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Zhi-Ling Zhang

Publications and source records attributed to Zhi-Ling Zhang.

16 recordsLinked to original sources
PubMed2006

pH effect on dynamic coating for capillary electrophoresis of DNA.

A buffer consisting of tris(hydroxymethyl)aminomethane, 2-(N-moropholino)ethanesulfonic acid (Mes) and EDTA with constant ion strength was used to investigate the effect of buffer pH on the dynamic coating behavior of poly(N-isopropylacrylamide) (PNIPAM) for DNA separation. The atomic force microscopy (AFM) image illustrated that PNIPAM in lower-pH buffer was much more efficient in covering a silica wafer than that in higher-pH buffer. The coating performance of PNIPAM was also quantitatively analyzed by Fourier transform IR attenuated total reflectance spectroscopy and by measuring the electroosmotic flow (EOF). These results indicated that the stability of the dynamic coating was dependent on the pH of the sieving matrix and was improved by reducing the pH to the weak-acid range. The lower pH of the sieving buffer may induce the polymer more efficiently to adsorb on the capillary wall to suppress EOF and DNA-capillary wall interaction for DNA separation. The enhanced dynamic coating capacity of PNIPAM in lower-pH buffer may be attributed to the hydrogen bonds between the hydroxyl groups of the silica surface and the oxygen atom of the carbonyl groups of PNIPAM.

DNA↗
PubMed2006

Quantum-dot-labeled DNA probes for fluorescence in situ hybridization (FISH) in the microorganism Escherichia coli.

Semiconductor quantum dots (QDs) as a kind of nonisotopic biological labeling material have many unique fluorescent properties relative to conventional organic dyes and fluorescent proteins, such as composition- and size-dependent absorption and emission, a broad absorption spectrum, photostability, and single-dot sensitivity. These properties make them a promising stable and sensitive label, which can be used for long-term fluorescent tracking and subcellular location of genes and proteins. Here, a simple approach for the construction of QD-labeled DNA probes was developed by attaching thiol-ssDNA to QDs via a metal-thiol bond. The as-prepared QD-labeled DNA probes had high dispersivity, bioactivity, and specificity for hybridization. Based on such a kind of probe with a sequence complementary to multiple clone sites in plasmid pUC18, fluorescence in situ hybridization of the tiny bacterium Escherichia coli has been realized for the first time.

DNA Probes↗
PubMed2005

Core/shell quantum-dot-photosensitized nano-TiO2 films: fabrication and application to the damage of cells and DNA.

Through the use of monodisperse core/shell quantum dots (QDs) as photosensitizers for the first time, a novel strategy for the fabrication of QD-photosensitized nano-TiO2 films was demonstrated. Core/shell QDs were self-assembled on nano-TiO2 films through carboxyls as anchoring groups to metal oxides. Atomic force microscopy and some other experiments showed the fabrication strategy is successful. Reactive oxygen species detection experiments indicated that such films have photosensitization ability. The results of bactericidal and DNA damage experiments demonstrate that such films have excellent photoactivity.

DNA↗
PubMed2005

Direct electrochemistry and electrocatalysis of heme proteins entrapped in agarose hydrogel films in room-temperature ionic liquids.

The electrochemistry and electrocatalysis of a number of heme proteins entrapped in agarose hydrogel films in the room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) have been investigated. UV-vis and FTIR spectroscopy show that the heme proteins retain their native structure in agarose film. The uniform distribution of hemoglobin in agarose-dimethylformamide film was demonstrated by atomic force microscopy. Cyclic voltammetry shows that direct electron transfer between the heme proteins and glassy carbon electrode is quasi-reversible in [bmim][PF(6)]. The redox potentials for hemoglobin, myoglobin, horseradish peroxidase, cytochrome c, and catalase were found to be more negative than those in aqueous solution. The charge-transfer coefficient and the apparent electron-transfer rate constant for these heme proteins in [bmim][PF(6)] were calculated from the peak-to-peak separation as a function of scan rate. The heme proteins catalyze the electroreduction of trichloroacetic acid and tert-butyl hydroperoxide in [bmim][PF(6)]. The kinetic parameter I(max) (maximum current at saturation concentration of substrate) and the apparent K(m) (Michaelis-Menten constant) for the electrocatalytic reactions were evaluated.

