Amide vibrations and their conformational dependences in β-peptide

Area of Science:

• Computational Chemistry
• Spectroscopy
• Biophysics

Background:

• Amide modes are crucial for understanding peptide structure and dynamics.
• Beta-peptides offer unique structural properties compared to alpha-peptides.
• Conformational changes significantly influence vibrational spectra.

Purpose of the Study:

• To investigate the conformational dependence of amide-A and amide-I vibrational modes in β-homoalanine dipeptides (β-HADP).
• To compare vibrational couplings in β-peptides with those in α-peptides.
• To elucidate the structural underpinnings of local amide modes in β-peptides.

Main Methods:

• Density Functional Theory (DFT) for harmonic frequencies.
• Morse potential for anharmonic frequencies and diagonal anharmonicities.
• Normal mode analysis for local-mode frequencies and intermode couplings.

Main Results:

• Vibrational frequencies of amide-A and amide-I modes are conformation-dependent in β-HADP.
• Inter-amide vibrational couplings are generally weaker in β-peptides than in α-peptides.
• Structural factors influencing local amide modes in β-peptides were identified.

Conclusions:

• The conformational flexibility of β-HADP significantly impacts its vibrational characteristics.
• Weaker inter-amide couplings in β-peptides suggest distinct vibrational energy transfer mechanisms.
• Understanding these modes provides insights into the unique structural and dynamic properties of β-peptides.