Tris

Chembox new
Name = Tris
ImageFile = Tris.png ImageSize = 160px
ImageName = Chemical structure of tris
IUPACName = 2-Amino-2-hydroxymethyl-propane-1,3-diol
OtherNames = TRIS, Tris, Tris base, Tris buffer,
Trizma^TM, Trisamine, THAM,
Tromethamine, Trometamol, Tromethane
Section1 = Chembox Identifiers
SMILES = C(C(CO)(CO)N)O
CASNo = 77-86-1
RTECS = TY2900000
Section2 = Chembox Properties
C = 4
H = 11
N = 1
O = 3
Appearance = White crystalline powder
Density =
Solubility = ~50 g/100 ml (25°C) in water
MeltingPt = >175-176°C (448-449 K)
BoilingPt = 219°C (492 K)
pKa = 8.1
Section7 = Chembox Hazards
ExternalMSDS = [http://www.jtbaker.com/msds/englishhtml/T7111.htm External MSDS]
MainHazards = Irritant
NFPA-H = 2
NFPA-F =
NFPA-R =
FlashPt = Non-flammable
RPhrases = R36, R37, R38.
SPhrases = S26, S36.

Tris is an abbreviation of the organic compound known as tris(hydroxymethyl)aminomethane, with the formula (HOCH₂)₃CNH₂. Tris is extensively used in biochemistry and molecular biology. [Gomori, G., Preparation of Buffers for Use in Enzyme Studies. Methods Enzymology., 1, 138-146 (1955).] 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 is a primary amine and thus undergoes the reactions associated with typical amines, e.g. condensations with aldehydes.

Buffering features

Tris has a pKa of 8.06, which implies that the buffer has an effective pH range between 7.0 and 9.2.

Buffer details

* The pK_a declines approximately 0.03 units per degree Celsius rise in temperature.
* 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.
* It is toxic to mammalian cells.
* A common variant of tris (aka tris base) is tris-HCl, the acid salt. When titrated to a specific pH with the corresponding counter ion (OH- for tris-HCl, H+ for tris base) they are equivalent. However, the molecular weights are different and must be correctly accounted for in order to arrive at the expected buffer strength.

Preparation

Tris is prepared in two steps from nitromethane via the intermediate (HOCH₂)₃CNO₂ . Reduction of the latter gives tris(hydroxymethyl)aminomethane. [Sheldon B. Markofsky “Nitro Compounds, Aliphatic” Ullmann's Encyclopedia of Industrial Chemistry 2002 by Wiley-VCH, Wienheim, 2002. DOI: 10.1002/14356007.a17_401.]

Uses

The useful buffer range for Tris (7-9) coincides with the typical physiological pH of most living things. This, and its low cost, make Tris one of the most common buffer elements in use in the biology/biochemistry lab.

References