Journal de médecine légale

Interactions between DNA and Lysozyme

Abstract

Nikolay Noskov

Various techniques including AFM, ellipsometry, surface tensiometry, surface dilational rheology, and infrared reflection-absorption spectroscopy (IRRAS) were employed to probe the interactions between DNA and lysozyme within the surface layer. In the experiments, a concentrated DNA solution was introduced into an aqueous subphase beneath a dispersed lysozyme layer. Notably, when compared to DNA's interactions with a monolayer of a cationic synthetic polyelectrolyte, the optical properties of the surface layer exhibited rapid changes following DNA injection, while the dynamic dilational surface elasticity remained relatively stable. This observation suggests the absence of a continuous network of DNA/lysozyme complexes. The swift increase in optical signals following DNA injection behind a lysozyme layer implies that DNA penetration is predominantly governed by diffusion. Furthermore, AFM images vividly illustrate the formation of elongated strands within the surface layer under low surface pressures. In contrast, increased surface compression leads to the emergence of folds and ridges, rather than the formation of a network of DNA/lysozyme aggregates. These results suggest that weaker interactions between lysozyme and duplex DNA, along with the stabilization of unpaired nucleotide loops at high local lysozyme concentrations in the surface layer, contribute to the generation of more disordered aggregates.