A Simple and Sensitive Resonance Scattering Spectral Assay for Detection of Melamine Using Aptamer-Modified Nanosilver Probe

Nanosilver of 10-nm size was prepared by the NaBH₄–sodium citrate procedure, and it was modified by a single-strand DNA (ssDNA) aptamer to fabricate an AgssDNA probe for melamine. The probe was stabile at pH 7.0 Na₂HPO₄–NaH₂PO₄ buffer solutions and in the presence of 25.0 mmol/L NaCl. Upon the addition of melamine, it interacted with the probe to aggregate big clusters, which led to the resonance scattering (RS) intensity at 470 nm increasing greatly. Under the selected conditions, the increased RS intensity (ΔI _470 nm) is linear to melamine concentration in the range of 6.31–378.4 μg/L, with a regression equation of DI_{470 nm} = 1.124c + 10.8 \Delta {I_{{47}0{\rm{ nm}}}} = {1}.{124}c + { 10}.{8} and a detection limit of 3.1 μg/L. The aptamer-modified nanosilver RS assay has been applied for the determination of melamine in milk, with satisfactory results.     

A Simple and Rapid Resonance Scattering Spectral Method for Detection of Trace Hg<Superscript>2+</Superscript> Using Aptamer-Nanogold as Probe

Single-strand deoxyribonucleic acid (ssDNA) were used to modified nanogold particle to obtain a aptamer-nanogold probe (NGssDNA) for Hg(II). The probe is not aggregated in high concentration of NaCl. In the pH 7.0 Na₂HPO₄-NaH₂PO₄ buffer solution and in the presence of high concentration of NaCl, NGssDNA interact with Hg(II) to form stable double-strand T-Hg(II)-T mismatches and to release nanogold particles from the probe. The released nanogold particles aggregated to form bigger clusters which leaded the resonance scattering (RS) intensity at 540 nm enhanced linearly with the concentration of Hg²⁺ in the range of 0.39–1666.7 nM, with detection of 0.1 nM. This simple, rapid, and sensitive aptamer-nanogold RS assay was applied to determination of Hg²⁺ in wastewater, with satisfactory results.     

A highly sensitive resonance scattering spectral assay for carcinoembryonic antigen using immunonanogold as probe and nanocatalyst of NH2OH�CCu(II) particle reaction

Nanogold of 10 nm was used to label carcinoembryonic antigen antibody (CEAAb) to prepare a probe (Au-CEAAb) for carcinoembryonic antigen (CEA). In a Na₂HPO₄–NaH₂PO₄ buffer solution of pH 6.8, CEA reacted with Au-CEAAb to form a big Au-CEAAb–CEA immunocomplex that can be removed by centrifugation. The unreacted Au-CEAAb in the centrifugal supernatant exhibited catalytic effect on the Cu₂O particle reaction, and the Cu₂O particles displayed a resonance scattering (RS) peak at 602 nm. When CEA increased, the RS intensity at 602 nm decreased, and the decreased RS intensity (ΔI _602 nm) was linear to CEA concentration (C _CEA) in the range of 0.02–12 ng mL⁻¹, with the regression equation of ΔI _602 nm = 27.1 C _CEA + 3.3, correlation coefficient of 0.9978 and detection limit of 3 pg mL⁻¹ CEA. The proposed method was applied to detect CEA in real samples, with satisfactory results.     

A label‐free DNAzyme‐cleaving fluorescence method for the determination of trace Pb2+ based on catalysis of AuPd nanoalloy on the reduction of rhodamine 6G

The substrate chain of double‐stranded DNA (dsDNA) could be specifically cleaved by Pb²⁺ to release single‐stranded DNA (ssDNA) that adsorbs onto the AuPd nanoalloy (AuPdNP) to form a stable AuPdNP–ssDNA complex, but the dsDNA can not protect AuPdNPs in large AuPdNP aggregates (AuPdNPA) under the action of NaCl. AuPdNP–ssDNA and large AuPdNPA could be separated by centrifugation. On increasing the concentration of Pb²⁺, the amount of released ssDNA increased; AuPdNP–ssDNA increased in the centrifugation solution exhibiting a catalytic effect on the slow reaction of rhodamine 6G (Rh6G) and NaH₂PO₂, which led to fluorescence quenching at 552 nm. The decrease in fluorescence intensity (ΔF) was linear to the concentration of Pb²⁺ within the range 0.33–8.00 nmol/L, with a detection limit of 0.21 nmol/L. The proposed method was applied to detect Pb²⁺ in water samples, with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.     

