Yersiniabactin metal binding characterization and removal of nickel from industrial wastewater

Yersiniabactin (Ybt) is a metal‐binding natural product that has been re‐purposed for water treatment. The early focus of this study was the characterization of metal binding breadth attributed to Ybt. Using LC‐MS analysis of water samples exposed to aqueous and surface‐localized Ybt, quantitative assessment of binding was completed with metals that included Pd²⁺, Mg²⁺, and Zn²⁺. In total, Ybt showed affinity for 10 metals. Next, Ybt‐modified XAD‐16N resin (Ybt‐XAD) was utilized to quantify the affinity for metal removal, showing a rank order of Fe³⁺ > Ga³⁺ > Ni²⁺ > Cu²⁺ > Cr²⁺≈Zn²⁺ > Co²⁺ > Pd²⁺ > Mg²⁺ > Al³⁺, and in the applied treatment of wastewater from a local precious metal plating company, showing selective removal of nickel from the aqueous effluent. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1548–1554, 2017     

A naphthalene derivative as ‘turn‐on’ fluorescent chemosensor for the highly selective and sensitive detection of Al3+

A Schiff base compound derived from naphthalene has been synthesized and characterized as an Al³⁺‐selective fluorescent probe. The chemosensor ( L ) exhibits high selectively for Al³⁺ in aqueous solution, even in the presence of biologically relevant cations such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Pb²⁺ and several transition metal ions. There was no observed interference from anions like Br^?, Cl^?, HSO₃^?, SO₃^2?, S₂O₃^2?, NO₂^?, CO₃^2? and AC^?. The lowest detection limit for the chemosensor L was found to be 1.89 × 10^?8 M with a linear response towards Al³⁺ over a concentration range of 5 × 10^?6 to 4 × 10^?5 M. Furthermore, the proposed chemosensor has been used for imaging of Al³⁺ in two different types of cells with satisfying results, which further demonstrates its value for practical application in biological systems.     

An OFF–ON–OFF type fluorescent probe based on a naphthalene derivative for Al3+ and F− ions and its biological application

A novel fluorescent probe‐based naphthalene Schiff, 1‐(C2‐glucosyl‐ylimino‐methyl)‐naphthalene‐2‐ol (L) was synthesized by coupling d ‐glucosamine hydrochloride with 2‐hydroxy‐1‐naphthaldehyde. It exhibited excellent selectivity and highly sensitivity for Al³⁺ in ethanol with a strong fluorescence response, while other common metal ions such as Pb²⁺, Mg²⁺, Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Fe²⁺, Mn²⁺, Hg²⁺, Li⁺, Na⁺, K⁺, Fe³⁺, Cr³⁺, Zn²⁺, Ag⁺, Ba²⁺ and Ca²⁺ did not cause the same fluorescence response. The probe selectively bound Al³⁺ with a binding constant (K_a) of 5.748 × 10³ M^?1 and a lowest detection limit (LOD) of 4.08 nM. Moreover, the study found that the fluorescence of the L ? Al³⁺ complex could be quenched after addition of F^? in the same medium, while other anions, including Cl^?, Br^?, I^?, NO₂^?, NO₃^?, ClO₄^?, CO₃^2?, HCO₃^?, SO₄^2?, HSO₄^?, CH₃COO^?, PO₄^3?, HPO₄^2?, S^2? and S₂O₃^2? had nearly no influence on probe behaviour. Binding of the [L ? Al³⁺] complex to a F^? anion was established by different fluorescence titration studies, with a detection limit of 3.2 nM in ethanol. The fluorescent probe was also successfully applied in the imaging detection of Al³⁺ and F^? in living cells.     

