An electrochemical DNA sensor based on electrodepositing aluminum ion films on stearic acid-modified carbon paste electrode and its application for the detection of specific sequences related to bar gene and CP4 Epsps gene

An electrochemical DNA biosensor was fabricated by immobilizing DNA probe on aluminum ion films that were electrodeposited on the surface of the stearic acid-modified carbon paste electrode (CPE). DNA immobilization and hybridization were characterized with cyclic voltammetry (CV) by using methylene blue (MB) as indicator. MB has a couple of well-defined voltammetric redox peaks at the CPE. The currents of redox peaks of MB decreased after depositing aluminum ion films on the CPE (Al(III)/CPE) and increased dramatically after immobilizing DNA probe (ssDNA/Al(III)/CPE). Hybridization of DNA probe led to a marked decrease of the peak currents of MB, which can be used to detect the target single-stranded DNA. The conditions for the preparation of Al(III)/CPE, and DNA immobilization and hybridization were optimized. The specific sequences related to bar transgene in the transgenic corn and the PCR amplification of CP4 epsps gene from the sample of transgenic roundup ready soybean were detected by differential pulse voltammetry (DPV) with this new electrochemical DNA biosensor. The difference between the peak currents of MB at ssDNA/Al(III)/CPE and that at hybridization DNA modified electrode (dsDNA/Al(III)/CPE) was applied to determine the Specific sequence related to the target bar gene with the dynamic range comprised between 1.0 X 10(-7) mol/L to 1.0 x 10(-4) mol/L. A detection limit of 2.25 x.10(-8) mol/L. of oligonucleotides can be estimated.

Fabrication of Bismuth/Multi-walled Carbon Nanotube Composite Modified Glassy Carbon Electrode for Determination of Cobalt

A bismuth/multi-walled carbon nanotube (Bi/MWNT) composite modified electrode for determination of cobalt by differential pulse adsorptive cathodic stripping voltammetry is described. The electrode is fabricated by potentiostatic pre-plating bismuth film on an MWNT modified glassy carbon (GC) electrode. The Bi/MWNT composite modified electrode exhibits enhanced sensitivity for cobalt detection as compared with the bare GC, MWNT modified and bismuth film electrodes. Numerous key experimental parameters have been examined for optimum analytical performance of the proposed electrode. With an adsorptive accumulation of the Co(II)-dimethylglyoxime complex at -0.8 V for 200 s, the reduction peak current is proportional to the concentration of cobalt in the range of 4.0x10(-11)-1.0x10(-7) mol/L with a lower detection limit of 8.1x10(-11) mol/L. The proposed method has been applied Successfully to cobalt determination in seawater and lake water samples.

Flocculation and removal of the brown tide organism, Aureococcus anophagefferens (Chrysophyceae), using clays

Previous attempts to remove the brown tide organism, Aureococcus anophagefferens, through flocculation with clays have been unsuccessful, in spite of adopting concentrations and dispersal protocols that yielded excellent cell removal efficiency (RE>90%) with other species, so a study was planned to improve cell removal. Four modifications in clay preparation and dispersal were explored: 1) varying the salinity of the clay suspension; 2) mixing of the clay-cell suspension after clay addition; 3) varying of concentration of the initial clay stock; 4) pulsed loading of the clay slurry. The effect of salinity was dependent on the clay mineral type: phosphatic clay (IMC-P2) had a higher RE than kaolinite (H-DP) when seawater was used to disperse the clay, but H-DP removed cells more efficiently when suspended in distilled water prior to application. Mixing after dispersal approximately doubled RE for both clays compared to when the slurry was layered over the culture surface. Lowering the concentration of clay stock and pulsing the clay loading increased RE, regardless of mineral type. However, this increase was more apparent for clays dispersed in seawater than in distilled water. In general, application procedures that decrease the rate of self-aggregation among the clay particles and increase the collision frequency between clay particles and A. anophagefferens achieve higher cell removal efficiency. These empirical studies demonstrated that clays might be an important control option for the brown tide organism, given the proper attention to preparation, dispersal methods, environmental impacts, and the hydrodynamic properties of the system being treated. Implications for the treatment of brown tides in the field are discussed.

A modified HPLC method for analysis of PSP toxins in algae and shellfish from China

Improvements to an established HPLC method are introduced. The modified method is more efficient for separation and detection of the toxins responsible for paralytic shellfish poisoning (PSP). The PSP toxin content of two strains of Alexandrium tamarense and approximately forty shellfish samples collected from different locations in China have been analyzed with this HPLC method. Only one shellfish sample, collected from Lianyungang, China, contained PSP toxins.

