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Biomedical subjects

Zhi-Xiong Xie

Publications and source records attributed to Zhi-Xiong Xie.

7 recordsLinked to original sources
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↗
PubMed2006

[Isolation, identification and over- siderophores production of Pseudomonas fluorescens sp-f].

Strain sp-f was isolated, a siderophores over producing bacterium, using an improved universal Chrome Azurol S(CAS)-agar plate method from Donghu Lake. The result of the CAS solution siderophores quantitative determination showed the lowest As/Ar (OD680) ratio could be as low as 0.09 with Su (Siderophore Unit) of 90%. Some more experiments were made to make out the pertinence between its growth and siderophores production, indicating that its siderophores quantity reached maximum amount during the prophase of logarithmic growth. After then, siderophores concentration stopped accumulating and turned to be stable at stationary phase. Based on the characteristics of morphology, cultivation, physiology, (G + C) mol % content, 16S rDNA sequence and BIOLOG Station system analysis, it was identified as Pseudomonas fluorescens sp-f strain. RP-HPLC analysis showed there exist at least 3 kinds of catecholate siderophores, including fluorescent and non-fluorescent pyoverdins. But only fluorescent pyoverdin's excretion was completely repressed by the 200 micromol/L Fe2+ in the medium. And the non-pyoverdin siderophores excretion was induced at the same time, contrarily.

Chromatography, High Pressure Liquid↗
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↗
PubMed2003

[Horizontal gene transfer].

In this paper the conception of horizontal gene transfer (HGT) was introduced,and main mode of HGT was also enumerated as follows: HGT by medium such as plasmid and virus etc., and the HGT without any medium. The transfer of genes from one species to another especially between remote species was emphasized by the information from genome sequencing. The problems about evolution phylogenies and safety of GEMs (gene engineered microorganisms) for HGT were discussed.

English Abstract↗
PubMed2002

[Genetic diversity analysis of mitochondrial D-loop region of Chinese sucker (Myxocyprinus asiaticus)].

Chinese sucker, Myxocyprinus asiaticus, is an endemic species of China and also the only representatives of family Catostomidae in Asia. The fish was naturally distributed in Yangtze River and Mingjiang River and now few could be captured because of pollution and overexploitation. The fish has been listed in the second class of preserved animal in China. Studying and assessing its population structure is an imperative and fundamental work for making effective protection strategies. We amplified and sequenced the D-loop region of mtDNA of 8 samples. The size of the D-loop region is about 958 bp. A total of 32 variation loci were detected and the mutation rate was 0.033. All the mutation came from nucleotide substitution except one nucleotide deletion. Most of the nucleotide variations were found between the 55-365 bp region. The individual mutation rate varied from 0-1.36%, which exhibited nucleotide polymorphism to some extent among 8 samples. Compared with RAPD and other PCR-based methods, the directily sequencing of mtDNA D-loop region revealed much more genetic diversity. Meanwhile, the D-loop region of Moxostoma robustum derived from GenBank was aligned with that of Chinese sucker through CLUSTAL software. By comparison, we found that the mutation rate (0.033) of D-loop of Chinese sucker is higher than that of Moxostoma robustum (0.016).

Animals↗
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↗