Chemical Transformation: this type of transformation is called as heat shock transformation as the sudden change in temperature causes the bacteria to take up the DNA, during the growth period, E.coli cells have number of pores known as adhesion zones. The cell membrane we know is made up of lipid bi layer which have negatively charged phosphates, the DNA also has negatively charges phosphates on its helix so when the small DNA plasmid comes near these pores (adhesion zones) these are repelled due to the negative charges of phosphates. Now in labs we use Calcium chloride which provides Calcium ions and thus helps in neutralizing the negative charges on the membrane and simultaneous lowering of temperature hardens the cell membrane. An instant change in temperature, heat shock or increase in temperature causes the plasmid DNA to pass through the adhesion zones and taken up by bacterial cell.

For carrying out this procedure in lab first the bacterial cells are treated with CaCl_2, then these cells are combined with the foreign DNA stored on ice for half an hour then for very short period this test tube is placed in hot water bath maintained at temperature of 42^o Celsius during this period the transformation occurs. After this the mixture is incubated at room temperature for allowing the bacterial cell to recover from the heat shock and express the transformed DNA. This method is suitable for circular plasmid DNA but not so effective for linear DNA, exonulceases of the bacterial cells may also degrade the linear DNA.

Dendrimers are also used for transformation, these are highly branched molecules which bind the DNA and then enter the cells, these are basically nanoparticles which are currently researched for their probable use in transformation.

Lipid carrier transformation is also used but are mostly specific to the eukaryotic cells, in this a lipid structure (liposome) is created such that it will carry the DNA to be transferred into the cells and by the help of endocytosis the cell takes up the liposome and along with it goes the foreign DNA too.

Another chemical method for transformation is with DEAE- dextran, it is a cationic polymer which links with the nucleic acids and the intake occurs presumably by endocytosis. It is a good method for studying expression for a brief period. Polymers such as polybrene, polyehtyleneimine are also used for transferring DNA into cells.