Journal de médecine légale

Connections of DNA with Lysozyme

Abstract

Nikolay Noskov

AFM, ellipsometry, surface tensiometry, surface dilational rheology and infrared reflection-absorption spectroscopy (IRRAS) were used to investigate the interactions of DNA with lysozyme in the surface layer (AFM). Under a dispersed lysozyme layer, an aqueous subphase was injected with a concentrated DNA solution. In contrast to DNA interactions with a monolayer of a cationic synthetic polyelectrolyte, where the surface layer's optical properties changed quickly after DNA injection, the dynamic dilational surface elasticity almost did not change. This suggests that no continuous network of DNA/lysozyme complexes formed. The relatively quick increase in optical signals following a DNA injection behind a lysozyme layer suggests that diffusion regulates DNA penetration. The AFM images demonstrate the development of lengthy strands in the surface layer at low surface pressures. In contrast to a mixed layer of DNA and synthetic polyelectrolytes, increased surface compression results in the emergence of folds and ridges rather than a network of DNA/lysozyme aggregates. It is likely that weaker interactions between lysozyme and duplex DNA and the stabilisation of loops of unpaired nucleotides at high local lysozyme concentrations in the surface layer are the causes of the creation of more disordered aggregates.