Isoelectric exchange

Heterogeneity. Natural aequorin is not a homogeneous protein it is a mixture of many isoforms having isoelectric points ranging from 4.2 to 4.9 (Blinks and Harrer, 1975). The isoform composition may vary to some extent by the purification method employed, due to uneven loss of isoforms during purification. Consequently, the properties of each preparation of aequorin may also vary. By anion-exchange... 

So, the sorption of PO on polysaccharides was not a classic ion-exchange interaction because the proteins were different in both isoelectric points and the molecular weights exhibited affinity for them. This conclusion was confirmed by the fact that the desorption of PO was facilitated by increasing NaCl concentrations as well as that isoPOs with a different pf can... 

Acetyl esterase (AE) has been purified to homogeneity from orange peels. The purification steps included cation exchange chromatography and gel filtration. The enzyme has affinity for triacetin and sugar beet pectin with K, of 39 mM and of 26 mg/ml, respectively. AE has a MW of 42 kD and is a monomer. The isoelectric point is at pH > 9. 

Santora, L.C., Krull, I.S., and Grant, K., Characterization of recombinant human monoclonal tissue necrosis factor-a antibody using cation-exchange HPLC and capillary isoelectric focusing, Anal. Biochem., 275, 98, 1999. 

Essader, A.S., Cargile, B.J., Bundy, J.L., Stephenson, J.L., Jr. (2005). A comparison of immobilized pH gradient isoelectric focusing and strong-cation-exchange chromatography as a first dimension in shotgun proteomics. Proteomics 5, 24—34. 

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