Unveiling Vibrational Couplings in Model Peptides in Solution by a Theoretical Approach

Area of Science:

• Computational chemistry
• Spectroscopy
• Biophysics

Background:

• Vibrational analysis of peptides is crucial for understanding their behavior.
• The microenvironment significantly impacts infrared and Raman spectra.
• Theoretical determination of these effects is essential across various chemical fields.

Purpose of the Study:

• To computationally investigate the vibrational behavior of peptide models.
• To analyze the effects of explicit water on peptide vibrational spectra.
• To establish a link between spectroscopic observables and molecular structure.

Main Methods:

• Combined static quantum mechanical calculations and ab initio molecular dynamics simulations.
• Analysis of vibrational spectra for amide I-III and A bands.
• Time-frequency analysis using wavelet transform for time-resolved vibrational analysis.

Main Results:

• Identified time-resolved frequency shifts in C=O and N-H stretching modes due to dynamical microsolvation.
• Observed modulation of vibrational couplings leading to spectral broadening and shifts.
• Correlated vibrational fluctuations with the local structuring of the solvent.

Conclusions:

• The proposed computational protocol effectively connects vibrational modes with local structural changes.
• Provides a direct link between spectroscopic data, peptide structure, and the surrounding microenvironment.
• Highlights the importance of dynamic solvent effects on peptide vibrational spectroscopy.