Biomolecular Adsorption to Interfacial Single Particle Layer of Organo-Modified Nanodiamond and Its Second-Order Structure.

Modifying the surface of nanodiamonds, which have antibacterial properties, with organic molecular chains enables biomolecular adsorption on a single particle layer on the water surface. For organo-modification, long-chain fatty acids act on the terminal hydroxyl groups present on the nanodiamond surface, and cytochrome C protein and trypsin enzyme are used as biomolecules. Cytochrome C and trypsin introduced into the subphase were electrostatically adsorbed onto the unmodified hydrophilic surface of the organo-modified nanodiamond monolayers on the water surface. The ampholyte protein is thought to exhibit Coulomb interactions with the positively charged unmodified nanodiamond surface. The protein adsorption was supported by morphological observations and spectroscopic properties; circular dichroism spectra suggested denaturation of the adsorbed proteins. However, the biopolymers could maintain their second-order structure even under a high-temperature environment, after being slightly denatured and adsorbed to the template. The nanodiamonds form excellent templates for structural retention in the atmosphere while yielding minor denaturation corresponding to the chirality of biomolecules upon adsorption.

Spherical Particle Formation that Deteriorates Thixotropic Property and its Suppression Strategy for Diamide-Based Additives having Two-Hydrocarbons.

Spherical particle formation degrades the performance of castor-oil-derived thixotropic additives, which are widely used to a dripping preventing agent in automobile paints and household waste oil treatment agent. Double-chain-type diamide is a heat-resistant thixotropic additive that causes nanofibrosis; its entanglement and gelation embracing solvent molecules-originating from the abundant intermolecular hydrogen bonds-and easy forming/rupturing tendency result in spherical particle formation, which can be confirmed by the temperature and time of reserve heating. Diamides with two hydrocarbons that have undergone thermal treatment leading to spheroidization were found exhibit significantly different sublimation/pyrolysis temperature, melting temperature, and crystal orientation than non-treated diamides. By comparing with the change observed under more extreme heating conditions, it can be considered that the amide bond site would increase the bond length and suppress the degree of freedom of rotation just before bond cleavage. In this state, verification of the origin of spherical particle formation by using the Langmuir-Blodgett method revealed that anisotropic suppression of hydrogen bonding occurs. In addition, it was found that spheroidization can be suppressed by adding a growth aid when preheating is conducted under a certain condition.

Extension of "Interfacial Adsorption Denaturation" Behavior Interpretation Based on Gibbs Monolayer Formation by Biomolecules.

Using glucose oxidase and salmon testis-derived DNA molecules, we sought to extend the recently proposed idea of interfacial adsorption denaturation. The surface pressure-time (π-t) isotherm of the glucose oxidase Gibbs monolayer exhibited a rapid increase in surface pressure and a relatively prompt transition to a liquid condensed film. The appearance of this rapid liquid expansion phase occurred much earlier than that previously identified for lysozyme, trypsin, cytochrome C, and luciferase. This experimental finding was linked to the number of hydrophobic residues in the constituent unit, and the number of hydrophobic residues in glucose oxidase was the highest among these biomolecules. On the other hand, DNA molecules do not have such hydrophobic groups, or present a positive surface on the π-t curve. However, interfacial adsorption occurred, and the existence of molecules at the air/water interface was confirmed, even in the two-dimensional gas phase state. Furthermore, it was confirmed that an increase in surface pressure was detected during the formation of a mixed film of DNA molecules and biomolecules, forming a stable Gibbs monolayer. This mimic the behavior of mixed monolayer formation with matrix molecules in Langmuir monolayers. Moreover, it was clarified that the interfacial adsorption denaturation behavior changed when pH dependence was evaluated considering the isoelectric point of the biomolecular group.