Speciation of platinum in blood plasma and urine by micelle-mediated extraction and graphite furnace atomic absorption spectrometry

A highly sensitive and selective technique for the speciation of platinum by cloud point extraction prior to determination by graphite furnace atomic absorption spectrometry (GFAAS) was described. The separation of Pt(II) from Pt(IV) was performed in the presence of 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) as chelating agent and Triton X-114 as a non-ionic surfactant. The extraction of Pt(II)–HCPTS complex needs temperature higher than the cloud point temperature of Triton X-114 and pH = 7, while Pt(IV) remains in the aqueous phase. The Pt(II) in the surfactant phase was analyzed by GFAAS, and the concentration of Pt(IV) was calculated by subtraction of Pt(II) from total platinum which was directly determined by GFAAS. The effect of pH, concentration of chelating agent, surfactant, and equilibration temperature were investigated. An enrichment factor of 42 was obtained for the preconcentration of Pt(II) with 50 mL solution. Under the optimum experimental conditions, the calibration curve was linear up to 30 μg L^?1 with detection limit of 0.08 μg L^?1 and the relative standard deviation was 1.8%. No considerable interference was observed due to the presence of coexisting anions and cations. The accuracy of the results was verified by analyzing different spiked samples (tap water, blood plasma and urine). The proposed method was applied to the speciation analysis of Pt in blood plasma and urine with satisfactory results.     

Simultaneous carbon and nitrogen removal from piggery wastewater using loop configuration microbial fuel cell

Simultaneous carbon and nitrogen removal using loop configuration microbial fuel cell (MFC) with relatively large size of 5 L was investigated in this study. Four MFC reactors were constructed with a loop configuration to eliminate the pH gradient, and the reactor performance was examined with different separators and cathode materials. The performance of the reactors in terms of electricity generation and contaminant removal rate was examined. Results showed that a maximum power density of 1415.6 mW/m³ (The empty bed volume of anode chamber) was obtained at a current density of 3258.5 mA/m³ with cation exchange membrane as separator and graphite felt (Pt coated) as cathode using the piggery wastewater as feed, and the organic removal rate obtained was approximately 0.523 kg COD/m³/d (total anode chamber) with nitrogen removal rate of 0.194 kg N/m³/d (total cathode chamber).     

Amperometric xanthine biosensors based on electrodeposition of platinum on polyvinylferrocenium coated Pt electrode

Novel xanthine biosensors were successfully fabricated by immobilizing xanthine oxidase on polyvinylferrocenium perchlorate matrix (PVF⁺ClO₄⁻) and platinum electrodeposited polyvinylferrocenium perchlorate matrix. PVF⁺ClO₄⁻ film was coated on Pt electrode at +0.7 V vs. Ag/AgCl by electrooxidation of polyvinylferrocene (PVF). Platinum nanoparticles were deposited on PVF⁺ClO₄⁻ electrode by electrochemical deposition in 2.0 mM H₂PtCl₆ solution at −0.2 V. Xanthine oxidase was incorporated into the polymer matrix via ion exchange process by immersing modified Pt electrodes in the enzyme solution. The amperometric responses of the biosensors were measured via monitoring oxidation current of hydrogen peroxide at +0.5 V. Under the optimal conditions, the linear ranges of xanthine detection were determined as 1.73 × 10⁻³–1.74 mM for PVF⁺XO⁻ and 0.43 × 10⁻³–2.84 mM for PVF⁺XO⁻/Pt. The detection limits of xanthine were 5.20 × 10⁻⁴ mM for PVF⁺XO⁻ and 1.30 × 10⁻⁴ mM for PVF⁺XO⁻/Pt. Moreover, the effects of applied potential, electrodeposition potential, H₂PtCl₆ concentration, amount of electrodeposited Pt nanoparticles, thickness of polymeric film, temperature, immobilization time, xanthine and xanthine oxidase concentrations on the response currents of the biosensors were investigated in detail. The effects of interferents, the operational and storage stabilities of biosensors and the applicabilities to drug samples of the biosensors analysis were also evaluated.     

