Transformation and Storage Solution (TSS) is used for the preparation of competentÊE. coliÊcells in a single step and to transform the cells without heat-shock. Amid Biosciences' TSS is optimized version of solution described initially byÊChung et al. (1) and contains DMSO, PEG, Mg²⁺ salts, along with proprietary additives. This solution allows rapid preparation of the competent cells with typical transformation efficiencies that range from 10⁵ to 10⁷Êcfu/µg of DNA, however, the transformation efficiencies up to 10⁸ can be obtained for someÊE. coliÊstrains.