TAE buffer

TAE buffer is a buffer solution used in agarose electrophoresis, typically for the separation of nucleic acids such as DNA and RNA. [Ogden, R.C., and Adams, D.A., Electrophoresis in agarose and acrylamide gels. Methods Enzymol., 152, 61-87 (1987).] It is made up of Tris-acetate buffer, usually at pH 8.0, and EDTA, which sequesters divalent cations. TAE has a lower buffer capacity than TBE and easily can become exhausted, but linear, double stranded DNA runs faster in TAE.

Uses

TAE buffer is used as both a running buffer and in agarose gel. [Sambrook, Fritsch, and Maniatis (1989) "Molecular Cloning: A Laboratory Manual", 2nd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, volume 3, apendices B.11 and B.23] Its use in denaturing gradient gel electrophoresis methods for broad-range mutation analysis has also been described. [Hayes, V.M. et al., Improvements in gel composition and electrophoretic conditions for broad-range mutation analysis by denaturing gradient gel electrophoresis. Nucleic Acids Res., 27(20), e29 (1999).] TAE has been used at various concentrations to study the mobility of DNA in solution with and without sodium chloride. [Stellwagen, E., and Stellwagen, N.C., The free solution mobility of DNA in Tris-acetate-EDTA buffers of different concentrations, with and without added NaCl. Electrophoresis, 23(12), 1935-1941 (2002).] However, high concentration of sodium chloride (and many other salts) in a DNA sample retards its mobility. This may lead to incorrect interpretations of the resulting DNA banding pattern.

Compared with TBE buffer, TAE buffer offers advantages in subsequent enzymatic applications for the DNA sample. For example, if a DNA sample is going to be used in a cloning experiment, the step that follows its running on a agarose gel is to ligate (covalently link) to a cloning vector (most likely a plasmid). DNA sample from TAE buffer is suitable for this purpose, while DNA from TBE buffer is not. Borate in the TBE buffer is a strong inhibitor for many enzymes. This enzyme inhibiting property made TBE buffer very popular in its realm for two reasons. First, a DNA sample run in a TBE buffer can better keep its integrity. The other main reason is that the purpose for many agarose gel electrophoreses is to analyze the size of DNA molecules. In particular, the kinds of DNA analyses shown on TV and other public media are more likely run in TBE buffer.

Preparation

For 1 litre of 50x TAE buffer use:
*242 g Tris base (2-amino-2-hydroxymethyl-propane-1,3-diol) (= 2 mole)
*57.1 ml glacial acetic acid (= 100% acetic acid) (57.19 ml = 1 mole)
*100 ml 0.5 M Na₂ EDTA (pH 8.0)
*H₂O up to 1000 ml

To prepare 0.5 M Na₂ EDTA (pH 8.0)add 186.1 g of disodium ethylenediaminetetraacetate x 2H₂O to 800 ml of H₂O. Stir vigorously. Adjust the pH to 8.0 with NaOH (ca. 20 g of NaOH). Sterilize by autoclaving. Hint: The disodium salt of EDTA will not go into solution until the pH of the solution is adjusted to ca. 8.0 by the addition of NaOH.

References

ee also

* TBE buffer