The Structure of the Protonated Serine Octamer

Area of Science:

• Chemical Physics
• Computational Chemistry
• Spectroscopy

Background:

• Protonated serine clusters, particularly the
• magic-number
• Ser₈H⁺, exhibit unusual abundance in mass spectra and strong homochiral preference.
• Previous experimental and theoretical studies have not reached a consensus on the Ser₈H⁺ structure.
• Understanding this cluster's structure is crucial for interpreting mass spectrometry data and exploring non-covalent interactions.

Purpose of the Study:

• To determine the three-dimensional structure of the protonated serine eight cluster (Ser₈H⁺).
• To elucidate the structural basis for the observed homochiral preference and facile substitution of serine units.
• To provide a definitive structure that reconciles experimental observations.

Main Methods:

• Infrared spectroscopy was employed to probe the vibrational modes of the cluster.
• Ab initio molecular dynamics simulations were used to explore the potential energy surface and identify stable structures.
• High-level quantum chemical calculations were performed to validate the proposed structure.

Main Results:

• A novel, highly stable three-dimensional structure for Ser₈H⁺ was determined.
• This structure is approximately 25 kcal mol^-1 more stable than previously reported structures.
• The determined structure successfully explains the observed homochiral preference and the facile replacement of two serine units.

Conclusions:

• The study presents a definitive structure for Ser₈H⁺ that aligns with experimental data.
• The findings resolve a long-standing ambiguity in the field of mass spectrometry and cluster science.
• This work provides a foundation for future investigations into serine cluster behavior and self-assembly.