Tris, or tris(hydroxymethyl)aminomethane, or known during medical use as tromethamine or THAM, is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

with the formula (HOCH₂)₃CNH₂, one of the twenty

Good's buffers Good's buffers (also Good buffers) are twenty buffering agents for biochemical and biological research selected and described by Norman Good and colleagues during 1966–1980. Most of the buffers were new zwitterionic compounds prepared and tested ...

. It is extensively used in

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology ...

and

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and phys ...

as a component of

buffer solution A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is ...

s such as in TAE and

TBE buffer TBE or Tris/Borate/EDTA, is a buffer solution containing a mixture of Tris base, boric acid and EDTA. In molecular biology, TBE and TAE buffers are often used in procedures involving nucleic acids, the most common being electrophoresis. Tris-acid ...

s, especially for solutions of

nucleic acid Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main ...

s. It contains a

primary amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such ...

and thus undergoes the reactions associated with typical amines, e.g. condensations with

aldehydes In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

. Tris also complexes with metal ions in solution. 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 Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidne ...

in specific circumstances. Some medications are formulated as the "tromethamine salt" including Hemabate (

carboprost Carboprost (INN, trade names for the tromethamine salts Hemabate, Tham) is a synthetic prostaglandin analogue of PGF2α (specifically, it is 15-methyl-PGF2α) with oxytocic properties. Carboprost's main use is in the obstetrical emergency of p ...

as trometamol salt), and "

ketorolac Ketorolac, sold under the brand names Toradol, and Biorolac among others, is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain. Specifically it is recommended for moderate to severe pain. Recommended duration of treatment is less ...

trometamol".

Buffering features

The

conjugate acid A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

of tris has a p''K''_a of 8.07 at 25 °C, which implies that the buffer has an effective pH range between 7.1 and 9.1 (p''K''_a ± 1) at room temperature.

Buffer details

*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. *In general, a 10-fold increase in tris buffer concentration will lead to a 0.05 unit increase in pH and vice versa. *

Silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...

-containing single-junction pH electrodes (e.g.,

silver chloride electrode A silver chloride electrode is a type of reference electrode, commonly used in electrochemical measurements. For environmental reasons it has widely replaced the saturated calomel electrode. For example, it is usually the internal reference elec ...

s) 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.

Buffer inhibition

*Tris inhibits a number of enzymes, and therefore should be used with care when studying proteins. *Tris can also inhibit enzyme activity via

chelation Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These ligands are ...

of metal ions.

Preparation

Tris is prepared industrially by the exhaustive condensation of

nitromethane Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as i ...

with

formaldehyde Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...

under basic conditions (i.e. repeated Henry reactions) to produce the intermediate (HOCH₂)₃CNO₂, which is subsequently

hydrogenated Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organi ...

to give the final product.

Uses

The useful buffer range for tris (pH 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 A primary standard in metrology is a standard that is sufficiently accurate such that it is not calibrated by or subordinate to other standards. Primary standards are defined via other quantities like length, mass and time. Primary standards are ...

to standardize acid solutions for chemical analysis. Tris is used to increase permeability of cell membranes. It is a component of the

Moderna COVID-19 vaccine The Moderna COVID19 vaccine (INN: elasomeran), sold under the brand name Spikevax, is a COVID-19 vaccine developed by American company Moderna, the United States National Institute of Allergy and Infectious Diseases (NIAID), and the Biomedi ...

and the Pfizer-BioNTech COVID-19 vaccine for use in children 5 through 11 years of age.

Medical

Tris (usually known as THAM in this context) is used as alternative to sodium bicarbonate in the treatment of

References

{{reflist, 2 Polyols Amines Buffer solutions