OVERVIEW

Tris-Borate-EDTA electrophoresis buffer is a common electrophoresis buffer for nondenaturing agarose gel electrophoresis. A 10x TBE buffer can be prepared by dissolving 108 g Tris base, 55 g Boric acid, and 5.84 g anhydrous EDTA in water to a final volume of 1000 ml. The solution is sterilized by autoclaving and is stored at room temperature.

REQUIREMENTS

Reagents and solutions
Tris base (C₄H₁₁NO₃, Molecular Weight: 121.14)
Boric acid (H₃BO₃, Molecular Weight: 61.83)
Anhydrous EDTA (Free Acid) (CAS Number: 60-00-4, Molecular Weight: 292.24)
Deionized / Milli-Q water

Equipment and disposables
Measuring cylinder
Conical flask / Beaker
Magnetic stirrer

COMPOSITION

Composition of 10X TBE electrophoresis buffer
0.89 M Tris borate
0.02 M EDTA
pH 8.2 – 8.4 (at 25°C)

Composition of 1X TBE electrophoresis buffer
89 mM Tris borate
2 mM EDTA
pH 8.2 – 8.4 (at 25°C)

OBJECTIVE

Preparation of 1000 ml of 10X TBE electrophoresis buffer, pH 8.3.

PROCEDURE

Step 1: To prepare 1000 ml of 10x TBE buffer, weigh out 108 g Tris base, 55 g boric acid, and 5.84 g anhydrous EDTA. Transfer them to a 2 L beaker / conical flask. Add 800 ml deionized / Milli-Q water. Dissolve all ingredients by  mixing vigorously using a magnetic stirrer.

Note
1. You can also use a 0.5M EDTA solution to prepare a 10x TBE electrophoresis buffer. Using 0.5M EDTA solution is convenient as it helps you to save time. But the electrophoresis buffer prepared this way generates more heat than the buffer prepared by anhydrous EDTA (Sanderson et al., 2014).
2. You can also use Disodium EDTA Dihydrate (EDTA.Na2.2H2O) which is more convenient to dissolve. You need to add 7.4448 g of EDTA.Na2.2H2O.

Tip
One can use manual shaking using a glass pipette to mix the ingredients. The magnetic stirrer makes the dissolving process automated and convenient.

Step 2: Add 20 ml of 0.5 M EDTA solution. Mix the solution again. Adjust the pH 8.3 if required.

Precaution
Since pH is dependent on temperature, we recommend adjusting the solution pH at room temperature (25°C).

Step 3: Adjust the solution volume to 1000 ml with deionized / Milli-Q water. Mix the solution again.

Step 4 (optional): One can filter the solution to remove any undissolved materials.

Step 5: Sterilize the solution by autoclaving (20 minutes at 15 lb/sq.in. (psi), 121-124°C on liquid cycle).

Tips:
1. Transfer the solution to autoclavable bottles. There should be sufficient empty space ≈ 15 – 20%) in the autoclave bottle after filling the solution. Don’t forget to loosen the cap slightly.
2. Depending on the consumption, one can make small aliquots of the solution.

STORAGE
Solution can be stored at 15 – 25 °C (room temperature) for several months.

Precaution:
Discard solution if there is a considerable amount of precipitates.

APPLICATIONS

• Agarose gel electrophoresis of DNA
• Non-denaturing agarose gel electrophoresis of RNA (MOPS buffer is used for denaturing gels)
• Polyacrylamide gel electrophoresis of nucleic acid (both non-denaturing or denaturing)
• DNA automated sequencing gel
• Electrophoretic Mobility Shift Assay (EMSA)

REFERENCES

• Cold Spring Harbor Protocols: Recipe TBE buffer; Full-Text Link: cshlp-pdb.rec12231. URL: http://cshprotocols.cshlp.org/content/2010/6/pdb.rec12231.full
• Sanderson et al., 2014. Modification of gel architecture and TBE/TAE buffer composition to minimize heating during agarose gel electrophoresis. Anal Biochem. 454, 44-52. PMID-24637158; Full-Text Links: Sciencedirect, PMC4021863  (download PDF)