The adsorption mechanism of titanium-binding ferritin to amphoteric oxide

Diffusion and reaction pathways of water near fully hydrated TiO2 surfaces from ab initio molecular dynamics

Ab initio molecular dynamics simulations are reported for water-embedded TiO₂ surfaces to determine the diffusive and reactive behavior at full hydration. A three-domain model is developed for six surfaces [rutile (110), (100), and (001), and anatase (101), (100), and (001)] which describes waters as "hard" (irreversibly bound to the surface), "soft" (with reduced mobility but orientation freedom near the surface), or "bulk." The model explains previous experimental data and provides a detailed picture of water diffusion near TiO₂ surfaces. Water reactivity is analyzed with a graph-theoretic approach that reveals a number of reaction pathways on TiO₂ which occur at full hydration, in addition to direct water splitting. Hydronium (H₃O⁺) is identified to be a key intermediate state, which facilitates water dissociation by proton hopping between intact and dissociated waters near the surfaces. These discoveries significantly improve the understanding of nanoscale water dynamics and reactivity at TiO₂ interfaces under ambient conditions.

Screening and structural and functional investigation of a novel ferritin from Phascolosoma esculenta

Ferritins are primary iron storage proteins and play a crucial role in iron storage and detoxification. Yeast two-hybrid method was employed to screen the cDNA library of Phascolosoma esculenta. Sequence of positive colony FER147 was analyzed. The higher similarity and conserved motifs for ferritin indicated that it belonged to a new member of ferritin family. The interaction between Ferritin and Fer147 was further confirmed through co-immunoprecipitation. The pET-28a-FER147 prokaryotic expression vector was constructed. The expressed recombinant Fer147 was then isolated, purified, and refolded. When ferritins were treated by different heavy metals, several detection methods, including scanning electron microscopy (SEM), circular dichroism (CD), and inductively coupled plasma-mass spectrometry (ICP-MS) were applied to examine the structures and functions of the new protein Fer147, recombinant P. esculenta ferritin (Rferritin), and natural horse-spleen ferritin (Hferritin). SEM revealed that the three ferritin aggregates changed obviously after different heavy metals treatment, meanwhile, a little different in aggregates were detected when the ferritins were trapped by the same heavy metal. Hence, changes in aggregation structure of the three proteins are related to the nature of the different heavy metals and the interaction between the heavy metals and the three ferritins. CD data suggested that the secondary structure of the three ferritins hardly changed after different heavy metals were trapped. ICP-MS revealed that the ferritins exhibit different enrichment capacities for various heavy metals. In particular, the enrichment capacity of the recombinant Fer147 and Rferritin is much higher than that of hferritin.

Thermo-stable carbon nanotube-TiO₂ nanocompsite as electron highways in dye-sensitized solar cell produced by bio-nano-process

We produced a thermostable TiO2-(anatase)-coated multi-walled-carbon-nanotube (MWNT) nanocomposite for use in dye-sensitized solar cells (DSSCs) using biological supuramolecules as catalysts. We synthesized two different sizes of iron oxide nanoparticles (NPs) and arrayed the NPs on a silicon substrate utilizing two kinds of genetically modified cage-shaped proteins with silicon-binding peptide aptamers on their outer surfaces. Chemical vapor deposition (CVD) with the vapor-liquid-solid phase (VLS) method was applied to the substrate, and thermostable MWNTs with a diameter of 6 ± 1 nm were produced. Using a genetically modified cage-shaped protein with carbon-nanomaterials binding and Ti-mineralizing peptides as a catalyst, we were able to mineralize a titanium compound around the surface of the MWNT. The products were sintered, and thin TiO2-layer-coated MWNTs nanocomoposites were successfully produced. Addition of a 0.2 wt% TiO2-coated MWNT nanocomposite to a DSSC photoelectrode improved current density by 11% and decreased electric resistance by 20% compared to MWNT-free reference DSSCs. These results indicate that a nanoscale TiO2-layer-coated thermostable MWNT structure produced by our mutant proteins works as a superior electron transfer highway within TiO2 photoelectrodes.

Water driven adsorption of amino acids on the (101) anatase TiO2 surface: an ab initio study

Arginine and lysine are stably adsorbed onto the (101) anatase TiO₂ surface in water solution.

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 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.