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Stellar™ Competent Cells (dam-/dcm-)

Cat. #	Product	Size		License	Quantity	Details
636764	Stellar™ Competent Cells (dam-/dcm-)	10 Transformations	USD $222.00
Stellar Competent Cells (dam-/dcm-) are an E. coli HST04 strain that lacks the genetic factors (dam and dcm) necessary for the methylation of DNA. Plasmids prepared using this product can be cut by restriction enzymes which are normally blocked by dam or dcm methylation. A dam/recA double mutation is lethal, so the parent strain is recA+. Therefore, it follows that transformation of extracellular DNA with repeat sequences can result in recombination by recA. This product is not a suitable cloning host. For transformation, it is highly recommended to use this product for constructing plasmids as mentioned above. A pUC19 vector is provided as well as SOC Medium. Notice to purchaser Our products are to be used for Research Use Only. They may not be used for any other purpose, including, but not limited to, use in humans, therapeutic or diagnostic use, or commercial use of any kind. Our products may not be transferred to third parties, resold, modified for resale, or used to manufacture commercial products or to provide a service to third parties without our prior written approval. Documents Components Image Data Back 636764: Stellar Competent Cells (dam-/dcm-) Back Stellar Competent Cells provided transformation efficiencies equivalent to or better than those obtained using DH5α or DH10B competent cells The high efficiency of Stellar Competent Cells was especially noticeable in the transformation of 10 kb and 20 kb plasmids. Using DNA plasmids of 2 kb (100 pg), 10 kb (1 ng), and 20 kb (1 ng), each strain of competent cells was transformed and plated on ampicillin-containing LB agar plates. Transformation efficiencies were determined based on the colony counts obtained. Back Stellar Competent Cells provided the highest transformation efficiencies for all the ligation reaction mixtures tested. The difference in transformation efficiencies of the competent cells was particularly prominent when cloning 20 kb fragments. Ligation reactions were set up with either 100 ng of a 2 kb, Hind III-cut DNA fragment + 50 ng of Hind III/BAP-cut pUC118 vector, or 75 ng of a 20 kb, Hind III-cut DNA fragment + 25 ng of Hind III/BAP-cut pUC118 vector. All reactions were performed at 16℃ for 6 hours using the Takara DNA Ligation Kit (Cat# 6023 or 6024). Each strain of competent cells was transformed using portions of these reaction mixtures and plated on ampicillin-containing LB agar (+ X-gal). Transformation efficiencies were determined based on the white colony counts obtained. Back Stellar Competent Cell colonies showed a faster growth rate than DH10B colonies Stellar colonies transformed with larger plasmid clearly showed a faster growth rate. DNA plasmids of 2 kb (Panel A) and 10 kb (Panel B) were each used to transform Stellar and DH10B competent cells with similar genetic characteristics, including methylation requiring restriction. This experiment used the same method as in Figure 1. Photographs of colonies on agar were taken after 15 hours of incubation.