Study on variation of transformation rate of E.coli DH5α competent cells

The competent cells of E.coli DH5α strain were prepared by calcium chloride,and the variation of transformation rate for different treatment temperatures and times was detected.Experimental results showed that the transformation rate of competent cells stored at 4℃ reached maximum for 8 hours.And the transformation rates reached maximum for 48 hours,when they were stored at-20℃ and-70℃.The competent cells of E.coli DH5α strain prepared by calcium chloride could satisfy general research needs when they were stored directly at-20℃ within 20 days.