Simulation of EPR spectra as a tool for interpreting the degradation pathway of hyaluronan

Electron paramagnetic resonance (EPR) spin trapping is one of the choice techniques for identifying free radicals and is often used in the study of biological systems. However, its sensitivity can result in a typical complicated EPR spectrum. The accurate simulation of these systems is essential for correct identification of the radical species, whenever more than one species contributes to the spectrum. Programs implementing the linear combination of single simulations allow the interpretation of EPR spectra without modifying experimental conditions. In this study, this approach was used to investigate the influence of the ferrous ion and the role of oxygen, as well on the formation of transient radical species, in the whole mechanism of hyaluronan degradation. Degradation was carried out under different environmental conditions (air, O2, Ar, N2, N2 ? CO2) and EPR spin trapping studies were performed. The advantages of the simulation of multiple species EPR spectra were applied to the obtained results and some aspects of hyaluronan degradation mechanism were elucidated. The depolymerization reaction pathway has been defined according to two possible subsequent steps: the first is consistent with formation of an amidyl radical that induces a series of strand scissions, which stabilize at two different levels of molecular weight. The second step occurs when the molecular weight is lower than before and two different adducts are generated.