Al<Superscript>3+</Superscript> and Fe<Superscript>2+</Superscript> toxicity reduction potential by acid-resistant strains of <Emphasis Type="Italic">Rhodopseudomonas palustris</Emphasis> isolated from acid sulfate soils under acidic conditions

This research aimed to evaluate the capacity of acid-resistant purple nonsulfur bacteria, Rhodopseudomonas palustris strains VNW02, TLS06, VNW64, and VNS89, to resist Al³⁺ and Fe²⁺ and to investigate their potential to remove both metals from aqueous solutions using exopolymeric substances (EPS) and biomasses. Based on median inhibition concentration (IC₅₀), strain VNW64 was the most resistant to both metals under conditions of aerobic dark and microaerobic light; however, strain TLS06 was more resistant to Al³⁺ under aerobic dark conditions. High metal concentrations resulted in an altered cellular morphology, particularly for strain TLS06. Metal accumulation in all tested PNSB under both incubating conditions as individual Al³⁺ or Fe²⁺ was in the order of cell wall?>?cytoplasm?>?cell membrane. This was also found in a mixed metal set only under conditions of aerobic dark as microaerobic light was in the degree of cytoplasm?>?cell wall?>?cell membrane. Of all strains tested, EPS from strain VNW64 had the lowest carbohydrate and the highest protein contents. Metal biosorption under both incubating conditions, EPS produced by strains VNW64 and TLS06, achieved greater removal (80 mg Al³⁺ L^?1 and/or 300 mg Fe²⁺ L^?1) than their biomasses. Additionally, strain VNW64 had a higher removal efficiency compared to strain TLS06. Based on the alteration in cellular morphology, including biosorption and bioaccumulation mechanisms, R. palustris strains VNW64 and TLS06 demonstrated their resistance to metal toxicity. Hence, they may have great potential for ameliorating the toxicity of Al³⁺ and Fe²⁺ in acid sulfate soils for rice cultivation.     

Determination of bergenin based on the electrochemiluminescence quenching of tris(2,2′‐bipyridine)‐ruthenium(II)

Quenching effects of bergenin, based on the electrochemiluminescence (ECL) of the tris(2,2′‐bipyridyl)‐ruthenium(II) (Ru(bpy)₃²⁺)/tri‐n‐propylamine (TPrA) system in aqueous solution, is been described. The quenching behavior can be observed with a 100‐fold excess of bergenin over Ru(bpy)₃²⁺. In the presence of 0.1 m TPrA, the Stern–Volmer constant (K_SV) of the ECL quenching is as high as 1.16 × 10⁴ M^?1 for bergenin. The logarithmic plot of the inhibited ECL versus logarithmic plot of the concentration of bergenin was linear over the range 3.0 × 10^?6–1.0 × 10^?4 mol/L. The corresponding limit of detection was 6.0 × 10^?7 mol/L for bergenin (S/N = 3). In the mechanism of quenching it is believed that the competition of the active free radicals between Ru(bpy)₃²⁺/TPrA and bergenin was the key factor for the ECL inhibition of the system. Photoluminescence, cyclic voltammetry, coupled with bulk electrolysis, supports the supposition mechanism of the Ru(bpy)₃²⁺/TPrA–bergenin system. Copyright © 2015 John Wiley & Sons, Ltd.     

Study on the interactions of mapenterol with serum albumins using multi‐spectroscopy and molecular docking

The interactions of mapenterol with bovine serum albumin (BSA) and human serum albumin (HSA) have been investigated systematically using fluorescence spectroscopy, absorption spectroscopy, circular dichroism (CD) and molecular docking techniques. Mapenterol has a strong ability to quench the intrinsic fluorescence of BSA and HSA through static quenching procedures. At 291 K, the binding constants, K_a, were 1.93 × 10³ and 2.73 × 10³ L/mol for mapenterol–BSA and mapenterol–HAS, respectively. Electrostatic forces and hydrophobic interactions played important roles in stabilizing the mapenterol–BSA/has complex. Using site marker competitive studies, mapenterol was found to bind at Sudlow site I on BSA/HSA. There was little effect of K⁺, Ca²⁺, Cu²⁺, Zn²⁺ and Fe³⁺ on the binding. The conformation of BSA/HSA was changed by mapenterol, as seen from the synchronous fluorescence spectra. The CD spectra showed that the binding of mapenterol to BSA/HSA changed the secondary structure of BSA/HSA. Molecular docking further confirmed that mapenterol could bind to Sudlow site I of BSA/HSA. According to Förster non‐radiative energy transfer theory (FRET), the distances r₀ between the donor and acceptor were calculated as 3.18 and 2.75 nm for mapenterol–BSA and mapenterol–HAS, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Light emission from the Fe2+–EDTA–ascorbic acid–H2O2 system strongly enhanced by plant phenolic acids

