Tris

Tris is an abbreviation of the organic compound known as trishydroxymethylaminomethane, with the formula (HOCH₂)₃CNH₂. In biochemistry, tris is widely used as a component of buffer solutions, such as in TAE and TBE buffer, especially for solutions of nucleic acids. It is a primary amine and thus undergoes the reactions associated with typical amines, e.g. condenstations with aldehydes.

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Buffering features

Tris has a pKa of 8.3 (at 20 °C), which implies that the buffer is effective pH range between 7.0 and 9.2. Being slightly basic, tris forms an effective buffer for slightly basic solutions, which keeps DNA deprotonated and soluble in water. Tris is commonly combined with EDTA to make "TE buffer" for stabilization and storage of DNA. EDTA binds to divalent cations, particularly magnesium (Mg²⁺). which is a co-factor for many DNA-modifying enzymes.

Buffer details

Because of its widespread use of tris buffers, detailed information on its use is available. Some features:

• The pK_a declines approximately 0.03 units per degree Celsius rise in temperature.
• Tris reacts strongly with pH electrodes.^{[citation needed]}
• It is toxic to mammalian cells.

Preparation

Tris is prepared in two steps from nitromethane via the intermediate (HOCH₂)₃CNO₂ . Reduction of the latter gives tris(hydroxymethyl)aminomethane.^[1]

Other uses

Tris is used as an intermediate for the preparation of surface active agents, vulcanization accelerators, and pharmaceuticals, and used as a titrimetric standard.

References

1. ^ Sheldon B. Markofsky “Nitro Compounds, Aliphatic” Ullmann's Encyclopedia of Industrial Chemistry 2002 by Wiley-VCH, Wienheim, 2002. DOI: 10.1002/14356007.a17_401.