A novel and sensitive resonance scattering assay for detection of urea in serum coupled urease catalytic reaction and NH4 + associated particle reaction

In the pH 6.6 Na₂HPO₄–NaH₂PO₄ buffer solutions and in the presence of urease catalyst, urea can be decomposed to form NH₄ ⁺. The NH₄ ⁺ reacted with sodium tetraphenyl boron (NaTPB) to form the association particles that exhibited a resonance scattering (RS) peak at 474 nm. When the urea concentration increased, NH₄ ⁺ increased, and RS intensity at 474 nm enhanced linearly. Under the chosen conditions, the increased RS intensity (ΔI _474 nm) had a linear response to the urea concentration in the range of 0.125–15 μM, with a detection limit of 0.058 μM urea, and a regression equation of ΔI _474 nm = 31.6C + 2.1, a correlation coefficient of 0.9986. This catalytic RS method was applied for the detection of urea in human serum sample, with good selectivity and sensitivity, and the results were consistent with the reference method.     

Highly Sensitive Resonance Scattering Detection of DNA Hybridization Using Aptamer-Modified Gold Nanopaticle as Catalyst

Gold nanoparticle particles in size of 10 nm were used to label the thiol-modified single-stranded DNA aptamer (SH-ssDNA) to obtain an aptamer-modified gold nanoparticle probe (AussDNA) for target DNA (tDNA). In pH 7.4 NaH₂PO₄–Na₂HPO₄ buffer solution, the hybridization reaction between AussDNA and tDNA took place to form larger aptamer-modified gold nanoparticle cluster complex. The excess aptamer-modified gold nanoparticle probe in the supernatant solutions was obtained by centrifuging and can be used as nanocatalyst for the 0.276 mmol/L CuSO₄-65.4 mmol/L potassium-sodium tartrate-0.37 mmol/L glucose system at 70 °C. The cubic Cu₂O particles generated by the nanocatalytic reducing exhibit a strong resonance scattering (RS) peak at 620 nm. In the selected conditions, the RS intensity at 620 nm decreased with addition of tDNA, and the decreased intensity ΔI _{620 nm} is proportional to tDNA concentration (C _tDNA) from 0.12 to 72 pM, with regress equation of ΔI _620 nm = 1.29C _tDNA + 4.05, correlation coefficient of 0.9917, and detection limit of 0.084 pM tDNA.     

Resonance scattering spectral detection of ultratrace Hg(II) using herring sperm DNA modified nanogold probe as catalyst

Herring sperm DNA (hsDNA) was used to modify 10 nm nanogold to obtain a resonance scattering (RS) probe (AuhsDNA) for detection of Hg²⁺. In the presence of salt, Hg²⁺ interacts with AuhsDNA to form stable Hg²⁺–hsDNA complexes, and releases nanogold particles to form larger nanogold clusters that can be removed by membrane filtration. The excess AuhsDNA in the filtrate solution exhibits a catalytic effect on the reaction between hydroxylamine (NH₂OH) and Cu(II). The excess AuhsDNA decreased with the addition of Hg²⁺, which led the RS intensity at 602 nm to decrease. The decreased RS intensity (Δl_{602 nm}) had a linear response to Hg²⁺ concentration in the range of 0.4–400 nM, with a detection limit of 0.2 nM Hg²⁺. This RS method was applied for the detection of Hg²⁺ in water samples, with sensitivity, selectivity and simplicity. Copyright © 2009 John Wiley & Sons, Ltd.     

Biosorption of Pb<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> by Non-Living Biomass of <Emphasis Type="Italic">Spirulina</Emphasis> sp.

Removal of heavy metals (Pb²⁺, Zn²⁺) from aqueous solution by dried biomass of Spirulina sp. was investigated. Spirulina rapidly adsorbed appreciable amount of lead and zinc from the aqueous solutions within 15 min of initial contact with the metal solution and exhibited high sequestration of lead and zinc at low equilibrium concentrations. The specific adsorption of both Pb²⁺ and Zn²⁺ increased at low concentration and decreased when biomass concentration exceeded 0.1 g l⁻¹. The binding of lead followed Freundlich model of kinetics where as zinc supported Langmuir isotherm for adsorption with their r ² values of 0.9659 and 0.8723 respectively. The adsorption was strongly pH dependent as the maximum lead biosorption occurred at pH 4 and 10 whereas Zn²⁺ adsorption was at pH 8 and 10.     

