IN-VITRO OBSERVATION OF INTERACTIONS OF IRON AND TRANSFERRIN BY CAPILLARY ISOELECTRIC-FOCUSING WITH A CONCENTRATION GRADIENT IMAGING DETECTION SYSTEM

A capillary isoelectric focusing-concentration gradient imaging detector system was used for in vitro observation of dynamics of interaction between iron and bovine transferrin. Transferrin was first focused inside the capillary by isoelectric focusing. A plug of ferric ion was then introduced into the capillary. The iron-free and the iron-complexed transferrins have different isoelectric points, hence they were focused at different positions inside the capillary. Concentration changes of different isoforms of iron-free and iron-complexed transferrins were monitored in an on-line fashion during the interaction by the imaging detector. One advantage of using this detector for studying the protein interaction is that the 633 nm wavelength probe beam used in the detector does not pump energy into the reaction system, which will interfere with the reaction. The results show that iron-binding and dissociation rates of different isoforms are different. This is the first report that the reaction speed of different isoforms of a protein can be observed in an on-line fashion.