The Inoue Method for Preparation and Transformation of ... At its best, this method for preparing competent E. coli from Inoue et al. .... Preparation of Cells. 1. Prepare Inoue transformation buffer (chilled to 0ºC before use). .... In DNA cloning: A Practical Approach (ed. D.M. Glover), vol. 1 pp. 109-135.