Sensitive and Rapid Detection of Genetic Modified Soybean (Roundup Ready) by Loop-Mediated Isothermal Amplification

Using the LAMP method, a highly specific and sensitive detection system for genetically modified soybean (Roundup Ready) was designed. In this detection system, a set of four primers was designed by targeting the exogenous 35S epsps gene. Target DNA was amplified and visualized on agarose gel within 45 min under isothermal conditions at 65 degrees C. Without gel electrophoresis, the LAMP amplicon was visualized directly in the reaction tube by the addition of SYBR Green I for naked-eye inspection. The detection sensitivity of LAMP was 10-fold higher than the nested PCR established in our laboratory. Moreover, the LAMP method was much quicker, taking only 70 min, as compared with 300 min for nested PCR to complete the analysis of the GM soybean. Compared with traditional PCR approaches, the LAMP procedure is faster and more sensitive, and there is no need for a special PCR machine or electrophoresis equipment. Hence, this method can be a very useful tool for GMO detection and is particularly convenient for fast screening.

Detection of transgenic DNA in tilapias (Oreochromis niloticus, GIFT strain) fed genetically modified soybeans (Roundup Ready)

We used nested-polymerase chain reaction (PCR) to detect Roundup Ready soybean in aquatic feeds and feeding tilapias. A template concentration of 10(-10) g mu L-1 DNA solution could be detected with a dilute degree of 0.01%. Most (90.6%) of the aquatic feeds containing soybean byproduct included exogenous DNA segments. We also compared genetically modified (GM) soybean with non-GM soybean diets in feeding tilapias (Oreochromis niloticus, GIFT strain) and examined the residual fragments (254 bp) of GM soybeans. Tilapias receiving GM soybean diets had DNA fragments in different tissues and organs, indicating that exogenous GM genes were absorbed systemically and not completely degraded by the tilapia's alimentary canal.

Recovery of silver (I) using a thiourea-modified chitosan resin

This work describes the preparation of a chelating resin from chemically modified chitosan. The resin was synthesized by using O-carboxymethylated chitosan to cross-link a polymeric Schiffs base of thiourea/glutaraldehyde and characterized by IR. Batch method was applied for testing the resin's adsorption behavior. Adsorption experiments showed the resin had good adsorption capacity and high selectivity for Ag(I) in aqueous solution. The maximum uptake of Ag(I) exhibited was 3.77 mmol/g, at pH 4.0. The results also indicated that the adsorption process was exothermic and fit well with the pseudosecond-order kinetic model. Ag(I) desorption could reach 99.23% using 0.5 M thiourea-2.0 M HCl solution. (C) 2010 Elsevier B.V. All rights reserved.

Synthesis and evaluation of a thiourea-modified chitosan derivative applied for adsorption of Hg(II) from synthetic wastewater

In this work, a thiourea-modified chitosan derivative (TMCD) was synthesized through two steps, O-carboxymethylated first and then modified by a polymeric Schiff's base of thiourea/glutaraldehyde. The adsorption behavior of mercury (II) ions onto TMCD was investigated through batch method. The maximum adsorption capacity for Hg(II) was found to be 6.29 mmol/g at pH 5.0 and both kinetic and thermodynamic parameters of the adsorption process were obtained. The results indicated that adsorption process was spontaneous exothermic reaction and kinetically followed pseudo-second-order model. The adsorption experiments also demonstrated TMCD had high adsorption selectivity towards Hg(II) ions when coexisted with Cu(II), Zn(II), Cd(II) and Ca(II) in solution and it could be easily regenerated and efficiently reused. (C) 2010 Elsevier B.V. All rights reserved.

Characterization of polyethylene glycol-modified proteins by semi-aqueous capillary electrophoresis

A new program to characterize polyethylene glycol-modified (PEGylated) proteins is outlined using capillary zone electrophoresis (CZE). PEGylated ribonuclease A and lysozyme were selected as examples. Five separation procedures were compared to select out the mixed buffer of acetonitrile-water (1:1, v/v) at pH 2.5 as the best to characterize the PEGylated proteins without sample pretreatment. Polyethylene oxide (PEO) with a high molecular mass of 8X10(6) was applied to rinse the capillary to form a dynamic coating which would decrease the undesirable proteins adsorbed to the inner wall of the silica. The electroosmotic flow (EOF) mobility of the five procedures was determined, respectively. It is found that acetonitrile is mainly responsible for the good resolution of PEGylated proteins with the help of PEO coating in the semi-aqueous system. The low EOF mobility and current in the semi-aqueous system might also have some responsibility for the high resolution. The semi-aqueous procedure described in this paper also demonstrates higher resolution of natural proteins than aqueous ones. (C) 2001 Elsevier Science B.V. All rights reserved.

A gas chromatographic analysis of light hydrocarbons on a column packed with modified silica gel

A one-meter long column packed with silica gel is used to separate light hydrocarbons. The silica gel has been modified with several kinds of gas chromatography stationary phases. Among these, PEG 2000 shows fairly good effect when using 80-100 meshes silica gel for the separation of mixture of methane, ethane, ethylene, acetylene, propane, propylene and n-, i-butane. The different behavior of silica gel between batch to batch is also found. When silica gel is coated with a small amount of Al2O3 prepared with sol-gel method, better resolution has been observed on a 2-meter column compared with the non-modified silica gel.