All steps of purification were performed at 4°C. After elution from the column, protein fractions were concentrated to
a final concentration of 12 μg/ml and analyzed by Western blot analysis with anti-c-Myc IgG antibodies (Sigma). For some of the planar lipid bilayer experiments, in order to improve the stability of the artificial membranes with the incorporated protein, we also purified TRPM8 from the TRPM8-his stable cell line. This modification allowed us to include into the procedure described above an additional step of purification with ion-affinity chromatography using Ni-NTA beads (Qiagen).