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ABSTRACT: Three methods were used to immobilize myoglobin (Mb) on chitosan/single-wall carbon nanotubes (SWNTs) film, and direct electrochemistry
of the immobilized Mb was extensively investigated. Immobilized Mb displayed a couple of stable and well-defined redox peaks
with the formal potential (E’) is at about −0.27 V (vs. SCE) in 0.1 M phosphate buffer solution (pH 7.0). The E′ was shifted linearly with pH in the range of 3.0 to 9.0 with a slope of −54.1 mV pH−1, denoting that one-electron accompanies with one-proton transfer in electrode reaction process. The FT-IR spectroscopy and
UV-vis spectroscopy showed that Mb on the film retained its secondary structure similar to its native state. The experimental
results demonstrated that the immobilized Mb exhibited excellent electrocatalytic activity to reduction of cimetidine with
a significant lowering of overpotential. The electrocatalytic current was proportional to the concentration of cimetidine
over the range from 9.80 × 10−6 to 1.1 × 10−4 M; the detection limit is 8.40 × 10−6 M (signal-to-noise ratio of 3). The proposed method exhibits good sensitivity, stability and reproducibility.
Key wordscimetidine–myoglobin–chitosan–single-wall carbon nanotubes–electrocatalysis
Russian Journal of Electrochemistry 04/2012; 44(2):218-225. · 0.53 Impact Factor
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ABSTRACT: An electrochemical sensor has been constructed for the determination of adriamycin (ADM) that is based on a glassy carbon
electrode modified with silver nanoparticles and multi-walled carbon nanotubes with carboxy groups. The modified electrode
was characterized by scanning electron microscopy and exhibits a large enhancement of the differential pulse voltammetric
response to ADM. Signals are linear with the concentrations of ADM in the range from 8.2 × 10−9M to 19.0 × 10−9M, with a detection limit of 1.7 × 10−9M. The sensor is highly reproducible and exhibits excellent stability. It was to detect calf thymus DNA.
KeywordsAdriamycin-Calf thymus DNA-Multi-walled carbon nanotubes-Silver nanoparticles
Microchimica Acta 04/2012; 169(1):161-165. · 3.03 Impact Factor
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ABSTRACT: Bioaugmentation was applied by introducing marine halophilic bacteria into an intermittently aerated biological filter (IABF) to improve the removal of nutrient pollutants from hypersaline synthetic wastewater (salinity: 3-13%). The bio-enhanced IABF showed improved performance on nutrient removal in the salinity range of 4-10% compared with the control IABF. The enhancement of eliminating chemical oxygen demand, total nitrogen and total phosphorus peaked at salinities of 7-10%, 7-9% and 5-7%, respectively, where the corresponding removal efficiencies were increased by about 8.6%, 15.7% and 17.3%, respectively. Inoculation with marine bacteria improved the degradation of nitrogenous organics and denitrification in nitrogen transformation. In hypersaline environments biofilter recovery after backwashing was significantly prolonged whereas the time required in the bio-augmented IABF was comparatively short. The results of dehydrogenase activity assays demonstrated that inoculation with marine bacteria improved the activity of biofilm in hypersaline environments.
Bioresource technology 01/2012; 113:280-7. · 4.25 Impact Factor
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ABSTRACT: Peptaibols are a family of antimicrobial peptides, which are synthesized by non-ribosomal peptide synthetases (NRPS) and contain high proportions of alpha-aminoisobytyric acid (Aib). Up to now, 317 peptaibols have been identified, and the majority of them are produced by Trichoderma strains. In this review, we described the diversity, fermation, purification, identification and biosynthesis of peptaibols from Trichoderma.
ACTA MICROBIOLOGICA SINICA 04/2011; 51(4):438-44.
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ABSTRACT: In this study, we reported a sensitive fluorescent biosensor for detection of DNA hybridization based on Fe/Au core/shell (Fe@Au) nanoparticles (NPs). First, Fe@Au NPs were synthesized using a reverse micelle method, with gold as the shell and iron as the core. The nanoparticle size was confirmed by transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was performed in order to elucidate the morphology of the Fe@Au NPs. Then probe DNA with -SH at the 5'-phosphate end was covalently immobilized onto the surface of the Fe@Au NPs. The DNA hybridization event can be detected by a fluorescent method and methylene blue (MB) as the fluorescent probe. The decline of the fluorescence intensity of MB (ΔF) was linear with the concentration of the complementary DNA from 3.0 × 10(-13) to 1.0 × 10(-9) M with a detection limit of 1.0 × 10(-13) M (S/N = 3). In addition, this approach of DNA detection exhibited excellent selectivity, even for single-mismatched DNA detection.
