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Articles by K. Zhu
Total Records ( 2 ) for K. Zhu
  J He , R Xu , X Chen , K Jia , X Zhou and K. Zhu

To reduce the immunogenicity of recombinant staphylokinase, structure-based mutagenesis of Glu80 residue in wild-type staphylokinase (wt-Sak) was rationally designed and carried out by a modified QuikChange site-directed mutagenesis. Sak mutants, including Sak(E80A) and Sak(E80S), were successfully expressed in E. coli DH5 as a soluble cytoplasmic proteins and accounted for more than 40% of the total cellular proteins. The expressed proteins were purified by a three-step chromatographic purification process. SDS–PAGE and HPLC analyses results indicated that the purified proteins were almost completely homogeneous and the purities of Sak mutants exceeded 97%. Analysis of fibrinolytic activity revealed that substitution of E80 residue with serine and alanine resulted in slightly increased specific activities of Sak mutants. Investigation of the immunogenicity of Sak mutants showed that the amount of specific anti-Sak IgG antibodies elicited by Sak(E80A) and Sak(E80S) in BALB/c mice decreased ~35% and 27%, respectively compared with wt-Sak. The abilities of Sak mutants to stimulate proliferation of T cells from BALB/c mice and to bind mouse anti-Sak polyclonal serum were significantly lower than those of wt-Sak. These results suggested that substitution of Glu80 residue by alanine and serine successfully eliminated part of T- and B-cell epitope of Sak molecule. Our findings suggested that simultaneous elimination of T- and B-cell epitopes was a useful method to reduce the immunogenicity of wt-Sak molecule and provided a strategy for engineering safe Sak-based fibrinolytics for the clinical treatment of acute myocardial infarction.

  K. Zhu , H. L. Choi , H. Q. Yao , A. Suresh and D. I. Oh
  Land application of the effluent of anaerobically digested pig slurry is becoming common practice in integrated crop and livestock farming. However, the loss of nutrients, in particular nitrogen and phosphorus, within the water bodies is still a main concern of this practice. The objective of this study was to evaluate nitrogen and phosphorus losses in runoff and leachate for four application rates of anaerobically digested pig slurry (25.0, 70.1, 140.2, and 210.3 kg N ha-1) for Chinese cabbage grown in lysimeters. Simulated rainfall events, occurring one week after slurry application, were used to generate runoff. The yields of nutrients, biochemical oxygen demand and chemical oxygen demand in runoff and leachate increased linearly or logarithmically with slurry application rates. A combination of long rainfall duration (90 minutes) and lower rainfall intensity (33.3 mm hr-1) induced higher nutrient concentrations in the runoff, but lowered the nitrogen concentration in the leachate. The application doses of anaerobically digested pig slurry before sowing, nutrient supplementation and fertilisation time management are the key factors in reducing nutrient contamination of water courses.
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