   1.1.1.307 | denaturation buffers of either pH 6.0 or 8.0, containing urea in concentrations of 2, 4, 6, and 8 M, are used and analysed in SDS-PAGE. Optimal solvation of the XylR giving the lowest background of Escherichia coli proteins is performed with 4 M urea at pH 8.0. For renaturation, a set of buffers containing 0, 0.1, 0.5, 1 and 1.5 mM glutathione (red:ox = 1:1) at pH values of 5.0, 6.0, 7.0, and 8.0 are tested. Refolding occurrs at 8°C and its progress is analysed by assaying the volumetric activity in the respective buffers. Best renaturation results are obtained in a 20 mM Tris/HCl buffer at pH 7.0 without glutathione. After 4 days about 70% of the activity of the XylR is recovered. Buffers at pH 8.0 work slightly less efficient compared to that of pH 7.0. At pH 5.0 and 6.0 refolding is drastically reduced. Increasing concentrations of glutathione do not improve renaturation |
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