Biosensing Techniques↗
PubMed2005

Electrochemical DNA sensing based on gold nanoparticle amplification.

A hybridization signal-amplified method based on a gold nanoparticle-supported DNA sequence for electrochemical DNA sensing has been investigated by cyclic voltammetry, differential-pulse voltammetry, and atomic-force microscopy (AFM). Quantitative analysis showed that the peak current increment (DeltaIp) is linearly dependent on the concentration of the gold nanoparticle-supported DNA sequence Au2 over the range 0.51-8.58 pmol L(-1). AFM results indicated that the extent of surface hybridization was dependent on the concentration of the gold-nanoparticle-supported DNA sequence. Moreover, a new pair of peaks, which might arise from the special configuration of the gold-nanoparticle-supported DNA sequence, appeared in the cyclic voltammogram after hybridization. Although quite sensitive, this DNA sensing surface was not easily regenerated, so this kind of amplified method was suitable for disposable DNA sensors and chip-based gene diagnosis sensors.

Base Sequence↗
PubMed2005

Preparation and characterization of overcoated II-VI quantum dots.

A convenient route for the synthesis of high-quality overcoated II-VI quantum dots (QDs) is reported in this paper. Simple salts, such as Cd(Ac)2 and Zn(Ac)2 were used to replace organometallics, whose disadvantage is obvious. Size-tunable core/shell structured QDs (CdSe/ZnS, CdSe/CdS, etc.) were synthesized. They were of narrow size distribution and had good monodispersivity and photoluminescence (PL) properties. The spectrum was symmetrical and sharp-pointed (with the full width at half-maximum (fwhm) of about 20-30 nm). The quantum yield (QY) was improved to 60-80% from 20-30% for bare QDs and remained stable at least for 6 months. The primary overcoated QDs were modified with biomacromolecules by a direct mechanical rubbing strategy, which is very simple and fast. The results obtained by UV-vis, PL, atomic force microscopy (AFM), and fluorescence microscopy imaging showed that the modified QDs were of good fluorescent and monodisperse characteristics. They are likely to be used further for biological labels.

Cadmium Compounds↗
PubMed2004

Combing DNA on CTAB-coated surfaces.

A fluorescence microscope (FM) coupled with an intensified charge-coupled device (ICCD) camera was used to investigate the combing of DNA on cetyltrimethyl ammonium bromide (CTAB)-coated glass surfaces. DNA molecules can be combed uniform and straight on CTAB-coated surfaces. Different combing characteristics at different pH values were found. At lower pH (ca. 5.5), DNA molecules were stretched 30% longer than the unextended and DNA extremities bound with CTAB-coated surfaces via hydrophobic interaction. At high pH values (e.g., 6.4 and 6.5), DNA molecules were extended about 10% longer and DNA extremities bound with CTAB-coated surfaces via electrostatic attraction. At pH 6.0, DNA molecules could be extended 30% longer on 0.2-mM CTAB-coated surfaces. CTAB cationic surfactant has both a hydrophobic motif and a positively charged group. So, CTAB-coated surfaces can bind DNA extremities via hydrophobic effect or electrostatic attraction at different pH values. It was also found that combing of DNA on CTAB-coated surfaces is reversible. The number of DNA base pairs binding to CTAB-coated surfaces was calculated.

Bacteriophage lambda↗
PubMed2004

Direct electrochemistry and electrocatalysis of heme-proteins entrapped in agarose hydrogel films.

