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Direct Imaging of Laser-driven Ultrafast Molecular Rotation

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Published on: February 4, 2017

Pi-helix preference in unsolvated peptides.

Rajagopalan Sudha¹, Motoya Kohtani, Gary A Breaux

¹Chemistry Department, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405-7102, USA.

Journal of the American Chemical Society

|March 5, 2004

Summary

Ion mobility studies show that incorporating glutamic acid (E) and lysine (K) pairs into peptides reduces helix formation. The i,i+5 arrangement favors a pi-helix conformation, stabilized by side-chain interactions.

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Area of Science:

Biophysical chemistry
Computational chemistry
Molecular dynamics

Background:

Peptide secondary structures, such as helices, are crucial for protein function.
Understanding factors influencing peptide conformation in the gas phase is important for deciphering biomolecular interactions.

Purpose of the Study:

To investigate the impact of incorporating glutamic acid (E) and lysine (K) pairs on peptide helix formation in the gas phase.
To determine the preferred helical conformation induced by the E-K pair.

Main Methods:

Ion mobility measurements were used to determine the cross-sectional areas of peptides.
Molecular dynamics simulations were employed to calculate average cross-sections for various conformations.

Main Results:

The presence of an E-K pair consistently lowered the percentage of helical conformations across different positions.
The highest helical content was observed when the E-K pair was in an i,i+5 arrangement.
Experimental cross-sections matched simulated data for a pi-helix conformation.

Conclusions:

The E-K pair stabilizes non-helical conformations through side-chain hydrogen bonding.
The i,i+5 arrangement suggests a preference for pi-helix formation.
An ion pair between E and K may form, stabilized by the helix macro-dipole.