Chelex 100 is a
chelating
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 ...
material from
Bio-Rad
Bio-Rad Laboratories, Inc. is an American developer and manufacturer of specialized technological products for the life science research and clinical diagnostics markets. The company was founded in 1952 in Berkeley, California, by husband an ...
used to purify other compounds via
ion exchange
Ion exchange is a reversible interchange of one kind of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, ...
. It is noteworthy for its ability to bind
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that ca ...
ions.
It is a
styrene
Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...
-divinylbenzene
co-polymer
In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...
containing
iminodiacetic acid
Iminodiacetic acid is the organic compound with the formula HN(CH2CO2H)2, often abbreviated to IDA. A white solid, the compound is a dicarboxylic acid amine (the nitrogen atom forms a secondary amino group, not an imino group as the name suggests ...
groups.
A concentrated solution of metals is obtained by eluting the resin with a small volume of 2
M nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
, which protonates the iminodiacetate groups.
Chelex
resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...
is often used for
DNA extraction
The first isolation of deoxyribonucleic acid (DNA) was done in 1869 by Friedrich Miescher. Currently, it is a routine procedure in molecular biology or forensic analyses. For the chemical method, many different kits are used for extraction, and s ...
in preparation for
polymerase chain reaction
The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...
by binding to cations including Mg
2+, which is an essential cofactor for
DNase Deoxyribonuclease (DNase, for short) refers to a group of glycoprotein endonucleases which are enzymes that catalyze the hydrolytic cleavage of phosphodiester linkages in the DNA backbone, thus degrading DNA. The role of the DNase enzyme in cells ...
s. Chelex protects the sample from DNases that might remain active after the boiling and could subsequently degrade the DNA, rendering it unsuitable for PCR. After boiling, the Chelex-DNA preparation is stable and can be stored at 4°C for 3–4 months.
Polar resin beads bind polar cellular components after breaking open cells, while DNA and RNA remain in water solution above the Chelex resin.
However, the heating steps do denature the double helix, and the resulting
single-stranded DNA is less stable in storage.
References
* Daniel Harris. ''Quantitative Chemical Analysis'', seventh edition, 2007. . Page 594.
* {{cite journal , author1=R. N. Ceo , author2=M. R. Kazerouni , author3=K. Rengan , doi = 10.1007/BF02040660 , title = Sorption of silver ions by Chelex 100 chelating resin , year = 1993 , journal = Journal of Radioanalytical and Nuclear Chemistry, Articles , volume = 172 , issue = 1 , pages = 43–48 , s2cid=94639747
External links
Official site
Chelating agents