Temperature driven transformations of glycine molecules embedded in interstellar ice.

Area of Science:

• Astrochemistry
• Computational Chemistry
• Biochemistry

Background:

• Glycine, a key amino acid, is found in interstellar ice grains.
• Its formation and stability in space are crucial for understanding the origins of life.
• Interstellar glycine chemistry requires understanding its behavior in icy environments.

Purpose of the Study:

• Investigate glycine's conformational space and tautomerization mechanisms.
• Simulate glycine in interstellar ice and water-like environments.
• Determine glycine's stability and potential transformations under space conditions.

Main Methods:

• Quantum Mechanics/Molecular Mechanics (QM/MM) molecular dynamics simulations.
• Studied four glycine isomers (cc, ct, tc, tt).
• Simulated conditions included interstellar low-density amorphous (LDA) ice at 20 K, and higher temperatures (250 K, 450 K) to model heating events. Also simulated glycine in water clusters (4, 17, 27 H2O molecules).

Main Results:

• Glycine isomers largely retain their neutral conformations in interstellar ice (20 K).
• Tautomerization is significantly influenced by the number of water molecules and specific glycine isomer.
• Simulations in water clusters showed varying tautomerization behaviors dependent on water cluster size.

Conclusions:

• Glycine's canonical neutral conformations are stable under typical interstellar ice conditions.
• Water molecules play a critical role in mediating glycine tautomerization.
• Understanding these processes is vital for astrobiology and the search for extraterrestrial life.