Oxidative reactions can result in the formation of electronically excited species that undergo radiative decay depending on electronic transition from the excited state to the ground state with subsequent ultra‐weak photon emission (UPE). We investigated the UPE from the Fe²⁺–EDTA (ethylenediaminetetraacetic acid)–AA (ascorbic acid)–H₂O₂ (hydrogen peroxide) system with a multitube luminometer (Peltier‐cooled photon counter, spectral range 380–630 nm). The UPE, of 92.6 μmol/L Fe²⁺, 185.2 μmol/L EDTA, 472 μmol/L AA, 2.6 mmol/L H₂O₂, reached 1217 ± 118 relative light units during 2 min measurement and was about two times higher (P < 0.001) than the UPE of incomplete systems (Fe²⁺–AA–H₂O₂, Fe²⁺–EDTA–H₂O₂, AA–H₂O₂) and medium alone. Substitution of Fe²⁺ with Cr²⁺, Co²⁺, Mn²⁺ or Cu²⁺ as well as of EDTA with EGTA (ethylene glycol‐bis(β‐aminoethyl ether)‐N,N,N′,N′‐tetraacetic acid) or citrate powerfully inhibited UPE. Experiments with scavengers of reactive oxygen species (dimethyl sulfoxide, mannitol, sodium azide, superoxide dismutase) revealed the dependence of UPE only on hydroxyl radicals. Dimethyl sulfoxide at the concentration of 0.74 mmol/L inhibited UPE by 79 ± 4%. Plant phenolics (ferulic, chlorogenic and caffec acids) at the concentration of 870 μmol/L strongly enhanced UPE by 5‐, 13.9‐ and 46.8‐times (P < 0.001), respectively. It is suggested that augmentation of UPE from Fe²⁺–EDTA–AA–H₂O₂ system can be applied for detection of these phytochemicals.     

Luminescence properties of novel deep‐red‐emitting Ca3Al2Ge2O10:Cr3+ phosphors

Ca₃Al₂Ge₂O₁₀:Cr³⁺ phosphors were prepared by a high‐temperature solid‐state method, and their luminescence properties were investigated. Under excitation at 550 nm, Ca₃Al₂Ge₂O₁₀:Cr³⁺ phosphors exhibited a broad red emission band at 697 nm in the range 650–750 nm that was caused by the ²E→⁴A₂ transition of Cr³⁺. For the 697 nm emission peak, emission intensity reached a maximum at x = 0.07, and there was concentration quenching of Cr³⁺ in Ca₃Al₂Ge₂O₁₀; the corresponding concentration quenching mechanism was analysed. Under excitation at 262 nm, the Ca₃Al₂Ge₂O₁₀:Cr³⁺ phosphor showed a weakly broad emission band in the range 350–600 nm that was caused by intrinsic defects (V′′_Ca and V′′_O). Copyright © 2016 John Wiley & Sons, Ltd.     

Characterization of an extracellular alkaline serine protease from marine <Emphasis Type="Italic">Engyodontium album</Emphasis> BTMFS10

An alkaline protease from marine Engyodontium album was characterized for its physicochemical properties towards evaluation of its suitability for potential industrial applications. Molecular mass of the enzyme by matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) analysis was calculated as 28.6 kDa. Isoelectric focusing yielded pI of 3–4. Enzyme inhibition by phenylmethylsulfonyl fluoride (PMSF) and aprotinin confirmed the serine protease nature of the enzyme. K _m, V _max, and K _cat of the enzyme were 4.727 × 10⁻² mg/ml, 394.68 U, and 4.2175 × 10⁻² s⁻¹, respectively. Enzyme was noted to be active over a broad range of pH (6–12) and temperature (15–65°C), with maximum activity at pH 11 and 60°C. CaCl₂ (1 mM), starch (1%), and sucrose (1%) imparted thermal stability at 65°C. Hg²⁺, Cu²⁺, Fe³⁺, Zn²⁺, Cd⁺, and Al³⁺ inhibited enzyme activity, while 1 mM Co²⁺ enhanced enzyme activity. Reducing agents enhanced enzyme activity at lower concentrations. The enzyme showed considerable storage stability, and retained its activity in the presence of hydrocarbons, natural oils, surfactants, and most of the organic solvents tested. Results indicate that the marine protease holds potential for use in the detergent industry and for varied applications.     

