The adsorption mechanism of titanium-binding ferritin to amphoteric oxide

We investigated the origin of selective adsorption of titanium-binding ferritin (TBF), the outer surface of which is genetically modified with titanium-binding peptides (TBPs). By varying pH conditions (7-9), TBF adsorption behavior onto amphoteric and acidic oxide substrates was observed using atomic force microscopy, and the zeta potential of substrates was measured. This suggests that a TBP interacted with local charges such as -O-, -OH+, and -OH2+ on substrates regardless of the constituent elements of the substrate, which makes it possible for TBF to adsorb on TiOX, ZrO2, Fe2O3, and SiO2 substrates despite the presence of an overall electrostatic repulsive force between TBF and the substrates. This also suggests that a surfactant, TWEEN20, can completely hamper attractive interaction between TBF and acidic oxide, but amphoteric oxide can withstand TWEEN20 interference. (c) 2012 Elsevier B.V. All rights reserved.