Potential of Typha angustifolia for phytoremediation of heavy metals from aqueous solution of phenol and melanoidin

Typha angustifolia was evaluated for various heavy metals (Cu, Pb, Ni, Fe, Mn, and Zn) bioremediation potential from aqueous solution containing variable concentrations of phenol (100–800 mg l^?1) and melanoidin (2500–8500 Co–Pt) at 20, 40, and 60 days. The concentration of phenol (200–400 mg l^?1) along with melanoidin 2500 Co–Pt showed optimum for phytoremediation of tested heavy metals, while, higher concentrations of melanoidin (5600–8500 Co–Pt) showed toxic effect on T. angustifolia along with phenol. Phenol and melanoidin showed adverse effect on T. angustifolia of up to 20 days incubation, but this leads to induction of peroxidase and ascorbic acid activity to cope with adverse conditions. Subsequently, as pollutants were decreased along with plant growth, peroxidase and ascorbic acid also declined. However, with reduction of peroxidase, catalase level was increased. The Cu, Zn, and Ni were accumulated at maximum in all tested conditions. The TEM observations of T. angustifolia showed clotted deposition of metals and shrinkage of cell in root, breakdown of spongy and palisade parenchyma of leaves at higher concentration of phenol (100 mg l^?1) and melanoidin (5500 Co–Pt). Thus, this study concluded that T. angustifolia could be a potential phytoremediator for heavy metals from metal, melanoidin, and phenol containing industrial wastewater at optimized condition.     

Anticancer activity of natural cytokinins: A structure–activity relationship study

Cytokinin ribosides (N⁶-substituted adenosine derivatives) have been shown to have anticancer activity both in vitro and in vivo. This study presents the first systematic analysis of the relationship between the chemical structure of cytokinins and their cytotoxic effects against a panel of human cancer cell lines with diverse histopathological origins. The results confirm the cytotoxic activity of N⁶-isopentenyladenosine, kinetin riboside, and N⁶-benzyladenosine and show that the spectrum of cell lines that are sensitive to these compounds and their tissues of origin are wider than previously reported. The first evidence that the hydroxylated aromatic cytokinins (ortho-, meta-, para-topolin riboside) and the isoprenoid cytokinin cis-zeatin riboside have cytotoxic activities is presented.Most cell lines in the panel showed greatest sensitivity to ortho-topolin riboside (IC₅₀ = 0.5–11.6 μM). Cytokinin nucleotides, some synthesized for the first time in this study, were usually active in a similar concentration range to the corresponding ribosides. However, cytokinin free bases, 2-methylthio derivatives and both O- and N-glucosides showed little or no toxicity. Overall the study shows that structural requirements for cytotoxic activity of cytokinins against human cancer cell lines differ from the requirements for their activity in plant bioassays. The potent anticancer activity of ortho-topolin riboside (GI₅₀ = 0.07–84.60 μM, 1st quartile = 0.33 μM, median = 0.65 μM, 3rd quartile = 1.94 μM) was confirmed using NCI₆₀, a standard panel of 59 cell lines, originating from nine different tissues. Further, the activity pattern of oTR was distinctly different from those of standard anticancer drugs, suggesting that it has a unique mechanism of activity. In comparison with standard drugs, oTR showed exceptional cytotoxic activity against NCI₆₀ cell lines with a mutated p53 tumour suppressor gene. oTR also exhibited significant anticancer activity against several tumour models in in vivo hollow fibre assays.     

Operation of a bioelectrochemical system as a polishing stage for the effluent from a two-stage biohydrogen and biomethane production process

