The genes encoding type II DNA topoisomerases were investigated in Giardia lamblia genome, and a type IIA gene, GlTop 2 was identified. It is a single copy gene with a 4476 bp long ORF without intron. The deduced amino acid sequence shows strong homology to eukaryotic DNA Top 2. However, some distortions were found, such as six insertions in the ATPase domain and the central domain, a ~100 aa longer central domain; a ~200 aa shorter C-terminal domain containing rich charged residues. These features revealed by comparing with Top 2 of the host, human, might be helpful in exploiting drug selectivity for antigiardial therapy. Phylogenetic analysis of eukaryotic enzymes showed that kinetoplastids, plants, fungi, and animals were monophyletic groups, and the animal and fungi lineages shared a more recent common ancestor than either did with the plant lineage; microsporidia grouped with fungi. However, unlike many previous phylogenetic analyses, the "amitochondriate" G. lamblia was not the earliest branch but diverged after mitochondriate kinetoplastids in our trees. Both the finding of typical eukaryotic type IIA topoisomerase and the phylogenetic analysis suggest G. lamblia is not possibly as primitive as was regarded before and might diverge after the acquisition of mitochondria. This is consistent with the recent discovery of mitochondrial remnant organelles in G. lamblia.
This paper explains how the Lignin peroxidase and Manganese Peroxidase from Coriolus Versicolor were co-immobilized by chitosan microspheres.It studies kinetic character of the enzyme after co-immobilization.Optimum Lip and MnP activity obtained at 30-35°C for 14 hours in pH 8.4 glutaraldehyde solutions during immobilized to chitosan microspheres which prepared by coagulation in NaOH: methanol=3:2. When kept at 50°C for 6h, more than 80% of the immobilized enzyme activity remained, while the free enzymes were inactive under the same conditions. The co-immobilized enzyme can remain 70% activity after two weeks while both of the free enzymes inactive. Compared with the free enzymes, temperature and time stability of the co-immobilized enzyme was considerably improved.
In order to achieve the design of mechatronic system rapidly, an integrated design process is used for a hydrostatic slideway driven by linear motor. Control model of the linear motor and FE model of the slideway carriage are established, besides, force analysis of the carriage and relevant optimization are carried out. Software Simulink is used to simulate the linear feeding system. Subsequently, the advantages of the integrated design compared with traditional method are analyzed. This study could provide important insights for the design of the hydrostatic slideway with linear motor driven system.
The dynamic characteristics of machine tool directly affect machining accuracy of the final parts. Taking the self-developed HRG ultra-precision polishing CNC machine tool as the research object, the simplified finite element model is established with the finite element analysis software to do the dynamic analysis and the natural frequency is detected as the index of the dynamic performances. Based on the comparative analysis of the natural frequency and vibration modes, the gantry and the supporting frame are recognized as structural weaknesses of the machine tool, and then the modal test is done to verify simulation results. Eventually the structural weaknesses are optimized effectively. The 1st order nature frequency of the optimized gantry and the optimized supporting frame is increased 75.5% and 80.8% respectively so that they have better dynamic performances, resulting in offering higher workpiece quality and process stability.
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