Ultraviolet Raman Optical Activity as a Window Into Peptide Backbone Structure.

Area of Science:

• Biophysical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Raman optical activity (ROA) typically uses visible light, providing insights into molecular structure.
• Ultraviolet Raman optical activity (UV ROA) is less explored but offers potential for enhanced sensitivity and spatial information due to the amide chromophore.

Purpose of the Study:

• To explore the potential of UV ROA spectroscopy for analyzing peptide and protein conformation.
• To investigate the relationship between UV ROA spectral shapes and molecular structure.
• To compare UV ROA spectra obtained with different excitation wavelengths.

Main Methods:

• Acquisition of UV ROA spectra for three peptides using a dedicated instrument.
• Analysis of spectral data using molecular dynamics and density functional theory simulations.
• Computational experiments on Ala4 peptide to assess secondary structure sensitivity.

Main Results:

• Significant differences observed between UV ROA spectra acquired at 244 nm and 532 nm excitations.
• Simulations rationalized spectral differences, highlighting enhanced peptide backbone signals at shorter wavelengths due to pre-resonance effects.
• UV ROA demonstrated enhanced sensitivity to secondary structure through combined geometric and resonance effects.

Conclusions:

• UV ROA spectroscopy shows significant potential for peptide and protein conformational analysis.
• The technique provides novel information on molecular geometric and electronic structure.
• UV ROA is a promising tool for applications in analytical chemistry and biochemistry.