Tris acetate EDTA (TAE) and tris borate EDTA (TBE) are the two most common running buffers used in nucleic acid electrophoresis. As buffers, they have a fairly constant pH and are able to conduct electricity because of their concentration of hydrogen ions. These properties are necessary for gel electrophoresis during which proteins are separated by electric charge
TBE and TAE are most often mixed from their constituent parts into laboratory stock solutions. Both buffers can be purchased at the working concentration or in a powdered or concentrated format that is simply prepared via dilution.
TAE vs. TBE Comparison Chart
| TAE Buffer | TBE Buffer | Notes | |
|---|---|---|---|
| Buffering Capacity | High | Low | TAE becomes exhausted during extended or repeated electrophoresis. |
| Migration of DNA | Slow | Fast | TAE has better conductivity. |
| Resolution | High resolution of >2KB DNA fragments | High resolution of <2KB DNA fragments | TBE supports agarose cross-linkage. |
| Enzyme Inhibitor | Yes | No | Borate from TBE inhibits many enzymes. |
| Cost | Higher | Lower |
Applications
Tris-acetate-EDTA (TAE) running buffer and tris-borate-EDTA (TBE) are commonly used buffers for DNA agarose gel electrophoresis that are especially useful in preparative work.
Compared to tris-borate-EDTA (TBE) and tris-phosphate-EDTA (TPE) buffers, double-stranded DNA tends to run faster in TAE. However, because TAE has the lowest buffering capacity of the three buffers, the buffering capacity can become exhausted during extended electrophoresis. Buffer circulation or replacement can remedy this situation.
TAE
The 1x TAE buffer is used both in the agarose gel and as a running buffer. Applied voltages of < 5 V/cm (the distance between the electrodes of the unit) are recommended for maximum resolution.
TAE buffer has been utilized in agarose gel electrophoresis of RNA.
A study of free DNA solution mobility in TAE at various buffer concentrations, in the presence and absence of added NaCl, has been reported.
The use of TAE buffer in a denaturing gradient gel electrophoresis method for broad-range mutation analysis has been described.
TBE
TBE buffer is recommended for resolution of RNA and DNA fragments smaller than 1500 bp.
TBE is used with both non-denaturing or denaturing (7 M urea) gels.
It is also routinely used for DNA automated sequencing gel.
Tris-borate-EDTA buffer has been used for pulsed-field gel electrophoresis (PFGE). Applied voltages of less than 5 V/cm are recommended for maximum resolution.