Three heme-proteins, including myoglobin (Mb), hemoglobin (Hb) and horseradish peroxidase (HRP), were immobilized on edge-plane pyrolytic graphite (EPG) electrodes by agarose hydrogel. The proteins entrapped in the agarose film undergo fast direct electron transfer reactions, corresponding to FeIII = e- --> FeII. The formal potential (E degrees'), the apparent coverage (Gamma), the electron transfer coefficient (alpha) and the apparent electron transfer rate constant (ks) were calculated by integrating cyclic voltammograms or performing nonlinear regression analysis of square wave voltammetric (SWV) experimental data. The E degrees's are linearly dependent on solution pH (redox Bohr effect), indicating that the electron transfer was proton-coupled. Ultraviolet visible (UV-Vis) and reflection-absorption infrared (RAIR) spectra suggest that the conformation of proteins in the agarose film are little different from that proteins alone, and the conformation changes reversibly in the range of pH 3.0-10.0. Atomic force microscopy (AFM) images of the agarose film indicate a stable and crystal-like structure formed possibly due to the synergistic interaction of hydrogen bonding between N,N-dimethylformamide (DMF), agarose hydrogel and heme-proteins. This suggests a strong interaction between the heme-proteins and the agarose hydrogel. DMF plays an important role in immobilizing proteins and enhancing electron transfer between proteins and electrodes. The mechanisms for catalytic reduction of hydrogen peroxide and nitric oxide (NO) by proteins entrapped in agarose hydrogel were also explored.

Absorption↗
PubMed2004

Improvement of homogeneity of analytical biodevices by gene manipulation.

Homogeneity is proposed for evaluation of the quality of analytical biodevices, such as biosensors and biochips. As a demonstration, glucose oxidase (GOx) was modified at its C-terminal with a linker peptide with a cysteine residue at the end. The fusion structure (GOx-linker-cysteine) enables the enzyme to immobilize on gold surfaces with a Cys-S-Au bond or to immobilize on a silanized glass surface via disulfide chemistry. With this fusion structure, the enzyme can be anchored onto the substrate with well-controlled orientation, thus forming a homogeneous biological layer on biodevices. The linker peptide between GOx and the cysteine acts as a spacer to reduce the steric hindrance caused by the bulky body of the enzyme. Biochemistry experiments showed that this genetically modified glucose oxidase (shortened to GOxm) retained most of its catalytic characteristics, with K(m) and K(cat) similar to those of the wild-type GOx. Electrochemistry experiments showed that GOxm-modified electrode gave higher and more stable current responses than the electrode modified with GOx which has no free -SH on its surface. The coefficients of variation (used for evaluation of the interchangeability of the enzyme device from the same batch preparation) were 9.5% for the GOxm gold electrode and 20.0% for the GOx gold electrode and the GOxm oxygen electrode. The relative errors (used for evaluation of the precision of the individual enzyme device) were 2.9% for the GOxm gold electrode, 12.0% for the GOx gold electrode, and 11.2% for the GOxm oxygen electrode. Atomic force microscopy images revealed that GOxm formed a self-assembled monolayer in a hexagonal-like lattice packing arrangement on the gold surface, while GOx formed multilayer assembling or aggregated particles. The homogeneity of the protein chips, the GOxm array that was prepared through -S-S- formation, and the GOx array that was prepared through nonspecific adsorption was evaluated. The coefficients of variation, calculated with the signal level of all dots, were 5.4% for the GOxm array and 81.8% for the GOx array. All experimental results pointed to the fact that the homogeneity of the analytical biodevices could be considerably improved by using the proposed method.

Aspergillus niger↗
PubMed2004

Effects of endothelin-1 on melanocyte adhesion and migration.

