Controlled charged amino acids of Ti-binding peptide for surfactant-free selective adsorption

• The adsorption mechanism of titanium-binding peptide (TBP) on metal oxide substrates was investigated.
• A positively charged amino acid, lysine (K) or arginine (R), in TBP is the primary factor in adsorption on metal oxide substrates.
• The adsorption force of K is stronger than R, although R reportedly is the main contributor to adsorption.
• Selective adsorption of ferritins was achieved by alanine-substituted TBP in the absence of a surfactant used in conventional selective adsorption.

The adsorption mechanism of titanium-binding peptide (TBP) on metal oxide substrates was investigated by evaluating the adsorption behavior of ferritins with various alanine-substituted TBPs. Results revealed that (a) a positively charged amino acid, lysine (K) or arginine (R), in TBP can anchor ferritin to negative zeta-potential substrates, (b) the adsorption force of K is stronger than R, and (c) local electrostatic interactions and flexibility of TBP directly affect adsorption. Based on these findings, selective ferritin adsorption on SiO2 with TiOX patterned surfaces in a surfactant-free condition was demonstrated. Alanine-substituted TBP with one positively charged amino acid (K) and one negatively charged amino acid (D), achieved ferritin-selective adsorption without a surfactant. The importance of controlled electrostatic forces between TBP and a substrate for selective adsorption without a surfactant was clearly demonstrated.

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