Anaerobic bioenergy production processes including fermentative biohydrogen (BioH₂), anaerobic digestion (AD) and bioelectrochemical system have been investigated for converting municipal waste or various biomass feedstock to useful energy carriers. However, the performance of a microbial fuel cell (MFC) fed on the effluent from a two-stage biogas production process has not yet been investigated extensively in continuous reactor operation on complex substrates. In this study we have investigated the extent to which a microbial fuel cell (MFC) can reduce COD and recover further energy from the effluent of a two-stage biohydrogen and biomethane system. The performance of a four-module tubular MFC was determined at six different organic loadings (0.036–6.149 g sCOD L⁻¹ d⁻¹) in terms of power generation, COD removal efficiency, coulombic efficiency (CE) and energy conversion efficiency (ECE). A power density of 3.1 W m⁻³ was observed at the OLR = 0.572 g sCOD L⁻¹ d⁻¹, which resulted in the highest CE (60%) and ECE (0.8%), but the COD removal efficiency decreased at higher organic loading rates (35.1–4.4%). The energy recovery was 92.95 J L⁻¹ and the energy conversion efficiency, based on total influent COD was found to be 0.48–0.81% at 0.572 g sCOD L⁻¹ d⁻¹. However, the energy recovery by the MFC is only reported for a four-module reactor and improved performance can be expected with an extended module count, as chemical energy remained available for further electrogenesis.     

Impact of microcarrier coverage on using permittivity for on-line monitoring high adherent Vero cell densities in perfusion bioreactors

The paper presents the interest of on-line permittivity monitoring to estimate the density of Vero cells growing on microcarriers (MCs), even when high cell densities were reached in perfusion bioreactors (4.5 × 10⁶ cells ml⁻¹). Cultures were performed with various MCs concentrations in a reactor equipped with a settling tube. A linear correlation between on-line permittivity and off-line volumetric cell concentration was observed provided that MCs are not fully covered by cells. High permittivities such as 250 pF cm⁻¹ could be measured without signal saturation of the Fogale Biomass system^®. The correlation was no longer linear when cell density per carrier exceeded 100% cell confluency corresponding to 150 cells MC⁻¹ (0.15 × 10⁶ cells cm⁻²). This behaviour was attributed to the decrease of cell volume when cells saturated MCs surface. It mainly happened when low MCs concentration and continuous medium renewing were used. Therefore, permittivity sensor can be considered as a reliable tool to monitor on-line adherent cell densities not exceeding total cell confluency. Moreover, it could be useful to detect when cell confluency occurs.     

Development of electrochemical sulfite biosensor based on SOX/PBNPs/PPY modified Au electrode

A sulfite oxidase (SO_X) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto Prussian blue nanoparticles/polypyrrole (PBNPs/PPY) nanocomposite film electrodeposited onto the surface of gold (Au) electrode. An electrochemical sulfite biosensor was fabricated using SO_X/PBNPs/PPY/Au electrode as working electrode, Ag/AgCl as standard electrode and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier Transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) at different stages of its construction. The biosensor showed optimum response within 2 s, when operated at 20 mV s⁻¹ in 0.1 M Tris–HCl buffer, pH 8.0 and at 30 °C. Linear range and minimum detection limit were 0.5–1000 μM and 0.1 μM (S/N = 3) respectively. The sensor was evaluated with 95.0% recovery of added sulfite in red wine samples and 1.9% and 3.3% within and between batch coefficients of variation respectively. There was a good correlation (r = 0.96) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was employed for determination of sulfite level in red, white and rose wine samples. The enzyme electrode was used 300 times over a period of 4 months, when stored at 4 °C.     

Production of the postharvest biocontrol agent Bacillus subtilis CPA-8 using low cost commercial products and by-products

The aim of this research was to identify a low cost medium based on commercial products and by-products that provided maximum Bacillus subtilis CPA-8 growth and maintained biocontrol efficacy. Low cost media combining economical nitrogen and carbon sources such as yeast extract, peptone, soy products, sucrose, maltose and molasses were tested. Tests were carried out in 250-ml flasks containing 50 ml of each tested medium. Maximum cell growth (>3 × 10⁹ CFU ml^?1) was obtained in defatted soy flour 44% combined with sucrose or molasses media. Second, CPA-8 production was scaled up in a 5-l fermenter and CPA-8 population dynamics, pH and oxygen consumption in the optimized medium (defatted soy flour 44% – molasses) was recorded. In these tests, there was a 5-h lag phase before growth, after which exponential growth occurred and maximum production was 3 × 10⁹ CFU ml^?1 after 20 h. Fruit trials with cells and cell free supernatants from CPA-8 grown in optimized medium maintained biocontrol efficacy against Monilinia fructicola on peaches, resulting in disease reductions up to 95%. CPA-8 populations survived in wounds on inoculated peaches, regardless of the culture media used. The results show that B. subtilis CPA-8 can be produced in a low cost medium combining inexpensive nitrogen and carbon sources (40 g l^?1 defatted soy flour 44%, 5 g l^?1 molasses plus mineral trace supplements) in shake flasks and a laboratory fermenter (5 l). The results could be used to provide a reliable basis for scaling up the fermentation process to an industrial level.     