Effects of Pb<Superscript>2+</Superscript> ions on Na<Superscript>+</Superscript> transport in the isolated skin of the toad <Emphasis Type="Italic">Pleurodema thaul</Emphasis>

The effects induced by lead ions on the short-circuit current (SCC) and on the potential difference (V) of the toad Pleurodema thaul skin were investigated. Pb²⁺ applied to the outer (mucosal) surface increased SCC and V and when applied to the inner (serosal) surface decreased both parameters. The stimulatory effect, but not the inhibitory action, was reversible after washout of the metal ion. The amiloride test showed that the increase was due principally to stimulation of the driving potential for Na⁺ (V-E_Na+) and that inhibition was accompanied by a reduction in the V-E_Na+ and also by a significant decrease in skin resistance indicating possible disruption of membrane and/or cell integrity. The effect of noradrenaline was increased by outer and decreased by inner administration of Pb²⁺. The results suggest that mucosal Pb²⁺ activates toad skin ion transport by stimulating the V-E_Na+ and that serosal Pb²⁺, with easier access to membrane and cellular constituents, inactivates this mechanism, revealing greater toxicity when applied to the inner surface of the skin. Abbreviations: SCC – short-circuit current; V – potential difference; V-E_Na+– driving potential for Na⁺; ENaC – epithelial sodium channel; R_Na+– active sodium resistance; RS – passive or shunt resistance; G_Na– active sodium conductance; GS – passive or shunt conductance; Gmax – total conductance; EC₅₀– half-maximal excitatory concentration; IC₅₀– half maximal inhibitory concentration; NA – noradrenaline.     

Free-Labeled Nanogold Catalytic Detection of Trace UO 2 2+ Based on the Aptamer Reaction and Gold Particle Resonance Scattering Effect

In pH?5.5 2-(N-morpholino)-ethanosulfonic acid buffer solution containing 0.0125?M NaCl at 80?°C, the single-stranded substrate DNA hybrid with enzyme DNA to form double-stranded DNA (dDNA). The substrate chain of dDNA could be cracked catalytically by UO ₂ ²⁺ to produce a short single-stranded DNA (ssDNA) that adsorbed on the nanogold (NG) surface to form stable NGssDNA conjugate, and the unadsorbed NG take place aggregation to produce the NG aggregations in blue color. Both NG and NGssDNA exhibited strong catalytic activity on the gold particle reaction between HAuCl₄ and ascorbic acid that can be monitored by resonance scattering (RS) spectral technique at 620?nm. However, the catalytic effect of NG aggregation was very weak and it cannot be separated from the cracked reaction solution. When the UO ₂ ²⁺ concentration increased, the ssDNA increased, the NGssDNA increased, the formed gold particles increased, and the RS intensity at 620?nm increased. The increased RS intensity ??I _620?nm was linear to UO ₂ ²⁺ concentration in the range of 3.35?C23.45?pM, with a regression equation of ??I _620?nm?=?27.6C?+?29.1, and detection limit of 0.1?pM. This new RS assay was applied to analysis of UO ₂ ²⁺ in water sample with satisfactory results.     

HNCA-TOCSY-CANH experiments with alternate <Superscript>13</Superscript>C-<Superscript>12</Superscript>C labeling: a set of 3D experiment with unique supra-sequential information for mainchain resonance assignment

Described here is a set of three-dimensional (3D) NMR experiments that rely on CACA-TOCSY magnetization transfer via the weak ³ \textJ_{\textCa\textCa} ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} coupling. These pulse sequences, which resemble recently described ¹³C detected CACA-TOCSY (Takeuchi et al. 2010) experiments, are recorded in ¹H₂O, and use ¹H excitation and detection. These experiments require alternate ¹³C-¹²C labeling together with perdeuteration, which allows utilizing the small ³ \textJ_{\textCa\textCa} ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} scalar coupling that is otherwise masked by the stronger ¹J_CC couplings in uniformly ¹³C labeled samples. These new experiments provide a unique assignment ladder-mark that yields bidirectional supra-sequential information and can readily straddle proline residues. Unlike the conventional HNCA experiment, which contains only sequential information to the ^{1 3} \textC^a ^{ 1 3} {\text{C}}^{\alpha } of the preceding residue, the 3D hnCA-TOCSY-caNH experiment can yield sequential correlations to alpha carbons in positions i−1, i + 1 and i−2. Furthermore, the 3D hNca-TOCSY-caNH and Hnca-TOCSY-caNH experiments, which share the same magnetization pathway but use a different chemical shift encoding, directly couple the ¹⁵N-¹H spin pair of residue i to adjacent amide protons and nitrogens at positions i−2, i−1, i + 1 and i + 2, respectively. These new experimental features make protein backbone assignments more robust by reducing the degeneracy problem associated with the conventional 3D NMR experiments.     

