Crystal phase and morphology of biominerals may be precisely regulated by controlled nucleation and selective crystal growth through biomineralization on organic templates such as a protein. We herein propose new control factors of selective crystal growth by the biomineralization process. In this study, a designed β-sheet Ac-VHVEVS-CONH2 peptide was used as a multifunctional template that acted as mineral source supplier and having crystal phase control ability of calcium carbonate (CaCO3) during a self-supplied mineralization. The peptides formed three-dimensional nanofiber networks composed of assembled bilayer β-sheets. The assembly hydrolyzed urea molecules to one carbonate anion and two ammonium cations owing to a charge relay effect between His and Ser residues under mild conditions. CaCO3 was selectively mineralized on the peptide assembly using the generated carbonate anions on the template. Morphology of the obtained CaCO3 was fiber-like structure, similar to that of the peptide template. The mineralized CaCO3 on the peptide template had aragonite phase. This implies that CaCO3 nuclei, generated using the carbonate anions produced by the hydrolysis of urea on the surface of the peptide assembly, preferentially grew into aragonite phase, the growth axis of which aligned parallel to the direction of the β-sheet fiber axis.

No abstract

We designed a novel multifunctional β-sheet peptide template for calcium carbonate mineralization. The template self-supplies the mineral source, a carbonate ion, by hydrolysis of urea, and regulates the crystal phase and morphology of the obtained calcium carbonate.

We investigated the drug releasing behavior of a novel nanocarrier system, utilizing a peptide to act as a nanogate to the mesopore, on a mesoporous silica nanoparticle. The surface peptide on mesoporous silica displayed pH-dependant mesopore cap-uncap switching behavior, enabled by the reversible β-sheet-to-random coil conformational transition resulting from slight pH changes between 8.0 and 6.0. The peptide adopted a β-sheet structure under weakly basic conditions (pH 8.0) and a random coil conformation under weakly acidic conditions (pH 6.0). We demonstrated the pH-dependant regulation of the material's drug release property by the reversible conformational transition of the surface peptide. Under basic pH conditions, the drug release from the nanocarrier was significantly inhibited. However, under acidic pH conditions, the drug in the mesopore was gradually released.

The enzyme subtilisin from Bacillus licheniformis (4.1 nm  7.8 nm  3.7 nm) was easily immobilized onto a mesoporous silica (MPS) surface by a direct one-step method and the amount of subtilisin immobilized on each functionalized MPS surface was similar (approximately 0.30 mg of enzyme/mg of MPS support). The catalytic performance (hydrolytic activity and enantioselectivity) of the immobilized subtilisin was found to depend on the properties of the organofunctional group on the MPS surface. In particular, the hydrolytic activity of enzyme immobilized on ethyl-group-modified MPS increased relative to the behavior of free subtilisin (relative activity 143%). The activity of subtilisin immobilized on the modified MPS was improved by facilitation of contact between enzyme and hydrophobic substrate by increase in hydrophobicity with an immobilized carrier. On the other hand, the enantioselectivity of subtilisin immobilized on 3-mercaptopropyl-group-modified MPS significantly decreased (enantioselectivity of 2.6 compared to 4.3 for free subtilisin). This decrease in enantioselectivity indicated that the mercapto group on the MPS surface was changed in the secondary structure of enzyme by interacting between enzyme and immobilized support. The denaturation temperature of subtilisin immobilized on no-substituted MPS increased (65 1C compared with 57 1C for free subtilisin). The denaturation temperature of immobilized subtilisin was dependent on the absorbed fraction of thermal energy by functional groups on the MPS surface.