Final answer:
In IMAC, when targeting phosphorylated proteins, you would attach metal ions with a high affinity for phosphate groups, such as Fe3+ or Ga3+, to the resin. Recently, metal oxides like ZrO2 or Al(OH)3 have also been used for phosphoprotein enrichment in MOAC.
Step-by-step explanation:
In Immobilized Metal Affinity Chromatography (IMAC), when targeting phosphorylated proteins, the resin is typically attached to metal ions that have a high affinity for phosphate groups. For this purpose, chelated metal ions such as Fe3+ or Ga3+ are often used as they can effectively bind to the phosphate groups present on serine, threonine, or tyrosine residues of the phosphorylated proteins. However, recently, the use of metal oxides such as zirconium dioxide (ZrO2) or aluminum hydroxide (Al(OH)3) have become popular in Metal Oxide Affinity Chromatography (MOAC) for phosphoprotein enrichment as well. These metals have specific affinity to the phosphate groups of phosphoproteins and allow for their selective enrichment from complex biological mixtures.