( Up to 25-fold higher transformation e...)New Competent Cells for Highest Transformation Efficiencies

Up to 25-fold higher transformation efficiency of ligated DNA

Bruce Jerpseth Marie Callahan Alan Greener
Stratagene Cloning Systems, Inc.

Stratagenes new, high-efficiency competent E. coli cell line significantly improves the transformation efficiency of ligated DNA. Epicurian Coli XL10-Gold ultracompetent cells* yielded transformation efficiencies for ligated DNA that were up to 25-fold higher than other commercially available cell lines. XL10-Gold cells are the host cells of choice for any cloning experiment that requires a high efficiency of retrieving transformants from ligation reactions, such as constructing plasmid libraries and PCR cloning.

The ability to efficiently introduce DNA into E. coli by chemical transformation and electroporation is a key step for many procedures, such as generating plasmid libraries, cloning large DNA fragments and cloning PCR products.¹ The cells that have set the industry standard for these types of procedures are Stratagenes ultracompetent cells, which yield greater than 5 x 10⁹ transformants/g of supercoiled pUC18 vector (2.7 kb). However, these transformation efficiencies are typically calculated using very small amounts of supercoiled pUC18 vector DNA. Ligated DNA molecules are known to transform cells at a significantly lower efficiency than supercoiled molecules, and large plasmids transform cells less efficiently than small plasmids. This observation has particular impact for researchers making plasmid libraries: the total number and size distribution of primary transformants is key to finding the gene of interest and affects how easily full-length clones can be located. The bias against transforming larger molecules influences the ability to retrieve full-length cDNA clones. For example, many plasmid library vectors, including two-hybrid vectors and eukaryotic expression
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