The core prepares competent cells by one of two methods: electrocompetent cells (cells successively washed in glycerol that are ready to receive DNA by electroporation) or CaCl2 competent cells (cells that are primed by treatment with CaCl2 to pick up DNA following heat shock). The core has an extensive collection of host cells, providing investigators with a wide range of options for transformation.
The following are most frequently requested:
We will also prepare competent cells of strains provided by the investigator. Cells are made in batches of ~60 aliquots of 50microliters each. The transformation efficiency of each batch is measured before it is released. Electrocompetent cells must have an efficiency >107 transformants per micrograms DNA; CaCl2 competent cells, >105.
Batches of standard strains may be ordered simply by contacting the laboratory with a request. Preparation of cells from custom strains is ordered by delivery of the plate to the core lab. Plates must be clearly labeled with the name of the PI, cost center to be charged for the procedure, and the person to contact when the plasmid is ready. Turnaround time is ≤ two weeks.