Bond distances in polypeptide backbones depend on the local conformation.

Area of Science:

• Structural Biology
• Computational Chemistry
• Biophysics

Background:

• Polypeptide backbone conformation is crucial for protein structure and function.
• Understanding the subtle variations in bond lengths within the polypeptide backbone is essential for accurate molecular modeling.

Purpose of the Study:

• To systematically investigate the conformational dependence of bond lengths in polypeptide backbones.
• To elucidate the underlying quantum mechanical and statistical drivers of these variations.

Main Methods:

• Quantum-mechanical analysis of small model peptides.
• Statistical surveys of high-resolution protein structures.

Main Results:

• Identified systematic variability in peptide bond (C-O, C-N) and C(α) atom bond lengths correlated with the ψ angle.
• Found agreement between computed and statistical data, indicating local effects drive these trends.
• Correlated bond length variations with specific orientations relative to the peptide plane and interactions involving lone pair electrons.

Conclusions:

• Local quantum mechanical interactions, particularly involving the C(α) moiety and peptide bond systems, govern polypeptide backbone bond length variations.
• The ψ angle plays a key role in modulating these interactions and, consequently, bond lengths.
• These findings provide a deeper understanding of peptide bond dynamics and protein structural nuances.