The Analyst 02/2011; 136(4):702-7. · 4.23 Impact Factor
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ABSTRACT: Although cellulases have been isolated from various microorganisms, no functional cellulase gene has been reported in the Vibrio genus until now. In this report, a novel endo-beta-1,4-glucanase gene, cel5A, 1,362 bp in length, was cloned from a newly isolated bacterium, Vibrio sp. G21. The deduced protein of cel5A contains a catalytic domain of glycosyl hydrolase family 5 (GH5), followed by a cellulose binding domain (CBM2). The GH5 domain shows the highest sequence similarity (69%) to the bifunctional beta 1,4-endoglucanase/cellobiohydrolase from Teredinibacter turnerae T7902. The mature Cel5A enzyme was overexpressed in Escherichia coli and purified to homogeneity. The optimal pH and temperature of the recombinant enzyme were determined to be 6.5-7.5 and 50 degrees C, respectively. Cel5A was stable over a wide range of pH and retained more than 90% of total activity even after treatment in pH5.5-10.5 for 1 h, indicating high alkali resistance. Moreover, the enzyme was activated after pretreatment with mild alkali, a novel characteristic that has not been previously reported in other cellulases. Cel5A also showed a high level of salt tolerance. Its activity rose to 1.6-fold in 0.5 M NaCl and remained elevated even in 4 M NaCl. Further experimentation demonstrated that the thermostability of Cel5A was improved in 0.4 M NaCl. In addition, Cel5A showed specific activity towards beta-1,4-linkage of amorphous region of lignocellulose, and the main final hydrolysis product of carboxymethylcellulose sodium and cellooligosaccharides was cellobiose. As an alkali-activated and salt-tolerant enzyme, Cel5A is an ideal candidate for further research and industrial applications.
Applied Microbiology and Biotechnology 07/2010; 87(4):1373-82. · 3.42 Impact Factor
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ABSTRACT: This work demonstrates gold nanoparticles (AuNPs)/functionalized multiwalled carbon nanotubes (f-MWCNT) composite film modified gold electrode via covalent-bonding interaction self-assembly technique for simultaneous determination of salsolinol (Sal) and uric Acid (UA) in the presence of high concentration of ascorbic acid (AA). In pH 7.0 PBS, the composite film modified electrode exhibits excellent voltammetric response for Sal and UA, while AA shows no voltammetric response. The oxidation peak current is linearly increased with concentrations of Sal from 0.24–11.76 μmol L−1 and of UA from 3.36–96.36 μmol L−1, respectively. The detection limits of Sal and UA is 3.2×10−8 mol L−1 and 1.7×10−7 mol L−1 , respectively.
Electroanalysis 11/2009; 21(23):2607 - 2610. · 2.87 Impact Factor
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ABSTRACT: In this work, we fabricated a sensitivity chronocoulometric DNA sensor (CDS) based on gold nanoparticles (AuNPs)/poly(L-lysine) complex film modified glassy carbon electrode. Hexaammineruthenium(III) chloride ([Ru(NH3)6]3+) was used as the electroactive indicator. The assembled process was investigated by cyclic voltammetry (CV) and chronocoulometry (CC). CC is used to monitor the DNA hybridization event by measurement of electrostatic binding [Ru(NH3)6]3+. Under the optimal conditions, the signal of [Ru(NH3)6]3+ was linear with the logarithm of the concentration of the complementary oligonucleotides from 1.0 x 10(-13) to 1.0 x 10(-11) M, and the detection limit is 3.5 x 10(-14) M.
