Structural effects on the conformational transition of transferrin induced by binding of flavonoids with different numbers and positions of hydroxyl groups

The effects of conformational changes to transferrin induced by the binding of flavonoids with different numbers and positions of hydroxyl groups were explored using spectroscopic and molecular modeling methods. The flavonoid hydroxyl group is not necessary for conformation changes of transferrin. However, the binding ability was found to increase with increasing numbers of hydroxyl groups and further conformational changes were observed. By molecular modeling calculations, intermolecular energy including van der Waals and electrostatic interactions, together with hydrogen bonding are found to have important roles in binding of flavonoids to transferrin. Additionally, the positions of the hydroxyl groups also affect the binding ability because they can alter the relative acidity of the hydroxyl groups, thereby changing the hydrogen bonding ability. Our results have indicated a mechanism for the interactions between flavonoids and transferrin, and provide information for possible flavonoid modification and design of methods to deliver drug molecules via transferrin to target tissues and cells effectively. (C) 2007 Elsevier B.V. All rights reserved.