抄録
Transformation of pBR322 DNA to Escherichia coli cells treated with CaCl2 was stimulated by addition of 8% polyethylene glycol (PEG) 600 to the DNA solution. Prolonged incubation of the competent cells in chilled CaCl2 solution (Dargert and Ehrlich, 1979) raised the transformation efficiency by a factor of 5. This prolonged incubation did not inhibit the stimulus effect of PEG. When PEG 600 or PEG 1, 000 was added to the mixture of plasmid pBR322 DNA to a final concentration of 2% and the competentcells were incubated at 0°C for 24 hr, weroutinely obtained over 107 transformants per μg of pBR322 DNA, and the competent cells transformed comprised 24% of the viable cells.