Analytical Biochemistry 10/2009; 396(2):304-9. · 3.00 Impact Factor
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ABSTRACT: The biosorption behaviors and mechanisms of a novel exopolysaccharide (EPS), which is secreted by a mesophilic bacterium (namely Wangia profunda (SM-A87)) isolated from deep-sea sediment, for heavy metals Cu(II) and Cd(II) have been studied in this paper. The effects of SM-A87 EPS concentration, solution pH and ionic strength on the metal uptake were investigated by employing batch adsorption techniques, respectively. The optimum biosorption capacities were observed at pH 5.0 for Cu(II) with 48.0 mg/g and pH 6.0 for Cd(II) with 39.75 mg/g, respectively. Addition of salts decreased Cu(II) or Cd(II) uptake in the order of K(+)<Na(+)<Ca(2+). Langmuir and Freundlich models were employed to describe the biosorption equilibrium data, indicating the favorable biosorption occurs and larger biosorption capacity and intensity for Cu(II) than for Cd(II). The biosorption kinetics for both metals can be well described by pseudo-second-order kinetic model, compared with pseudo-first-order and intraparticle diffusion kinetic models. The competitive biosorption was also studied, indicating that in two-component solution with different metal ratios, the selective biosorption of SM-A87 EPS for Cu(II) was much higher than for Cd(II). The Fourier transform infrared spectroscopy (FT-IR) analysis indicated possible functional groups (e.g., OH, COO and COC) of SM-A87 EPS involved in metal biosorption process, which indicated the potential of using SM-A87 EPS as an effective sorbent for Cu(II) or Cd(II) removal from water.
Colloids and surfaces. B, Biointerfaces 09/2009; 72(2):295-302. · 2.60 Impact Factor
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ABSTRACT: In this work, we fabricated a sensitive electrochemical DNA biosensor for the detection of target DNA. Aminobenzoic acid (ABA) was firstly electropolymerized on the surface of the glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes with carboxyl groups (MWCNTs) by cyclic voltammetry (CV). Gold nanoparticles (AuNPs) were subsequently introduced to the surface of PABA-MWNTs composite film by electrochemical deposition mode. Probe DNA was immobilized on the surface of AuNPs through Au-S bond. Scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) were used to investigate the film assembly process. Differential pulse voltammetry (DPV) was used to monitor DNA hybridization event by measurement of the intercalated adriamycin. Under the optimal conditions, the increase of reduction peak current of adriamycin was linear with the logarithm of the concentration of the complementary oligonucleotides from 1.0 x 10(-12) to 5.0 x 10(-9)M with a detection limit of 3.5 x 10(-13)M. This DNA biosensor has a good stability and reproducibility.
Colloids and surfaces. B, Biointerfaces 09/2009; 75(1):179-85. · 2.60 Impact Factor
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ABSTRACT: In this work, we present an electrochemical DNA sensor based on silver nanoparticles/poly(trans-3-(3-pyridyl) acrylic acid) (PPAA)/multiwalled carbon nanotubes with carboxyl groups (MWCNTs-COOH) modified glassy carbon electrode (GCE). The polymer film was electropolymerized onto MWCNTs-COOH modified electrode by cyclic voltammetry (CV), and then silver nanoparticles were electrodeposited on the surface of PPAA/MWCNTs-COOH composite film. Thiol group end single-stranded DNA (HS-ssDNA) probe was easily covalently linked onto the surface of silver nanoparticles through a 5' thiol linker. The DNA hybridization events were monitored based on the signal of the intercalated adriamycin by differential pulse voltammetry (DPV). Based on the response of adriamycin, only the complementary oligonucleotides gave an obvious current signal compared with the three-base mismatched and noncomplementary oligonucleotides. Under the optimal conditions, the increase of reduction peak current of adriamycin was linear with the logarithm of the concentration of the complementary oligonucleotides from 9.0 x 10(-12) to 9.0 x 10(-9) M with a detection limit of 3.2 x 10(-12) M. In addition, this DNA sensor exhibited an excellent reproducibility and stability during DNA hybridization assay.
Analytical Biochemistry 12/2008; 387(1):13-9. · 3.00 Impact Factor
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ABSTRACT: In this work, we report on the preparation of a simple, sensitive DNA impedance sensor. Firstly gold nanoparticles were electrodeposited on the surface of a gold electrode, and then probe DNA was immobilized on the surface of gold nanoparticles through a 5′-thiol-linker. Electrochemical impedance spectroscopy (EIS) was used to investigate probe DNA immobilization and hybridization. Compared to the bare gold electrode, the gold nanoparticles modified electrode could improve the density of probe DNA attachment and the sensitivity of DNA sensor greatly. The difference of electron transfer resistance (ΔRet) was linear with the logarithm of complementary oligonucleotides sequence concentrations in the range of 2.0×10−12 to 9.0×10−8 M, and the detection limit was 6.7×10−13 M. In addition, the DNA sensor showed a fairly good reproducibility and stability during repeated regeneration and hybridization cycles.
