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Structure and Magnetic Properties of L-α-Alanine Radicals in Radiation Dosimetry Applications: An Ab Initio Molecular Dynamics Simulation
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  • Mehdi Janbazi,
  • Yavar Taghipour Azar,
  • Farhood Ziaie,
  • Khashayar Ghandi,
  • Chérif Matta,
  • Muhammad Shadman Lakmehsari
Mehdi Janbazi
Nuclear Science and Technology Research Institute
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Yavar Taghipour Azar
Nuclear Science and Technology Research Institute
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Farhood Ziaie
Nuclear Science and Technology Research Institute
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Khashayar Ghandi
University of Guelph
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Chérif Matta
Mount Saint Vincent University
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Muhammad Shadman Lakmehsari
University of Zanjan
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Abstract

Alanine is a transfer standard dosimeter using in gamma-ray and electron beam calibration. One of the important factor affecting its dosimetric response is amount of humidity which can deviate the dosimetry expert from the exact value of absorbed doses. Ab initio molecular dynamics calculations were performed to determine the environmental effects on the EPR parameters of L-α-Alanine radicals in acidic and alkaline solutions. Similar to the closed-shell amino acid molecule alanine, the zwitterionic form of alanine radical is the stable form in the gas phase while the non-zwitterionic neutral alanine radical is not a stable structure. Geometric and EPR parameters of radicals in both gas and solution phases are found to be dependent on hydrogen bonding of water molecules with the polar groups and by dynamic solvation. Calculations on the optimized free radicals in the gas phase revealed that for neutral radical, hydrogen bonding to water molecules drives a decrease in the magnitudes of g-tensor components gxx and gyy without affecting neither gzz component nor the HFCCs. For the transfer from the gas to solution phase of the alanine radical anion is accompanied with an increase in the spin density on the carboxylic group’s oxygen atoms. However, for the neutral radical, this transfer from gas to solution phase is accompanied with the decrease in the spin density on oxygen atoms. Calculated isotropic HFCCs and g-tensor of all radicals were in good agreement with their experimental counterparts in both acidic and alkaline solutions, which enhances the confidence in our calculated results.

Peer review status:ACCEPTED

04 Jan 2020Submitted to International Journal of Quantum Chemistry
06 Jan 2020Submission Checks Completed
06 Jan 2020Assigned to Editor
22 Jan 2020Reviewer(s) Assigned
01 Feb 2020Review(s) Completed, Editorial Evaluation Pending
03 Feb 2020Editorial Decision: Revise Major
18 Feb 20201st Revision Received
19 Feb 2020Submission Checks Completed
19 Feb 2020Assigned to Editor
28 Feb 2020Reviewer(s) Assigned
28 Feb 2020Review(s) Completed, Editorial Evaluation Pending
28 Feb 2020Editorial Decision: Accept