Competitive binding of Fe<Superscript>3+</Superscript>, Cr<Superscript>3+</Superscript>, and Ni<Superscript>2+</Superscript> to transferrin

Competitive binding of Fe³⁺, Cr³⁺, and Ni²⁺ to transferrin (Tf) was investigated at various physiological iron to Tf concentration ratios. Loading percentages for these metal ions are based on a two M ⁿ⁺ to one Tf (i.e., 100% loading) stoichiometry and were determined using a particle beam/hollow cathode–optical emission spectroscopy (PB/HC-OES) method. Serum iron concentrations typically found in normal, iron-deficient, iron-deficient from chronic disease, iron-deficient from inflammation, and iron-overload conditions were used to determine the effects of iron concentration on iron loading into Tf. The PB/HC-OES method allows the monitoring of metal ions in competition with Fe³⁺ for Tf binding. Iron-overload concentrations impeded the ability of chromium (15.0 μM) or nickel (10.3 μM) to load completely into Tf. Low Fe³⁺ uptake by Tf under iron-deficient or chronic disease iron concentrations limited Ni²⁺ loading into Tf. Competitive binding kinetic studies were performed with Fe³⁺, Cr³⁺, and Ni²⁺ to determine percentages of metal ion uptake into Tf as a function of time. The initial rates of Fe³⁺ loading increased in the presence of nickel or chromium, with maximal Fe³⁺ loading into Tf in all cases reaching approximately 24%. Addition of Cr³⁺ to 50% preloaded Fe³⁺–Tf showed that excess chromium (15.0 μM) displaced roughly 13% of Fe³⁺ from Tf, resulting in 7.6 ± 1.3% Cr³⁺ loading of Tf. The PB/HC-OES method provides the ability to monitor multiple metal ions competing for Tf binding and will help to understand metal competition for Tf binding.     

Response surface optimized peroxyoxalate chemiluminescence of octahydro‐Schiff base derivative as new luminophor and study of the quenching effect of some cations,amino acids and cholesterol

We report the first detailed study of the characteristics of an octahydro‐Schiff base derivative as a new luminophor in the peroxyoxalate chemiluminescence (POCL) system. The effect of reagents on this new POCL system was investigated. In addition, the response surface methodology was used for evaluating the relative significance of variables in this POCL system, establishing models and determining optimal conditions. The quenching effect of some cations and compounds such as Cu²⁺, Fe³⁺, Hg²⁺, imidazole, histidine and cholesterol on an optimized POCL reaction were studied. The dynamic ranges were up to approximaterly 100 and 175 × 10^?6 M for Cu²⁺ and cholesterol respectively. The detection limits were 3.3 × 10^?6 m and 2.58 × 10^?6 m for Cu²⁺ and histidine, respectively. In all cases the relative standard deviations were 4–5% (n = 4). Copyright © 2014 John Wiley & Sons, Ltd.     

Characterization of a highly Al3+‐selective fluorescence probe based on naphthalimide‐Schiff base and its application to practical water samples

A new fluorescent Al³⁺‐probe, N‐allyl‐4‐[3,3′‐((2‐aminoethyl)azanediyl)‐bis(N´‐(2‐hydroxybenzylidene)propanehy‐drazide)]‐1,8‐naphthalimide ( L ), was designed and synthesized based on 1,8‐naphthalimide. The probe L contains 1,8‐naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. The structure of L was determined by single crystal X‐ray. L emission at 526 nm increased on addition of Al³⁺ under excitation wavelength at 350 nm. L exhibited high selectivity and sensitivity fluorescence emission towards to Al³⁺ in ethanol/Tris–HCl buffer solution (1:1, v/v, pH = 7.2) as compared with other tested metal ions. A good linearity with a correlation coefficient (R²) of 0.99 was observed in the concentration range 2–10 μM. The binding constant and the detection limit of L for Al³⁺ were calculated to 2.6 × 10⁴ M^?1 and 0.34 μM, respectively. The results of experiments that including Job plot, ultraviolet–visible (UV–Vis) light titration, fluorescence titration, ESI‐MS and ¹H NMR titration, indicated a 1:1 stoichiometric complex between L and Al³⁺. L was highly effective in monitoring Al³⁺ in real‐life Yellow River and tap water samples.     

