| Source | Human 293 Cells | M.W. | 37-40 kDa | CAS No. | |
|---|---|---|---|---|---|
| Structural Info | |||||
| Formulation | Lyophilized in sterile filtered solution of PBS. | ||||
| Reconstitution | Before reconstitution, a brief spin is recommend todrive down any material dislodged from the bottom of the tube. The lyophilized protein should bereconstituted in sterile H2O to a desired concentration. | ||||
| Stability | The lyophilized protein is stable for at least oneyear if stored at -80 °C. Reconstituted protein is stable for at least four weeks at 4 °C,but should be stored in aliquots at -80 °C for longer term. Avoidrepeated freeze and thaw. | ||||
| Purity | Greater than 90% as determined by SDS-PAGE analysis | ||||
| Biological Activity | The activity was determined by using a TCF reporter gene assay in cultured human cells.The IC50 ranges from 100 - 500 ng/ml in the inhibition of 100 ng/mL WNT-3a activity.Activity in other assays | ||||
| Country of Origin | USA | ||||
DKK-1, Dickkopf-related protein-1, is a member of the DKKprotein family which includes DKK-1 through DDK-4. DKK was originally identified as ahead-forming molecule in Xenopus. Mechanisticstudies showed that DKK-1 inhibits the Wnt /β-catenin signaling pathway byforming inhibitory complexes with co-receptor LRP5/6. Inhibition of Wnt/β-catenin signaling isessential for posterior patterning and anterior development in vertebrates, supportedby the discovery that DKK-1 knock-out mice lack head formation. StemRDexpressed recombinant human DKK-1 in human 293 cells as a 37-40 kDaglycoprotein containing 235 amino-acid residues. It is purified by a series of chromatography including HPLC.
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调节至最适合温度(一般是37度),合适的酸碱度时,酶的活性最高
1,底物DNA上没有该限制酶的识别、切断位点。特别是一些经过重组等处理的DNA,碱基易发生缺失、变化等。
2,限制酶识别位点上的A或C被甲基化。部分限制酶对识别位点中的碱基是否被甲基化比较敏感,从而无法切断该位点。
3,底物不纯。如果底物DNA中有限制酶阻害物质,回影响限制酶的酶切作用。在此种情况下,底物DNA须重新进行精制。
4,限制酶的识别、切断位点在底物DNA的高级构造中所处的位置,对酶切反应也有一定的影响,例如,限制酶NaeI在切断pBR322DNA时,就有着非常难以切断的部位。
5,限制性内切酶本身无活性或低活性
决定酶促反应最大速度Vm的因素是什么?是同一底物,尽管加不同种酶,其Vmax都相同吗?可以画曲线图解释一下吗?可是根据米曼氏方程来看又有点矛盾,Km变大,Vmax也需变大,才可使v变大。所以题目所述到底应该怎么理解呢

