Isotope Effects Induced by Molecular Compression.

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Molecular Physics

Background:

• Zero-point energies (ZPEs) are fundamental quantum mechanical properties of molecules.
• Isotope effects, particularly large ones in enzymatic reactions, are not fully understood.
• Molecular compression can alter molecular properties, but its effect on ZPEs and isotope effects is less explored.

Purpose of the Study:

• To compute the zero-point energies (ZPEs) of hydroxyl ion, hydrogen, and water molecules.
• To investigate the impact of compression within C60 cages on molecular ZPEs and isotope effects.
• To explore the potential of compression-induced isotope effects as a probe for enzymatic reactions.

Main Methods:

• Quantum mechanical calculations were employed to determine ZPEs.
• Molecules (hydroxyl ion, hydrogen, water) were studied both in free states and compressed within C60 cages.
• Isotopic variations (including deuterium and tritium) were considered.

Main Results:

• Compression within C60 cages results in excess molecular energy of 2-3 kcal/mol, dependent on isotopes.
• Differences in ZPE for compressed isotopic molecules are significantly larger than for free molecules.
• This leads to substantial deuterium and tritium isotope effects induced by compression.

Conclusions:

• Compression of molecules, such as water in C60 cages, dramatically enhances isotope effects.
• These compression-induced isotope effects can serve as a valuable probe for molecular compression in enzymatic sites.
• The findings may offer insights into the large isotope effects observed in enzymatic reactions, potentially linked to tunneling.