A new quaternary photoluminescence enhancement system of Eu−N‐(o‐vanillin)‐1,8‐diaminonaphthalene−1,10‐phenanthroline−Zn and its application in determining trace amounts of europium and zinc

A new sensitive quaternary photoluminescence enhancement system has been successfully developed to determine trace amounts of Eu³⁺ and Zn²⁺. The photoluminescence intensity of Eu ? N‐(o‐vanilin)‐1,8‐diaminonaphthalene systems was greatly increased by the addition of specific concentrations of 1, 10‐phenanthroline and Zn²⁺. The excitation and emission wavelengths were 274 and 617 nm, respectively. Under optimal system conditions, the photoluminescence intensity showed a linear response toward Eu³⁺ in the range of 5.0 × 10^–6 ~ 2.0 × 10^–5 M with a limit of detection (= 2.2 × 10^–9 M) and the photoluminescence intensity of the system decreased linearly by increasing the Zn²⁺ concentration in the range of 5.0 × 10^–8 ~ 1.0 × 10^–6 M with a limit of detection (= 8.8 × 10^–11 M). This system was successfully applied for the determination of trace amounts of Eu³⁺ in a high purity La₂O₃ matrix and in the synthetic rare earth oxide mixture, and of Zn²⁺ in a high purity Mg(NO₃)₂ · 6H₂O matrix and in synthetic coexisting ionic matrixes. The energy transfer mechanism, photoluminescence enhancement of the system and interference of other lanthanide ions and common coexisting ions were also studied in detail. Copyright © 2013 John Wiley & Sons, Ltd.     

The behaviors of metal ions in the CdTe quantum dots–H2O2 chemiluminescence reaction and its sensing application

The behaviors of 15 kinds of metal ions in the thiol‐capped CdTe quantum dots (QDs)–H₂O₂ chemiluminescence (CL) reaction were investigated in detail. The results showed that Ag⁺, Cu²⁺ and Hg²⁺ could inhibit CdTe QDs and H₂O₂ CL reaction. A novel CL method for the selective determination of Ag⁺, Cu²⁺ and Hg²⁺ was developed, based on their inhibition of the reaction of CdTe QDs and H₂O₂. Under the optimal conditions, good linear relationships were realized between the CL intensity and the logarithm of concentrations of Ag⁺, Cu²⁺ and Hg²⁺. The linear ranges were from 2.0 × 10^?6 to 5.0 × 10^?8 mol L^?1 for Ag⁺, from 5.0 × 10^?6 to 7.0 × 10^?8 mol L^?1 for Cu²⁺ and from 2.0 × 10^?5 to 1.0 × 10^?7 mol L^?1 for Hg²⁺, respectively. The limits of detection (S/N = 3) were 3.0 × 10^?8, 4.0 × 10^?8 and 6.7 × 10^?8 mol L^?1 for Ag⁺, Cu²⁺ and Hg²⁺, respectively. A possible mechanism for the inhibition of CdTe QDs and H₂O₂ CL reaction was also discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Enhanced electrochemiluminescence from reduced graphene oxide–CdTe quantum dots for highly selective determination of copper ion

An electrochemiluminescence (ECL) sensor based on reduced graphene oxide–CdTe quantum dots (RGO–CdTe QDs) composites for detecting copper ion (Cu²⁺) was proposed. The ECL behaviours of the RGO–CdTe QD modified electrode were investigated with H₂O₂ as the co‐reactant. Quantitative detection of Cu²⁺ was realized as Cu²⁺ could effectively quench the ECL signal of the RGO–CdTe QDs. A wide linear range of 1.00 × 10^?14 to 1.00 × 10^?4 M (R = 0.9953) was obtained under optimized conditions, and a detection limit (S/N = 3) was achieved of as low as 3.33 × 10^?15 M. The proposed sensor also exhibited good stability and selectivity for the detection of copper ions. Finally, the analytical application of the proposed sensor was also evaluated using river water.     

