The Hanahan Method for Preparation and Transformation of Competent Escherichia coli: High-Efficiency Transformation

Abstract Chemical transformation is a highly efficient, commonly used method to transform Escherichia coli with plasmid DNA. Hanahan's procedure works well with many strains of E. coli commonly used in molecular cloning. Many variations on the basic technique have been described, all directed toward optimizing the efficiency of transformation. It is now possible on a routine basis to achieve transformation frequencies ranging from 106 to 109 transformants/µg of superhelical plasmid DNA.