Chelex 100 is a
chelating material from
Bio-Rad used to purify other compounds via
ion exchange
Ion exchange is a reversible interchange of one species of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid. Ion exchange is used in softening or demineralizing of water, purification of ch ...
. 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. The lanthanide and actinid ...
ions.
It is a
styrene
Styrene is an organic compound with the chemical formula C6H5CH=CH2. Its structure consists of a vinyl group as substituent on benzene. Styrene is a colorless, oily liquid, although aged samples can appear yellowish. The compound evaporates easi ...
-divinylbenzene
co-polymer containing
iminodiacetic acid groups.
A concentrated solution of metals is obtained by eluting the resin with a small volume of 2
M nitric acid
Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
, which protonates the iminodiacetate groups.
Chelex
resin
A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...
is often used for
DNA extraction in preparation for
polymerase chain reaction
The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...
by binding to cations including Mg
2+, which is an essential cofactor for
DNases. 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 , volume = 172 , issue = 1 , pages = 43–48 , s2cid=94639747
External links
Official site
Chelating agents