2‐Hydroxynaphthalene‐1‐carbaldehyde‐ and 2‐(Aminomethyl)pyridine‐Based Schiff Base CuII Complexes for DNA Binding and Cleavage

Three mononuclear Cu^II complexes, [CuCl(naph‐pa)] ( 1 ), [Cu(bipy)(naph‐pa)]Cl ( 2 ), and [Cu(naph‐pa)(phen)]Cl ( 3 ) ((naph‐pa)=Schiff base derived from the condensation of 2‐hydroxynaphthalene‐1‐carbaldehyde and 2‐picolylamine (=2‐(aminomethyl)pyridine), bipy=2,2′‐bypiridine, and phen=1,10‐phenanthroline) were synthesized and characterized. Complex 1 exhibits square‐planar geometry, and 2 and 3 exhibit square pyramidal geometry, where Schiff base and bipy/phen act as NNO and as NN donor ligands, respectively. CT (Calf thymus)‐DNA‐binding studies revealed that the complexes bind through intercalative mode and show good binding propensity (intrinsic binding constant K_b: 0.98×10⁵, 2.22×10⁵, and 2.67×10⁵ M ^?1 for 1 – 3 , resp.). The oxidative and hydrolytic DNA‐cleavage activity of these complexes has been studied by gel electrophoresis: all the complexes displayed chemical nuclease activity in the presence and absence of H₂O₂. From the kinetic experiments, hydrolytic DNA cleavage rate constants were determined as 2.48, 3.32, and 4.10 h^?1 for 1 – 3 , respectively. It amounts to (0.68–1.14)×10⁸‐fold rate enhancement compared to non‐catalyzed DNA cleavage, which is impressive. The complexes display binding and cleavage propensity to DNA in the order of 3 > 2 > 1 .     

Luminescent sensor for Cd2+, Hg2+ and Ag+ in water based on a sulphur‐containing receptor: quantitative binding–softness relationship

A water‐soluble, high‐output fluorescent sensor, based on a lumazine ligand with a thiophene substituent for Cd²⁺, Hg²⁺ and Ag⁺ metal ions, is reported. The sensor displays fluorescence enhancement upon Cd²⁺ binding (log  β = 2.79 ± 0.08) and fluorescence quenching by chelating with Ag⁺ and Hg²⁺ (log β = 4.31 ± 0.15 and 5.42 ± 0.1, respectively). The mechanism of quenching is static and occurs by formation of a ground‐state non‐fluorescent complex followed by rapid intersystem crossing. The value of the Stern–Volmer quenching rate constant (k_q) by Ag⁺ ions is close to 6.71 × 10¹² mol/L/s at 298 K. The thermodynamic parameters (ΔG, ΔH and ΔS) were also evaluated and indicated that the complexation process is spontaneous, exothermic and entropically favourable. The quantitative linear relationship between the softness values of Klopman (σ_K) or Ahrland (σ_A) and the experimental binding constants (β) being in the order of Hg²⁺ > Ag⁺ > Cd²⁺ suggests that soft–soft interactions are the key for the observed sensitivity and selectivity in the presence of other metal ions, such as: Pb²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Co²⁺, Zn²⁺ and Mg²⁺ ions. Copyright © 2008 John Wiley & Sons, Ltd.     

Prevention by Ce3+ of DNA destruction caused by Hg2+ in fish intestine

The interactions between Hg²⁺, Ce³⁺, and the mixuure of Ce³⁺ and Hg²⁺, and DNA from fish intestine in vitro were investigated by using absorption spectrum and fluorescence emission spectrum. The ultraviolet absorption spectra indicated that the addition of Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ to DNA generated an obviously hypochromic effect. Meanwhile, the peak of DNA at 205.2 nm blue-shifted and at 258.2 nm red-shifted. The size of the hypochromic effect and the peak shift of DNA by metal ion treatments was Hg²⁺>Hg²⁺+Ce³⁺>Ce³⁺. The fluorescence emission spectra showed that with the addition of Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ the emission peak at about 416.2 nm of DNA did not obviously change, but the intensity reduced gradually and the sequence was Hg²⁺>Hg²⁺+Ce²⁺>Ce³⁺. Hg²⁺, Ce³⁺, and the mixture of Ce³⁺ and Hg²⁺ had 1.12, 0.19, and 0.41 binding sites to DNA, respectively; the fluorescence quenching of DNA caused by the metal ions all attributed to static quenching. The binding constants (K _A ) of binding siees were 8.98×10⁴ L/mol and 1.02×10⁴ L/mol, 5.12×10⁴ L/mol and 1.10×10³ L/mol, 6.66×10⁴ L/mol and 2.36×10³ L/mol, respectively. The results showed that Ce³⁺ could relieve the destruction of Hg²⁺ on the DNA structure.     

