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

Various enantiomer separations were performed by affinity capillary electro phoresis with a partial filling technique (PFACE) using egg white avidin (A VI) and two avidin analogues: succinylated avidin (Suc-AVI) and streptavidi n (STAV). Basic AVI was useful for enantiomer separation of acidic racemate s, while the chemical modified acidic Suc-AVI was useful for that of basic racemates. Such a chemical modification of protein was effective in extendi ng the applicability of the chiral selector in PFACE. STAV, which was a neu tral nonglycosylated protein, was useful for both acidic and basic enantiom er separations. Although AVI and AVI analogues show similar biotin-binding activities, enantioselectivity was different among the proteins in this stu dy. Additionally, we investigated whether the enantioselectivity was due to interaction of enantiomers with biotin-binding sites or not. Not only enan tioselevtivity but also interaction with enantiomers was entirely lost by t he formation of AVI-biotin complex.