Electroanalysis 08/2008; 20(19):2127 - 2133. · 2.87 Impact Factor
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ABSTRACT: A homogeneous cellulose-binding module (CBM) of cellobiohydrolase I (CBHI) from Trichoderma pseudokoningii S-38 was obtained by the limited proteolysis with papain and a series of chromatographs filtration. Analysis of FT-IR spectra demonstrated that the structural changes result from a weakening and splitting of the hydrogen bond network in cellulose by the action of CBM(CBHI) at 40 degrees C for 24 h. The results of molecular dynamic simulations are consistent with the experimental conclusions, and provide a nanoscopic view of the mechanism that strong and medium H-bonds decreased dramatically when CBM was bound to the cellulose surface. The function of CBM(CBHI) is not only limited to locating intact CBHI in close proximity with cellulose fibrils, but also is involved in the structural disruption at the fibre surface. The present studies provided considerable evidence for the model of the intramolecular synergy between the catalytic domain and their CBMs.
Science in China Series C Life Sciences 08/2008; 51(7):620-9. · 1.61 Impact Factor
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ABSTRACT: A novel DNA biosensor has been fabricated for the detection of DNA hybridization based on layer-by-layer (LBL) covalent assembly of gold nanoparticles (GNPs) and multiwalled carbon nanotubes (MWCNTs). The stepwise LBL assembly process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The hybridization events were monitored by differential pulse voltammetry (DPV) measurement of the intercalated doxorubicin, and the factors influencing the performance of the DNA hybridization was investigated in detail. The signal was linearly changed with target DNA concentration increased from 0.5 to 0.01 nM, and had a detection limit of 7.5 pM (signal/noise ratio of 3). In addition, the DNA biosensor showed an excellent reproducibility and stability under the DNA-hybridization conditions.
Electroanalysis 03/2008; 20(11):1220 - 1226. · 2.87 Impact Factor
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ABSTRACT: The authors consider the problem of on-line scheduling of unit execution time jobs on uniform machines with rejection penalty.
The jobs arrive one by one and can be either accepted and scheduled, or be rejected. The objective is to minimize the total
completion time of the accepted jobs and the total penalty of the rejection jobs. The authors propose an on-line algorithm
and prove that the competitive ratio is
\frac12(2+Ö3) » 1.86602\frac{1}{2}(2+\sqrt{3})\approx 1.86602
.
Journal of Systems Science and Complexity 01/2008; 21(1):114-118. · 0.37 Impact Factor
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ABSTRACT: Trans-3-(3-pyridyl) acrylic acid (PAA) was deposited on glassy carbon electrode (GCE) by electropolymerization in pH 7.0 phosphate buffer solution (PBS). The poly (3-(3-pyridyl) acrylic acid) (PPAA) film modified glassy carbon electrode shows an excellent electrochemical response for dopamine (DA), ascorbic acid (AA) and uric acid (UA). The cyclic voltammetry oxidation peaks for DA and AA, DA and UA, AA and UA are separated by 150 mV, 130 mV and 280 mV, respectively. This permits the simultaneous determination of AA, DA and UA. The interference of AA with the determination of DA could be eliminated because of the electrostatic interaction between DA cations and the negatively charged PPAA film at pH 7.0. The anodic peak currents of DA, AA and UA increase linearly with concentration in the range of 1-40 micromol L(-1), 10-400 micromol L(-1) and 1.6-80 micromol L(-1), respectively, with a correlation coefficient (r) always higher than 0.998. The detection limit is 0.06 micromol L(-1), 0.8 micromol L(-1) and 1.1 micromol L(-1) for DA, AA and UA, respectively.
Annali di Chimica 09/2007; 97(8):665-74. · 0.99 Impact Factor
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ABSTRACT: MCP-01, the main protease secreted by the deep-sea cold-adapted bacterium Pseudoalteromonas sp. SM9913, is a cold-adapted serine protease. Gene mcp01 encoding MCP-01 contains an ORF of 2508 bp encoding a protein of 835 amino acid residues with an M(r) of 87 773 Da, which is a multidomain subtilase precursor. Mature MCP-01 purified from the culture of strain SM9913 with an M(r) of 65.84 kDa is a multidomain protein composed of a catalytic domain, a linker, a P_proprotein domain and a polycystic kidney disease (PKD) domain. To the best of the authors' knowledge, no mature subtilase has been reported to date with this domain architecture. Phylogenetic analyses of subtilases showed that MCP-01 and 12 hypothetical proteins retrieved from public databases form a strongly supported group within the subtilase subfamily. These 13 proteins are predicted to share a similar domain architecture and represent a structurally novel group within the S8A subfamily. The substrate specificities of MCP-01 towards synthetic peptides differed from that of a typical S8A protease, subtilisin Carlsberg. Since most of this new subgroup of subtilases, including MCP-01 and the 12 MCP-01-like subtilases, are from deep-sea bacteria, they are termed deseasins. MCP-01 is the type example of a deseasin, since it is the only one that has been purified and characterized. In addition, the structural characteristics and catalytic properties of deseasin MCP-01 show that structurally and kinetically it is adapted to low temperatures.
