Evaluation of α-fetoprotein (AFP) in human serum by chemiluminescence enzyme immunoassay with magnetic particles and coated tubes as solid phases

In this work, the monoclonal antibodies (McAbs) to α-fetoprotein (AFP) were immobilized on two different solid phases, i.e., magnetic particles (MP) and coated tubes (CT). Based on this, a MP based chemiluminescence enzyme immunoassay (MP-CLEIA) and a CT based CLEIA (CT-CLEIA) were proposed for the evaluation of AFP in human serum and their analytical merits were studied and compared. By detailed discussion of several performance variants, including the concentration of immobilized McAb, dilution ratio of horseradish peroxidase (HRP) labeled McAb (HRP-McAb), total assay time, substrate volume, chemiluminescent kinetics, and hook effect concentration, the advantages of MP-CLEIA became conspicuously apparent. Moreover, in the presence of MP, the catalytic activity of labeled enzyme was kept to high extent and the stability of immunoreagents was satisfied. Finally, 59 human serum samples were detected by the MP-CLEIA and a good correlation was obtained when comparing the results with that from a commercial electrochemiluminescence immunoassay kit.     

Synthesis and characterization of a monomeric and a dihydroxo-bridged dimeric complexes of iron(III) with α-benzoinoxime

The reaction of α-benzoinoxime, H₂BNO with FeCl₃ in the presence of Et₃N as a base gives the mononuclear Fe(III) complex, Fe(HBNO)₃ (1). Treatment of 1 with a methanolic solution of KOH at room temperature leads to a dinuclear Fe(III)–Fe(III) complex, [Fe(HBNO)₂OH]₂ (2). The complexes were initially characterized on the basis of their elemental, mass and thermal analyses. The IR studies were useful in assigning the coordination mode of the benzoinoxime ligand to the iron metal. In addition, the presence of a hydroxo-bridge in the dimeric complex 2 is inferred from the IR spectral studies. Room-temperature Mössbauer studies indicated octahedral, high-spin iron(III). Variable-temperature magnetic susceptibility measurements supported the existence of the μ-dihydroxo-bridging structure core, Fe^III(μ-OH)₂Fe^III in the dinuclear complex 2. Theoretical modelling of the magnetic data indicated a weak antiferromagnetic spin exchange between the iron(III) centers (J = −8.35 cm⁻¹, g = 2.01, ρ = 0.02 and TIP = 1.7 × 10⁻⁴ cm³ mol⁻¹ for H = −2JS₁ · S₂). The electronic spectra of the complexes revealed two bands due to d–d transitions and one band assignable to an oxygen (p_π) → Fe(d_π∗) LMCT transition observed in each complex. An additional charge-transfer transition, assignable to μ-hydroxo(p_π) → Fe(d_π∗), was observed for the dimeric complex 2. The structural and vibrational behaviors of these complexes have been elucidated with quantum mechanical methods.     

Synthesis and structure of iron(III) complexes with a new ligands based on Girard’s reagent

Condensation of 5-bromosalicylaldehyde with Girard’s reagent T yields a new ligand in the form of a salt, 5-bromosalicylaldehyde (carboxymethyl)trimethylammonium chloride hydrazone (5-BrH₂SalGT)Cl (I). Ligand I is readily soluble in water and reacts with iron chloride to give the complex [Fe(5-BrSalGT)Cl₂] (II). Treatment of II with KCNS leads to the compound [Fe(5-BrSalGT)(NCS)₂(H₂O)] (III). At any ratio of the initial reagents, only complexes with the ratio metal: ligand = 1: 1 are isolated. Comparison of the structural data for compounds I–III shows that ligand I is deprotonated in the course of complex formation and is coordinated in the anionic form. Its conformational rearrangement is minimal and involves only a change in the orientation of the terminal group N(CH₃)₃. In complexes II and III, ligand I is coordinated to the metal ion through the ONO donor atoms. The structures of the complexes with different acido ligands are significantly different. Although the complexes contain each two inorganic anions, their coordination polyhedra differ from each other. In II, the iron atom is at the center of a trigonal bipyramid, whereas in III the iron atom has a tetragonal-bipyramidal environment due to the extra coordination of a water molecule. In both complexes, the iron atom is in the high-spin state: at room temperature, μ_eff is 5.86 and 5.81 μ_B for II and III, respectively. Complexes II and III are ordinary paramagnets down to 2 K.     