OBJECTIVE: To investigate the effect of endothelin-1 (ET-1) on the adhesion and migration of melanocyte in vitro. METHODS: Human epidermal melanocytes that had been cultured and purified were treated with ET-1 and observed for adhesion to bovine serum fibronectin-coated culture dishes. Stem cell factor (SCF) and ET-1 treated cells were also examined for migration into micropore filters coated with the same protein. RESULTS: Compared with the SCF group, ET-1 treated melanocytes were easier to adhere to the dishes and to be moved into the filters, especially when the concentration was 32 nmol/L. When the concentration of ET-1 was 128 nmol/L or more, it could inhibit the adhesion and migration of melanocyte. At any concentration of ET-1 except at 2 nmol/L, there was a significant difference between ET-1-treated and untreated melanocytes (P < 0.01) when the adhesion test was carried out. However, even at 2 nmol/ L ET-1, there was obviously increased migration compared with those of ET-1 untreated melanocytes and SCF-treated cells (P < 0.01). CONCLUSION: ET-1 may influence the adhesion and migration of melanocyte, which can partly explain the capacity of ET-1 to regulate the melanocyte function in vitiligo lesions.

Cell Adhesion↗
PubMed2003

Visual gene diagnosis of HBV and HCV based on nanoparticle probe amplification and silver staining enhancement.

A visual gene-detecting technique using nanoparticle-supported gene probes is described. With the aid of gold nanoparticle-supported 3'-end-mercapto-derivatized oligonucleotide serving as detection probe, and 5'-end -amino-derivatized oligonucleotide immobilized on glass surface acting as capturing probe, target DNA was detected visually by sandwich hybridization based on highly sensitive "nano-amplification" and silver staining. Different genotypes of Hepatitis B and C viruses in the serum samples from infected patients were detected using home-made HBV, HCV, and HBV/HCV gene chips by the gold/silver nanoparticle staining amplification method. The present visual gene-detecting technique may avoid limitations with the reported methods, for its high sensitivity, good specificity, simplicity, speed, and cheapness. This technique has potential applications in many fields, especially in multi-gene detection gene chips coupled with the detection will find applications in clinic. Additionally, resonance Rayleigh light scattering (RLS) spectroscopy is used, for the first time, to judge and monitor the immobilization of gene probes on gold nanoparticle surfaces.

DNA Probes↗
PubMedDate not supplied

Investigation of DNA orientation on gold by EC-STM.

The immobilization of thiol-derivatized DNA on a Au (111) single crystal surface by self-assembly has been investigated by electrochemical scanning tunneling microscopy (EC-STM). Continuous potential-dependent orientation changes of double-stranded oligodeoxynucleotides (ODN) have been observed in a certain potential range from 200 to 600 mV (versus SCE). It is suggested that the DNA duplexes stand straight on the gold surface at potentials negative of the potential of zero charge (pzc) and then lay down on the surface when the potential shifts positively. These results are in agreement with the expectation based on the Coulombic interaction consideration between negatively charged DNA helices and gold surface. As the applied potential shifts positively, the surface charge changes from negative to positive, that is, the Coulombic force between negatively charged DNA helices and gold surfaces changes from repulsion to attraction. However, for the single-stranded oligodeoxynucleotides, no distinct changes in the surface structure were observed with the applied potential.

DNA↗
PubMedDate not supplied

Yeast transformation process studied by fluorescence labeling technique.

A new method based on fluorescence imaging and flow cytometry was developed to investigate the transformation process of Saccharomyces cerevisiae AY. Yeast and fluorescent-labeled plasmid pUC18 were used as models of cells and DNA molecules, respectively. Binding of DNA molecules to yeast cell surfaces was observed. Factors influencing DNA binding to cell surfaces were investigated. It has been found that poly(ethylene glycol) (PEG) could induce DNA binding to yeast surfaces, while Li(+) showed a weak effect on the binding. When both Li(+) and PEG were used, synergetic effect occurred, resulting in the binding of pUC18 to the surface of more yeast cells compared with that in the presence of PEG or Li(+) only. It was also confirmed that heat shock, Li(+), and PEG all can increase the permeability of yeast cells. This simple method is helpful for understanding the process of yeast transformation and can be used to investigate the interaction of DNA with cell surfaces.

Cell Membrane Permeability↗