Reactive oxygen species production and antioxidative defense system in pea root tissues treated with lead ions: the whole roots level

The lead absorbed by the roots induce oxidative stress conditions through the Reactive oxygen species (ROS) production for the pea plants cultivated hydroponically for 96 h on a Hoagland medium with the addition of 0.1 and 0.5 mM of Pb(NO₃)₂. The alterations in \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } and H₂O₂ concentrations were monitored spectrophotometrically which show a rapid increase in \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } production during the initial 2 h, and in case of H₂O₂, during the eighth hour of cultivation. The level of ROS remained higher at all the time points for the roots of the plants cultivated with Pb²⁺ and it was proportional to metal concentration. The production of \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } and H₂O₂ was visualized by means of fluorescence microscope technique. They are produced in nonenzymatic membrane lipid peroxidation and its final product is Malondialdehyde, the level of which increased together with the level of H₂O₂. As stress intensity raised (duration of treatment and Pb²⁺ concentration), so did the activities of superoxide dismutases, catalase and ascorbate peroxidase antioxidative enzymes and of low-molecular antioxidants, particularly glutathione (GSH), homoglutathione (h-GSH) and cysteine substrate toward their synthesis. The root cells redox state (GSH/GSSG) dropped proportionally to lead stress intensity.     

Effects of Copper on T-Type Ca<Superscript>2+</Superscript> Channels in Mouse Spermatogenic Cells

Low voltage-activated, rapidly inactivating T-type Ca²⁺ channels are found in a variety of cells, where they regulate electrical activity and Ca²⁺ entry. In whole-cell patch-clamp recordings from mouse spermatogenic cells, trace element copper (Cu²⁺) inhibited T-type Ca²⁺ current (I _T-Ca) with IC₅₀ of 12.06 μM. Inhibition of I _T-Ca by Cu²⁺ was concentration-dependent and mildly voltage-dependent. When voltage stepped to −20 mV, Cu²⁺ (10 μM) inhibited I _T-Ca by 49.6 ± 4.1%. Inhibition of I _T-Ca by Cu²⁺ was accompanied by a shift of −2.23 mV in the voltage dependence of steady-state inactivation. Cu²⁺ upshifted the current–voltage (I-V) curve. To know the change of the gating kinetics of T-type Ca²⁺ channels, we analyzed the effect of Cu²⁺ on activation, inactivation, deactivation and reactivation of T-type Ca²⁺ channels. Since T-type Ca²⁺ channels are a key component in capacitation and the acrosome reaction, our data suggest that Cu²⁺ can affect male reproductive function through T-type Ca²⁺ channels as a preconception contraceptive material.     

Enhancement of the luminescence properties of Sr3(PO4)2:Dy3+,Li+ white‐light‐emitting phosphors by charge compensator Li+ co‐doping

Sr₃(PO₄)₂:Dy³⁺,Li⁺ phosphors were prepared using a simple high temperature solid method for luminescence enhancement. The structures of the as‐prepared samples agreed well with the standard phase of Sr₃(PO₄)₂, even when Dy³⁺ and Li⁺ were introduced. Under ultraviolet excitation at 350 nm, the Sr₃(PO₄)₂:Dy³⁺ sample exhibited two emission peaks at 483 nm and 580 nm, which were due to the ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transitions of Dy³⁺ ions, respectively. A white light was fabricated using these two emissions from the Sr₃(PO₄)₂:Dy³⁺ phosphors. The luminescence properties of Sr₃(PO₄)₂:Dy³⁺,Li⁺ phosphors, including emission intensity and decay time, were improved remarkably with the addition of Li⁺ as the charge compensator, which would promote their application in near‐ultraviolet excited white‐light‐emitting diodes.     

