Editing Affinity chromatography (section)

===Immobilized metal ion affinity chromatography===
Immobilized metal ion affinity chromatography (IMAC) is based on the specific coordinate covalent bond of amino acids, particularly histidine, to metals. This technique works by allowing proteins with an affinity for metal ions to be retained in a column containing immobilized metal ions, such as cobalt, nickel, or copper for the purification of histidine-containing proteins or peptides, iron, zinc or gallium for the purification of phosphorylated proteins or peptides. Many naturally occurring proteins do not have an affinity for metal ions, therefore [[recombinant DNA technology]] can be used to introduce such a protein tag into the relevant gene. Methods used to [[Elution|elute]] the protein of interest include changing the pH, or adding a competitive molecule, such as [[imidazole]].<ref>{{cite book |last1=Singh|first1=Naveen K. |last2=DSouza|first2=Roy N. |last3=Bibi|first3=Noor S. |last4= Fernández-Lahore|first4=Marcelo |chapter=Direct Capture of His6-Tagged Proteins Using Megaporous Cryogels Developed for Metal-Ion Affinity Chromatography |year=2015 |editor1-last=Reichelt|editor1-first=S. |title=Affinity Chromatography |journal=<!-- Citation bot bypass--> |chapter-url=https://www.springer.com/us/book/9781493924462 |series=Methods in Molecular Biology |language=en |volume=1286 |location=New York |publisher=Humana Press |pages=201–212 |doi=10.1007/978-1-4939-2447-9_16 |pmid=25749956 |isbn=978-1-4939-2447-9}}</ref><ref>{{cite journal |last1= Gaberc-Porekar |first1= Vladka K.|last2= Menart |first2= Viktor|date=2001|title= Perspectives of immobilized-metal affinity chromatography|journal=J Biochem Biophys Methods |volume=49 |issue= 1–3 |pages= 335–360|doi= 10.1016/S0165-022X(01)00207-X|pmid= 11694288}}</ref>
[[File:Nickel resin.jpg|thumb|150px|A chromatography column containing nickel-agarose beads used for purification of proteins with histidine tags]]
{{See also|Polyhistidine-tag}}