Validation of cell density and viability assays using Cedex automated cell counter

A method using Cedex automatic cell counter (Innovatis) to determine the cell density and viability of a whole cell-based immunotherapy product has been developed and validated for the assay performance characteristics including specificity, accuracy, precision, linearity, range, and robustness. Instrument-to-instrument variation due to intrinsic differences in handmade flow cells was also evaluated. For cell density, Cedex demonstrated acceptable specificity, accuracy and precision for cell densities ranging from 3.13 × 10⁵ to approximately 1.0 × 10⁷ cells/mL, with intermediate precision of about 5% relative standard deviation (RSD). However, a marked difference was observed between the two instruments studied and they therefore could not be used interchangeably without additional calibration procedures that went beyond the manufacturer's recommendation. For viability, mixing known numbers of non-viable cells with highly viable cells allowed evaluation of the specificity, accuracy and linearity of the viability determination. Acceptable levels of accuracy (95.3–106.4% recovery) and precision (RSD < 5%) were demonstrated for the viability range from 50 to 100%. The instrument-to-instrument difference was less than 4.6%. The assays for both cell density and viability were sufficiently robust for assay parameters. However, the effect of certain parameters was cell line-dependent, suggesting that Cedex performance should be verified for each cell line of interest.     

A green and efficient procedure for the preconcentration and determination of cadmium,nickel and zinc from freshwater,hemodialysis solutions and tuna fish samples by cloud point extraction and flame atomic absorption spectrometry

Cloud point extraction (CPE) was used to simultaneously preconcentrate trace-level cadmium, nickel and zinc for determination by flame atomic absorption spectrometry (FAAS). 1-(2-Pyridilazo)-2-naphthol (PAN) was used as a complexing agent, and the metal complexes were extracted from the aqueous phase by the surfactant Triton X-114 ((1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol). Under optimized complexation and extraction conditions, the limits of detection were 0.37 μg L⁻¹ (Cd), 2.6 μg L⁻¹ (Ni) and 2.3 μg L⁻¹ (Zn). This extraction was quantitative with a preconcentration factor of 30 and enrichment factor estimated to be 42, 40 and 43, respectively. The method was applied to different complex samples, and the accuracy was evaluated by analyzing a water standard reference material (NIST SRM 1643e), yielding results in agreement with the certified values.     

Cation selectivity of the plasma membrane of tobacco protoplasts in the electroporated state

Cation selectivity of the cellular membrane of tobacco culture cells (cell line ‘bright yellow-2’) exposed to pulsed electric fields in the millisecond range was investigated. The whole cell configuration of the patch clamp technique was established on protoplasts prepared from these cells. Ion selectivity of the electroporated membrane was investigated by measuring the reversal potential of currents passing through field-induced pores. To this end the membrane was hyper- or depolarized for 10 ms (prepulse); subsequently the voltage was driven to opposite polarity at a constant rate (+ 40 or ? 40 mV/ms, respectively). The experiment was started by polarizing the membrane to moderately negative or positive voltages (prepulse potential ± 150 mV) that would not induce pore formation. Subsequently, an extended voltage range was scanned in the porated state of the membrane (prepulse potential ± 600 mV). IV curves in the porated and the non-porated state (obtained at the same prepulse polarity) were superimposed to determine the voltage at which both curves intersected (‘Intersection potential’). Using a modified version of the Goldmann–Hodgkin–Katz equation relative permeabilities to Ca^2 + and various monovalent alkali and organic cations were calculated. Pores were found to be fairly cation selective, with a selectivity sequence determined to be Ca^2 + > Li⁺ > Rb⁺ ≈ K⁺ ≈ Na⁺ > TEA⁺ ≈ TBA⁺ > Cl^?. Relative permeability to monovalent cations was inversely related to the ionic diameter. By fitting a formalism suggested by Dwyer at al. (J. Gen. Physiol. 75 (1980), 469–492) the effective average diameter of field induced pores was estimated to be about 1.8 nm. Implications of these results for biotechnology and electroporation theory are discussed.     

