conjugated to AuNPs to form signal tags that recognize ssDNA with anti-ssDNA Ab to form beads containing the amplified probe (AuMNPs-cDNA@anti-ssDNA Ab/PV-AuNPs). The PV on their surface catalyzes the oxidation of the substrate 3,3’,5,5’-tetramethylbenzidine to produce a color change which is quantified by absorptiometry at 652 nm. The assay has a linear calibration plot for CAP in the 0.01 to 100 ng mL⁻¹ range, with a detection limit as low as 3 pg mL⁻¹. The method was successfully employed to detect CAP in real samples. Results were consistent with data obtained using a conventional enzyme-linked immunosorbent assay.

PowerVision- labeled gold nanoparticles acting as signal tag catalyze the H₂O₂-mediated oxidation of TMB for color development, which can be observed by bare eyes and quantified by ultraviolet-visible spectroscopy.