Maintenance Properties of Enzyme Molecule Stereostructure at High Temperature by Adsorption on Organo-Modified Magnetic Nanoparticle Layer Template

The transition behavior of Gibbs monolayers of biomolecules at the air/water interface, and the sustainability of their three-dimensional structure during heating by adsorption/immobilization on inorganic particle nanosheets were investigated. Lysozyme (enzyme), cytochrome C (protein), trypsin (digestive enzyme), and luciferase (luminescent enzyme) were the biomolecules used in this study. The surface pressure-time isotherms of these biomolecules showed that the crystal transition of the Gibbs monolayer corresponding to denaturation and deactivation was systematically different. The Gibbs monolayers of these biomolecules were observed to become increasingly unstable with an increase in the number of apparent hydrophobic units, and were susceptible to denaturation by crystal transition. These biomolecules were adsorbed/immobilized on a nanosheet of organo-modified magnetic fine particles. After forming a monolayer on the water surface of the organo-magnetic nanoparticles, these biomolecules were introduced into the subphase and electrostatic interaction between the nanoparticle hydrophilic surface and the biomolecules was induced. When the bio-adsorbed single particle layer was transferred onto the solid substrate, an infra-red (IR) band derived from the adsorbed species was confirmed in this multi-particle layer. In addition, shapeless adsorbed matter was observed by atomic force microscopy images. From the IR measurement under heating, it was found that the secondary structure of the adsorbed lysozyme enzyme was maintained up to about 100 °C by substrate adsorption. This is probably because the three-dimensional structure of biomolecules is less likely to be denatured by using inorganic nanosheets with high density and low defects as the templates.