An amperometric H2O2 biosensor based on cytochrome c immobilized onto nickel oxide nanoparticles/carboxylated multiwalled carbon nanotubes/polyaniline modified gold electrode

Cytochrome c was immobilized covalently onto nickel oxide nanoparticles/carboxylated multiwalled carbon nanotubes/polyaniline composite (NiO-NPs/cMWCNT/PANI) electrodeposited on gold (Au) electrode. An amperometric H₂O₂ biosensor was constructed by connecting this modified Au electrode along Ag/AgCl as reference and Pt wire as counter electrode to the galvanostat. The modified Au electrode was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and Fourier transform infra-red spectroscopy (FTIR). Cyclic voltammetric (CV) studies of the electrode at different stages demonstrated that the modified Au electrode had enhanced electrochemical oxidation of H₂O₂, which offered a number of attractive features to develop an amperometric biosensor based on split of H₂O₂. There was a good linear relationship between the current (mA) and H₂O₂ concentration in the range 3–700 μM. The sensor had a detection limit of 0.2 μM (S/N = 3) with a high sensitivity of 3.3 mA μM^?1 cm^?2. The sensor gave accurate and satisfactory results, when employed for determination of H₂O₂ in different fruit juices.     

Effect of environmental and nutritional factors on growth and azaspiracid production of the dinoflagellate Azadinium spinosum

Azadinium spinosum, a small dinoflagellate isolated from the North Sea, is a producer of azaspiracids (AZAs), a group of biotoxins associated with human illness following ingestion of contaminated shellfish. Using batch and continuous cultures of A. spinosum, the present study investigated the effects of different environmental and nutritional factors (salinity, temperature, photon flux density, aeration, culture media, nitrogen sources, phosphate source, and N/P ratios) on growth, maximum cell concentration, and AZA cell quota.Azadinium spinosum grew in a wide range of conditions; from 10 ̊C to 26 ̊C and salinities from 30 to 40, under irradiances ranging from 50 μmol m⁻² s⁻¹ to 250 μmol m⁻² s⁻¹, with or without aeration. Growth and maximum cell concentration were highest at a salinity of 35, at temperatures between 18 ̊C and 22 ̊C, and with aeration. Concerning AZA cell quota, the most significant effect was observed at low temperature; the AZA cell quota was more than 20 times higher at 10 ̊C (220 fg cell⁻¹) than at temperatures between 18 ̊C and 26 ̊C. A. spinosum grew on all media tested with only slight differences in growth rate and AZA cell quota. In continuous culture, lowering the concentration of nutrients (0.5 strength of a modified K-medium) in the inflow improved AZA cell quota whereas higher concentration (doubling the normal strength of K-medium) improved maximal cell concentration. A. spinosum grew on different sources of nitrogen tested (nitrate, urea, ammonium) with almost no effect on toxin cell quota and growth, except that adding ammonium caused a decrease in growth.These first experiments on Azadinium spinosum increased our knowledge on factors affecting its growth and toxin production; furthermore, these results allowed and improved particularly A. spinosum production in pilot scale photobioreactors for AZA isolation.     

