Tris, or tris(hydroxymethyl)aminomethane, or known during medical use as tromethamine or THAM, is an organic compound with the formula (HOCH2)3CNH2. It is extensively used in biochemistry and molecular biology as a component of buffer solutions[1] such as in TAE and TBE buffers, especially for solutions of nucleic acids. 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.[2] 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 in specific circumstances.[3][4] Some medications are formulated as the "tromethamine salt" including hemabate (carboprost as trometamol salt), and "ketorolac trometamol".[5]
The useful buffer range for tris (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.
The conjugate acid of tris has a pKa of 8.07 at 25 °C, which implies that the buffer has an effective pH range between 7.1 and 9.1 (pKa ± 1) at room temperature.
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.[10]
In general, a 10-fold increase in tris buffer concentration will lead to a 0.05 unit increase in pH and vice versa.[10]
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.
Tris is prepared industrially by the exhaustive condensation of nitromethane with formaldehyde under basic conditions (i.e. repeated nitroaldol reactions) to produce the intermediate (HOCH2)3CNO2, which is subsequently hydrogenated to give the final product.[13]
↑Hoste, Eric A.; Colpaert, Kirsten; Vanholder, Raymond C.; Lameire, Norbert H.; De Waele, Jan J.; Blot, Stijn I.; Colardyn, Francis A. (May 2005). "Sodium bicarbonate versus THAM in ICU patients with mild metabolic acidosis". Journal of Nephrology. 18 (3): 303–307. ISSN1121-8428. PMID16013019.
↑BNF 73 March-September 2017. British Medical Association,, Royal Pharmaceutical Society of Great Britain. London. 21 March 2017. ISBN978-0857112767. OCLC988086079.{{cite book}}: CS1 maint: others (link)
↑"Archive copy"(PDF). Archived(PDF) from the original on 2021-07-05. Retrieved 2021-07-06.{{cite web}}: CS1 maint: archived copy as title (link)
↑Kallet, RH; Jasmer RM; Luce JM; et al. (2000). "The treatment of acidosis in acute lung injury with tris-hydroxymethyl aminomethane (THAM)". American Journal of Respiratory and Critical Care Medicine. 161 (4): 1149–1153. doi:10.1164/ajrccm.161.4.9906031. PMID10764304.
↑Hoste, EA; Colpaert, K; Vanholder, RC; Lameire, NH; De Waele, JJ; Blot, SI; Colardyn, FA (2005). "Sodium bicarbonate versus THAM in ICU patients with mild metabolic acidosis". Journal of Nephrology. 18 (3): 303–7. PMID16013019.
↑Ghalanbor, Z; et al. (2008). "Binding of Tris to Bacillus licheniformis alpha-amylase can affect its starch hydrolysis activity". Protein Pept. Lett. 15 (2): 212–214. doi:10.2174/092986608783489616. PMID18289113.