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Articles by Yan Xu
Total Records ( 3 ) for Yan Xu
  Yingmei Fu , Lishuang Guo , Yan Xu , Wenli Zhang , Jiaao Gu , Jianfeng Xu , Xiaobei Chen , Yuehui Zhao , Jiayu Ma , Xinghan Liu and Fengmin Zhang
  Resistance to ciprofloxacin was detected in 111 (48.1%) isolates of Klebsiella pneumoniae from China. GyrA alterations were identified in the ciprofloxacin-resistant and ciprofloxacin-susceptible isolates. The results, including previously published data, indicate that the single substitution Ser83→Ile and three types of double mutations at Ser83 and Asp87 were required for ciprofloxacin resistance (P < 0.05).
  Natascha Pogori , Ahmad Cheikhyoussef , Yan Xu and Dong Wang
  The aim of the study was to investigate the extracellular lipase production by the fungus, Rhizopus chinensis CCTCC M201021. The biochemical characteristics of this lipase were also identified. The inducing effect of vegetable oils (soybean oil, sunflower oil, sesame oil, rice bran oil and olive oil), fatty acids (palmitic acid, oleic acid, linoleic acid and stearic acid) and surfactants (Tween 80, sodium dodecyl sulphate, gum arabic and Triton X-100) on lipase production by Rhizopus chinensis CCTCC M201021 was investigated. Soybean oil enhanced lipase production by 102% and was the highest among other oils studied. There was no significant effect on lipase production by surfactants at p<0.05. The unsaturated fatty acids, oleic and linoleic acid significantly enhanced the lipase production by 147%. The optimum temperature for lipase activity was 30°C and the optimum pH was 6.0. The enzyme had stability in the pH range of 4.0 to 10.0 for 1 h. The enzyme retained stability of 60% of the maximum at 70 °C after pre-incubation for 1 h. Zn2+ and Cu2+ ions depressed the lipase activity but Mg2+ and Ca2+ ions were found to stimulate the lipase activity. The enzyme had broad substrate specificity towards both p-nitrophenyl esters and triglyceride substrates since it efficiently hydrolyzed long-chain and short-chain fatty acids but greater preference was observed for the long-chain fatty acids. The lipase was able to hydrolyze both the 1, 3-position and the internal position of triolein.
  Chenping Xu , Yan Xu and Bingru Huang
  Protein extraction for two-dimensional gel electrophoresis (2-DE) from plant samples is challenging due to low protein content and high level of contaminants. Proteomic research in turfgrass is limited by the lack of efficient protein extraction methods. To establish an effective protocol of protein extraction suitable for 2-DE analysis in turfgrasses, four protein extraction methods (chloroform/acetone, tris-base/acetone, phenol/ammonium acetate, and trichloroacetic acid [TCA]/acetone methods) were evaluated for creeping bentgrass (Agrostis stolonifera L.). Proteins were extracted from leaves and roots of mature plants using the above four methods and separated by 2-DE. The TCA/acetone extraction had higher protein yield and resolution of protein separation for leaves, compared to the other three methods. For roots, both the TCA and phenol methods had higher protein yields and number of protein spots than the other two methods. The phenol method had more protein spots and higher spot intensities in the low molecular weight (Mr) region or high isoelectric point (pI) region than the TCA extraction, while more protein spots and higher spot intensity in the region of high Mr were detected by the TCA method than by the phenol method. Our results suggested that the TCA method was the most effective among the four methods for leaves, and a combination of the TCA and phenol methods may provide enhanced proteomic information for roots in turfgrass.
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