Difference between revisions of "Calcium chloride heat shock transformation"
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Revision as of 19:02, 13 July 2014
Calcium chloride heat shock is a common method of transformation used with E. coli cells.
It is not precisely known what the mechanisms are but the current theory is that the DNA enters the cell through pores in the cell membrane known as adhesion zones. Rapidly growing E. coli cells contain a large number of these adhesion zones where the inner and outer cell membrane fuse with each other. The hydrophilic phosphate groups on the surface of the lipid bilayer are strongly negatively charged as is the DNA so normally they repel each other. A solution of calcium chloride (CaCl2) is added to the cells and the calcium makes the environment more electrostatically neutral so the DNA can be closely associated with the membrane. The cells which have been kept at a cool temperature the entire time are then "heat shocked" by rapidly transferring them from approximately 0 C to 42 C. This creates local strong temperature gradients and disruptive currents in the system that results in some of the DNA being taken up into the cell through the adhesion zone pores.