β‐Cell Function and Insulin Sensitivity in Adolescents From an OGTT

Given the increase in the incidence of insulin resistance, obesity, and type 2 diabetes in children and adolescents, it would be of paramount importance to assess quantitative indices of insulin secretion and action during a physiological perturbation, such as a meal or an oral glucose‐tolerance test (OGTT). A minimal model method is proposed to measure quantitative indices of insulin secretion and action in adolescents from an oral test. A 7 h, 21‐sample OGTT was performed in 11 adolescents. The C‐peptide minimal model was identified on C‐peptide and glucose data to quantify indices of β‐cell function: static φ_s and dynamic φ_d responsivity to glucose from which total responsivity φ was also measured. The glucose minimal model was identified on glucose and insulin data to estimate insulin sensitivity, S_I, which was compared to a reference measure, S_I^ref, provided by a tracer method. Disposition indices, which adjust insulin secretion for insulin action, were then calculated. Indices of β‐cell function were φ_s = 51.35 ± 8.89 × 10^?9min^?1, φ_d = 1,392 ± 258 × 10^?9, and φ = 82.09 ± 17.70 × 10^?9min^?1. Insulin sensitivity was S_I = 14.19 ± 2.73 × 10^?4, not significantly different from S_I^ref = 14.96 ± 3.04 × 10^?4 dl/kg·min per µU/ml, and well correlated: r = 0.98, P < 0.0001, thus indicating that S_I can be accurately measured from an oral test. Disposition indices were DI_s = 1,040 ± 201 × 10^?14 dl/kg/min² per pmol/l, DI_d = 33,178 ± 10,720 × 10^?14 dl/kg/min per pmol/l, DI = 1,844 ± 522 × 10^?14 dl/kg/min² per pmol/l. Virtually the same minimal model assessment was obtained with a reduced 3 h, 9‐sample protocol. OGTT interpreted with C‐peptide and glucose minimal model has the potential to provide novel insight regarding the regulation of glucose metabolism in adolescents, and to evaluate the effect of obesity and interventions such as diet and exercise.     

A terbium‐sensitized spectrofluorimetric method for determination of catecholamines in a serum sample with micelle medium

A terbium‐sensitized spectrofluorimetric method has been developed for determination of catecholamines such as norepinephrine (NE), epinephrine (EP) and dopamine (DA), using sodium dodecyl benzene sulphonate (SDBS). Fluorescence sensitization of terbium ions (Tb³⁺) by complexation with catecholamines in the presence of SDBS was observed. The fluorescence intensities of the Tb³⁺–catecholamine complexes were highly enhanced by introducing SDBS with an emission maximum at 545 nm after excitation at 290 nm. The conditions for the complex formation of Tb³⁺–catecholamine were investigated systematically and optimized to determine catecholamines in a serum sample. Under the optimum conditions, the fluorescence intensities of the Tb³⁺–catecholamine complexes were increased linearly with the concentration of NE, EP and DA over the ranges 2.5 × 10^–10–1.0 × 10^–8, 2.5 × 10^–10–1.0 × 10^–8 and 2.5 × 10^–9–1.0 × 10^–7 g/mL with correlation coefficients of 0.999, 0.999 and 0.9996, respectively. The limits of detection (3δ) of NE, EP and DA were found to be 4.6 × 10^–11, 7.8 × 10^–11 and 8.38 × 10^–10 g/mL, respectively. Precision of the method was tested at the concentration level of 1.2 × 10^?7 g/mL for five replicate measurements of NE, EP and DA, giving relative standard deviations (RSDs) of 1.41%, 1.23% and 1.89%, respectively. The interaction mechanism of the Tb³⁺–catecholamine complexes system was investigated and presented with ultraviolet absorption spectra. The proposed method has been applied for the quantitative determination of NE, EP and DA in a spiked serum sample and a pharmaceutical preparation sample. Copyright © 2011 John Wiley & Sons, Ltd.