Electrochemical detection of xanthine in fish meat by xanthine oxidase immobilized on carboxylated multiwalled carbon nanotubes/polyaniline composite film

A commercial xanthine oxidase (XOD) was immobilized covalently onto carboxylated multiwalled carbon nanotubes (c-MWCNT) and polyaniline (PANI) composite film electrodeposited on the surface of a Pt electrode, using N-ethyl-N′-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry. A xanthine biosensor was fabricated using XOD/c-MWCNT/PANI/Pt electrode as a working electrode, Ag/AgCl (3 M KCl) as standard electrode and Pt wire as auxiliary electrode connected through a potentiostat. The enzyme electrode was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrophotometry and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 4 s at pH 7.0 and 35 °C, when polarized at 0.4 V. The optimized xanthine biosensor showed linear response range of 0.6–58 μM, with a detection limit of 0.6 μM (S/N = 3), and a correlation coefficient of 0.98. The biosensor was applied to determine xanthine in fish meat. The biosensor lost 50% of its initial activity after its 200 uses over a period of 100 days.     

The influence of light quality on akinete formation and germination in the toxic cyanobacterium Anabaena circinalis

Physiological control of akinete formation and subsequent germination is likely to be important in understanding and predicting how natural populations of cyanobacteria respond to their environment. While previous research has indicated nutrient limitation may be important in akinete formation new results presented here indicate that in the toxic and bloom-forming species Anabaena circinalis there was a profound effect of spectral quality. Under 40 μmol photons m^?2 s^?1 photosynthetically active irradiance (PAR) of predominately red irradiance akinete production was maximal at 2.1 × 10^?4 akinetes vegetative cell^?1 d^?1, some 3000 times greater than the 6.5 × 10^?8 akinetes vegetative cell^?1 d^?1 observed under equivalent PAR but predominately blue light. For cells grown under a range of predominantly red, white and green irradiance even short exposures to blue light reduced akinete formation rates by a factor of ten relative to controls, indicating that exposure to blue light inhibits akinete formation. Germination of akinetes was not influenced by the irradiance under which akinetes were formed: 88 ± 4.1% (mean ± 1 S.D.) of akinetes germinated with no evidence of an effect on germination success due to their production under predominately red, white or green irradiance (germination of akinetes produced under blue light was not tested). Spectral quality had a significant impact on both vegetative cell and germling growth rates. The results indicate a significant reduction in the cellular differentiation of A. circinalis vegetative cells into akinetes that is mediated by blue light. In an ecological context the production of akinetes will be greater in environments with less blue light; potentially including those with slower flow, more stratification, less vertical mixing and more turbidity. The resulting spatial pattern of akinete production is likely to influence the location of akinetes in sediments and the development of subsequent blooms from excysting germlings.     

Amperometric electrode for determination of urea using electrodeposited rhodium and immobilized urease

An amperometric biosensor was developed for determination of urea using electrodeposited rhodium on a polymer membrane and immobilized urease. The urease catalyzes the hydrolysis of urea to NH₄⁺ and HCO₃⁻ ions and the liberated ammonia is catalytically and electrochemically oxidized by rhodium present in the rhodinized membrane on the Pt working electrode. Three types of rhodinized polymer membranes were prepared by varying the number of electrodeposition cycles: membrane 1 with 10 deposition cycles, membrane 2 with 40 cycles and membrane 3 with 60 cycles. The morphologies of the rhodinized membranes were investigated by scanning electron microscopy and the results showed that the deposition of rhodium was like flowers with cornices-like centers. The influence of the amount of electrodeposited rhodium over the electrode sensitivity to different concentrations of ammonia was examined initially based on the cyclic voltammetric curves using the three rhodium modified electrodes. The obtained results convincingly show that electrode with rhodinized membrane 1, which contain the lowest amount of electrodeposited rhodium is the most active and sensitive regarding ammonia. It was found that the anodic oxidation peak of ammonia to nitrogen occurs at 0.60 V. In order to study the performance of urease amperometric sensor for the determination of urea, experiments at constant potential (0.60 V) were performed. The current–time experiments were carried out with urease rhodinized membrane 1 (10 cycles). The amperometric response increased linearly up to 1.75 mM urea. The detection limit was 0.05 mM. The urea biosensor exhibited a high sensitivity of 1.85 μA mM⁻¹ cm⁻² with a response time 15 s. The Michaelis–Menten constant K_m for the urea biosensor was calculated to be 6.5 mM, indicating that the immobilized enzyme featured a high affinity to urea. The urea sensor showed a good reproducibility and stability. Both components rhodium and urease contribute to the decreasing of the production cost of biosensor by avoiding the use of a second enzyme.     

