Transformation & Storage Solution (2X TSS) enables researchers to take advantage of the simple system described by Chung et al., 1989 (DOI:10.1073\/pnas.86.7.2172) for the transformation of E. coli cells. Early log-phase cells are suspended in 1X TSS, a solution containing polyethylene glycol, dimethyl sulfoxide, and divalent cations in a bacterial growth medium.This protocol is an alternative to the transformation method with chemically CaCl2-competent cells. Advantage: You can use any fresh E. coli cells Disadvantage: Low efficiency. Use only for transformation of plasmids, not for ligation mixtures in molecular cloning. It is possible to transform at least two plasmids at the same time.CaCl2-Transformation does not work for E. coli strains W3110 and W3110 Z1, thus TSS transformation is a method of choice.