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Electrostatic Effects on the Stability of Peptide Radicals
Harish Jangra1, Hendrik Zipse1
1Department of Chemistry , LMU München , Butenandtstrasse 5-13 , 81377 München , Germany.
The Journal of Physical Chemistry. B
|September 11, 2018
Summary
External electric fields (EEFs) significantly impact glycine dipeptide radical stability. Ion orientation and distance from the radical center are key factors influencing these effects.
Area of Science:
- Computational chemistry
- Theoretical chemistry
- Molecular modeling
Background:
- Understanding the stability of peptide radicals is crucial in various chemical and biological contexts.
- External electric fields (EEFs) are known to influence molecular properties, but their specific effects on peptide radicals require detailed investigation.
- Previous studies have not fully elucidated the role of remote charges and their orientation in modulating radical stability.
Purpose of the Study:
- To investigate the influence of external electric fields (EEFs) on the stability of a glycine dipeptide model radical.
- To determine the impact of remote ion charges (Cl-/Na+) and their orientation on radical stability.
- To compare the effectiveness of different quantum mechanics methods in describing these EEF effects.
Main Methods:
- High-level quantum chemical calculations were employed to model the glycine dipeptide radical.
- External electric field effects were simulated using remotely located ions (Cl-/Na+) and background point charges.
- The influence of charge distance and orientation relative to the Cα radical center was systematically analyzed.
Main Results:
- Remote charges, even at distances up to 900 pm, significantly alter the stability of the Cα radical.
- Both stabilizing and destabilizing effects were observed, strongly dependent on the relative orientation of the charges.
- The magnitude of the EEF effects is sensitive to the distance between the radical center and the charge.
- Di-peptide radicals with protonable/deprotonable side chains showed stability dependent on the charge-carrying side chain's orientation.
Conclusions:
- External electric fields, implemented via remote charges, play a critical role in the stability of dipeptide model radicals.
- The orientation and distance of charged species are paramount in determining stabilizing or destabilizing influences.
- Quantum chemical methods need careful selection to accurately capture these charge-mediated effects on radical stability.
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