A kind of recombinant human cystatin c protein with natural activity and its preparation method
A cystatin and protein technology, applied in the field of recombinant human cystatin C protein and its preparation, can solve the problems of poor purity, high purification cost, and large batch-to-batch variation
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Embodiment 1
[0038] Example 1 Preparation of recombinant human cystatin C protein
[0039] (1) Artificially synthesize human cystatin C gene and construct expression plasmid
[0040] According to the reported cystatin C gene sequence, overlapping PCR primers were designed to artificially synthesize the human cystatin C gene, the sequence of which is described in SEQ ID NO:1. The gene was connected with the pMD18-T vector, transformed into Escherichia coli, a single clone was picked, the correct positive plasmid was identified by PCR, and the plasmid was extracted and identified by enzyme digestion. The plasmids with correct PCR identification and enzyme digestion identification were sent to Invagen Company for sequencing, and the results were completely consistent with the designed sequence. The plasmid with correct sequencing was digested with the corresponding enzymes designed at the two ends of the restriction site, and the excised target sequence was connected into the PET-15b vector ...
Embodiment 2
[0056] Example 2 The mass ratio of trypsin is 50:1 to digest recombinant human cystatin C protein
[0057] The undigested recombinant human cystatin C protein prepared in Example 1 was added with recombinant trypsin at a mass ratio of recombinant cystatin C:trypsin of 50:1, and digested in a water bath at 37° C. for 5 min. After digestion, the sample was adjusted to pH 9.5 with 0.5M NaOH, and placed at 4°C for 1 hour to completely inactivate trypsin. After enzyme digestion, the protein was dialyzed with 20mMPBS overnight, bound on a nickel agarose gel FF column for 1 hour, the excised part with his tag and residual recombinant trypsin were removed by reverse affinity, and the flow-through protein sample after binding was collected, that is, The final purified recombinant human cystatin C protein is analyzed by SDS-PAGE electrophoresis, and the protein purity is over 95%. Activity was evaluated according to step (5) in Example 1.
Embodiment 3
[0058] Example 3 The mass ratio of trypsin is 1000:1 to digest recombinant human cystatin C protein
[0059] The undigested recombinant human cystatin C protein prepared in Example 1 was added with recombinant trypsin at a mass ratio of recombinant cystatin C:trypsin of 1000:1, and digested in a water bath at 37° C. for 30 min. After digestion, the sample was adjusted to pH 9.5 with 0.5M NaOH, and placed at 4°C for 1 hour to completely inactivate trypsin. After enzyme digestion, the protein was dialyzed with 20mMPBS overnight, bound on a nickel agarose gel FF column for 1 hour, the excised part with his tag and residual recombinant trypsin were removed by reverse affinity, and the flow-through protein sample after binding was collected, that is, The final purified recombinant human cystatin C protein is analyzed by SDS-PAGE electrophoresis, and the protein purity is over 95%. Activity was evaluated according to step (5) in Example 1.
[0060] Table 2: Comparison of enzyme cl...
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