Microcalorimetric Study on the Toxic Effect of Pb<Superscript>2+</Superscript> to <Emphasis Type="Italic">Tetrahymena</Emphasis>

The toxic effect of Pb²⁺ has been studied in eukaryotic cells by using Tetrahymena as a target. The maximum power (P _m) and the growth rate constant (k) were determined, which showed that values of P _m and k were linked to the concentration (C) of Pb²⁺. The addition of Pb²⁺ caused a decrease of the maximum heat production and growth rate constant, indicating that Tetrahymena growth was inhibited in the presence of Pb²⁺, and Pb²⁺ took part in the metabolism of cells. From micrographs, morphological changes of Tetrahymena were observed with addition of Pb²⁺, indicating that the toxic effect of Pb²⁺ derived from destroying the membrane of surface of Tetrahymena. According to the thermogenic curves and photos of Tetrahymena under different conditions, it is clear that metabolic mechanism of Halobacterium halobium R1 growth has been changed with the addition of Pb²⁺.     

Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> exchange activity in the alkaliphile halotolerant cyanobacterium <Emphasis Type="Italic">Aphanothece halophytica</Emphasis>

The activity of Na⁺/H⁺ exchanger to remove toxic Na⁺ is important for growth of organisms under high salinity. In this study, the halotolerant cyanobacterium Aphanothece halophytica was shown to possess Na⁺/H⁺ exchange activity since exogenously added Na⁺ could dissipate a pre-formed pH gradient, and decrease extracellular pH. Kinetic analysis yielded apparent K _m (Na⁺) and V _max of 20.7 ± 3.1 mM and 3,333 ± 370 nmol H⁺ min⁻¹ mg⁻¹, respectively. For cells grown under salt-stress condition, the apparent K _m (Na⁺) and V _max was 18.3 ± 3.5 mM and 3,703 ± 350 nmol H⁺ min⁻¹ mg⁻¹, respectively. Three cations with decreasing efficiency namely Li⁺, Ca²⁺, and K⁺ were also able to dissipate pH gradient. Only marginal exchange activity was observed for Mg²⁺. The exchange activity was strongly inhibited by Na⁺-gradient dissipators, monensin, and sodium ionophore as well as by CCCP, a protonophore. A. halophytica showed high Na⁺/H⁺ exchange activity at neutral and alkaline pH up to pH 10. Cells grown at pH 7.6 under high salinity exhibited higher Na⁺/H⁺ exchange activity than those grown under low salinity during 15 days of growth suggesting a role of Na⁺/H⁺ exchanger for salt tolerance in A. halophytica. Cells grown at alkaline pH of 9.0 also exhibited a progressive increase of Na⁺/H⁺ exchange activity during 15 days of growth.     

Concentration-Dependent Effects on Intracellular and Surface pH of Exposing <Emphasis Type="Italic">Xenopus</Emphasis> oocytes to Solutions Containing NH<Subscript>3</Subscript>/NH<Subscript>4</Subscript><Superscript>+</Superscript>

Others have shown that exposing oocytes to high levels of (10–20 mM) causes a paradoxical fall in intracellular pH (pH_i), whereas low levels (e.g., 0.5 mM) cause little pH_i change. Here we monitored pH_i and extracellular surface pH (pH_S) while exposing oocytes to 5 or 0.5 mM NH₃/NH₄ ⁺. We confirm that 5 mM causes a paradoxical pH_i fall (−ΔpH_i ≅ 0.2), but also observe an abrupt pH_S fall (−ΔpH_S ≅ 0.2)—indicative of NH₃ influx—followed by a slow decay. Reducing [NH₃/NH₄ ⁺] to 0.5 mM minimizes pH_i changes but maintains pH_S changes at a reduced magnitude. Expressing AmtB (bacterial Rh homologue) exaggerates −ΔpH_S at both levels. During removal of 0.5 or 5 mM NH₃/NH₄ ⁺, failure of pH_S to markedly overshoot bulk extracellular pH implies little NH₃ efflux and, thus, little free cytosolic NH₃/NH₄ ⁺. A new analysis of the effects of NH₃ vs. NH₄ ⁺ fluxes on pH_S and pH_i indicates that (a) NH₃ rather than NH₄ ⁺ fluxes dominate pH_i and pH_S changes and (b) oocytes dispose of most incoming NH₃. NMR studies of oocytes exposed to ¹⁵N-labeled show no significant formation of glutamine but substantial accumulation in what is likely an acid intracellular compartment. In conclusion, parallel measurements of pH_i and pH_S demonstrate that NH₃ flows across the plasma membrane and provide new insights into how a protein molecule in the plasma membrane—AmtB—enhances the flux of a gas across a biological membrane.

