Studies on enantioselectivities of avidin, avidin-biotin complex and streptavidin by affinity capillary electrophoresis

Various enantiomer separations were performed by affinity capillary electrophoresis with a partial filling technique (PFACE) using egg white avidin (AVI) and two avidin analogues: succinylated avidin (Suc-AVI) and streptavidin (STAV). Basic AVI was useful for enantiomer separation of acidic racemates, while the chemical modified acidic Suc-AVI was useful for that of basic racemates. Such a chemical modification of protein was effective in extending the applicability of the chiral selector in PFACE. STAV, which was a neutral nonglycosylated protein, was useful for both acidic and basic enantiomer separations. Although AVI and AVI analogues show similar biotin-binding activities, enantioselectivity was different among the proteins in this study. Additionally, we investigated whether the enantioselectivity was due to interaction of enantiomers with biotin-binding sites or not. Not only enantioselevtivity but also interaction with enantiomers was entirely lost by the formation of AVI-biotin complex.