Tris, or tris(hydroxymethyl)aminomethane, or known during medical use as tromethamine or THAM, is an organic compound with the formula (HOCH₂)₃CNH₂, one of the twenty Good's buffers. It is extensively used in biochemistry and molecular biology as a component of buffer solutions such as in TAE and TBE buffers, especially for solutions of

nucleic acid Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cl ...

s. It contains a primary amine and thus undergoes the reactions associated with typical amines, e.g. condensations with aldehydes. Tris also complexes with metal ions in solution. In medicine, tromethamine is occasionally used as a drug, given in intensive care for its properties as a buffer for the treatment of severe

metabolic acidosis Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidneys ...

in specific circumstances. Some medications are formulated as the "tromethamine salt" including Hemabate ( carboprost as trometamol salt), and "

ketorolac Ketorolac, sold under the brand names Toradol, and Biorolac among others, is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain. Specifically it is recommended for moderate to severe pain. Recommended duration of treatment is less ...

trometamol".

Buffering features

The conjugate acid of tris has a p''K''_a of 8.07 at 25 °C, which implies that the buffer has an effective pH range between 7.1 and 9.1 (p''K''_a ± 1) at room temperature.

Buffer details

*In general, as temperature decreases from 25 °C to 5 °C the pH of a tris buffer will increase an average of 0.03 units per degree. As temperature rises from 25 °C to 37 °C, the pH of a tris buffer will decrease an average of 0.025 units per degree. *In general, a 10-fold increase in tris buffer concentration will lead to a 0.05 unit increase in pH and vice versa. * Silver-containing single-junction pH electrodes (e.g., silver chloride electrodes) are incompatible with tris since an Ag-tris precipitate forms which clogs the junction. Double-junction electrodes are resistant to this problem, and non-silver containing electrodes are immune.

Buffer inhibition

*Tris inhibits a number of enzymes, and therefore should be used with care when studying proteins. *Tris can also inhibit enzyme activity via chelation of metal ions.

Preparation

Tris is prepared industrially by the exhaustive condensation of nitromethane with formaldehyde under basic conditions (i.e. repeated Henry reactions) to produce the intermediate (HOCH₂)₃CNO₂, which is subsequently hydrogenated to give the final product.

Uses

The useful buffer range for tris (pH 7–9) coincides with the physiological pH typical of most living organisms. This, and its low cost, make tris one of the most common buffers in the biology/biochemistry laboratory. Tris is also used as a primary standard to standardize acid solutions for chemical analysis. Tris is used to increase permeability of cell membranes. It is a component of the Moderna COVID-19 vaccine and the Pfizer-BioNTech COVID-19 vaccine for use in children 5 through 11 years of age.

Medical

Tris (usually known as THAM in this context) is used as alternative to

sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...

in the treatment of

References

{{reflist, 2 Polyols Amines Buffer solutions