Electrochemical immunoassay for α-fetoprotein through a phenylboronic acid monolayer on gold

A novel reusable electrochemical immunosensor for α-fetoprotein (AFP) based on phenylboronic acid monolayer on gold was proposed. The sensor was fabricated by immobilizing of 3-aminophenylboronic acid (APBA) conjugated thiol-mixed monolayer on gold through 2-(5-norbornene-2,3-dicarboximido)-1,1,3,3-tetramethyluronium tetrafluoroborate (TNTU) as linkage. AFP and enzyme-conjugated antibody were further trapped to the modified electrode surface through sugar-boronic acid and immunoaffinity interactions, respectively. The attached enzyme-conjugated antibody on the electrode surface could catalyze the reduction of hydrogen peroxide in the presence of thionine, which can be used to detect AFP in human serum by a competitive mechanism. Cyclic voltammetric, electrochemical impedance studies and photometric activity assays were used to probe the assembly and regeneration process of the immunosensor. The influences of the competitive ratio of antigen and antibody, pH value of the measuring solution, incubation temperature and time were explored for optimizing the analytical performance. The whole assay process including incubation, detection and regeneration of the electrode could be completed in 35 min. The detection of AFP in five serum samples provided from clinically diagnosed patients with liver cancer showed acceptable accuracy. The proposed immunosensor enabled fast, low-cost and would be valuable for clinical diagnosis.     

αPicolinic acid as a colorimetric reagent : Determination of iron and aluminium

A new spot test for stannous tin has been evolved, using the ammonium salt of 6-nitro-2-naphthylamine-8-sulphonic acid as reagent, an intense blue fluorescence being produced under ultraviolet light. Of 47 metallic ions tested only Sn⁺² fluoresced under the conditions of the test, as little as one microgram being capable of detection.     

Determination of Coenzyme II Using Balofloxacin–Terbium(III) as a Fluorescence Probe by Spectrofluorometry

Abstract

A new spectrofluorometric method was developed for determination of coenzyme II. We studied the interactions between balofloxacin–terbium(III) complex and coenzyme II by using ultraviolet–visible absorption and fluorescence spectra. While balofloxacin–terbium(III) was used as a fluorescence probe, under the optimum conditions, coenzyme II could remarkably enhance the fluorescence intensity of the balofloxacin–terbium(III) complex at λ = 545 nm, and the enhanced fluorescence intensity was in proportion to the concentration of coenzyme II. Optimum conditions for the determination of coenzyme II were also investigated. The dynamic range for the determination of coenzyme II was 6.0 × 10^?8 to 6.0 × 10^?6 mol L^?1, and the detection limit (3σ/k) was 3.5 × 10^?8 mol L^?1. This method was simple, practical, and relatively free interference from coexisting substances and could be successfully applied to determination of coenzyme II in synthetic samples. The mechanism of fluorescence enhancement of balofloxacin–terbium(III) complex by coenzyme II was also discussed.     

A micro-heterometric determination of traces of iron (III) in alloys and salts with α-nitroso β-naphthol

Ferric iron constituting approximately 0.01% — 0.1% may be determined by a heterometric titration with α-nitroso-β-naphthol. The solution may contain 99.9% or more of calcium, barium, magnesium, aluminium, chromium, manganese, nickel, cadmium or lead salts. No previous separation is necessary. The α-nitroso-β-naphthol is dissolved in alcohol. The analysed solution must be acidified. No complexing agents are necessary. Citrate or tartrate must be absent. The maximum optical density values which are obtained at the end of the titration are proportional to the amount of iron which is analysed. These maximum values are entirely unaffected by the concentrated salt solutions. The heterometric sensitivity of the reaction between iron and α-nitroso-β-naphthol is three times higher in 50% alcoholic solution than in water. The titration takes about one hour. The error is 0.0—4%.     

Crystal structure of a μ-oxo-bridged dimeric iron(III) complex

A dimeric [{Fe(5-ClL1)}₂(μ-O)], [H₂-5-ClL1 = N,N′-bis(5-chloro-2-hydroxybenzylidene)-2-methylpropane-1,2-diamine] tetradentate Schiff-base complex, 1, has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis. Structural analysis of complex 1 shows that the complex is a centrosymmetric dimer. Each of the Fe(III) ions has a five-coordinate geometry and one oxygen atom bridges two Fe(III) ions to form a μ-oxo structure. The geometry around iron atom can be described as a square based pyramid with the FeN₂O₂ coordination plane and oxo ligand.     

Crystal structure of Co(III) α-dimethylglyoximates with imidazole

Two new dimethylglyoximate complexes [Co(DmgH)₂(Im)Cl] (I) and (ImH)[Co(DmgH₂)₂Cl₂] (II), where DmgH^? is the dimethylglyoxime residue and Im is the imidazole molecule, are synthesized. The composition and structure of the crystals are determined from the elemental analysis, IR spectra, and single crystal X-ray diffraction. Complex I is molecular, containing the Im molecule as a coordinated ligand; complex II is of the ionic type with (ImH)⁺ involved as an outer-sphere organic cation. The mode of component packing in the crystals mainly depends on the imidazole position in the compounds.     

