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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
ATC code B05BB03
77-86-1 YesY
ChEMBL ChEMBL1200391 N
ChemSpider 6257 YesY
Jmol-3D images 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
SDS External MSDS
Main hazards Irritant
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 noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N verify (what isYesY/N?)
Infobox references

Tris (tris(hydroxymethyl)aminomethane, 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. 
  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.