Co-remediation of pentachlorophenol and Cr6+ by free and immobilized cells of native Bacillus cereus isolate: Spectrometric characterization of PCP dechlorination products,bioreactor trial and chromate reductase activity

In this study, Bacillus cereus isolate efficiently remediated 57% PCP and 74% Cr⁶⁺ simultaneously with uptake rate of 0.65 mg Cr⁶⁺ g^?1 biomass h^?1 at initial 200 mg Cr⁶⁺ and 500 mg PCP l^?1 concentration under optimized 0.4% glucose, 0.2% NH₄Cl, pH 7.0, 35 °C, 1.0% inoculum during 60 h incubation. Optimization of agitation (100 rpm) and aeration (0.6 vvm) in bioreactor further enhanced PCP dechlorination by ～5.0% and Cr⁶⁺ removal 7.5%. Presence of other heavy metals variedly affected bioremediation of both the toxicants. Maximum and minimum inhibition was exhibited by mercury and lead, respectively. Out of 74% Cr⁶⁺ remediated, 90% reduced to Cr³⁺, of which 52.8% was associated with cell biomass and 37.2% with culture supernatant. Maximum chromate reductase activity was evident in culture supernatant followed by cytosolic fraction and cell debris. A direct correlation existed between chromate reductase activity and reduced Cr³⁺ in different cell fractions. Among matrices, alginate was most suitable for biomass immobilization, which enhanced Cr⁶⁺ removal by 20.2% compared to free cells at 36 h. Gas chromatography and mass spectrometry detected 2,3,4,6-tetrachlorophenol, 2,4,6-trichlorophenol, 2,6-dichlorophenol and 6-chlorohydroxyquinol as PCP dechlorination products. Our promising strain can be efficiently employed for simultaneous bioremediation of PCP and Cr⁶⁺ under wide environmental conditions.     

A concise synthesis and evaluation of new malonamide derivatives as potential α-glucosidase inhibitors

A series of new malonamide derivatives were synthesized by Michael addition reaction of N¹,N³-di(pyridin-2-yl)malonamide into α,β-unsaturated ketones mediated by DBU in DCM at ambient temperature. The inhibitory potential of these compounds in vitro, against α-glucosidase enzyme was evaluated. Result showed that most of malonamide derivatives were identified as a potent inhibitors of α-glucosidase enzyme. Among all the compounds, 4K (IC₅₀ = 11.7 ± 0.5 μM) was found out as the most active one compared to standard drug acarbose (IC₅₀ = 840 ± 1.73 μM). Further cytotoxicity of 4a–4m were also evaluated against a number of cancer and normal cell lines and interesting results were obtained.     

Magnetic susceptibility of iron in malaria-infected red blood cells

During intra-erythrocytic maturation, malaria parasites catabolize up to 80% of cellular haemoglobin. Haem is liberated inside the parasite and converted to haemozoin, preventing haem iron from participating in cell-damaging reactions. Several experimental techniques exploit the relatively large paramagnetic susceptibility of malaria-infected cells as a means of sorting cells or investigating haemoglobin degradation, but the source of the dramatic increase in cellular magnetic susceptibility during parasite growth has not been unequivocally determined. Plasmodium falciparum cultures were enriched using high-gradient magnetic fractionation columns and the magnetic susceptibility of cell contents was directly measured. The forms of haem iron in the erythrocytes were quantified spectroscopically. In the 3D7 laboratory strain, the parasites converted approximately 60% of host cell haemoglobin to haemozoin and this product was the primary source of the increase in cell magnetic susceptibility. Haemozoin iron was found to have a magnetic susceptibility of (11.0 ± 0.9) × 10^? 3 mL mol^? 1. The calculated volumetric magnetic susceptibility (SI units) of the magnetically enriched cells was (1.88 ± 0.60) × 10^? 6 relative to water while that of uninfected cells was not significantly different from water. Magnetic enrichment of parasitised cells can therefore be considered dependent primarily on the magnetic susceptibility of the parasitised cells.