Computational study of the stability of guanine through redox potential for potential existence in Martian brines Público

Abstract

Martian brines consistent of sodium perchlorate and water could have the potential to sustain microbial life. However, perchlorate is a strong oxidizer with the ability to cause oxidative deoxyribonucleic acid (DNA) damage. The Martian brine environment can be computationally simulated to see if DNA is likely to be oxidized or if it can remain stable. Because guanine is the nucleotide most susceptible to oxidation, it can be used as the initial solute when modeling this type of environment. This research aims to use computational methods to study the redox potential of guanine in various solvation models to ultimately determine its stability in a Martian brine environment. TeraChem was used for the implicit solvation of guanine in water, approximating the redox potential to be 1.90 V. The redox potentials for adenine, cytosine, and thymine were also calculated in implicit solvation and it was verified that guanine has the lowest redox potential. AutoSolvate was then used for the explicit solvation model of guanine in water. The average energy value for the molecular dynamic simulation was -7677.24 Hartree. Future steps include the explicit solvation of guanine in sodium cations, perchlorate anions, and water. The same methods can be employed for this simulation. If it can be determined that guanine and DNA are not readily susceptible to oxidation in a Martine brines environment, then DNA has the potential to be stable on Mars. This information could help provide evidence for the potential existence of life on Mars or other brine-bearing worlds.

Table of Contents

1. INTRODUCTION (1)

2. THEORY (2)

2.1 Redox Potential (2)

2.2 Density Functional Theory (3)

2.3 Implicit Solvation (4)

2.4 Explicit Solvation (4)

3. COMPUTATIONAL DETAILS (5)

3.1 TeraChem (5)

3.2 AutoSolvate (6)

4. METHODOLOGY (7)

4.1 Implicit Solvation (7)

4.2 Explicit Solvation (8)

5. RESULTS (10)

6. DISCUSSION (13)

7. REFERENCES (18)

About this Honors Thesis

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• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Emory College
Department	Chemistry
Degree	B.A.
Submission	Honors Thesis
Language	English
Research Field	Physics, Quantum Chemistry, General Physics, Astrophysics
Palavra-chave	basis set DNA perchlorate redox potential Mars simulation solute-solvent box generation guanine MM 6-31G** MD brines density functional theory QM TeraChem explicit solvation AutoSolvate b3lyp DFT implicit solvation
Committee Chair / Thesis Advisor	Fang Liu, Emory University
Committee Members	Matthew Weinschenk, Emory University Tracy McGill, Emory University

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