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This article is about the chemical widely used as a biochemical buffer. For other uses, see Tris (disambiguation).
Chemical structure of tris
IUPAC name
Other names
TRIS, Tris, Tris base, Tris buffer, Trizma, Trisamine, THAM, Tromethamine, Trometamol, Tromethane, Trisaminol
77-86-1 YesY
ChEMBL ChEMBL1200391 N
ChemSpider 6257 YesY
Jmol interactive 3D Image
KEGG D00396 YesY
PubChem 6503
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
ATC code B05BB03
Main hazards Irritant
Safety data sheet External MSDS
R-phrases R36 R37 R38
S-phrases 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. Tris 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 in two steps from nitromethane via the intermediate (HOCH2)3CNO2. Reduction of the latter gives tris(hydroxymethyl)aminomethane.[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. and 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.  Cite uses deprecated parameter |coauthors= (help)
  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. doi:10.1016/S0969-2126(02)00810-9. PMID 12176384. 
  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. doi:10.2174/092986608783489616. PMID 18289113. 
  6. ^ Markofsky, Sheldon B. (2000). "Nitro Compounds, Aliphatic". doi:10.1002/14356007.a17_401. 
  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. doi:10.1164/ajrccm.161.4.9906031. PMID 10764304. 
  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.