Genetic parameters and predicted selection responses for timber production traits in a Castanea sativa progeny trial: developing a breeding program

Total height, diameter, index volume, stem straightness, apical dominance, and survival were assessed at 8 years from seed in an open-pollinated progeny test of 36 families of European chestnut (Castanea sativa Miller) established at two sites in the Atlantic area of Galicia, Spain. Iterative spatial analysis was applied to eliminate the effect of the spatial dependence in the original data and to estimate accurately genetic parameters for evaluating the potential for selection of the measured trees. Spatial analysis was very beneficial for growth traits and survival, but less so if at all for form traits. Estimated individual heritabilities ranged from moderate to high for growth traits ([^(h)]_i² = 0.29 - 0.42 \widehat{h}_i^2 = 0.29 - 0.42 ) and stem straightness ([^(h)]_i² = 0.24 - 0.42 \widehat{h}_i^2 = 0.{24} - 0.{42} ). High coefficients of additive genetic variance were obtained for volume ( [^(\textC)]\textV_\textA = 36.5 - 41.5% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {36}.{5} - {41}.{5}\% ) and straightness ( [^(\textC)]\textV_\textA = 44.26 - 53.84% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {44}.{26} - {53}.{84}\% ). Phenotypic and estimated genetic correlations between growth traits were very high, and correlations between sites indicated that there was no important family × site interaction. No adverse correlations between traits were evident. The results indicate the ample potential for selection in the current progeny trial, where responses to within-family and combined selection for growth traits may be high. Accordingly, three selection scenarios were addressed with the aim to initiate the selection of individuals for implementing the Forest Breeding Plan of Galicia for European chestnut.     

Toxic effects of Pb2+ on the growth and mineral nutrition of signal grass (Brachiaria decumbens) and Rhodes grass (Chloris gayana)

Although grasses are commonly used to revegetate sites contaminated with lead (Pb), little is known regarding the Pb-tolerance of many of these species. Using dilute solution culture to mimic the soil solution, the growth of signal grass (Brachiaria decumbens Stapf cv. Basilisk) and Rhodes grass (Chloris gayana Kunth cv. Pioneer) was related to the mean activity of Pb²⁺ {Pb²⁺} in solution. There was a 50% reduction in fresh mass of signal grass shoots at 5 μM {Pb²⁺} and at 3 μM {Pb²⁺} for the roots. Rhodes grass was considerably more sensitive to Pb in solution, with shoot and root fresh mass being reduced by 50% at 0.5 μM {Pb²⁺}. The higher tolerance of signal grass to Pb appeared to result from the internal detoxification of Pb, rather than from the exclusion of Pb from the root. At toxic {Pb²⁺}, an interveinal chlorosis developed in the shoots of signal grass (possibly a Pb-induced Mn deficiency), whilst in Rhodes grass, Pb²⁺ caused a bending of the root tips and the formation of a swelling immediately behind some of the root apices. Root hair growth did not appear to be reduced by Pb²⁺ in solution, being prolific at all {Pb²⁺} in both species.     

Highly selective resonance scattering detection of trace thrombin using aptamer-modified AuRe nanoprobe

The gold-rhenium (AuRe) composite nanoparticle was prepared by NaBH₄ reduction procedure, and was modified by the aptamer to obtain an AuRe nanoprobe (AuRessDNA) for thrombin. In pH 7.0 Tris–HCl buffer solution and in the presence of salt, the nanoprobe specifically combined with thrombin to form AuRe-aptamer-thrombin cluster that resulted in the resonance scattering intensity (I _560 nm) increasing at 560 nm. The increased intensity ΔI _{560 nm} was linear to the thrombin concentration in the range of 0.115–6.93 nmol/L, with a regression equation of ΔI _{560 nm} = 53.0 C + 2.5, a correlation coefficient of 0.9989, and a detection limit of 13 pmol/L. This method was applied to detect thrombin in human plasma samples, with satisfactory results.