EPR parameters and spectrum of the solid-state L-α-alanine: cluster or periodic, static or dynamic

Abstract

L-α-alanine (LαA) is a non-essential α-amino acid in the human body. Free radicals formations in LαA induced by solid-state radiation have been the subject of investigations by electron paramagnetic resonance (EPR) spectroscopy. The Density Functional Theory (DFT) formalism has been used to calculate the EPR parameters of the radiation-induced radicals in the solid-state LαA in this article. Here, the effects of various factors such as the kind of hydrogen bonding (short and long-range) and the temperature have considered to calculate the EPR parameters. An atomic static cluster model has been used to evaluate the short-range hydrogen bonding effects, and Molecular Dynamic (MD) cluster model has been used simultaneously to study the influence of the short-range hydrogen bonding and temperature. A static periodic technique has been used to consider hydrogen bonds (short and long-range) effect. Finally, the MD periodic calculations have been used simultaneously to study the influence of the hydrogen bonds and temperature. These MD periodic calculations are more consistent with experiments than static periodic calculations and clusters. The EPR spectrums of LαA powder and crystal have been simulated and compared with the experimental EPR spectrums. The results show that they are in good agreement with the experimental results.