Tritium-Probe Method in a Study of Adsorption Layers of Lysozyme on the Surface of Detonation Nanodiamonds

Tritium-labeled lysozyme was used to determine its adsorption on the surface of nanodiamonds produced by detonation synthesis. It was found that the amount of the adsorbed protein depends on the charge of the nanodiamond surface. A multilayer coating is formed on the originally positively charged nanodiamonds, with the adsorption becoming 4–5 times stronger on negatively charged nanodiamonds produced from the original nanodiamonds via their annealing in air. According to IR spectroscopic data, the adsorption of lysozyme results in that the number of loops and turns in the protein structure decreases in the adsorption on two types of nanodiamonds. The use of a tritium probe did not find any significant difference between the structures of protein molecules in their adsorption on nanodiamonds with different functional surface compositions. The orientation of molecules in the surface layer was found to be the same: Protein parts containing amino acid residues of phenylalanine are contacting with the sorbent, and the amino acid residues of proline, which are contained in the loops, are on the surface of the adsorption layer.