Formation of variable-composition iron(III) hydrosilicates with the сhrysotile structure

The process of formation of iron hydrosilicates (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was studied. It was shown that the stage of coprecipitation of magnesium and iron hydroxides in the presence of silica nanoparticles forms poorly crystallized layered Mg–Fe double hydroxides having Fe³⁺ ions in the octahedral sites. Hydrothermal treatment of the mixtures of coprecipitated hydroxides and silica nanoparticles gives rise to layered hydrosilicates, where Fe³⁺ ions occupy both the octahedral (preferentially) and tetrahedral sires. The possibility of the formation and a fairly stable existence of the variable-composition layered hydrosilicate (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was shown to correlate with the stability range of its precursor brucite-like Mg–Fe layered double hydroxide.     

Formation of iron(III) meso-chloro-isoporphyrin as a reactive chlorinating agent from oxoiron(IV) porphyrin π-cation radical

Iron(III) isoporphyrin, a tautomer of porphyrin with a saturated meso carbon, is one of the isoelectronic forms of oxoiron(IV) porphyrin π-cation radical, which is known as an important reactive intermediate of various heme enzymes. The isoporphyrin has been believed to be incapable of catalyzing oxygenation and oxidation reactions. Here, we report that an oxoiron(IV) porphyrin π-cation radical can be converted to iron(III) meso-chloro-isoporphyrin in the presence of trifluoroacetic acid and chloride ion. More importantly, this study shows the first evidence that iron(III) meso-chloro-isoporphyrin is an excellent reactive agent for chlorinating aromatic compounds and olefins. The results of this study suggest that the mechanism involves electrophilic chlorination of substrate with iron(III) meso-chloro-isoporphyrin.     

Synthesis,magnetic and spectral studies of chromium(III), manganese(III), iron(III) and cobalt(III) complexes of thiosemicarbazones derived from benzil α-monoxime and unsubstituted/substituted thiosemicarbazides as biological agents

Cr(III), Mn(III), Fe(III) and Co(III) complexes of thiosemicarbazones, derived from benzil α-monoxime and thiosemicarbazides (BMTH₂), benzil α-monoxime and phenyl thiosemicarbazides (BMPTH₂), benzil α-monoxime and 4-bromophenyl thiosemicarbazides (BMBTH₂), benzil α-monoxime and 4-chlorophenyl thiosemicarbazides (BMCTH₂) and benzil α-monoxime and 4-nitrophenyl thiosemicarbazides (BMNTH₂), have been prepared. These complexes have been characterized by elemental analyses, magnetic susceptibilities, molar conductance measurements, electronic, IR, ¹H and ¹³C NMR spectra (in the case of Co(III) complexes), FAB mass spectra and thermogravimetric analysis to arrive at the geometry of the ligand environment around the metal ion and to elucidate the bonding sites of the ligands with the central metal. The complexes contain two monoprotonic tridentate ligands with NNS donor sites. Coordination to metal ion the oxime nitrogen, imine nitrogen and thione sulfur is confirmed in the complexes by IR spectral studies. The antifungal and antibacterial activities of the ligands and complexes have been screened.     

Synthesis and crystal structure of cobalt(III) α-dioximates with pyrazine

A series of new coordination compounds of cobalt(III) trans-dioximates with pyrazine [CoCl(DH)₂Pz] · H₂O (I), [CoBr(DH)₂Pz] · H₂O (II), [Co(DH)₂Pz₂]NO₃ · H₂O (III), [Co(DH)₂Pz₂][BF₄] (IV), [Co(MgH)₂Pz₂][BF₄] (V), and [Co(NioxH)₂Pz₂][BF₄] (VI), where DH, MgH, and NioxH are dimethylglyoxime, methylglyoxime, and 1,2-cyclohexanedionedioxime monoanions, respectively, Pz is a pyrazine molecule were synthesized. The structures of compounds I, II, and VI were determined by X-ray diffraction. The Co(III) environment in these compounds is octahedral and the pseudomacrocyclic (DioxH⁻)₂ fragment occurs in the equatorial plane. This fragment is stabilized by O-H…O hydrogen bonds. The neutral Pz ligand is monodentate in all three compounds.     

N-Chlorosuccinimide as a versatile reagent for the sulfenylation of ketones: a facile synthesis of α-ketothioethers

The sulfenylation of ketones having α-hydrogens has been achieved using N-chlorosuccinimide (NCS) under mild reaction conditions to produce α-ketothioethers in excellent yields with high selectivity. The use of NCS makes this method quite simple, convenient and practical.     