Microbiology 08/2007; 153(Pt 7):2116-25. · 3.06 Impact Factor
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ABSTRACT: Multilayer films of negatively charged single-wall carbon nanotubes (SWCNTs) and positively charged cetylpyridinium bromide (CPB) have been deposited on a glassy carbon electrode (GCE) using layer-by-layer (LBL) technique. The assembled multilayer films have been investigated by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and quartz crystal microbalance (QCM) measurements. The voltammetric signal of dopamine (DA), uric acid (UA), and ascorbic acid (AA) could be observed well-separated with the assembled SWCNTs/CPB multilayer films in pH 7.0 PBS. The oxidation peak potentials of DA, UA, and AA are centered at about 169 mV, 292 mV and −10 mV on differential pulse voltammograms (DPVs), respectively. The peak-to-peak potential separation was 123 mV, 179 mV, and 302 mV for DA-UA, DA-AA, and UA-AA in DPVs, respectively. This permits the simultaneous detection of DA and UA in the presence of AA.
Electroanalysis 06/2007; 19(16):1695 - 1701. · 2.87 Impact Factor
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ABSTRACT: Pseudoalteromonas sp. SM9913 is a psychrotolerant bacterium isolated from deep-sea sediment. The structural characterization and ecological roles of the exopolysaccharide (EPS) secreted by this strain were studied in this work. The yield of the EPS increased as the culture temperature decreased in the range 30-10 degrees C, and it reached 5.25 g l(-1) (dry weight) under optimal growth conditions (15 degrees C, 52 h). EPS fraction was purified and its structure was identified by the combination of NMR spectra, high-resolution mass spectrometry (HRMS) analysis and methylation analysis. The ratio of the sugar units, the acetyl group and the ethoxyl group was close to 4 : 5 : 1. The major sugar unit of the EPS was 6-linked glucose (61.8 %); other sugar units present included terminal arabinofuranosyl (11.0 %) and glucopyranosyl (11.2 %) residues and a small amount of other sugar derivatives. Its structure was different from EPSs reported for other marine bacteria. Besides the structural elucidation of the EPS, its ecological roles were studied. This EPS could enhance the stability of the cold-adapted protease MCP-01 secreted by the same strain through preventing its autolysis. It could bind many metal ions, including Fe(2+), Zn(2+), Cu(2+), Co(2+). It was also a very good flocculating agent and could conglomerate colloidal and suspended particles. These results indicated that the EPS secreted by strain SM9913 might help this strain enrich the proteinaceous particles and the trace metals in the deep-sea environment, stabilize the secreted cold-adapted proteases and avoid its diffusion. This is believed to be the first report on the structure of the EPS secreted by a deep-sea psychrotolerant bacterium and its ecological roles. According to these results and other studies, a schematic diagram of the lifestyle of the deep-sea psychrotolerant strain SM9913 is suggested.
Microbiology 06/2007; 153(Pt 5):1566-72. · 3.06 Impact Factor
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ABSTRACT: In pH 6.0 phosphate buffer solutions (PBS), a glassy carbon electrode (GCE) modifying by nano-tin oxide/polyvinyl sulfonic potassium (nano-SnO2/PVS) exhibited an enhanced effectiveness for the oxidation of ciprofloxacin (CFX), which compared with a bare GCE or a nano-SnO2 modified electrode. In addition we also investigated the electrooxidation mechanism of the fluoroquinolone antibiotics (utilizing ciprofloxacin, ofloxacin, sparfloxacin and lomefloxacin) at the modified electrode. Furthermore, gel electrophoresis coupled with electrochemistry and spectra techniques were used to study the interaction of CFX and calf thymus DNA (ctDNA). These acquired data showed that the binding mode of CFX and DNA was mainly an intercalation mechanism.
Frontiers in Bioscience 02/2007; 12:1946-55. · 3.52 Impact Factor
