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Chemical structure of tris
Preferred IUPAC name
Other names
TRIS, Tris, Tris base, Tris buffer, Trizma, Trisamine, THAM, Tromethamine, Trometamol, Tromethane, Trisaminol
3D model (JSmol)
ECHA InfoCard 100.000.969
RTECS number TY2900000
Molar mass 121.14 g·mol−1
Appearance White crystalline powder
Density 1.328g/cm3
Melting point >175-176 °C (448-449 K)
Boiling point 219 °C (426 °F; 492 K)
~50 g/100 mL (25 °C)
Acidity (pKa) 8.07
B05BB03 (WHO) B05XX02 (WHO)
Main hazards Irritant
Safety data sheet External MSDS
R-phrases (outdated) R36 R37 R38
S-phrases (outdated) S26 S36
NFPA 704
Flammability (red): no hazard code Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity (yellow): no hazard code Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Tris, or tris(hydroxymethyl)aminomethane, or THAM, is an organic compound with the formula (HOCH2)3CNH2. It is extensively used in biochemistry and molecular biology.[1] 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 contains a primary amine and thus undergoes the reactions associated with typical amines, e.g. condensations with aldehydes.

Buffering features[edit]

Tris has a pKa of 8.07 at 25 °C, which implies that the buffer has an effective pH range between 7.5 and 9.0.

Buffer details[edit]

  • The pKa declines approximately 0.03 units per degree Celsius rise in temperature.[2][3]
  • Silver-containing single-junction pH electrodes (e.g., silver chloride electrode) are incompatible with Tris (Ag-tris precipitation clogs the junction). Double-junction electrodes are resistant to this problem, and non-silver containing electrodes are immune.
  • Making buffer solutions by neutralizing TrisHCl requires attention to the attendant changes in ionic strength.

Buffer inhibition[edit]

  • Tris inhibits a number of enzymes,[4][5] and therefore it should be used with care when studying proteins.


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.[6]


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.

Tris is used to increase membrane permeability of cell membranes.[7]


Tris (usually known as THAM in this context) is used as alternative to sodium bicarbonate in the treatment of metabolic acidosis.[8][9]

See also[edit]


  1. ^ Gomori, G., Preparation of Buffers for Use in Enzyme Studies. Methods Enzymology., 1, 138-146 (1955).
  2. ^ El-Harakany, A.A.; Abdel Halima; F.M.; Barakat, A.O. (1984). "Dissociation constants and related thermodynamic quantities of the protonated acid form of tris-(hydroxymethyl)-aminomethane in mixtures of 2-methoxyethanol and water at different temperatures". J. Electroanal. Chem. 162 (1–2): 285–305. doi:10.1016/S0022-0728(84)80171-0. 
  3. ^ Vega, C.A.; Butler, R.A.; et al. (1985). "Thermodynamics of the Dissociation of Protonated Tris(hydroxymethy1)aminomethane in 25 and 50 wt % 2-Propanol from 5 to 45 °C". J. Chem. Eng. Data. 30 (4): 376–379. doi:10.1021/je00042a003. 
  4. ^ Desmarais, WT; et al. (2002). "The 1.20 Å resolution crystal structure of the aminopeptidase from Aeromonas proteolytica complexed with Tris: A tale of buffer inhibition". Structure. 10 (8): 1063–1072. PMID 12176384. doi:10.1016/S0969-2126(02)00810-9. 
  5. ^ Ghalanbor, Z; et al. (2008). "Binding of Tris to Bacillus licheniformis alpha-amylase can affect its starch hydrolysis activity". Protein Peptide Lett. 15 (2): 212–214. PMID 18289113. doi:10.2174/092986608783489616. 
  6. ^ Markofsky, Sheldon, B. (15 October 2011). "Nitro Compounds, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. 24: 296. doi:10.1002/14356007.a17_401.pub2. 
  7. ^ Irvin, R.T.; MacAlister, T.J.; Costerton, J.W. (1981). "Tris(hydroxymethyl)aminomethane Buffer Modification of Escherichia coli Outer Membrane Permeability". J. Bacteriol. 145 (3): 1397–1403. 
  8. ^ 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. PMID 10764304. doi:10.1164/ajrccm.161.4.9906031. 
  9. ^ 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. PMID 16013019.