β-Cyclodextrin as a mimetic of the natural GFP-chromophore environment

The green fluorescent protein (GFP) chromophore has been anchored to β-cyclodextrin (βCD) via a copper(I)-catalyzed azide-alkyne cycloaddition. The photophysical properties of this new GFP-CD derivative have been evaluated, showing the formation of a self-inclusion complex and enhancement of fluorescence of the GFP-chromophore covalently bound to the βCD. This enhancement of fluorescence by encapsulation and hence fixation of the chromophore in a binding pocket mimics the effect exerted by the natural protein environment.     

Mössbauer spectroscopic study of an iron(III) complex with crown porphyrin

A complex of ⁵⁷Fe with 5-{4-[((4′-hydroxybenzo-15-crown-5)-5′-yl)diazo]phenyl}-10,15,20-triphenylporphyrin was studied by Mössbauer spectroscopy. The presence of signals of two types in the spectra (a doublet and an extended absorption band over a wide velocity range) suggests that the Fe atoms occupy two structurally different positions in this complex. The dependences of the doublet asymmetry on temperature and the angle between the normal to the sample plane and the γ-ray beam were studied. The isomer shift δ of the doublet in the temperature range from 360 to 5 K changes from 0.25 to 0.41 mm/s, while the quadrupole splitting remains virtually unchanged (Δ ≈ 0.65 mm/s). The relaxation-type absorption over a wide velocity range, the relative area of which strongly varies with temperature, can be described by a broad singlet with the following parameters: δ = 0.30–0.44 mm/s and Γ = 2.8–3.38 mm/s. According to the δ values, both signals are due to Fe(III) derivatives.     

Specific features of the structures of iron(II) α-benzyl dioxymate solvates with pyridine

Coordination compounds [Fe(DfgH)₂Py₂] (I) and [Fe(DfgH)₂Py₂] · A, where DfgH is the α-benzyldioxime monoanion and A = Py (II), DMF (III), and methyl ethyl ketone (IV), have been synthesized and studied by X-ray diffraction analysis. Diamagnetism and the gamma-resonance (GR) spectral parameters confirm that iron exists in the oxidation state +2 in the low-spin state. The octahedral trans configuration of the iron polyhedra is a common feature of all complexes. The equatorial plane of the octahedron contains two intramolecular hydrogen bonds O-H...O between two organic anions DfgH⁻ affording a pseudomacrocycle. The axial coordinate of the octahedron is occupied by the pyridine molecules, which are almost perpendicular to the equatorial plane N₄(oxime) in complexes I–IV. The structure of the compounds is a framework with allowance for weak interactions C-H...O and C-H...C. The manner of inclusion of solvents into the crystal and their functioning in structure formation of compounds II–IV are discussed.     

2,4,6-Tris(4-iodophenoxy)-1,3,5-triazine as a new recyclable “iodoarene” for in situ generation of hypervalent iodine(III) reagent for α-tosyloxylation of enolizable ketones

The synthesis of 2,4,6-tris[(4-iodo)phenoxy)]-1,3,5-triazine 6, as a new recyclable nonpolymeric analogue of iodobenzene is achieved using the reaction of 2,4,6-trichloro-1,3,5-triazine with 4-iodophenol in the presence of KOH. The application of 6 as a recyclable ‘iodoarene’ is demonstrated for α-tosyloxylation of enolizable ketones via in situ generation of hypervalent iodine(III) species using PTSA and MCPBA as the terminal oxidant. The recyclability of the reagent 6 was possible owing to the facile recovery and reuse from the reaction mixture due to its near insolubility in methanol.     

Liquid-liquid extraction of α-activation products of iron with HDEHP

The carrier-free radiotracers,^52,56Mn,^55,56,58Co and^56,57Ni were produced simultaneously by accelerated -particle activation of iron. They were subsequently studied through LLX using the liquid cation exchanger, HDEHP, as an extractant. A considerable enrichment of individual carrier free radionuclides of manganese, cobalt and nickel was achieved. Production and verification of purity of the carrier-free radiotracers at different stages of their extraction were carried out by -ray spectroscopic studies.     

Solvatochromism and piezochromism of pentacyanoferrates(II) and of mixed valence iron(II)—iron(III) and ruthenium(II)—ruthenium(III) species

Pressure effects on the MLCT bands of the pyrazine- and 4-cyanopyridine-pentacyanoferrate(II) anions have been established. The relation of these piezochromic effects to the solvatochromism of each complex is put into the correlation between these parameters developed for other d⁶ ternary complexes. The conformance of piezochromic and solvatochromic efrects on MMCT bands for diiron and diruthenium mixed valence complexes to this correlation is examined.